Insects and Diseases of Trees in the South

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Title: Insects and Diseases of Trees in the South
Author: Anonymous
Language: English
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INSECTS
AND
DISEASES
OF TREES
IN THE SOUTH

U.S. Department of Agriculture—Forest Service
State and Private Forestry—Southeastern Area
Forest Pest Management Group

INTRODUCTION

This publication has been prepared to assist forest managers and
homeowners in identifying pests of southern trees. The insects and
diseases discussed are the more common ones attacking forest and
ornamental trees. Prompt identification and treatment of these pests may
mean the difference between losing or saving a valuable shade tree.
Underlying all successful forest and ornamental pest control efforts,
however, is the necessity to keep trees in a healthy, vigorous
condition.

We have attempted to include pictures of the damage as well as pictures
of the damage-causing organism or stage. Chemical suppression
recommendations are not included in this publication. For pesticide
information contact the local State or Federal extension specialist,
forester, entomologist, or pathologist.

Credit for some of the pictures in this guide goes to the Southern and
Southeastern Forest Experiment Stations and universities. We acknowledge
the help of the Forest Pest Management field personnel who assisted in
compiling this booklet.

TABLE OF CONTENTS

INSECTS
Hardwood Insects
Defoliators
Elm Spanworm 1
Fall Cankerworm 2
A Looper 3
Eastern Tent Caterpillar 4
Forest Tent Caterpillar 5
Fall Webworm 6
Oak Leaf Tier 7
Variable Oakleaf Caterpillar 8
Locust Leafminer 9
Cottonwood Leaf Beetle 10
Walkingstick 11
Gypsy Moth 12
Bark Beetles and Borers
Hickory Bark Beetle 13
Smaller European Elm Bark Beetle 14
Columbian Timber Beetle 15
Cottonwood Twig Borer 16
Cottonwood Borer 17
White Oak Borer 18
Red Oak Borer 19
Carpenterworm 20
Conifer Insects
Defoliators
Pine Webworm 21
Bagworm 22
Pine Colaspis 23
Pine Sawfly 24
Arkansas Pine Sawfly 25
Virginia Pine Sawfly 26
Redheaded Pine Sawfly 27
Texas Leaf Cutting Ant 28
Bark Beetles and Borers
Southern Pine Beetle 29
_Ips_ Engraver Beetles 30
Black Turpentine Beetle 31
Ambrosia Beetle 32
Southern Pine Sawyers 33
Meristem Feeders
Nantucket Pine Tip Moth 34
Pales Weevil 35
White Pine Weevil 36
Pitch Eating Weevil 37
Deodar Weevil 38
Coneworms 39
Pine Seedworms 40
Sapsucking Insects
Balsam Woolly Aphid 41

DISEASES
Conifer Diseases
Foliage
Needle Cast 42
Brown Spot 43
Needle Rust 44
Cedar Apple Rust 45
Cedar Blight 46
Stem, Branch, Cone
Southern Fusiform Rust 47
White Pine Blister Rust 48
Comandra Blister Rust 49
Eastern Gall Rust 50
Cone Rust 51
Pitch Canker 52
Wood Decay 53
Red Heart 54
Root and Butt Rots
Annosus Root Rot 55
Brown Cubical Rot 56
Red Root and Butt Rot 57
Littleleaf Disease 58
Hardwood Diseases
Foliage and Twig
Sycamore Anthracnose 59
Walnut Anthracnose 60
Oak Anthracnose 61
Dogwood Anthracnose 62
Cottonwood Rust 63
Black Knot of Cherry 64
Stem and Canker
Nectria Canker 65
Strumella Canker 66
Spiculosa Canker 67
Irpex Canker 68
Hispidus Canker 69
Botryosphaeria Canker 70
Septoria Canker 71
Cytospora Canker 72
Chestnut Blight 73
Vascular Wilts
Oak Wilt 74
Dutch Elm Disease 75
Elm Phloem Necrosis 76
Mimosa Wilt 77
Verticillium Wilt 78
Root and Butt Rots
Armillaria Root Rot 79
Cylindrocladium Root Rot 80
Lucidus Root and Butt Rot 81

INSECTS

ELM SPANWORM, _Ennomos subsignarius_ (Hbn.)

The elm spanworm is a native insect which is widely distributed over the
eastern half of the United States and Canada from Nova Scotia south to
Georgia and west to Colorado. The most widespread outbreak on record
occurred during the period 1954-1963 when over one million acres of
hardwood forests were defoliated in the mountains of western North
Carolina, eastern Tennessee and northern Georgia. The elm spanworm feeds
upon hickories and a variety of hardwoods; white oak, chestnut oak, and
northern red oak are the species most heavily defoliated in the
Appalachians. Repeated defoliation causes growth loss, reduces mast
crops, and will eventually kill the tree.

[Illustration: Sixth instar elm spanworm larva.]

Eggs are laid in masses of 12 to 200 on the undersides of host tree
branches in early July. Winter is spent in the egg stage. Larvae hatch
in early spring when foliage opens. The larval stage is an “inchworm” or
“looper”, approximately 1½ inches long when mature. Larval coloring
varies from green or light brown to black, depending upon population
density. The typical color of the larva in heavy populations is dark
brown to black, with a dark-red head, legs, and anal shield. The larvae
feed for about 1½ months, and then pupate in a loose cocoon for six to
ten days. The adult, a snow-white moth, emerges in late June or early
July. There is one generation per year.

Natural enemies help keep populations of the elm spanworm in check. One
of the most important is _Telenomus alsophilae_, a tiny wasp which
parasitizes eggs. Persistent outbreaks on high-value stands may require
treatment with chemicals.

[Illustration: Elm span worms feeding on oak.]

FALL CANKERWORM, _Alsophila pometaria_ (Harris)

The fall cankerworm is widespread in the northern part of the United
States, ranging south through the Appalachian Mountains to North
Carolina. Larvae defoliate many species of hardwoods, but in the South
seem to prefer oaks, hickories, and ash.

[Illustration: Mature fall cankerworm larva.]

The winged male and wingless female adults emerge on mild days in
November and December and mate. Females lay 6-300 eggs in neatly
arranged masses encircling small branches and twigs. The pale green
larvae hatch in late April or early May. As they mature they may remain
light green, or change to a very dark brownish-green depending on the
host. Newly hatched inch-worms (larvae) of the fall cankerworm chew
small holes in expanding leaves of their hosts, or may completely
skeletonize the leaves. Mature larvae consume all but the mid-rib and
major veins of the leaf. Feeding is usually completed in four to five
weeks, at which time larvae drop to the ground to pupate in the soil.

Cold, wet weather during the early larval period, and parasitization,
are responsible for sudden declines in established populations. Chemical
control has also been effective. A small wasp, _Telenomus alsophilae_
Viereck, has caused a sharp decline in outbreaks of cankerworm
populations. Usually, however, outbreak conditions must exist for
several years before the parasite can attain the density needed to cause
a decline.

[Illustration: Female cankerworm adult depositing eggs.]

A LOOPER, _Phigalia titea_ (Cramer)

Larvae of this moth, one of the measuring worms, have periodically been
responsible for scattered mortality of hardwoods throughout the eastern
United States. Mortality is most likely to occur in stands on
low-quality sites, particularly during periods of drought which favor
this insect’s development and further weaken infested trees. This
species is likely to be found in almost any hardwood area in the eastern
United States. The insect feeds on a wide variety of trees and shrubs.
Host trees in the Southeast include oaks, hickories, black tupelo, and
black locust.

[Illustration: Phigalia adult male moth.]

_Phigalia titea_ overwinters as a pupa. Adults emerge in late March to
mid-April, and mate. The female lays her eggs in protected sites on
branches and trunks of hardwoods. Eggs are most often laid in crevices
and beneath the bark of dead branches. Eggs hatch in April, and larvae
feed until early June. Larvae often feed on unopened buds, causing
irregular holes in the developing leaves. Larvae first eat just the
surfaces of leaves, but later consume all leaf tissue between the major
veins. When larvae are dislodged by wind or feeding predators they fall
or descend on a silken thread and continue feeding in the lower crown or
on understory vegetation. Pupation occurs on the soil surface or in the
litter.

[Illustration: Phigalia larva.]

Weather regulates populations of this insect. Soil-inhabiting insects
and rodents are believed to destroy many pupae during the winter.

EASTERN TENT CATERPILLAR, _Malacosoma americanum_ (F.)

The presence of the eastern tent caterpillar is objectionable more from
an aesthetic standpoint than from its effect on the host tree. The ugly
tents constructed by the feeding larvae make this pest highly
objectionable on shade trees. Black cherry and other species of the
genus _Prunus_ are preferred hosts, but other trees in the family
_Rosaceae_ are sometimes attacked. This insect is widely distributed
wherever host trees are found east of the Rocky Mountains.

[Illustration: Larvae and tent of eastern tent caterpillar.]

The caterpillars appear at about the same time the leaves of black
cherry begin to unfold. The larvae construct a web or tent in the crotch
of a small branch, and begin feeding. Usually they consume entire
leaves, except for the large veins. As the larvae mature, they add to
the tent, which may reach a foot in diameter and two feet in length.
Reaching maturity in about six weeks, the larvae drop to the ground and
pupate. The moths emerge in June and the females lay eggs. Eggs of the
eastern tent caterpillar are shiny black masses which encircle the
smaller twigs and are quite noticeable. The insect overwinters in the
egg stage.

Control on ornamental, fruit, and shade trees is achieved by pruning off
and burning the tents containing the caterpillars.

[Illustration: Tent caterpillar-infested black cherry.]

FOREST TENT CATERPILLAR, _Malacosoma disstria_ (Hbn.)

The forest tent caterpillar has caused repeated serious defoliation of
hardwood forests throughout North America. Aspen, water tupelo, hard
maple, gums, and oaks are preferred hosts but this insect will feed on a
variety of other broadleaf trees.

[Illustration: Forest tent caterpillar larvae.]

The shiny black egg masses encircling the twigs of host trees can be
seen during winter months. Small black, hairy larvae hatch out just as
the leaves are beginning to unfold. They do not construct a tent, but
make a silken mat on the larger branches or trunk of the tree on which
they rest between feeding periods. When full grown, the larvae are about
two inches long, brownish-black with distinctive white, keyhole-shaped
spots down the middle of the back, and blue lines along the sides. Just
before pupating, the larvae spin a whitish silk cocoon on the bark or
leaf of the host. In about ten days the light brown moths emerge, mate,
and the females begin laying their eggs.

Parasitic flies are one of the more important agents which normally keep
this insect under control. Outbreaks occur with some regularity,
however, and chemicals may be required to prevent defoliation.

[Illustration: Colony of third instar larvae.]

FALL WEBWORM, _Hyphantria cunea_ (Drury)

The fall webworm is not considered an important forest pest. However,
ugly webs can seriously detract from aesthetic values. The preferred
hosts in the South are persimmon, pecan, and sourwood, but it is also
found on black walnut, hickory, cherry, sycamore, crab apple, and
sweetgum. The insects range throughout North America.

[Illustration: Fall webworm larva.]

The adult is a pure white moth about 1¼ inches long. The forewing is
sometimes marked with blackish dots. The larva is about one inch long
when full grown, generally pale yellow or greenish with a broad dark
longitudinal stripe on the back and a yellowish stripe extending from
black and orange warts. The insect has one generation per year in the
northern part of its range, and two in the southern part. Moths of the
first generation emerge from May to July and those of the second in July
and August. Adult females lay 400-500 eggs in white cottony patches on
the underside of the leaves of host plants. The eggs hatch in about a
week, and the larvae form a web and begin to skeletonize the leaves by
feeding in rows. As the larvae grow they expand the web to cover the
colony. When the larvae are ready to pupate, they crawl or drop to the
ground and form a brownish cocoon in the duff around the tree where they
overwinter.

[Illustration: Fall webworm infestation.]

Natural enemies usually keep this insect under control. Webs can be
pruned from high-value trees in scenic or recreation areas.

OAK LEAF TIER, _Croesia albicomana_ (Clem.)

This oak leaf tier has been associated with the decline and mortality of
several species of oak in the northeastern United States and southern
Appalachians. An outbreak population in the mountains of West Virginia
and Virginia in 1966-68 resulted in the loss of several thousand acres
of scarlet oak. Usually such outbreaks coincide with periods of drought
which increase the impact of defoliation on the host. Its hosts include
northern red oak, black oak, scarlet oak, and pin oak. The latter two
species seem to be hit hardest by this insect.

[Illustration: Leaf tier adult and pupa.]

_Croesia albicomana_ spends the winter in the egg stage. Eggs are glued
to small twigs in the crown of the host tree. Hatch occurs from
mid-April to early May. Young larvae, which emerge before bud-break,
bore into and mine the expanding buds. When large numbers of this insect
are present they can destroy most of the vegetative buds on a tree.
Later the older larvae tie down a folded-over portion of a leaf and feed
on it. Leaves fed on by the oak leaf tier appear to be full of shot
holes. As the larvae near maturity they may tie the apical portion of
two or more leaves together and feed on them. Mature larvae then drop to
the ground to pupate in the litter. Adult moths emerge in June or early
July, mate, and the female immediately begins laying eggs. The small,
flat, oval eggs are deposited individually on small twigs, generally
around nodes or leaf scars.

[Illustration: Scarlet oak killed by leaf tier.]

Little is known of the natural factors which regulate population levels
of this insect, but undoubtedly weather is important.

VARIABLE OAK LEAF CATERPILLAR, _Heterocampa maneto_ (Dbldy.)

The variable oak leaf caterpillar periodically defoliates extensive
areas of hardwood forest in the eastern United States. Its range covers
all of the southern and eastern states as far west as east Texas. The
larvae feed primarily on oaks but will also feed on beech, basswood,
birch and elm. Other defoliating insects may be associated with
outbreaks causing additional damage. Young larvae skeletonize the leaf
while older larvae devour the entire leaf except the primary veins.
Infestations are generally more severe in the South, where the insect
has two generations per year causing two periods of defoliation in a
single year. While infestations usually subside before many trees are
killed, heavy defoliation reduces the tree’s growth and vigor.

[Illustration: Larva of the variable oak leaf caterpillar.]

The variable oak leaf caterpillar overwinters as a non-feeding larva in
a cocoon on the forest floor. It pupates and emerges as a moth the
following spring. The female moth, gray in color and about 1¾ inches
long, lays about 500 eggs singly on the leaves of host trees. The larvae
feed on foliage for five or six weeks, drop to the ground to pupate, and
emerge as adults in mid-summer. Larvae hatching from eggs laid by the
second generation of moths defoliate the trees for a second time during
late summer. By late October the mature larvae of the second generation
have dropped to the forest floor to overwinter. The full grown larva is
approximately 1½ inches long. Color varies among individuals. The head
is generally amber brown with curved diagonal white and black bands. The
body is usually yellow green with a narrow white stripe down the center
of the back bordered by wider dark bands.

