Produced by Stephen Hutcheson, Dave Morgan and the Online Distributed Proofreading Team at http://www.pgdp.net INSECTS AND DISEASES OF TREES IN THE SOUTH U.S. Department of AgricultureâForest Service State and Private ForestryâSoutheastern 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 âinchwormâ or âlooperâ, approximately 1Â½ 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 1Â½ 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 insectâs 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 1Â¼ 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 treeâs 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 1Â¾ 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 1Â½ 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 Â¼-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 walkingstickâs 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 1/32â³ to 1/16â³ 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 treeâs 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. âCradlesâ (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 1Â¼ to 1Â½ 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 â  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 âovipositorâ 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 â  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 1920âs. 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 antâs 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 âscooped outâ posteriors which are surrounded by varying numbers of tooth-like projections. It takes only
{'title': 'Insects and Diseases of Trees in the South by Anonymous', 'source': 'Project Gutenberg', 'lang': 'en'}