The Bugwood Network

Forest Pest Control

Douce, G.K., Moorhead, D.J., and Bargeron, C.T., Forest Pest Control, The University of Georgia, College of Agricultural and Environmental Sciences, Special Bulletin 16, Revised January 2002.

Insects

Insects are the most destructive agents affecting forest and shade trees in the South. Tree roots, stems, limbs, needles, leaves of healthy or weakened trees, or logs waiting to be sawed into lumber are all subject to attack. Insects (Class: Insecta) are by far the most numerous animal life inhabiting the forest. They have become well adapted to their surroundings and occupy a wide variety of ecological niches. Although the majority of insect species are either beneficial or innocuous, some are exceedingly harmful. Insect outbreaks that cause economic damage to forests vary greatly in frequency, size and duration. Fortunately, most outbreaks are small and short-lived, and usually consist of one or a few spots in a stand or region. Others, however, may expand and encompass hundreds or thousands of acres and can last for several years.

Managers can reduce the risks and incidence of insect attack by maintaining healthy and vigorously growing stands and trees. Research is being conducted to determine what conditions are conducive to forest insect outbreaks. This research may lead to improved control measures.

Losses Caused by Forest Insects

These data are summarized from Special Bulletins published annually by The University of Georgia, College of Agricultural and Environmental Sciences, Department of Entomology, Insect Survey and Losses Committee. These figures have not been adjusted for inflation.

Estimated Average Yearly Losses and Control Costs of Forest Insects in Georgia
Rank Insect Cost of Control Damage Loss Total Cost
1. Southern pine beetle $317,600 $4,680,400 $4,998,000
2. Pine tip moths1 $916,000 $2,310,000 $3,226,000
3. Defect & degrade2
causing insects
$90,000 $2,874,000 $2,964,000
4. Seed & cone3 insects $80,400 $2,514,200 $2,594,600
5. Ips spp. beetles4 and
black turpentine beetle
$485,000 $2,016,400 $2,501,400
6. Reproduction weevils5 $1,153,000 $928,000 $2,081,000
7. Other insects6 $83,800 $1,215,000 $1,298,800
8. Gypsy moth $94,000 $-- $75,200
  Totals $3,201,000 $16,538,000 $19,739,000

1 Includes Nantucket pine tip moth and pitch pine tip moth.
2 Includes carpenter ants, ambrosia beetles, lepidopterous oak borers, shothole borers and various other cerambycid,
   buprestid and scolytid beetles.
3 Includes coneworms, seedworms, seed bugs and cone beetles.
4 Ips avulsus, I. grandicollis, I. calligraphus and I. pini.
5 Pales weevil and pitch-eating weevil.
6 Primarily aphids, scale insects, sawflies and lepidopterous hardwood defoliators including eastern tent caterpillar, forest
   tent caterpillar, fall webworm, oak skeletonizer and various Anisota spp.

Bark Beetles

Bark beetle populations vary tremendously between years and between locations. The important bark beetles in the South attack pines and belong to the Family Scolytidae. However, some species such as the native elm bark beetle Hylurgopinus rufipes, the small European elm bark beetle Scolytus multistriatus (Marsham), and the hickory bark beetle S. quadrispinosus Say are hardwood pests. The remainder of this bark beetle discussion will be about southern pine beetles, black turpentine beetles and Ips engraver beetles that attack southern pines.

Large numbers of attacking bark beetle adults can often overwhelm a tree’s natural defenses, lay eggs and successfully initiate an infestation. After the eggs hatch, the grub-shaped larvae can girdle the tree by feeding under the bark. Blue-stain fungi are also carried on the bodies of most species and introduced into the tree during adult attack. Proliferation of these introduced fungi in the water-conducting tissues hastens the death of the infested trees.

Pines under stress are particularly susceptible to bark beetle attacks, especially if beetle outbreak conditions exist. Bark beetle attacks can be recognized by boring dust and pitch tubes on the outside of the bark, characteristic galleries under the bark, and adult beetles and larvae in the inner bark. After a tree is successfully attacked, the foliage fades from bright-green to yellowish-green to red. These “faders” are generally the first apparent sign of a bark beetle attack. Unfortunately, foliage color change often does not occur until well after the tree is dead and the beetles have completed their development and have left the tree.

Bark beetle brood development time ranges from 25 to120

Figure 1. The southern pine bark
beetles. Top to bottom: Ips avulsus,
Ips grandicollis, Ips calligraphus,
Dendroctonus frontalis
(SPB),
Dendroctonus terebrans
(BTB),
Gerald J. Lenhard, LSU.

Figure 2. Sections of the trunk which
three types of bark beetles attack.
days, depending upon species and temperature. It is common for more than one species of bark beetles to infest individual trees. Since many other insects are associated with dead and/or dying trees, make positive identification of the insects before you take any remedial actions.