Outbreaks of the variable oak leaf caterpillar may be severe but
generally subside before serious tree mortality occurs. Parasites and
predators are not effective in controlling rising populations of the
insect. Mice and predaceous beetles feed on the resting larvae and pupae
in the litter and soil of the forest floor. While no chemical is
currently registered for control of this insect, chemical spraying has
been effective and safe in controlling closely related insects.

LOCUST LEAFMINER, _Xenochalepus dorsalis_ (Thunberg)

The locust leafminer is a destructive pest of black locust and honey
locust in both the adult and larval stages. It is found throughout the
range of these trees in the eastern half of North America. The adults
also feed on other species of trees.

The adult beetles overwinter in crevices in the bark of trees and under
litter on the forest floor. The beetles emerge and begin feeding in the
spring, usually after mid-April. After feeding for a short time they
deposit eggs on the undersides of leaves, piling them one upon another,
somewhat shingle-like. Eggs are covered with brownish fecal matter.
Larvae soon hatch and eat into the leaf tissue to form a mine. Newly
emerged larvae feed gregariously in a single mine for a short time. They
then construct new mines where the insects live singly. Several mines
are constructed before the larvae reach maturity. The larvae pupate in
the mines and emerge as adults in July to begin the second generation.
The adult beetles are foliage feeders, eating irregular holes in leaves.
When sufficient in number they may defoliate host trees.

[Illustration: Damage to black locust caused by the locust leaf
miner.]

Under forested conditions no control is recommended. Rarely do trees die
from attacks by this insect. Damage is objectionable mostly from an
aesthetic viewpoint.

COTTONWOOD LEAF BEETLE, _Chrysomela scripta_ (F.)

Willows, poplars, aspens and alders are attacked by the cottonwood leaf
beetle in the eastern United States. Cottonwood is the most important
host in the South. Damage has been especially severe in Louisiana and
Mississippi where thousands of acres of cottonwood plantations are
intensively managed. Adult beetles and larvae feed on the foliage.
Damage is most critical during the first three years after the
cottonwood is planted. Adults chew holes in the leaves and may attack
the terminal shoots causing reduced growth or stem deformity. Young
larvae skeletonize the foliage but older larvae consume all foliage
except the leaf midribs. Damage may become severe enough to cause
mortality.

[Illustration: Cottonwood leaf beetle adult.]

The cottonwood leaf beetle overwinters in the adult stage. Eggs are laid
in the spring. The female lays a cluster of about 75 yellowish eggs on
the underside of a leaf. As the larvae mature they become yellow with
black spots. After about nine days in the larval stage the beetle
transforms into the non-feeding pupal stage which lasts five to ten
days. The adult is about ¼-inch long and has a black head and thorax.
The wing covers are yellow with longitudinal black stripes. The life
cycle is completed in 25 to 30 days and several generations occur in a
single year.

[Illustration: Larvae and pupae of the cottonwood leaf beetle.]

Control may be needed in a plantation only during the first three years.
Chemical sprays have been successful in the past but at the present time
no insecticides are registered for cottonwood leaf beetle control.

WALKINGSTICK, _Diapheromera femorata_ (Say)

The walkingstick is a defoliator of broadleaved trees in North America.
The black oaks, basswood, and wild cherry are the most common preferred
hosts but numerous other hardwood species are attacked. This insect is
widely distributed over the United States east of the Rocky Mountains as
well as Manitoba and Ontario in Canada. At times, populations build in
sufficient numbers to defoliate trees over large areas.

[Illustration: Male walkingsticks feeding on oak.]

These slender, wingless, stick-like insects are pale green when young,
but gradually change to a dark green, gray, or brown at maturity. The
adult female measures up to three inches in length and is more
stout-bodied than the male. Mating usually takes place in August and egg
laying begins six to ten days later. The eggs are dropped to the ground
where they overwinter in the leaf litter. In the northern part of the
walkingstick’s range the eggs take two years to hatch. In the South,
walkingstick eggs hatch the summer after they are laid, usually starting
in mid-May. The newly hatched walkingstick looks like a miniature adult.

Parasitic wasps and flies are active against the immature walkingsticks
but are not efficient enough to cause a substantial population
reduction. Flocks of robins, blackbirds, and grackles have a much
greater impact, however. The defoliation caused by walkingsticks
generally occurs on upland sites in stands which are not of high value
or intensively managed. For this reason there has been little interest
in control.

GYPSY MOTH, _Porthetria dispar_ (L.)

The gypsy moth is an introduced forest insect. It was brought into this
country from Europe in 1869 and has been restricted to the Northeast.
The gypsy moth feeds aggressively on oak, alder, apple, basswood,
willow, and birch. As the caterpillars reach maturity they will also
feed on hemlock, cedar, pine, and spruce.

[Illustration: Gypsy moth larvae.]

In the Northeast, the gypsy moth has a single generation per year,
overwintering in the egg stage. Eggs hatch in late April and May and
larvae are present for approximately two months. Full-grown caterpillars
measure more than two inches long and are easily identified by the five
pairs of blue spots and six pairs of red spots arranged in a double row
along the back. The adult moths are active from late June to early
September. Female moths, their bodies heavy with eggs, are unable to fly
and must rely on a powerful sex attractant to lure male moths. This sex
attractant has been chemically synthesized and is used as a trap bait in
surveys designed to determine the presence of gypsy moths in areas
suspected to be infested. Each female deposits from 200 to 800 eggs in a
buff-colored mass which she attaches to any convenient surface including
cars, trailers, and other vehicles.

[Illustration: Female gypsy moths depositing egg masses.]

During the past 75 years the gypsy moth has been the target of many
large-scale control programs, and much money has been spent trying to
reduce the impact of gypsy moth infestations. Current control efforts
are handicapped by the unavailability of a safe and effective persistent
chemical. In the North two predators and nine parasites have been
successfully established to help control the gypsy moth. The greatest
problem in controlling gypsy moth spread, however, lies in the fact that
recreational vehicles transport egg masses and larvae from infested
sites into uninfested areas.

HICKORY BARK BEETLE, _Scolytus quadrispinosus_ (Say)

The hickory bark beetle is reported to be the most serious insect pest
of hickory in the United States. Population explosions where thousands
of trees were killed have been reported from New York, Pennsylvania,
Maryland, Virginia, and recently from Georgia. Hickory bark beetles are
distributed throughout the range of their host in eastern United States.
All species of hickory are subject to attack, as well as pecan and
possibly butternut. Adult beetles emerge in May and June in the southern
portion of their range. They feed for a short time by boring into the
petioles of leaves and into small twigs of the host. Dying leaves and
twigs are the first evidence of attack. After feeding, the beetles fly
to the trunk and larger branches of the host and bore into the inner
bark to lay their eggs. Short, longitudinal egg galleries are etched
into the sapwood and from 20 to 60 eggs deposited in small niches cut on
either side of the gallery. As the larvae develop, their galleries
radiate out from the egg gallery. Two generations per year have been
reported from northern Mississippi. The beetle overwinters in the larval
stage. With the coming of warm weather in the early spring, it changes
into the pupal stage, and finally, in May, to an adult.

[Illustration: Hickory bark beetle adult.]

Outbreaks of this insect begin in periods of hot, dry weather and
subside when rains commence.

[Illustration: Larval galleries of the hickory bark beetle.]

SMALLER EUROPEAN ELM BARK BEETLE, _Scolytus multistriatus_ (Marsham)

The smaller European elm bark beetle was first reported in the United
States in 1909. Its presence in this country was given significance with
the introduction of the Dutch elm disease in 1930. The beetle attacks
all native and introduced species of elms and now occurs wherever the
hosts are present. The feeding of the adult beetles in the spring is
responsible for transmitting the Dutch elm disease from diseased to
healthy trees. The Dutch elm disease is now our most important shade
tree disease.

[Illustration: Smaller European elm bark beetle adult.]

Adult bark beetles emerge in the spring from dead or dying elms and
begin feeding on the twigs of healthy elms. The female then excavates an
egg gallery in the bark of dead or weakened elms. Eggs are deposited
along the walls of the gallery. The larvae, upon hatching, burrow into
the bark at right angles to the egg gallery. Pupation occurs at the end
of the larval tunnel. New adults tunnel to the bark surface and leave
the tree through circular emergence holes. There are usually two
generations a year. The beetles overwinter in the larval stage.

Chemical control and good tree maintenance are the two methods used to
reduce bark beetle populations. Insecticides are used to prevent feeding
by the adults in the spring. Tree sanitation involves removal and
disposal of dead elms and elm limbs which eliminate breeding and larval
development sites.

COLUMBIAN TIMBER BEETLE, _Corthylus columbianus_ (Hopkins)

All hardwood trees in the eastern half of the United States are subject
to attack by the Columbian timber beetle, but oaks, maples, birch,
basswood, yellow-poplar, and elm are the preferred hosts in the South.
The beetle causes two major types of damage: 1) physical damage caused
by the 1/32″ to 1/16″ hole excavated by the adult into the sapwood, and
2) degrade caused by stain which may extend for a considerable distance
above and below the gallery. Large diameter trees are preferred as
hosts, but trees as small as one and one-fourth inches in diameter may
be attacked.

[Illustration: Callow adult and pupae of the Columbian timber
beetle.]

There are two and sometimes three generations of this insect each year.
Adults from the first generation emerge from late May through June and
those from the second in October. The first evidence of attack is the
white dust which collects at the entrance hole. Later, depending on the
tree’s physiological condition, a sap-soaked area may develop around the
entrance hole. The adult bores a horizontal hole into the sapwood of a
healthy tree for a few inches and later constructs two or three shorter
lateral branches. “Cradles” (or egg chambers) are then constructed for a
short distance perpendicular to these galleries. The female deposits a
single egg in each chamber. The offspring spend their entire
developmental period within the cradles feeding on fungi which grow on
the sapwood. It is this fungus which causes the extensive staining
characteristic of Columbian timber beetle attack. Winter is spent in
both the pupal and adult stages in the brood galleries.

[Illustration: Columbian timber beetle entrance holes in
yellow-poplar.]

Chemical control is not practical for forest trees.

COTTONWOOD TWIG BORER, _Gypsonoma haimbachiana_ (Kearfott)

The cottonwood twig borer is widely distributed throughout the entire
range of eastern cottonwood, from Canada to the Gulf States and west to
Missouri. The larvae of the cottonwood twig borer feed in the terminals
of the host. This feeding results in reduction of terminal growth and
forked and crooked trunks. Damage is especially severe on young trees.

[Illustration: Cottonwood twig borer damage to cottonwood sapling.]

[Illustration: Three-year-old cottonwood stunted by twig borers.]

The female moth lays eggs on the upper surface of leaves along the
mid-rib, singly or in groups of two to eight. Hatching occurs in about
five days and the young larvae cover themselves with silk mixed with
trash, and then tunnel into the mid-rib. After the first molt, larvae
leave the tunnels and bore into tender shoots. Larvae reach maturity in
about 21-23 days and begin moving down the trunk of the tree where they
spin cocoons in sheltered bark crevices, in litter, or between leaf
folds. The adult moths emerge in eight or nine days. It takes from 40-45
days to complete the life cycle in mid-summer.

The most effective natural control is a potter wasp, _Eumenes_ sp. which
tears open tender cottonwood shoots and removes twig borer larvae from
their galleries. Other wasps parasitizing the twig borer include _Bracon
mellitor_ (Say), _Apanteles clavatus_ (Provancher) and _Agathis_ sp.

COTTONWOOD BORER, _Plectrodera scalator_ (F.)

The cottonwood borer is limited in range to the southern half of the
United States. Hosts include cottonwood, poplars and willows. The adults
feed on the tender shoots of young trees causing them to shrivel and
break off. The larval stage of this insect tunnels in the inner bark and
wood at the base of the tree and may kill or severely weaken it.

[Illustration: Adult cottonwood borer.]

The adult beetles appear in midsummer. After feeding briefly on the
tender bark of the terminals the adults descend to the bases of host
trees where the female deposits her eggs in small pits gnawed in the
bark. Eggs hatch in about three weeks. The larvae bore downward in the
inner bark, entering a large root by fall. Larval feeding continues into
the second year as the larvae bore into the inner bark and wood. The
larvae transform into the non-feeding pupal stage and finally into an
adult in the summer of the second year thus completing a two year life
cycle. Adult beetles are 1¼ to 1½ inches long. They are black with lines
of cream-colored scales forming irregular black patches.

The best control for the cottonwood borer is to maintain a vigorous,
healthy stand. Slow growing, off-site plantings of host trees are the
most severely damaged. While some systemic insecticides have shown
promise, there is currently no registered chemical control method.

WHITE OAK BORER, _Goes tigrinus_ (De Geer)

A recent survey of damage caused by various wood borers to three species
in the white oak group revealed an estimated annual loss in the South
exceeding 20 million dollars. One of the more important borers
responsible for this damage is the white oak borer.

[Illustration: Adult white oak borer.]

Usually the white oak borer attacks oaks one to eight inches in
diameter. The damage, like that of other hardwood borers, is the result
of larval feeding in the wood. Galleries up to one-half inch in diameter
extend upward through the sapwood into the heartwood. The white oak
borer takes three to four years to complete one generation. The mated
adult female beetle lays her eggs singly in the inner bark through a
small oval niche chewed through the outer bark. After about three weeks
the eggs hatch and the larvae immediately bore into the sapwood. Later
they bore upward into the heartwood. The boring frass ejected out of the
entrance is evidence of an active infestation. Pupation occurs behind a
plug of excelsior-like frass at the upper end of the gallery in the
heartwood. In about three weeks, adults emerge by boring separate and
perfectly round holes through the wood and bark. In the South, adults
generally emerge in May and June and feed for a short time on oak leaves
and the tender bark of twigs before the females lay their eggs.

Woodpeckers may destroy up to 25 percent of the larvae during the winter
months, but this and the small toll taken by insect predators and
parasites are not sufficient to keep the white oak borer population low
enough to avoid serious economic loss.

[Illustration: Entrance and emergence holes in white oak.]

RED OAK BORER, _Enaphalodes rufulus_ (Hald.)

The red oak borer is a serious pest of trees in the red oak group. It
ranges throughout eastern North America wherever host species grow. It
is estimated that defects caused by larval tunnels in the sapwood and
heartwood of host trees costs the hardwood timber industry millions of
dollars each year.

