Insects and Diseases of Trees in the South

Part 1

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.

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.

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.

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.

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.

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.

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.

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.

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.

Part 2

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.

Continue reading Insects and Diseases of Trees in the South free in the Wunder reader →