Reduce the potential for bark beetle attack by ensuring that trees are rapidly growing and healthy. Removing or treating lightning and storm damaged trees promptly and maintaining proper stand densities can reduce the likelihood of bark beetle attack. For specific management and control practices, contact your county Extension Service agent or State Forestry office.

Southern Pine Beetle
The southern pine beetle (SPB), Dendroctonus frontalis Zimmermann, is the most destructive of the eastern species of pine bark beetles (Figures 1-5). It is a small reddish-brown to black beetle, about 1/8 of an inch long. The rear end of the body is rounded. SPB normally infest boles of trees from the base to the crown, with initial attacks at mid-bole or higher. The life cycle generally requires 35-60 days to complete. There may be up to six generations per year. Small pitch tubes, usually less than 2 inch in diameter, are often present at the site of adult attacks.

Adult SPB bore directly through the bark and mate. The females excavate the characteristic S-shaped, crisscrossing egg galleries in the inner bark. Eggs, which are deposited in niches on either side of these galleries, hatch into small, legless grubs within 4-9 days. The grubs mine for a short distance before boring into the outer bark where they pupate. Galleries are usually filled with larval fecal material and boring dust. Soon after a tree is attacked, all the needles turn yellow and then brown. Drought seems to trigger major outbreaks of this insect. In addition to direct damage caused by the larval feeding, SPB introduce stain-causing fungi, which invade the tree and hasten death. Once southern pine beetles have successfully infested a tree, no remedial treatments are available to prevent the death of the tree.

Black Turpentine Beetle
The black turpentine beetle (BTB), Dendroctonus terebrans (Oliver) is the largest of the major southern bark beetles (Figures 1-2, 6-7). It is ¼ of an inch or more in length, with a rounded rear end, and is reddish-brown to black in color. Large purplish colored pitch tubes (50 cent piece in size) are often present at the site of adult attacks. BTBs

Figure 3. Southern pine beetle: pine killed by
beetle with blues stain fungus, a cross section
of log, Ron Billings, Texas Forest Service.

Figure 4. Southern pine beetle: 'S'
shaped galleries under bark,
Ron Billings, Texas Forest Service.

Figure 5.Southern pine beetle pitch tubes on loblolly pine, Jim Meeker, Florida Dept. of
Agriculture and Consumer Services.
attack fresh stumps and living trees by boring through the bark and constructing galleries on the face of the sapwood where 50-200 eggs are laid in a group. BTBs attacks usually only occur on the trunks of trees up to a height of eight feet. After hatching, the white larvae feed on the inner bark. Unlike southern pine beetles and Ips engraver beetles, black turpentine beetles do not introduce blue stain fungi into the tree and developing larvae feed in “patches” rather than completely encircling the tree. However, when several broods occur at about the same height, the feeding larvae may completely girdle and kill the tree. Without prompt treatment, from 70 to 90 percent of the trees attacked by the BTB die. The BTB life cycle takes from 2 ½ to 4 months, depending on the temperature. In the South, there are usually two generations and part of a third each year.


Figure 6. Black turpentine beetle larval
feeding patch, NC State University Archives.
Figure 7. Black turpentine beetle
pitch tube, NC State University Archives.

Ips Beetles
The four species of Ips beetles commonly found in the South (Ips grandicollis, I. calligraphus, I. avulus, and I. pini) vary from 1/10 to ¼ of an inch long, and are yellowish, dark reddish-brown to black (Figures 1-2, 8-10). They are easily recognized by their scooped out posteriors which are surrounded by varying numbers of tooth-like projections. In hot weather, it may take as few as 25 days to complete one generation. Populations of these beetles increase rapidly during favorable conditions. Ips spots usually contain only one to a few trees killed, but under favorable conditions Ips can become epidemic and kill many trees. The fully grown, grublike larvae are yellowish-white and vary from ¼ to 1/3 inch long. Gallery patterns are more or less Y- or H-shaped except for I. avulus, which deviates from these patterns. Small, white eggs are laid singly in small egg niches cut along the main tunnels. Larval feeding tunnels are usually filled with boring dust and frass (excrement).

Adults girdle trees quickly as they construct their egg galleries in the inner bark. The tree’s 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 an attack. These tubes are usually absent in trees suffering from drought. As with SPB, once Ips beetles have successfully infested a tree, the tree cannot be saved!

Pine Bark Beetle Control

Several methods reduce the likelihood of expanded attacks by bark beetles. Most of these are based on good silvicultural practices to keep trees rapidly growing or by reducing stress on trees. Techniques currently used are:

Figure 8. Ips avulsus adult and larval
galleries, Ron Billings, Texas Forest Service.

Figure 9. Eastern fivespined Ips adult and
larval galleries, Gerald J. Lenhard, LSU.