[Illustration: Adult red oak borer.]

Eggs of the red oak borer are laid during early and mid-summer in bark
crevices or under patches of lichen on host trees. After hatching,
larvae bore into the inner bark region where they feed until mid-summer
of the next year. This feeding in the inner bark causes characteristic
catfaces or bark pockets. Once larvae enter the wood they bore upward
through the sapwood and into the heartwood and pupate behind a plug of
excelsior-like frass. The larval galleries are from one-fourth to
one-half inch in diameter, and six to ten inches long. Usually the
galleries are within six inches of the center of the tree. The adult
emerges at the lower end of the tunnel, using a hole cut through the
bark by the larva just prior to pupating. Adults emerge in June and
July. The timing of the two-year life cycle of the red oak borer is such
that the adult population is greatest in odd-numbered years.

Generally, borers such as the red oak borer infest trees of poor vigor.
It is possible, therefore, to reduce borer populations by maintaining
vigorous stands and by removing cull trees.

[Illustration: Red oak borer attack on Nuttall oak.]

CARPENTERWORM, _Prionoxystus robiniae_ (Peck)

The carpenterworm bores in the wood of living hardwood trees, causing
costly damage to commercial timber species. In the South, oak species
are preferred hosts but black locust, maples, willows, and fruit trees
are also attacked. The carpenterworm is distributed throughout the
United States.

[Illustration: Carpenterworm adults.]

Adult moths emerge in late April to early June, mate, and the females
lay groups of eggs in bark crevices or wounds. Each female lays 200 to
500 eggs during her one-week life span. After hatching, the larvae
wander over the bark for a short time before boring into the inner bark
where they feed until half-grown. The larvae then bore into the sapwood
and heartwood, returning occasionally to feed in the inner bark. The
larval period lasts from two to four years. Pupation usually occurs deep
within the heartwood. Just prior to emergence, the pupa wiggles to the
entrance hole where it remains slightly protruding until the adult moth
emerges. The large winding tunnels constructed by the larvae in the
sapwood and heartwood of living hardwoods serve as an entrance for
wood-rotting fungi and insects such as the carpenter ant. In extreme
cases, the tree may be structurally weakened and subject to wind
breakage.

[Illustration: Carpenterworm galleries in nuttall oak.]

Some chemicals which have a fumigating action have proved effective in
controlling this insect in shade trees, but no practical control has yet
been found for forest trees.

PINE WEBWORM, _Tetralopha robustela_ (Zell.)

Ugly, compact masses of brown excrement or frass pellets around the stem
of pine seedlings mark infestations of the pine webworm. Rarely is the
defoliation severe enough to kill the seedlings, but it undoubtedly has
an impact on growth. Found throughout the eastern United States, the
webworm commonly attacks red, white, jack, loblolly, shortleaf, and
slash pines.

[Illustration: Pine webworm damage to loblolly pine.]

[Illustration: (cont.)]

The adult moth has a wingspread of about one inch. The forewing usually
is gray in the middle portion and darker at the base and tip. The hind
wings and body are smokey gray. The full-grown larva is a caterpillar
approximately ⅘ of an inch long. The head is tan with darker markings
and the body light brown with dark longitudinal stripes running down
each side.

Eggs are usually laid on seedlings, occasionally on larger trees,
between May and September. After eggs hatch, the caterpillars live in
silken webs surrounded by masses of frass, and feed on the needles.
Generally each web contains one or two larvae but occasionally 25 or
more may be found. After feeding is completed, the caterpillars drop to
the ground and pupate below the soil surface. In the South, there are
usually two generations each year.

In plantations, hand picking is an effective method of control. When
high value nursery stock becomes infested, chemical control may become
necessary.

BAGWORM, _Thyridopteryx ephemeraeformis_ (Haw.)

The bagworm is distributed throughout the eastern half of the United
States. It is generally recognized as a defoliator of conifers,
particularly juniper, cedars, and arborvitae, but it is also found on
many hardwood trees including maple, wild cherry, poplars, oaks, and
apple.

[Illustration: Bagworm cases on pine.]

The wingless, maggot-like adult female bagworms are present in September
and October and spend their entire lives within the protective cover of
the tough, silken bag which they construct as larvae. Males are quite
agile fliers and can often be seen in the fall flying around infested
shrubs in search of a mate. Mating takes place through the open end of
the bag. Shortly thereafter the female deposits her egg mass containing
500 to 1,000 eggs in her pupal case. The eggs remain in the bag
throughout the winter. In the deep South, hatching can occur as early as
April, but occurs in May or June further north. During the early stage
of development, the larvae, housed in their tiny bags, are quite
inconspicuous. As they mature, the bags become quite noticeable, and the
amount of foliage consumed increases rapidly.

Outbreak populations of bagworm are in most cases quickly reduced by low
winter temperatures and a complex of several parasites. On shrubs and
shade trees around a home, it is often practical to control bagworms by
picking and destroying the bags.

PINE COLASPIS, _Colaspis pini_ (Barber)

Colaspis beetles are found throughout the Southeast, but are more common
in the Gulf states. They seem to prefer slash pine but have been found
on many of the southern pines. The pine colaspis beetle is not a serious
forest pest but feeding damage caused by large populations occasionally
produces a spectacular browning effect of the needles similar to that
caused by fire.

[Illustration: Adult pine colaspis beetle feeding damage on pine.]

The adult beetles chew the edges of needles to produce an irregular,
saw-like edge which turns brown. Occasionally only the tips of the
needles show signs of the infestation. Later, however, the entire needle
may die, causing the whole tree to become brown as though scorched by
fire. Trees that have been attacked do not die, and little or no growth
loss results. Attacks usually occur in early summer; by late summer the
trees appear green and healthy again. This pest is sporadic in its
occurrence and may not develop again in the same area for several years.
The adult female lays her eggs in the soil during the summer. Larvae
hatch and feed on roots of grasses and other vegetation, and overwinter
in this stage. The larvae pupate in the spring; adults emerge in early
summer to feed. There is only one generation a year.

Under forest conditions, no control measures are recommended for the
pine colaspis beetle. On ornamentals and shade trees, insecticides can
be used to prevent unsightly damage.

PINE SAWFLY, _Neodiprion excitans_ (Roh.)

This pine sawfly is found throughout the southeast from Virginia to
Texas. Loblolly and shortleaf pine are preferred hosts, but pond, slash,
longleaf, and Sonderegger pine are also attacked. The larvae do not do
well on the latter two species. As with most sawflies, the larvae feed
in groups on the host needles. Generally the old needles are preferred,
but all of the needles are eaten when large numbers of larvae are
present. Three or four young larvae usually encircle a needle and,
starting from the tip, consume all but a central core. When nearing
maturity they eat the entire needle.

[Illustration: Pine sawfly larvae.]

Four or five generations of this sawfly may occur each year. Adult
females begin to lay their eggs in slits cut in the needles during late
March. The eggs hatch in 10-21 days, and the larvae feed for about five
weeks. When mature the larvae usually crawl to the ground and spin a
cocoon in the loose litter at the base of the tree. Although all stages
of the life history can be found at any time during the growing season,
the peak adult emergence occurs in late summer. Larvae from this late
summer generation are responsible for most of the damage which, although
never directly responsible for mortality, may predispose the trees to
attack by other insects (particularly bark beetles) and diseases.

Natural control factors generally bring outbreak populations under
control after one season. Hogs, armadillos, mice, and shrews are
reported as being of significant value in regulating the sawfly
population. Insect parasites, predators, and disease are also effective
control agents.

ARKANSAS PINE SAWFLY, _Neodiprion taedae linearis_ (Ross)

Loblolly and shortleaf pines are the only trees attacked by the Arkansas
pine sawfly. Periodic outbreaks of this insect over large areas in the
south-central states cause substantial growth losses, but the insects
seldom kill trees.

[Illustration: Arkansas pine sawfly larvae.]

This insect has a single generation each year. In the spring, eggs which
have overwintered hatch into tiny caterpillar-like larvae. The larvae
feed in groups for 30-40 days (primarily on the older foliage) before
crawling to the ground and pupating in the topsoil or litter. Adults
emerge during warm days in October and November, mate, and the females
begin laying eggs. Sawflies get their name from the manner in which the
eggs are laid. The female is equipped with a saw-like “ovipositor” with
which she cuts a slit in the needle into which the egg is inserted. From
two to ten eggs are laid in a single needle. Each female deposits from
90 to 120 eggs.

An important natural control agent of this sawfly is a polyhedral virus
disease that sometimes destroys large numbers of the larvae. Rodents
destroy many cocoons. Several species of larval parasites are also known
to exist. Of these, a parasitic fly, _Anthrax sinuosa_ (Wied.) and an
ichneumon wasp, _Exenterus canadensis_ (Prov.) appear to be the most
important.

VIRGINIA PINE SAWFLY, _Neodriprion pratti pratti_ (Dyar)

The Virginia pine sawfly is found from Maryland to North Carolina, and
west to Illinois. The insect prefers Virginia and shortleaf pine, but it
will also oviposit and feed on pitch and loblolly pine.

[Illustration: Virginia pine sawfly larva.]

On warm sunny days in late October and early November, the adult
sawflies emerge from their cocoons in the litter, mate, and the females
lay eggs. The female is equipped with a saw-like ovipositor with which
she cuts a slit at the edge of a needle and inserts a small, white, oval
egg. Several eggs are usually laid at evenly spaced intervals in each
needle, but in only one needle per fascicle. From 30 to 100 eggs are
deposited in this manner by each female. The eggs hatch the following
April and the young larvae feed gregariously on the old needles. Larval
development is usually completed by the time the new needles come out,
giving heavily defoliated trees a tufted appearance. Mature larvae crawl
to the ground and spin cocoons in the litter or surface soil. They
remain as prepupae until late September when pupation occurs.

[Illustration: Pine defoliated by the Virginia pine sawfly.]

Heavy defoliation for two or more years can weaken trees and make them
more susceptible to other insects and diseases, particularly when
associated with drought. In commercial stands the growth loss caused by
several years of 50% defoliation by this insect can amount to ⅓ of the
expected growth.

Several parasites, predators, and a virus attack the Virginia pine
sawfly, but weather conditions seem to be primarily responsible for the
drastic fluctuations in sawfly populations. Several chemicals have
proven effective in preventing damage to ornamentals.

REDHEADED PINE SAWFLY, _Neodiprion lecontei_ (Fitch)

The redheaded pine sawfly did not become an important pest until
extensive planting of pine in pure plantations began in the 1920’s.
Since then, outbreaks in young natural pine stands and plantations have
been common in the South, the north-central states, and eastern states.
Feeding is primarily restricted to the two- and three-needled pines
under fifteen feet in height. Shortleaf, loblolly, longleaf, and slash
are the species most commonly attacked in the southern states.

[Illustration: Redheaded pine sawfly larva.]

In the fall, sawfly larvae drop to the ground, spin cocoons in the duff
or topsoil, and overwinter as prepupae in a small, brown cocoon. With
the coming of spring, pupation occurs and adult emergence follows in
about two weeks. Some prepupae may remain in a resting stage for more
than one season before emerging. Each female lays about 120 eggs. She
cuts a small slit in the edge of a needle and deposits a single egg
inside each slit. Eggs laid by a single female are generally clustered
on the needles of a single twig. Eggs hatch in three to five weeks,
depending on temperature and locality. Larvae feed gregariously on the
host for 25 to 30 days. When fully grown, larvae drop to the ground and
spin their cocoons. In the South there are at least two generations per
year with a maximum of five being recorded. Colonies of different ages
may co-exist in the late fall or early winter.

Outbreaks occur periodically and tend to subside after a few years of
heavy defoliation. Numerous parasitic and predatory insects play an
important role in causing the decline of infestations, as do adverse
weather conditions during the larval stage. When deemed necessary,
chemical treatment is an effective control.

TEXAS LEAF-CUTTING ANT, _Atta texana_ (Buckley)

Damage caused by the Texas leaf-cutting ant, or town ant, is confined in
the United States to southeast Texas and west-central Louisiana. The ant
causes damage to a variety of green plants throughout the year and
causes serious damage to pine seedlings during the winter when other
green plants are scarce. During this period, stands of young seedlings
may be completely defoliated and the stems girdled. The ant carries bits
of needles, buds, and bark back to its nest to serve as the medium on
which it cultivates a fungus. The fungus is the ant’s only known food.

[Illustration: Texas leaf cutting ant.]

Ant colonies are characterized by numerous crescent-shaped mounds five
to fourteen inches high, and by a series of well defined foraging trails
cleared of vegetation. The mounds may be confined to a relatively small
area or extend over an acre or more. Each mound serves as the entrance
to a football-sized, hemispherical-shaped nest which the ants construct
at depths up to 20 feet below the surface. The nests are interconnected
by a series of narrow tunnels, and connected to lateral foraging tunnels
which may surface a hundred yards or more from the colony. Leaf-cutting
ants, like many other social insects, are segregated into castes. The
queen dominates the colony and is responsible for its reproduction.
Large worker ants, or soldiers, provide protection from intrusion by
other insects, while the smaller workers collect the leaves and tend the
fungus gardens.

Various chemicals such as fumigants, contact poisons, and baits have
been used to control the leaf-cutting ants with varying success. No
natural control has yet been found.

SOUTHERN PINE BEETLE, _Dendroctonus frontalis_ (Zimm.)

Probably no other insect is of more concern to managers of southern pine
forests than the southern pine beetle. Loblolly and shortleaf pine seem
to be preferred hosts, but all of the southern pines may be attacked
wherever they occur in North and Central America.

Adult beetles are about the size of a grain of rice, stout and
reddish-brown in color. While they commonly attack lightning-struck or
weakened trees, they can also quickly build up to high populations
capable of successfully attacking healthy trees during periods favorable
to their development. Adult beetles bore directly through the bark,
mate, and the females begin to excavate S-shaped egg galleries in the
inner bark. Eggs are deposited in niches on either side of these
galleries and hatch into small legless grubs within four to nine days.
The grubs mine for a short distance before boring into the outer bark
where they pupate. There are from three to seven generations per year
depending on locality and weather. Drought seems to be associated with
major outbreaks of this insect.

[Illustration: Adults of the black turpentine beetle, the southern
pine beetle and three species of _Ips_ engraver beetles.]

Control includes rapid salvage and utilization of infested trees and
piling and burning of infested material. Outbreaks usually subside with
the advent of unfavorable weather and improved host vigor.

[Illustration: Southern pine beetle larval galleries.]

[Illustration: Southern pine beetle pitch tubes.]

IPS ENGRAVER BEETLES, _Ips_ spp.

With the possible exception of the southern pine beetle, no other
insects cause as much mortality to southern pine forests as do the three
species of _Ips_ engravers. Usually they attack severely weakened trees,
lightning-struck trees, or fresh slash left by logging operations.
During drought periods they can successfully attack otherwise healthy
pines.

[Illustration: Pine showing typical symptoms of _Ips_ attack.]

Attacked trees are quickly girdled by the adults as they construct their
egg galleries in the inner bark. Death is usually hastened by the
introduction of blue-stain fungi which blocks the flow of sap. Small
reddish pitch tubes are frequently the first sign of attack, but they
are usually absent in trees suffering from drought. Peeling back the
bark of an infested tree will reveal typical Y- or H-shaped egg
galleries with short larval galleries extending perpendicular to them on
either side. _Ips_ beetles are easily recognized by their “scooped out”
posteriors which are surrounded by varying numbers of tooth-like
projections. It takes only 18-25 days to complete one generation,
allowing populations of these beetles to increase very rapidly during
favorable conditions.

At present the best control is the speedy removal and utilization of
actively infested trees, making sure that the bark and slabs are
destroyed.

BLACK TURPENTINE BEETLE, _Dendroctonus terebrans_ (Oliv.)

The black turpentine beetle is found from New Hampshire south to
Florida, and from West Virginia to east Texas. It is a particularly
serious pest in the Gulf States where recent outbreaks have killed large
acreages of timber. Attacks have been observed on all pines native to
the Southeast, and also on red spruce.

[Illustration: Life stages of the black turpentine beetle: adult,
callow adult, pupa, larva and eggs.]

This is the largest of the southern bark beetles, varying in length from
⅕ to ⅓ of an inch, or about the size of a raisin. They are reddish-brown
to black in color. The beetle attacks fresh stumps and living trees by
boring through the bark and constructing galleries on the face of the
sapwood where eggs are laid. Fifty to 200 eggs are laid in a group. They
hatch into white larvae which feed on the inner bark. The beetle may
girdle trees when several broods occur at approximately the same height,
killing the trees. From 70 to 90 percent of the trees attacked by the
beetle die.

After the larvae complete their development, they pupate. Adult beetles
emerge and infest more pine trees. The entire life cycle takes from 2½
to 4 months, depending on temperature. In the insect’s southern range
there usually are two generations and part of a third each year. In its
northern range, the third generation does not develop; consequently the
beetle is not a serious pest there.

Weather is probably the most influential factor in regulating the
numbers of this insect. During outbreaks the removal or chemical
treatment of infested trees helps to keep losses to a minimum.

[Illustration: Close-up of black turpentine beetle pitch tubes.]

AMBROSIA BEETLE, _Platypus flavicornis_ (F.)

Ambrosia beetles are represented in the South by several species of the
genus _Platypus_ of which only _P. flavicornis_ (F.) is known to attack
dead or dying southern pines. _P. flavicornis_ (F.) will secondarily
invade other conifers and on some occasions may be found in hardwood
trees. It is so abundant in the South that few dying pines, stumps, or
logs escape attack. The beetle is found from Texas east to Florida and
north to New Jersey.

[Illustration: Adult of the _Platypus_ ambrosia beetle.]

The adult is a reddish-brown elongate beetle approximately one-fourth
inch in length. The male of the species has a pair of blunt tooth-like
structures on the third abdominal segment. Several males are usually
found in the presence of a single female. This species requires moist
wood which is favorable to the growth of fungi upon which they feed. The
adults bore into sapwood or heartwood of logs and lumber, making
pin-sized holes which are stained by the ambrosia fungus. The female
lays eggs in small clusters in the tunnel and the developing larvae
excavate tiny cells extending from the tunnel parallel to the grain of
wood. There may be several generations a year.

Ambrosia beetle damage to green sawlogs and lumber may result in
considerable degrade and strength reduction. The best control is rapid
utilization of dead or dying trees. Lumber should be seasoned as soon as
possible to reduce or eliminate losses.

SOUTHERN PINE SAWYERS, _Monochamus_ spp.

In the South, dying pines and fresh logs are quickly attacked by the
pine sawyers. In sufficient numbers they may cause a significant loss of
wood fiber and degrade sawlogs. These species are commonly found in the
South infesting southern pine, fir, and spruce wherever the hosts grow.

[Illustration: Adult southern pine sawyer beetle.]

The adults emerge in the spring or summer and begin to feed on the bark
of twigs. After mating, the female gnaws pits through the bark of
freshly felled or dying pine. The female beetle lays one to several eggs
in each pit. After eggs hatch the larvae bore beneath the bark for 40-60
days, converting the inner bark into coarse, shredded frass. The larvae
then enter the wood and make deep U-shaped cells through the heartwood
and sapwood. The entrance is plugged with frass and the far end is
excavated into a pupal chamber. The larvae pupate the following spring
or early summer, transform into adults, and emerge that same season. The
insect has two or three generations per year in the South.

Pine sawyers render storm- or fire-damaged pines unfit for salvage and
are also a problem in wood-holding yards. Rapid salvage and utilization
of dead or dying trees or green logs will reduce losses significantly.

NANTUCKET PINE TIP MOTH, _Rhyacionia frustrana_ (Comstock)

The impact of the Nantucket pine tip moth on pine plantations varies
widely with tree species, host vigor, and environmental factors. Heavily
infested trees may be severely stunted or deformed but mortality is
rare. Generally, the tree grows out of the susceptible stage within a
few years. In seed orchards, the tip moth is receiving increasing
attention because of its impact on height growth and, more importantly,
because of its effect on flower and cone production. All species of pine
within the range of the tip moth except white pine and longleaf pine,
are attacked. It has been reported from all states in the eastern
hard-pine region extending across east Texas, Oklahoma, Illinois,
Indiana, Ohio, and southern New York State.

[Illustration: Nantucket pine tip moth larva on pine bud.]

The tip moths overwinter as pupae in the tips of infested trees. In the
South the adults emerge on warm days during the late winter months,
mate, and the females lay eggs in the axils between needles and stem
near the terminal bud of host trees. On hatching, larvae bore first into
the base of developing needles, and later into the new terminal growth
or buds. There are two to four generations per year in the southern part
of the tip moth’s range.

Chemical control is generally not considered practical in forest
plantations, but several pesticides have proved effective in reducing
insect damage in seed orchards.

[Illustration: Newly emerged adult tip moth on a damaged shortleaf
pine tip.]

PALES WEEVIL, _Hylobius pales_ (Hbst.)

Pales weevil is perhaps the most serious insect pest of pine
reproduction in the southeastern United States. Losses in susceptible
areas commonly run 20-25 percent, but exceed 90 percent under
circumstances favoring weevil development. Pales weevil is found
throughout pine-growing regions of eastern United States and Canada.
Feeding has been reported on most coniferous species, and all species of
southern pines appear to be susceptible in varying degrees.

[Illustration: Pitch-eating weevils in the genera _Pachylobius_,
_Hylobius_, and _Pissodes_.]

Adult weevils are attracted by the odor of fresh pine resin, and quickly
invade logging areas. Eggs are laid in lateral roots of fresh pine
stumps, where they hatch in approximately five to ten days. Larvae feed
on the inner-bark tissues of roots. At maturity, larvae usually
construct a chip cocoon in a chamber cut into the wood, and pupate in
the cocoon. On emerging, adults feed on the tender bark of seedlings, or
twigs of trees. The small irregular feeding patches in the bark are
characteristic of weevil damage. Heavy feeding girdles the stem or twig,
causing wilting and eventual death. Newly emerged adult females feed for
approximately one month before laying eggs. Females may lay eggs
sporadically through two growing seasons. The average female lays about
50 eggs in her lifetime. In the South there are two peaks in adult
weevil population each year; the first occurs in the early spring
(March-May) followed by a second somewhat lower peak in July and August.

This insect can be controlled by delaying planting in cut-over areas for
at least nine months, or by treating seedlings with a suitable
insecticide.

[Illustration: Adult pales weevil feeding on seedling.]

WHITE PINE WEEVIL, _Pissodes strobi_ (Peck)

The white pine weevil is generally regarded as the most serious insect
pest of white pine. Although it usually does not cause mortality, trees
suffering repeated attacks become stunted and deformed to the point of
being commercially unusable. The weevil has become such a problem in
some areas that it prohibits the growing of white pine. In addition to
eastern white pine, the white pine weevils also attack Norway spruce and
jack pine. Other pines and spruces are attacked to a lesser degree. The
weevil is found throughout the range of eastern white pine.

[Illustration: Pine leader damaged by the white pine weevil.]

During the latter half of April, the adults may be found on the terminal
shoots of host trees where the female lays her eggs. Up to 200 eggs are
deposited over a six-week period. The eggs are laid in feeding punctures
in the bark, and hatch about two weeks later. Characteristically, the
young larvae position themselves around the shoot and begin feeding as a
group down the terminal through the inner bark. Small holes scattered
over the bark are characteristic of white pine weevil attacks. After
five or six weeks the larvae construct pupal chambers in the pith or
wood of the terminal shoot and transform into adults. The young adults
remain in the dead terminal until late October and November when they
move to favorable overwintering sites on the ground, usually at the base
of the host tree.

Control of the white pine weevil is difficult. It is possible, however,
to reduce the damage by making conditions in a young stand unfavorable
for egg laying. This is possible because the female weevil will only lay
eggs within a rather narrow range of temperature and relative humidity.
Various techniques involving the use of shade from “nurse trees” have
been developed but require intensive management. Under certain
circumstances, chemical control can be used.

PITCH-EATING WEEVIL, _Pachylobius picivorus_ (Germar)

In the Gulf Coast States the pitch-eating weevil is probably the most
troublesome insect pest of pine seedlings. No accurate figures are
available on the damage directly attributable to this pest, but
mortality losses are estimated to average about 30 percent in
susceptible areas. All of the southern hard pines and other conifers are
probably suitable breeding and host material for the pitch-eating
weevil. Its range overlaps that of the pales weevil, being reported from
Labrador, Canada, south to Florida and west to Texas. It occurs in
damage-causing numbers only in the Gulf Coast States.

Pitch-eating weevils breed in the roots of freshly cut stumps. The
adults burrow down through the soil, sometimes a considerable distance
from the stump, and lay their eggs in niches chewed in the root bark. On
hatching, larvae mine the inner bark, packing their galleries with
frass. Pupal cells are excavated in the sapwood, and a chip cocoon is
constructed from the excelsior-like material removed during the cells’
construction. Development time varies from six to ten months depending
on when the stumps are initially infested. Emerging adult pitch-eating
weevils feed by night on the tender bark of seedlings. Small irregular
patches of bark are removed, eventually girdling the seedling and
causing its death. The pitch-eating weevil exhibits a population trend
similar to that of the pales weevil, and is a threat mostly in early
spring and in the fall.

The most effective control for pine reproduction weevils is to wait nine
months before replanting or until the stumps in an area are no longer
attractive to the weevil. Chemical control can be used when such a delay
is considered impractical.

DEODAR WEEVIL, _Pissodes nemorensis_ (Germ.)

This snout beetle is very similar to the white pine weevil both in
appearance and habits. It is found throughout the south- and
mid-Atlantic states from southern New Jersey west to Missouri. Although
deodar cedar is the preferred host, Atlas cedar, Lebanon cedar, and
several species of southern pines are also attacked.

[Illustration: Galleries and chip cocoons of the deodar weevil.]

Adults emerge from April to May and feed briefly on the inner bark of
leaders and lateral branches of host trees. Heavy feeding frequently
girdles the stem and can kill small trees. The adults are dormant during
the summer, but resume activity in the fall to lay their eggs. From one
to four eggs are deposited in feeding punctures. The newly hatched
larvae bore into the inner bark where they construct winding galleries
which girdle the stem. Evidence of such infestations is often delayed
until January when the branches begin to turn brown. Winter is spent in
the larval stage. The larvae pupate in March or April and the cycle is
complete.

Keeping shade trees in a vigorous condition by proper watering and
fertilization helps reduce their susceptibility to weevil attack.

CONEWORMS, _Dioryctria_ spp.

Coneworms are perhaps the most destructive insect pests of pine cones in
the South. They are particularly serious in superior-tree seed orchards
where they frequently cause substantial economic loss. There are five
important species of coneworms in the South, one or more of which attack
all of the native and exotic pines.

[Illustration: Coneworm larva feeding on a pine shoot.]

Although the number of generations per year varies with the species,
their general life history is similar. Female moths lay their eggs
around wounds, cankers, galls, etc., but also deposit particularly on
terminal growth. Eggs generally hatch in about a week. Larvae may stay
at a single feeding site, or move to several different sites before
completing their development. This latter behavior often results in a
single larva destroying several cones or shoots. Pupation takes place in
a chamber constructed by the larva at the feeding site. Depending on the
species and time of year, the adult may emerge in two to three weeks or
overwinter in the pupal stage. Coneworms cause several kinds of damage.
They may mine through the inner bark, bore up the center of a shoot, or
completely hollow out a cone. Their attacks are sometimes marked by
fecal pellets and large pitch masses.

[Illustration: Slash pine cone damaged by coneworm larva.]

Several parasites attack coneworms but are seldom effective enough to
prevent population build-ups. Chemical control is often necessary on
seed orchards to ensure adequate protection of the cone crop.

PINE SEEDWORMS, _Laspeyresia_ spp.

Until recent years little has been known about pine seedworms. These
insects are found throughout the South but seldom have population
explosions. An exception to this is on slash pine in Florida where over
70 percent of one year’s cones were reported infested. Longleaf pine
cones in Texas and Louisiana have also had over 60 percent cone
infestation on occasion. Loblolly and shortleaf pine cones are seldom
over 20 percent infested. Seedworms have been found infesting longleaf,
loblolly, shortleaf, slash, and Virginia pine cones. _Laspeyresia
anaranjada_ Miller attacks primarily slash pine, occasionally longleaf
pine, and rarely loblolly pine. _L. ingens_ Heinrick attacks primarily
longleaf and slash pine. _L. toreuta_ Grote attacks Virginia, shortleaf,
and loblolly pine in the South.

[Illustration: Adult pine seedworm.]

The female moth lays eggs from April through May on second-year cones.
There is one generation per year. Larvae feed within developing seeds
until the cone matures. In late fall, larvae either bore into the cone
axis or remain in a hollowed-out seed, and overwinter. Pupation occurs
within the cone and moths emerge through the hollow seeds. External
evidence of seedworm attack is not visible in immature cones. As cones
mature, damaged seeds are retained in the cone. Heavily damaged cones do
not open properly. In high-value seed orchards and seed production areas
some protection from seedworm attack may be obtained through the use of
pesticides applied in a carefully timed program.

[Illustration: Pine seedworm larva in longleaf pine seed.]

BALSAM WOOLLY APHID, _Adelges piceae_ (Ratzeburg)

[Illustration: Eggs and wool-covered adult balsam woolly aphids.]

The balsam woolly aphid was introduced into northeastern North America
from Europe around the turn of the century. Since then it has become a
pest of major importance to true firs on the east and west coasts of the
continent, and threatens some 60,000 acres of Fraser fir in the southern
Appalachians. Usually the balsam woolly aphid has two generations per
year in the southern Appalachians. Eggs of the first generation hatch in
late June and July followed by the second generation in September and
October. The immature stage of the aphid known as a “crawler” is the
only motile stage in the aphid’s life cycle. Once the crawler begins
feeding, it transforms into an adult and never again moves. Reproduction
is parthenogenic with each female laying approximately 100 eggs during
her lifetime.

In the feeding process the aphid injects a salivary substance into the
host tree, which causes growth abnormalities. Initial symptoms of aphid
attack may include “gouting” of buds or twig nodes and some twig and
branch die-back. Heavy stem attacks reduce the tree’s ability to
translocate food and water. Usually a heavily infested tree dies within
two to seven years.

Chemical control is effective but extremely costly and thus limited to
very high-value areas along scenic road-ways. Other control measures
include removal and destruction of infested material.

[Illustration: Fraser fir infested by balsam woolly aphid.]

DISEASES

NEEDLE CAST

Needle cast is a very common disease of conifers throughout eastern and
southern United States. Eastern white, loblolly, longleaf, pitch, pond,
shortleaf, table mountain, and Virginia pines are all susceptible.
_Hypoderma lethale_ is probably the most common cause of needle cast on
the above hosts, with the exception of longleaf pine. _Lophodermium
pinastri_ is also associated with needle cast.

[Illustration: Hypoderma needle cast on loblolly pine.]

Current pine needles are infected in the early summer, and by winter or
early spring begin to turn brown at the tips. At this time the tree
usually has a scorched appearance. Later, the browning progresses down
the needle and the fungal fruiting bodies are produced. These are small,
black, elongated structures known as hysterothecia, which open along a
slit during moist weather to release their spores. The infected needles
are often “cast,” leaving only the new growth, and causing the tree to
have a tufted appearance.

Controls are seldom needed for this disease in forest stands. Infected
trees usually recover and put out new foliage the year following heavy
attacks. Nurseries or plantations should not be established in areas
where needle cast is prevalent.

[Illustration: Lophodermium needle cast on 2-0 nursery stock and 5
year old scotch pine, Spanish variety.]

[Illustration: (cont.)]

BROWN SPOT NEEDLE BLIGHT

Brown spot or brown spot needle blight is caused by the fungus _Scirrhia
acicola_. Brown spot occurs in all the coastal states from Virginia to
Texas, and inland to Arkansas and Tennessee. All southern pines are
attacked by the fungus, but only longleaf pine seedlings are seriously
damaged.

[Illustration: Brown spot needle blight on longleaf pine
reproduction.]

Initial infection of pine needles results in the development of small,
circular spots of grey green color, which later turn brown. As the
fungus continues to grow, a necrotic area encircles the needle,
appearing as a brown band. The infected area will then increase in size,
eventually resulting in the death of the needle. Fruiting bodies, called
acervuli, develop in the dead areas of the needle. Spores are extruded
from the acervuli in a water soluble gelatinuous matrix throughout the
entire year. The spores are washed apart and splashed short distances by
rain drops. These spores spread the disease from seedling to seedling.
During the winter and early spring, the sexual stage of the fungus is
produced on dead needles. Ascospores, produced in a fruiting body called
a perithecium, are light and wind-disseminated. These spores are
responsible for disease spread. During the grass stage, seedlings often
become heavily infected by the brown spot fungus, resulting in partial
to complete defoliation. Seedlings which are nearly defoliated every
year remain in the grass stage and eventually die. Three successive
years of complete defoliation will result in death. The disease is very
damaging during wet years, especially in areas where the fungus has
become well established in the absence of controls.

The disease can be reduced by control burning during the winter months.
On seedlings, fire burns the diseased needles and reduces the amount of
available inoculum for reinfection, leaving the large terminal bud
unharmed. Often a single prescribed burn reduces the disease intensity
to such low levels that vigorous seedling height growth begins the
following year. Fungicide sprays will also reduce brown spot on high
valued trees.

PINE NEEDLE RUST

[Illustration: Fruiting bodies of pine needle rust on loblolly
pine.]

Nearly all the native pines in southern United States are attacked by
various needle rust fungi of the genus _Coleosporium_. This disease is
very common, but causes little harm to the trees. Many species of this
rust also attack broadleaved weeds in addition to the pines, needing
both host types to complete their life cycle.

Needle rusts are most prevalent on young trees in the seedling to
sapling stage. In the spring or early summer small, delicate white
fungus “cups” filled with yellow to orange spores are produced on the
needles. From a distance entire seedlings may appear to have a whitish
or yellowish cast. Individual needles which are heavily infected may
die, turn brown, and drop from the tree. However, the entire tree is
rarely defoliated. Small red “rust pustules” form on the undersurface of
the weed leaves. These are replaced by dark structures later in the
summer.

The needle rusts are not important enough to warrant control in natural
forests or plantations. If the weed (alternate) host is known, it can be
eradicated around nurseries of susceptible pine species. However, it
would be better to establish nurseries in rust free areas.

CEDAR APPLE RUST

Cedar apple rust, caused by _Gymnosporangium juniperi-virginianae_, is
important commercially in the apple-growing regions of the Virginias,
Carolinas, and the Mississippi Valley. The alternate hosts of this rust
are eastern red cedar and several species of junipers.

[Illustration: Fruiting galls containing spores on cedar tree.]

[Illustration: Fruiting on apple leaf the alternate host.]

Cedar “apples” or galls are the characteristic signs of the fungus on
cedars. Cedar needles are infected in the summer by wind-borne spores
from apple leaves. By the next spring or early summer galls begin to
appear as small greenish brown swellings on the upper needle surfaces.
By fall, the infected needle turns into a chocolate brown gall covered
with small circular depressions. The following spring, orange jelly-like
tendrils protrude from the galls producing an attractive ornament for
the cedar tree. Spores produced from these orange spore masses are then
capable of reinfecting apple leaves, thus completing the fungus life
cycle.

No practical control of the rust on cedars is available because of the
low value of cedar. However, considerable effort is expended to protect
apple trees. Where apple is to be protected, cedars should be eliminated
in the vicinity or, rust galls should be picked or cut off cedars before
the galls mature.

CEDAR BLIGHT

Cedar blight, caused by _Phomopsis juniperovora_, is most severe on
eastern red and Rocky Mountain cedars. Other hosts include arborvitae,
cypress, and Atlantic white cedar. The disease ranges from the mid-West
to the Atlantic coast and south to Alabama where it is most common in
nurseries.

[Illustration: Needle symptoms on 1-0 eastern red cedar nursery
stock and 5 year old Arizona cypress.]

[Illustration: (cont.)]

Symptoms on red cedar resemble that of drought. The tips of branches are
killed back and sometimes entire trees will turn brown. The fungus forms
black fruiting bodies on needles and stem lesions. Fungus spores are
distributed by rainwater; nursery overhead sprinkling systems also
facilitate blight spread.

Control of cedar blight is initiated by removing and burning infected
nursery stock early in the season before infection becomes heavy.
Seedbeds should be well drained. Avoid introducing cedar stock to an
infected nursery. The location of cedars in the nursery should be
changed frequently and, where possible, cedar beds should be kept well
away from older cedar or cedar hedges. Seedlings growing in low-density
seed beds are more vulnerable to the blight; thus beds should be fully
stocked. Cedar mulch should never be used on cedar beds. Avoid wounding
nursery transplants. No economically feasible control is available for
forest stands.

FUSIFORM RUST

[Illustration: Galls on 1-0 pine nursery stock.]

[Illustration: Damage caused by fusiform rust infection.]

Fusiform rust, caused by _Cronartium fusiforme_, is one of the most
important diseases on southern pines. This rust is found from Maryland
to Florida and west to Texas and southern Arkansas. The rust’s most
important impact is in nurseries, seed orchards, and young plantations.
Loblolly and slash pines are very susceptible to this rust. Pitch and
pond pines are moderately susceptible, longleaf pine is fairly
resistant, and shortleaf pine is highly resistant.

The most easily recognized symptom is the spindle-shaped canker on the
pine branches or main stem. In early spring these swellings appear
yellow to orange as the fungus produces powdery spores. As host tissue
is killed, older stem cankers may become flat or sunken. Cankers often
girdle trees and wind breakage at the canker is common. Fungus spores
from the pine infect oak leaves. Brown hair-like structures, produced on
the underside of the leaves in late spring, are the most conspicuous
signs. These projections produce spores which in turn reinfect the pine
trees, completing a “typical” rust cycle.

[Illustration: Fruiting fusiform-shaped canker on main stem of
southern pine.]

Silvicultural practices may lessen the incidence of infection in
plantations. Avoid planting highly susceptible species such as slash and
loblolly pines in areas of known high rust incidence. In these areas
more resistant species such as longleaf or shortleaf pine should be
planted. Pruning infected branches will prevent stem infection in young
plantations. Rust-resistant pines should be readily available from the
nurseries in the near future. Culling out seedlings with obvious galls
before outplanting will reduce the disease incidence in new plantations.

WHITE PINE BLISTER RUST

White pine blister rust, caused by _Cronartium ribicola_, was introduced
to North America on nursery stock about 1900. It is the most important
disease on white pine in the United States. In the South, the disease is
found on eastern white pine in the Appalachian mountains.

[Illustration: Fruiting cankers showing yellow-colored spores of
blister rust on eastern white pine.]

[Illustration: (cont.)]

The disease is caused by a fungus that attacks both white pine and wild
and cultivated currant and gooseberry bushes, called _Ribes_. Both hosts
must be present if the fungus is to complete its life cycle. Attack by
the disease is followed by the development of cankers on the main stem
or branches. Infected pines die when a canker completely girdles the
main stem or when many of the branches are killed by girdling. The most
conspicuous symptoms of the disease are the dying branches or crowns
(“flags”) above the girdling cankers, and the cankers themselves.

Initially, a narrow band of yellow-orange bark marks the edges of the
canker. Inside this band are small irregular dark brown scars. As the
canker grows, the margin and bank of dark scars expand and the portion
formerly occupied by the dark scars is now the area where the spores
that infect _Ribes_ are produced. During the months of April through
June white sacs or blisters containing orange-yellow spores (called
aeciospores) push through the diseased bark. The blisters soon rupture
and the orange-yellow spores are wind-dispersed for great distances.
Generally, there is some tissue swelling associated with the canker,
which results in a spindle-shaped swelling around the infected portion
of the stem.

Loss of white pines from blister rust can be prevented by destroying the
wild and cultivated _Ribes_ bushes. Bushes may be removed by uprooting
by hand, grubbing with a hand tool, or with herbicides. Pruning infected
branches on young trees will prevent stem infections and probably tree
mortality.

COMANDRA BLISTER RUST

[Illustration: Fruit gall showing orange colored spores on loblolly
pine.]

[Illustration: Alternate host—false toadflax.]

Comandra blister rust, caused by the fungus _Cronartium comandrae_, is a
canker disease of hard pines. The disease presently occurs in widely
scattered areas throughout the western, central, and southern United
States. In the South, the primary hosts are loblolly, shortleaf, pond,
and Virginia pine. Herbaceous plants of the genus Comandra, commonly
known as false toadflax or comandra, are also attacked.

The fungus infects pines through the needles and grows from the needle
into the branch or main stem where it forms a gall or canker. Dark
orange-colored spores which are produced on the surface of the gall in
the spring are wind-blown and infect the leaves or stems of the comandra
plants. Two to three weeks after infection, urediospores are produced on
the underside of the comandra leaf. These are wind-blown and can only
infect other comandra plants. Eventually hair-like structures known as
telia are produced on the comandra leaves and stems. The telia produce
spores which are wind-blown and infect the pine host through the needle.
The necessary combination of a susceptible pine host, the alternate
host, and the pathogen is presently known to occur only in northern
Arkansas, eastern Tennessee, and northern Alabama.

No effective method of controlling the disease in forest stands is
presently known. Silvicultural or forest management practices which
reduce the abundance of the alternate host offer promise of long term
control. Maintenance of dense stands and heavy ground cover as a means
of shading out the intermediate host plants, may be helpful in reducing
rust damage in many areas.

EASTERN GALL RUST

Eastern gall rust, caused by the fungus _Cronartium cerebrum_, attacks
many species of eastern hard pines. The disease ranges eastward from the
Great Plains and is most severe in the South on Virginia and shortleaf
pines. Like most rusts this fungus requires an alternate host in
addition to its pine host. In this case oaks, especially the red oak
group (black, red, scarlet and pin) are the alternate hosts. Damage to
the oaks is generally not of economic importance as only the leaves are
affected.

[Illustration: Fruiting gall showing red-orange spores on Virginia
pine.]

On pines the fungus causes the formation of globose to sub-globose
galls. Canker formation occurs occasionally but mortality generally
results from wind breakage at the gall rather than by canker formation
as literally hundreds of galls may appear on a single tree. They are not
lethal to the tree, but may ruin tree form and on a large stem they can
lead to an open decayed wound, as decay fungi are often secondary
invaders of rust infections. The shape of galls and the arrangement of
the spore sacs filled with red-orange spores present a cerebroid
(brain-like) appearance. During the spring the bright orange galls are
very striking.

This disease is sometimes a problem in nurseries where seedlings are
attacked and killed. This is where control efforts are concentrated.
Fungicide protectants are applied to the seedling foliage to prevent
infection from spores produced on oaks. Contact your local forestry
extension agent or the nearest Division of Forest Pest Management for
the latest recommendations. Under forest conditions, control is not
economically feasible. Trees of poor form should be removed during
thinning operations.

SOUTHERN CONE RUST

Southern cone rust is caused by the fungus _Cronartium strobilinum_. It
has been reported to completely destroy slash and longleaf pine cone
crops in Georgia and along the Gulf Coast from Florida to Texas.

[Illustration: Cone rust symptoms on slash pine.]

[Illustration: (cont.)]

Like most other rusts, the fungus requires oaks and pines to complete
its life cycle. Although infection of oak leaves occurs annually, no
significant economic damage is done to the oaks. Fungus spores produced
on oak leaves infect the mature female pine flowers about the time of
pollination (January-February). The fungus grows through the developing
conelet causing it to swell abnormally. By early April or late May the
infected cones are three to four times larger than the normal first-year
cones and even exceed the maturing second-year cones in size. The
swollen cone scales are reddish in color. Cavities in the cone filled
with orange-yellow spores burst and the cones become orange-yellow. The
swollen orange-yellow cones in the tree crowns can be easily
distinguished from normal cones by an observer on the ground. By late
summer most of the diseased cones have died and fallen.

Control at present is confined to seed orchards. Hydraulic spraying of
the flowers with fungicides gives a significant reduction in infections.
Consult your local forester, county extension agent or the nearest
Forest Pest Management Office for current control recommendations.

PITCH CANKER

Pitch canker, caused by the fungus _Fusarium lateritium forma pini_, is
rapidly becoming widespread throughout the South. The disease apparently
is most serious on Virginia, slash and south Florida slash pine. The
fungus also attacks shortleaf, pitch, and table-mountain pine.

[Illustration: Pitch canker infection in terminal branch and main
stem of pine.]

[Illustration: (cont.)]

Pitch canker may cause tree mortality. On Virginia pines the fungus
reportedly enters through small insect wounds in the twigs or mechanical
wounds in the bole. Shoots may be girdled and killed within a few weeks,
but it takes a period of years for the fungus to girdle the bole of
larger trees. On slash pine the disease apparently attacks plantations
in wave years. During years of heavy attack the fungus can cause rapid
crown deterioration in addition to causing bole canker infections.
Cankers on leaders in the crown can result in death of two-thirds or
more of the crown by mid-summer in a tree that appeared healthy in the
spring. In the majority of tree infections only the leader and one or
two laterals will be infected. The tree recovers in a few years with a
crook in the bole as the only evidence of attack. Pitch cankers usually
retain the bark and old cankers on the hole may be sunken. The most
diagnostic characteristic of the disease, and the one that definitely
separates it from similar disease, is the heavy pitch soak of the wood
beneath the canker. Pitch cankers are often so soaked with pitch that
heavy flow of pitch is observed flowing down the bole.

At the present time, no known method of control exists. Observations in
slash pine plantations indicate that some trees are resistant while
others range in their degree of susceptibility.

WOOD DECAY

Wood decay of southern forest trees is responsible for nearly 80 percent
of all loss attributed to disease. This decay is caused by fungi which
mainly attack heartwood in the central portion of stems, branches, and
roots. Wood-rotting fungi gain entrance into the tree through broken
branches, wounds, and damaged or exposed roots. Spores, which land at
these damaged areas, germinate and produce a microscopic mycelium which
attacks and spreads throughout the heartwood. The decay is caused by the
action of the mycelium, which penetrate the cell walls and dissolve or
alter the wood in various ways. Fungus development within the tree may
continue for many years without any apparent effect on the growth of the
host. Eventually the mycelium will aggregate and break through the bark
to form the reproductive stage, either before or after the death of the
host. The fruiting body (sporophore, conk) produces vast amounts of
spores which are capable of spreading the fungus to other trees.

Heartrots may be separated into broad classes on the basis of the host
portion attacked, such as root rots, root and butt rots, stem rots, and
top rots. Decay fungi may be further separated into two broad classes
based on their effect on wood. The first class causes white rots,
decomposing all components of the wood and reducing it to a spongy mass
with white pockets or streaks separated by firm wood. The second class,
causing brown rots, utilize the cellulose, leaving the lignin more or
less unaffected. This usually results in a rot which appears as some
shade of brown.

The separation of wood decay fungi on the basis of their host range, the
portion of the host attacked, and the type of rot produced are useful
aids to a pathologist in determining a tentative identification of the
fungus responsible for a particular type of rot. However, there are
numerous fungi which cause decay, many of which are exceptions to the
various methods of classification. This forces the pathologist to use
microscopic examination and various artificial keys to arrive at the
proper identification of a given rot-producing fungus.

[Illustration: Sectioned stump showing rot and decay in heartwood.]

RED HEART

The fungus, _Fomes pini_, is the cause of a heartrot of widespread
distribution. Common names for the rot produced by this fungus are: red
heart, red ring rot, or white peck. The disease is commonly associated
with mature and over-mature conifers, especially Douglas fir, larch,
spruce, and pine. In the southern United States, the fungus attacks all
species of mature pine.

[Illustration: Fruiting body of redheart on southern pine.]

Generally, infection of all hosts occurs through dead branch stubs.
Early stages of decay caused by _F. pini_ are characterized by a
discoloration of the heartwood, often appearing light red to reddish
brown. The advanced stages of heartrot appear as elongated white pockets
or flecks, formed parallel to the grain and separated by apparently firm
wood. Often the pockets become resin filled. On southern pine hosts, the
conks are often bracket-like or hoof-shaped. The upper surface appears
dull grey to dark brown, with concentric furrows parallel to the margin
of the fruiting body. The lower side is a light brown to brownish gold,
rimmed by a velvety golden brown margin. Swollen knots result from the
living wood tissue trying to overgrow the knot where a conk is forming.

[Illustration: Cross section of infected tree showing rotted and
decayed heart wood.]

In southern forest stands, heartrot damage may be reduced by harvesting
mature pines prior to the age of extreme susceptibility to fungus
attack. Some degree of shade tree protection can be obtained by pruning
dead and dying branches flush with the main stem. This will allow the
knot to be quickly overgrown by sap wood, preventing the heartrot fungus
from entering through the branch stub.

ANNOSUS ROOT AND BUTT ROT

[Illustration: Fomes annosus fruiting bodies on stump.]

Annosus root and butt rot is caused by the fungus _Fomes annosus_. This
pathogen is common throughout coniferous stands of the North Temperate
Zone. Hardwoods may be attacked, but damage is usually of minor
consequence. In the South, the disease is most serious in pine
plantations on sandy soils with low organic matter. All species of
southern pine are susceptible. Slash and loblolly plantations are often
severely affected.

The disease gains entry into plantations by spore infection of freshly
cut stumps during thinnings. The fungus then spreads from the infected
stumps to residual trees by growth along the roots to points of root
contact. Residual trees usually begin to die within a few years after
thinning. The sporophores or fruiting bodies are generally found at
ground line or in the root crotch. Pines in initial stages of the
disease usually exhibit sparsely foliated crowns; however, white pine
with full crown may have extensive butt and root decay. Occasionally
trees may die rapidly with a sudden red discoloration of a nearly full
crown. Diseased trees are often found in groups or circular pockets in
the stand. The indication of _F. annosus_ decay may include the pink to
violet stain of incipient decay, the narrow elongated white pockets and
scattered black flecks in the wood of the early decay stages, and the
yellow stringy rot of the late stages of decay.

[Illustration: Infection center in pulpwood size pine stand.]

Control includes avoidance of planting on soils of low organic matter
and elimination of thinning. Stump infection following thinning or
harvest may be prevented using various methods.

BROWN CUBICAL BUTT ROT

_Polyporus schweinitzii_ is a common cause of root and butt rot of
conifers throughout North America. The primary hosts of the fungus are
Douglas fir, spruce, and pine. All southern pines are susceptible to
attack by _P. schweinitzii_. Common names of the rot are: red-brown butt
rot and brown cubical butt rot.

[Illustration: Fruiting body of brown cubical root and butt rot of
pine.]

The fungus enters living hosts through damaged roots, fire scars, and
other wounds near the tree base. The initial stage of decay appears as a
light yellow stain. In the advanced stage, the heartwood becomes brittle
and breaks into large yellow-brown to reddish-brown cubes. The fungus
develops primarily in the roots and butt and seldom extends more than 15
or 20 feet up into the stem. Diseased trees are subject to wind-throw
and wind breakage. Although the volume of wood destroyed by the rot is
small, the total volume lost through wind-throw is quite large. Mature,
suppressed, and weakened off-site trees are commonly attacked by the
fungus. It is assumed that the fungus may also spread from infected to
healthy trees through root contacts and grafts. The only outward signs
of decay are the annual sporophores, which develop in late summer and
fall during moist weather. Conks formed at the base of infected trees
are bracket shaped, while those arising from decayed roots appear
circular, sunken in the center, and supported by a short stalk. When
fresh, the upper surface is velvety, concentrically zoned, and
reddish-brown in color with a light yellow margin. The underside is dark
olive or green with large irregular pores.

In forest stands, no method of controlling the disease is known. Losses
may be prevented to some extent by reducing the amount of root damage
and wounding from heavy logging equipment. The prevention of basal fire
scars in conifer stands will also reduce the incidence of this disease.
Trees which show signs of advanced root and butt rot should be removed
from around recreation areas, parking lots, power lines, and buildings
to avoid damage from wind-throw and wind breakage.

RED ROOT AND BUTT ROT

[Illustration: Fruiting body of red root and butt rot of pine.]

_Polyporus tomentosus_ causes red root and butt rot of living conifers
throughout North America. Common hosts of the fungus are: spruce, larch,
pine, fir, Douglas fir, hemlock, and cedar. Throughout the southern
United States, _P. tomentosus_ has been reported in two general areas;
causing extensive degrade of mature shortleaf pine in northern Arkansas
and root and butt rot of slash pine in South Carolina, Georgia, and
Florida.

The fungus is believed to enter living hosts through basal wounds and
damaged roots. Under ideal conditions, the fungus may spread from
infected to healthy trees by way of root contacts or grafts. Growth of
the fungus is very slow, often causing host mortality 20 to 30 years
after initial infection. Wood decayed initially appears firm, but dark
reddish-brown in color. In advanced stages, the wood is flecked with
elliptical white pockets separated by brown-colored wood. Infected
conifers generally express typical root rot symptoms. Trees show
evidence of reduced radial and internodal growth, accompanied by death
of the crown from the base upward. The foliage appears off-color and
reduced in length. Under moist conditions, sporophores are produced
either at the base of infected trees or on the forest floor.
Bracket-shaped sporophores are produced at the base of infected trees
while stipitate conks are produced on the ground directly over infected
or dead roots. Fresh sporophores appear yellow-brown in color from above
with a lighter colored pore surface below.

No effective method of controlling the disease in forest stands is
presently known. However, damage and losses may be reduced by management
practices which reduce or eliminate the chance introduction of the
disease into healthy stands. In areas where red root and butt rot is
common, attempts should be made to conduct logging and thinning
operations during the dry season to avoid mechanical damage to the root
systems of the residual trees.

LITTLELEAF OF PINE

Littleleaf of pine, caused by _Phytophthora cinnamomi_, is the most
serious disease of shortleaf pine in the Piedmont region of the South.
Loblolly is also affected, usually where associated with infected
shortleaf pine. The disease is most evident in older age classes, rarely
attacking stands under 20 years old.

[Illustration: Needle symptoms and damage of littleleaf on shortleaf
pine.]

[Illustration: (cont.)]

The disease is caused by a malfunctioning of the root system due to a
combination of biological and physical factors. A fungus, _Phytophthora
cinnamomi_ attacks and kills the root tips. When conditions of moisture,
fertility, and drainage are adverse, they reduce tree vigor and prevent
the tree from rapidly replacing the destroyed root tips. Trees on good
sites are reportedly also attacked by the fungus, but their vigor is
such that they quickly overcome the disease by producing new root tips.
The disease usually progresses rather slowly. Some trees may persist
fifteen or more years after the appearance of initial symptoms. In
general, trees live only five or six years after attack, but they may
die in as little as one year. Symptoms are those typical of trees in
stress due to a malfunction of the root system. In the early stage of
the disease the foliage may turn yellow-green and the current year’s
needles are shorter than normal. Later stages of the disease are
sparsely foliated crowns with short needles (reduced from three to five
to only one-half to three inches in length) and dead branches. Abundant
foliage sprouting on the hole of infected shortleaf is common.

Losses are minimized by salvage cuttings and by favoring loblolly and
hardwoods in regeneration plans.

SYCAMORE ANTHRACNOSE

[Illustration: Defoliation of sycamore tree caused by sycamore
anthracnose.]

Sycamore anthracnose, caused by _Gnomonia veneta_, is common on American
sycamore throughout its range in the eastern United States.

Anthracnose is a disease characterized by distinctive limited lesions on
stem, leaf, or fruit, often accompanied by dieback or blight and usually
caused by fungi that produce slimy spores that ooze from small
cup-shaped fruiting bodies that are visible with a hand lens. This
disease has four distinct symptom stages identified as twig blight, bud
blight, shoot blight, and leaf blight. Twig blight appears before leaf
emergence and kills the tips of small one-year-old twigs. Infection
comes initially from leaf litter and twig cankers. The second stage, bud
blight, develops during bud expansion in April and early May. Shoot
blight, the most frequently observed symptom, causes the sudden dying of
expanding shoots and also young leaves. Leaf blight, the final stage,
involves the actual infection of expanding or mature leaves. Diseased
portions of the leaf involve irregular brown areas adjacent to the
midrib and veins which are dotted with diseased spots. Incidence of
anthracnose is directly related to the amount of spring rainfall. Shoot
blight is severe if the weather for two weeks after leaf emergence is
cool and moist. The disease may defoliate trees, which usually put out a
new crop of leaves by late spring or summer.

Control of sycamore anthracnose under forest conditions is not
economically feasible. Where the disease is prevalent, other species
should be favored during thinnings. In shade and ornamental trees,
pruning of infected twigs, burning of leaves, and fertilization will
reduce the disease impact.

[Illustration: Leaf and twig symptoms.]

WALNUT ANTHRACNOSE

Walnut anthracnose is a fungus disease caused by _Gnomonia leptostyla_.
This worldwide disease attacks most species of walnut in the United
States. Black walnut is most severely affected, but with favorable
weather for the fungus, even less susceptible individuals may be
defoliated. Butternut, Persian walnut, and two species from California
(Hinds walnut and California walnut) are all susceptible. Anthracnose
has also been reported on species of walnut from most of the European
countries, Argentina, Canada, and South Africa.

Wet weather greatly favors this leaf disease which may defoliate black
walnuts by late July or early August. Defoliation slows growth, weakens
trees, and sometimes causes mortality. Infected leaves reveal circular
spots of dark brown or black. These spots often grow together, leaving
large dead areas. These spots or blotches are bordered with yellow to
golden tissue. While severely affected leaves fall, some “anthracnose”
leaves remain on the tree. This disease also affects the growth and
quality of the nuts. Nutmeats from infected trees are dark,
unattractive, and shrivelled. Sunken, killed areas appear on the husks
as dark circular spots smaller than those on the leaves. Infected nuts,
like the leaves, may also fall from the tree. Lesions may appear on the
current year’s shoots and later form dead sunken areas that are oval to
irregularly circular with reddish brown margins.

As with the other anthracnose diseases, no practical control is
available for forest trees. Control of walnut anthracnose on ornamentals
and nut trees is partially achieved by raking and burning of old leaves.

OAK ANTRHACNOSE

[Illustration: Leaf symptoms of oak anthracnose.]

Oak anthracnose is caused by the fungus _Gnomonia veneta_. Trees of the
white oak group, particularly white oak, are susceptible to this
disease. Oaks throughout the entire eastern United States are affected
by the disease, although it is less common in the Northeast.

Infection occurs in the early spring or mid-summer. Symptoms on leaves
develop as irregular brown diseased areas (blotches) along the midrib
and the major side veins. These blotches may grow together by late
spring or early summer if infection occurs early. Blotches are usually
confined to the areas bordered by the larger veins. Leaves on the lower
branches are frequently killed and occasionally trees will be
defoliated. However, a second crop of leaves soon develops and mortality
is rare. Fruiting bodies of _Gloeosporium_, the imperfect fungus
fruiting stage of anthracnose, are located on the midrib and veins of
infected leaves. When the disease spreads to the twigs, cankers and
crown dieback may occur. The anthracnose fungus overwinters on diseased
twigs and in the leaf litter. Oak anthracnose has the same causal agent
as sycamore anthracnose, and the weather conditions favoring the
sycamore disease also increases the anthracnose on oak.

Control is similar to sycamore anthracnose and involves an integrated
program of pruning disease tissue, fertilization, and burning of leaf
litter. No practical control is available for forest trees.

DOGWOOD ANTHRACNOSE

Dogwood anthracnose, caused by the fungus _Elsinoe corni_, occurs in
states bordering the Atlantic Ocean and has also been reported in
Louisiana. Its primary host is flowering dogwood, _Cornus florida_ L.

[Illustration: Leaf and flower symptoms of dogwood anthracnose.]

[Illustration: (cont.)]

Anthracnose occurs in the spring and affects not only the leaves, but
also the buds and “flowers”. The buds may fail to open or they may
produce stunted flowers. These have many circular to elongated spots
with light tan centers. Margins of these spots are purple to brown.
Often the flowers abort before development. Foliage spots (1-2 mm. in
diameter) are raised at the margins. They are purple at the edges and
yellow-gray in the center. Later centers of spots may fall out causing a
“shothole” effect. Dozens of spots may be present on a single leaf and
may be scattered or concentrated at tip, margin, or midrib. Twisting and
malformation of the leaves are common. In addition to floral and foliage
spots, infected areas may also occur on petioles, stems, and fruit
clusters. All three areas have spots similar to those on the foliage.

Other diseases which may be confused with anthracnose include _Septoria_
and _Ascochyta_ leaf spots. _Septoria_ usually begins around July and
unlike anthracnose has more angular lesions that are between the veins.
_Ascochyta_ spots may be larger (6 mm. in diameter) than anthracnose,
and tissue discoloration may extend outside of their borders.
Occasionally the leaves may totally blacken. This disease may occur as
early as June.

Wet, humid weather at certain stages of plant development is required
for infection. Homeowners may obtain effective control by removing and
burning infected plant parts. Various fungicide sprays are recommended
by authors of ornamental handbooks.

COTTONWOOD RUST

[Illustration: Rust infected cottonwood leaf.]

Cottonwood rust, caused by _Melampsora medusae_, is probably the most
important leaf disease of cottonwoods wherever they are grown. In the
Lower Mississippi Valley, all sizes of eastern cottonwood trees may be
infected with this rust. However, the disease is probably of most
importance in cottonwood nurseries.

In mid-summer, yellow to orange pustules containing spores of the fungus
form on the under surface of the cottonwood leaves. In late summer and
early fall, dark brown fungal growths replace the orange structures.
Cottonwood may be prematurely defoliated or even killed by successive
attacks. The rust may weaken trees and subject them to attack by other
disease-causing organisms. Also, there is often a reduction in growth in
these normally fast growing species. This is very important since there
is presently a wide interest in the use of hybrid poplars for pulp and
timber production.

There is generally no accepted control for cottonwood rust.
Rust-resistant varieties of hybrid and exotic cottonwoods are being
developed and may provide the best control of this disease.

BLACK KNOT

[Illustration: Black swellings of cherry black knot.]

Black knot, caused by _Dibotryon morbosum_, is prevalent throughout the
Southeast (with the exception of southern Florida) wherever black cherry
grows, and in orchards on plums and domestic cherries.

The most prominent symptoms are the elongated black swellings which
appear in summer on small twigs and branches. Heavily infected trees
appear quite grotesque, with large swellings which may be several times
the diameter of the twigs. Cankers occurring on black cherry trunks
usually ruin the commercial tree value. Initial infection occurs on
lateral branches and twigs in the spring, but the swellings do not
become noticeable until the following spring.

The most practical control for black knot is removal of infected black
cherry from the stand. Twigs and branches with knots should be burned.

NECTRIA CANKER

Nectria canker of hardwoods, caused by _Nectria galligena_ and _N.
magnoliae_, is frequently found on yellow birch and black walnut. Common
hosts also include bigtooth aspen, sassafras, northern red oak, red
maple, beech, Carolina poplar, paper birch, and sweet birch. A closely
related canker disease is also found on yellow-poplar and magnolias. The
range of this disease includes the Lake States, the Northeast, and the
southern Appalachians.

[Illustration: Target-shaped canker of Nectria on sassafras and
yellow-poplar.]

[Illustration: (cont.)]

Older Nectria cankers are easily recognized in forest stands because of
their typical “target” shape. “Target” cankers have rings, each of which
represent a year’s growth. Younger cankers tend to be grown over by bark
and callus tissue attempting to heal the wound. Such cankers are
difficult to recognize, but close examination of the affected area may
reveal tiny red bodies, which are the fruiting bodies of the Nectria
fungi. Mortality rarely occurs from this disease, but stems may break at
canker locations during high winds.

Control of Nectria canker is the same as for Strumella canker—the
removal of infected trees during thinning operations.

STRUMELLA CANKER

Strumella canker of hardwoods, caused by _Strumella coryneoidia_, most
frequently attacks trees of the red oak group. Other hosts include
species in the white oak group. Beech, basswood, blackgum, shagbark
hickory and red maple are also occasionally affected. This disease is
found in the East, from the southern Appalachians to northern New
England.

[Illustration: Strumella canker on black oak.]

Strumella cankers are of two types: diffuse, and the more common
“target-shaped.” The first develops on smooth-barked saplings and
rapidly girdles and kills the tree. Killing results because callus
tissue, which tends to heal over cankers, does not have time to develop.
Target-shaped cankers are more common. “Targets” are formed by the
alternation of killing of bark by the fungus around the canker’s
perimeter and the formation, in turn, of a callus ridge by the host
tree. The fungus is active usually in the dormant season, while
callusing occurs in the spring. As with most canker-causing fungi,
Strumella usually enters the tree through a branch stub. Cankers are
quite large and may reach several feet in circumference or length. The
presence of the causal fungus is revealed by dark brown, cushion-like
structures about one to three millimeters in diameter on the dead bark
and surrounding tissue.

No feasible control method is available under forest conditions.
However, the disease impact can be greatly reduced by removing cankered
trees during thinning operations.

SPICULOSA CANKER

Spiculosa canker, caused by _Poria spiculosa_, is found on bottomland
oaks in the South. Occasionally this disease will also degrade hickories
and honeylocust.

[Illustration: Fruiting body of Poria rot and canker on oak.]

[Illustration: Cross section of tree showing rot and decay.]

Spiculosa canker is considered to be a canker-rot disease, a type of
decay in which the causal organism incites not only heart-rot but also
large irregular cankers. Infected trees have cankers that appear as
rough circular swellings on the bole. The canker centers are depressed
and old branch stubs are discernible. Fungus fruiting bodies, or conks,
usually are not present on living trees but develop on snags or decayed
logs. The conks grow flat under the bark and push it off to expose the
brown fungus fruiting surface.

Control for Spiculosa canker is similar to other canker rots: salvage to
remove undesirable cankered trees that may be later replaced by better
quality trees.

IRPEX CANKER

Irpex canker, caused by _Irpex mollis_, is prevalent in bottomlands and
on upland areas of the Southeast. In the bottoms, Nuttall, water, and
willow oaks are affected. White, chestnut, southern red, and black oaks
are the hosts of this disease on upland sites.

[Illustration: Fruiting body of Irpex rot.]

[Illustration: Cross section of tree showing rot and decay.]

Irpex canker is also considered to be a canker-rot disease. Symptoms on
infected trees frequently involve irregular cankers up to two feet in
length. Cankers are usually found on trees eight to ten inches in
diameter or larger, at a height of twenty feet above the ground. Branch
stubs, signifying probable infection points, are usually present in the
centers of cankers. The portion of the trunk affected is usually swollen
but sometimes may be sunken. At the base of the sunken portion of the
canker are small, creamy-white, toothed fruiting bodies or conks with a
leathery texture. Conks also appear on hardwood logs. The wood behind
cankers is characterized by a tough, spongy, white rot which extends as
much as eight feet above and below the canker. The decay pattern may
also extend downward into the roots. In cross-section, the rotted areas
appear as finger-like projections radiating out toward the sapwood.
Gradually the rot column tapers to a thin central core beyond which
white flecks appear, and this early rot stage is concentrated along the
rays of the oaks.

Control for Irpex canker is the same as for other canker-rots—salvage of
undesirable cankered trees.

HISPIDUS CANKER

_Polyporus hispidus_ is the cause of trunk cankers and localized decay
of hardwoods throughout eastern, central, and southern United States.
The fungus is also known to attack hardwoods in Oregon and California.
Reported hosts are: hickory, ash, mulberry, willow, walnut, and oak. In
the south, _P. hispidus_ is common on oaks, including willow, water,
black, white, Nuttall, and cherrybark.

[Illustration: Fruiting body and canker of Hispidus on oak.]

The fungus usually enters the tree through dead branch stubs, from which
it grows into the heartwood. After becoming established, the fungus
begins penetrating the sapwood and attacks the living cambium. Callus
folds are formed by the host around the dead cambial area, forming an
elongated swollen canker, commonly referred to as a “hispidus canker”.
The cankered area of the stem is bark-covered and sunken, usually
containing a remnant of a branch stub or branch scar. During late
summer, fall or early winter, the fungus produces conks (sporophores) on
the surface of the cankers. The annual bracket-shaped conks are large,
spongy, and yellowish-brown to rusty-brown on the upper surface. When
fresh, the under surface is a light tan color. After a few months, the
mature conks dry to a rigid black mass and fall from the canker. Old
conks are commonly found at the base of cankered trees during the spring
and early summer. Decay produced by the fungus appears spongy, light
yellow, and is commonly separated from the sound wood by a black zone
line. The rot is of the delignifying white rot type. On southern oaks,
the rate of canker elongation has been estimated at one-half foot per
year, with the internal rot usually extending about one foot above and
below the cankered area.

No effective control in forest stands is known. Removal of diseased
trees provides additional growing space for crop trees. Some degree of
shade tree protection can be obtained by pruning of dead branches flush
with the main stem of the tree.

BOTRYOSPHAERIA CANKER

_Botryosphaeria ribis_ causes cankering and mortality of more than 50
woody plants. The fungus is widely distributed throughout the eastern
one-half of the United States. The pathogen infects the following
economically important hosts: sweetgum, redbud, willow, poplar, tupelo,
pecan, and hickory.

[Illustration: Botryosphaeria canker on sweetgum.]

The fungus gains entry into susceptible hosts primarily through wounds
or dead and dying twigs. Small oval cankers on stems or branches are the
first symptoms of infection. As the fungus continues to attack and kill
the cambium, the sunken cankers enlarge, eventually girdling and killing
the branch or stem above the cankered area. In the spring and early
summer, cankers on living portions of the host often produce an exudate.
Infected sweetgums generally produce the exudate in great quantities, to
which the common name of bleeding necrosis has been applied.
Reproductive structures called stroma are produced by the fungus on dead
cankered stems and branches during moist periods of the spring and
summer.

No practical method of control is known. Diseased trees seldom recover.
Infection of high value shade and ornamental trees may be prevented to
some degree by avoiding mechanical damage. Dead limbs and branches
should be pruned and wounds covered with a suitable tree paint. Infected
trees should be removed and burned.

SEPTORIA CANKER

[Illustration: Septoria canker on young cottonwood saplings.]

Septoria canker is caused by the fungus _Septoria musiva_. Although this
is a disease of poplars, native poplar species are not severely
attacked. However, this is an important problem wherever hybrid or
introduced poplars are grown. With the ever-increasing emphasis on
poplar planting, this will probably become a much more important problem
in the near future.

Young stem cankers usually develop around openings such as wounds,
lenticels, or leaf scars, appearing first as sunken, dark areas of the
bark. The infected area later becomes more depressed and darker as
tissue dies, and often a black margin will be formed around the canker.
Small, pink, hair-like spore tendrils are produced by the fungus around
the canker margin, especially during moist weather. These tendrils
contain spores which can cause further infection, and arise from small
dark fungal fruiting structures called pycnidia. This cankered area is
often invaded by insects and other fungi and is also a weakened area at
which wind breakage may occur. The fungus also causes a gray to black
leaf spot, which usually has a light colored center. These spots may
coalesce on a severely infected leaf and involve the entire leaf
surface. This leaf spot in itself causes slight damage, but acts as a
source of fungus spores which can cause stem cankers, and thus is
important in the overall consideration of the disease.

[Illustration: Defoliation in cottonwood caused by Septoria
leafspot.]

A control for this disease is to use native poplars or resistant hybrids
wherever possible. Wider spacing in plantations may also reduce the
humidity, decreasing the amount of infection.

CYTOSPORA CANKER

Cytospora canker is caused by _Cytospora chrysosperma_. This fungus
attacks more than 70 species of hardwood trees and shrubs as well as
some conifers. Poplars and willows are among the most common hosts, and
are attacked throughout their range. Trees used for shade or windbreak,
and also cuttings in propagation beds are particularly susceptible to
this canker. This disease is most severe on trees growing under stress,
such as those growing on an unfavorable site, or injured by drought,
frost, fire, or severe pruning. The fungus is a normal inhabitant of the
bark and becomes parasitic only when the tree is weakened.

[Illustration: Cytospora canker on cottonwood.]

A canker begins as a gradual, circular killing of the bark of a limb or
stem. This infected tissue soon appears as a brownish, sunken patch,
around which the host often produces raised callus tissue. Small black
fungal structures (pycnidia) appear as small pimples on the dead bark.
During moist weather, thin threads of spores exude out from the
pycnidia. The inner diseased bark becomes dark and odorous. The cambium
is killed and the sapwood becomes watery and reddish brown as it becomes
infected. Water spouts may form below the canker before the tree dies.

Since this disease is most severe on weakened trees, shade trees should
be watered and fertilized to maintain healthy, vigorous growth. Wounding
and severe pruning should be avoided. Cuttings should be selected from
healthy planting material grown in disease free areas. If cuttings are
to be stored for any length of time, they should be kept at a
temperature below 35°. This low temperature will keep new infections
from occurring, even if spores are present.

CHESTNUT BLIGHT

[Illustration: Stem canker caused by chestnut blight organism.]

Chestnut blight is caused by the fungus _Endothia parasitica_. It can be
found on American chestnut throughout its range where it has virtually
eliminated this valuable species from eastern hardwood forests. The
chestnut blight fungus is also parasitic on other hosts including common
chinkapin, Spanish chestnut, and post oak. Japanese and Chinese
chestnuts are resistant.

Stem cankers are either swollen or sunken and the sunken type may be
grown over with bark. The fungus forms fruiting bodies some distance
back from the advancing cankers, and the spores may exude from bark
crevices as orange curl-like masses during moist weather. Young cankers
are yellow-brown in sharp contrast to the normal olive-green color of
the bark. The chestnut is a vigorous sprouting species but the fungus
survives in previously killed stumps and later kills the new sprout
growth.

No effective control has been developed for chestnut blight, even after
several decades of intensive research. The most promising control
involves the development of a blight-resistant species. Research is
presently underway on this matter but results are inconclusive.

[Illustration: Fruiting bodies on surface of canker.]

OAK WILT

This serious vascular wilt of oaks is caused by the fungus _Ceratocystis
fagacearum_. At least fifty species and varieties of oak are
susceptible. The disease has been most damaging in the Lake States but
is also found in the eastern United States.

[Illustration: Oak wilt symptoms on red oak trees and leaves.]

[Illustration: (cont.)]

Oak wilt symptoms are most noticeable during late spring or early
summer. Red oaks may be killed in as little as three weeks, the lower
branches being affected last. In white oaks, symptoms are usually
confined to a few branches each year and trees may live several years
before death. Leaf symptoms are similar for both red and white oaks.
Leaves turn yellow or brown and become dry progressively from the edge
or tip to the midrib and base. Mature leaves may fall at any symptom
stage from green to brown. Premature leaf shedding is the most
outstanding symptom. A definite characteristic of the disease is the
raising and cracking of the bark due to pressure of mats of the fungus
growing between the bark and wood.

Oak wilt is spread over long distances by insects that pick up spores
while crawling on the mats of infected trees. The disease may also
spread from tree to tree via root graft. Short-distance spread is
controlled by severing all roots of living trees around infected trees
by use of a ditchdigger. Another control is to fell all trees in a
50-foot radius of infected trees; felling and burning of all parts of
infected trees is sometimes done to prevent overland spread.

DUTCH ELM DISEASE

[Illustration: Dying tree infected with Dutch elm disease.]

Dutch elm disease, caused by _Ceratocystis ulmi_, is the most
devastating disease of elm trees in the United States. This disease has
been recorded in most states east of the Mississippi and as far as Idaho
in the Northwest and Texas in the Southwest. All of the native elm
species are susceptible, while many of the ornamental Asiatic species
are highly resistant.

Trees suffering from Dutch elm disease may show a variety of symptoms.
Leaves become yellow, wilt, and turn brown. Premature defoliation and
death of branches usually occurs, causing the crown to appear thin and
sparse. Internally, a brown discoloration appears in the outer sapwood.
_C. ulmi_ is transmitted from diseased to healthy elms by elm bark
beetles, mainly the small European elm bark beetle and the native elm
bark beetle. These beetles make characteristic galleries under the bark
of dead and dying elms. Adult beetles pick up the sticky fungus spores
from under the bark and then feed on the young tender elm twigs of
healthy trees, inadvertently inoculating the healthy tree with the
fungus. The fungus may also spread from diseased elms to adjacent
healthy elms through root grafts.

[Illustration: Discoloration and streaking symptoms in the sapwood.]

Controls to combat this disease generally involve sanitary measures
aimed at the beetles. Dead and dying elms should be burned. This
eliminates the elm wood which normally serves as a breeding place for
elm bark beetles and thus reduces the beetle population. In areas where
most native elms are infected, other tree species or resistant elm
species, such as the Chinese or Siberian elm, should be planted rather
them native elms.

ELM PHLOEM NECROSIS

Elm phloem necrosis is a disease of elm, caused by a virus or virus-like
organism. The disease has occurred in the United States for many years,
probably as early as 1882. The pathogen is transmitted from infected to
healthy trees by the adult white-banded elm leafhopper, _Scaphoideus
luteolus_, which feeds on the leaf veins. It is now present throughout
most of the central, eastern, and southern portions of the United
States. The disease is known to occur on American and winged elm, but
all native elms are probably susceptible to attack by the pathogen.

[Illustration: Foliage symptoms of elm phloem necrosis.]

The earliest symptoms of the disease appear in the top of the crown, at
the outer tips of the branches. Here the elm leaves suddenly wilt, turn
yellow, the margins curl upward and the leaves die. Leaf-fall causes the
crown to appear sparse. In large trees, the foliage symptoms may
initially appear on one branch or only a portion of the crown. However,
the symptoms during the advanced stage of the disease are exhibited
throughout the crown. The most reliable symptom appears as a yellow to
butterscotch discoloration on the inner bark surface or phloem. This
symptom initially appears under the bark of large roots, later spreading
to the base of the main stem and finally to the larger branches. Phloem
and cambial discoloration is often found in advance of the foliage
symptoms. The moderately discolored phlomen has a slight odor of
wintergreen. Thus far, all trees known to be infected with the pathogen
have died. Acutely infected trees, while initially appearing healthy,
may wilt and die in three to four weeks.

[Illustration: Stem sample showing discoloration of sapwood.]

No effective controls are known. The “Christine Buisman” elm, which is
highly resistant to Dutch elm disease, has demonstrated resistance to
elm phloem necrosis.

MIMOSA WILT

[Illustration: Mimosa branches showing wilt symptoms.]

A vascular wilt of the mimosa (silktree) is caused by the fungus
_Fusarium oxysporum forma perniciosum_. The fungus is known only to
attack the mimosa, a tree imported from eastern Asia and grown
throughout the southeast as an ornamental. Since the discovery of the
disease in North Carolina in 1935, the fungus has spread north to
Maryland, south to Florida, and west to Texas.

The fungus causing mimosa wilt is soil-borne and gains entrance into the
tree by attacking the roots. Once entrance is gained by the fungus, the
pathogen enters the outer water-conductive system in the sapwood. As the
fungus grows throughout the system, it hinders or completely inhibits
the water movement from the roots to the aerial portion of the tree. The
first outward symptom of disease is the wilting of leaflets, usually in
the upper portion of the crown. The wilted leaflets turn yellow, then
brown, and die. Often a branch or two will succumb at a time until the
entire crown is dead. A second symptom of the disease is found in the
outer sapwood of the tree. A brown discoloration, appearing as spots or
a ring, is observed by cutting into the outer sapwood of the infected
stem or branch.

Control of the fungus is very difficult, since it is soil-borne and
enters through the roots. However, resistant varieties of mimosa trees,
developed by the U.S. Department of Agriculture, are now available at
most commercial nurseries.

[Illustration: Branch sample showing brown discoloration of
sapwood.]

VERTICILLIUM WILT

Verticillium wilt, caused by common soil-inhabiting fungi belonging to
the genus _Verticillium_, is found on a number of hardwood hosts. In
southern and eastern United States elms and maples are attacked
throughout their natural ranges.

[Illustration: Wilting foliage and defoliation of elms caused by
Verticillium wilt.]

Infected trees may die within a few weeks after the first symptoms are
observed, or they may survive for years. The first symptoms of the
disease involve a wilting of the foliage, with the leaves turning yellow
and finally brown. The early symptoms are often restricted to a single
limb or portion of the crown. Vascular discoloration, which is brown in
elms and green in maples, is present in the outer sapwood. In elms, this
discoloration is similar to that produced in trees having Dutch elm
disease.

This disease is not of serious consequence in forest stands. However, it
is often extremely important in high value shade trees. Dead or dying
limbs on lawn trees may be pruned out. This may not always save the
tree, but may help keep it alive for years. Trees should be well watered
and fertilized as necessary. If a lawn tree dies from Verticillium wilt,
it should be replaced by a resistant species.

ARMILLARIA ROOT AND BUTT ROT

[Illustration: Mushroom or fruiting bodies of the “honey mushroom”
rot.]

Armillaria root and butt rot is caused by the fungus _Armillaria
mellea_. This disease is common in orchards, vineyards, gardens, parks,
and forests throughout the world. Both coniferous and hardwood forest
trees are attacked. The fungus is especially troublesome in plantations,
particularly in stands recently thinned.

The fungus is spread by spores produced by honey-colored mushrooms,
rhizomorphs, and root contacts between diseased trees or stumps and
healthy trees. Rhizomorphs are visible strands of compacted mycelium
(fungus material) that appear as black or reddish-brown “shoestrings.”
They may be flattened when found between bark and wood or cylindrical
when found in decayed wood or soil. Rhizomorphs increase in length at
their tips and in this manner the fungus may move through the soil from
infected trees to uninfected trees. The honey-colored mushrooms are
produced annually and are fairly short lived; they are subject to
desiccation, and are favored by small mammals. The size of the top
varies from two to five inches in diameter. The top is usually flecked
with dark brown scales. White to light yellow gills are borne
underneath. Crown symptoms of the trees affected are similar to those
caused by any malfunctioning of the roots. A reduction in size and
production of leaves or needles, a general thinning of the crown, branch
dying, and yellowing of foliage may precede death or trees may die
rapidly with a rapid red discoloration of the foliage. Trees often die
in groups, but single-tree kill is also common. Cankers bleeding resin,
gum or other exudate at the tree base are common symptoms.

Control is not attempted for this disease under forest conditions.
Losses may be reduced by following proper planting procedures, and by
salvage cutting.

[Illustration: Shoestrings of armillaria.]

CYLINDROCLADIUM ROOT ROT

This nursery disease is caused by two fungi species. _Cylindrocladium
scoparium_ and _C. floridanum_: Cylindrocladium root rot has been found
on two hardwoods (yellow-poplar and black walnut) and two conifers
(white pine and Fraser fir) in forest tree nurseries in six southern
states. These include Virginia, West Virginia, North Carolina,
Tennessee, Alabama, and Mississippi.

[Illustration: Leaf symptoms on 1-0 black walnut nursery stock.]

Root rot symptoms on hardwoods and conifers are quite different. The
most characteristic root symptoms on yellow-poplar and black walnut are
the blackened and longitudinally-cracked infected roots that are in
sharp contrast with healthy white roots of these two species. Infected
seedling leaves become yellow and later turn reddish-brown.

Root rot symptoms on conifers involve either rotting of the seed or
seedling (pre-emergence damping off) before emergence from the soil or
seedling root rot following emergence. These symptoms also involve a
shrivelling and reddening of foliage, needle blight, and stem cankers.
The most characteristic symptoms are the “patchy” irregularly scattered
pattern of infection in conifer seedling beds and the loosening of the
root epidermis on infected roots—making it very easy to pull off.

[Illustration: Root symptoms on 1-0 yellow-poplar nursery stock.]

The most practical and effective control for root rot diseases of this
type involves strict quarantine to either keep the disease out of the
nursery or keep it confined to known infected areas by avoiding the
transportation of root material, organic matter, and soil from infected
to non-infected seed beds. Soil fumigation may control this disease if
applied under favorable conditions.

LUCIDUS ROOT AND BUTT ROT

[Illustration: Fruiting body of Lucidus root and butt rot on
mimosa.]

_Polyporus lucidus_ is the cause of root and basal stem decay of
hardwood trees throughout the eastern, central, and southern portions of
the United States. The fungus is known to attack and kill maple,
hackberry, orange, lemon, ash, sweetgum, oak, locust, elm, tupelo,
willow, and mimosa. Mimosa trees are very susceptible to attack by _P.
lucidus_ throughout the South.

The disease is characterized by a rapid decline and death of the host.
Examination of infected roots will reveal a soft spongy white rot with
black spots scattered throughout. Fruiting bodies are formed at the base
of infected trees or on the surface of exposed roots. The mature
fruiting bodies are a reddish brown above and white below, with the tops
and stems appearing glazed or varnished. The fungus is believed to gain
entrance into the host through bark and root injuries and can spread
from infected to healthy trees through root contacts and grafts.

No control is known for this disease. Avoidance of lawnmower and other
mechanical injuries to the base of roots of susceptible shade trees will
reduce the chance of infection by the fungus. The spread of the disease
from infected to healthy trees can be reduced by planting at a wide
enough spacing to avoid root contacts and grafts.

_If you find damage on your trees from insects or diseases you may
consult with any of the following offices or your state forester._

FIELD OFFICES:
_Alexandria Office_
U.S. Forest Service
2500 Shreveport Highway
Pineville, Louisiana 71360
Phone A/C 318 445-6511 Ext. 311
FOR STATES OF:
Alabama
Arkansas
Louisiana
Mississippi
Oklahoma
Texas
_Asheville Office_
U.S. Forest Service
P.O. Box 5895
Asheville, North Carolina 28803
Phone A/C 704 254-0961 Ext. 625
FOR STATES OF:
Florida
Georgia
Kentucky
North Carolina
South Carolina
Tennessee
Virginia
_AREA OFFICE_
Group Leader
Forest Pest Management Group
U.S. Forest Service
1720 Peachtree Street, N.W.
Atlanta, Georgia 30309
Phone A/C 404 526-3734

[Illustration: Forest Environment: WEATHER FIRE PEOPLE SOIL ABUSE
PESTS]

FOREST PEST MANAGEMENT GROUP

Southeastern Area S. and P. F.—7 1972

Transcriber’s Notes

—Silently corrected a few palpable typos.

—In the text versions, delimited italics or underlined text in
_underscores_ (the HTML version reproduces the font form of the
printed book.)

*** End of this LibraryBlog Digital Book "Insects and Diseases of Trees in the South" ***

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