Figure 10. Ips pini gallery on small pine,
David McComb, USDA Forest Service.
  • Prompt removal (and/or treatment) of trees damaged by lightning, storms or by construction
  • Salvage removal
  • Cut and leave
  • Pile and burn
  • Insecticide treatments
  • Cut and spray
  • Behavioral modifying chemicals

Prompt Removal of any damaged trees, whenever possible, significantly reduces the likelihood of successful bark beetle attacks. Since bark beetles are attracted to odors exuded from damaged trees, initial attacks in an area often occur on damaged trees. As the beetle brood matures and exits the infested tree, the infestation frequently expands to other trees in the area.

Salvage Removal is only feasible when a relatively large volume of wood is available and makes the operation cost effective for the logger. Prompt removal of dead and dying trees is essential to prevent significant degradation of the wood. Steps involved in a successful salvage removal operation include:

  1. the removal of a 50-100 feet wide buffer strip of green uninfested trees around the most recently attacked trees;
  2. removal of recently attacked trees containing developing beetle brood; and
  3. removal of older standing trees from which the brood has already emerged.

Cut and Leave is best for controlling small spots of trees (10-50) when salvage is not practical or cost effective. Attacked trees and a border of healthy trees are felled toward the center of the spot. It is helpful to cut the limbs on the underside of the felled trees so that the trunks are lying on the ground. The increased sunlight and subsequent higher temperatures, along with increased humidity resulting from the trunks lying on the ground, are thought to cause high mortality of the developing brood.

In Pile and Burn, trees with live brood are felled, piled and burned. Although effective, this technique requires heavy equipment to pile the trees so that they can be burned. Additionally, managers must be aware of appropriate weather conditions and prescribed fire and smoke management issues.

Insecticides in bark beetle control are more preventative than corrective. Consequently, with the possible exception of the BTB which does not introduce blue-stain fungi into the tree, trees that have been successfully attacked by bark beetles cannot be saved by insecticide applications. However, bark beetles still in or under the bark can be killed by spraying the tree with appropriate insecticides to prevent spread of the attack. Additionally, non-infested high value trees, judged to be at high risk, can be sprayed with an insecticide as a preventative measure against attack. The area of the tree requiring insecticide treatment depends upon the insect species for which the application is being made. The appropriate area of the tree should be thoroughly wetted with the insecticide spray mixture.

Applications made for BTB only require that the lower 8-10 feet of the main bole be treated and can be accomplished with a small hand or backpack sprayer. If applications are being made for SPB or any of the Ips beetles, spray to wet the entire bole of the tree from ground level up to the upper crown, including the base of large scaffold limbs. On larger trees, this requires high-pressure sprayers for thorough coverage.

A Cut and Spray method may stop further spread of bark beetle attack. If beetle infested trees can be felled but cannot be hauled from the site or burned, they can be limbed and bucked into workable lengths. Once cut into workable lengths, the tree sections can be turned as they are thoroughly sprayed with an appropriate insecticide.

Behavioral Chemicals are being tested by researchers to develop SPB control tactics by manipulating the various chemicals that the beetles (and their natural enemies) use to orient, attack or disperse their populations. To date, these promising, nonpesticide-based tactics are not yet ready for large scale field implementation.

Boring Insects

Included in this group are the insects that infest terminals, shoots, twigs and roots of living trees as well as those that obtain food and shelter from wood. Terminal and shoot insects are of particular importance in the initial stages of forest regeneration and early stand growth. These insects are also of great importance in forest nurseries and ornamental trees. We will discuss in detail the Nantucket pine tip moth, and the white pine and deodar weevils which are frequently encountered in and cause significant damage to pine stands in the South.

Other insects in this category damage or destroy trees that would otherwise produce quality lumber or other wood products. Most insects that cause this damage are borers, either adult or larval stages or both. Most borers are secondary invaders, attacking bark and wood of trees that are seriously weakened, dying, or recently cut. Carpenterworms, ambrosia beetles, oak clearwing borers, metallic wood borers, Columbia timber beetles and southern pine sawyers are some of the pests that cause damage in this category. Trees attacked by these pests are usually scattered so that most control measures are difficult and not economically feasible. Additionally, there are several species of insects that attack, infest and damage wood and wood products that are discussed in the Wood Treatment manual and in other manuals devoted to Pest Control Operator training and are not covered in this manual. Included among the wood product pest group are certain beetles in the family Cerambycidae (notably, the old house borer Hyloupes bajulus), ambrosia beetles (Scolytidae and Platypodidae), and the powderpost beetle complex (includes members of the Families Lyctidae, Anobiidae, and Bostrichidae).

Nantucket Pine Tip Moth
The Nantucket pine tip moth, Rhyacionia frustrana (Comstock), and its close relative the subtropical pine tip moth, R. subtropica Miller are widely distributed in the southern states (Figures 11-13). The importance of pine tip moths on pine and Christmas tree plantations and nurseries 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. All species of pines are attacked except white and longleaf pines, but slash pine is rarely attacked. Loblolly, Virginia and shortleaf pines are most susceptible.

The adult moth is mixed gray and shiny copper-colored, with a wingspan of about ½ inch. The young larvae are light cream-colored, while mature larvae are light brown and approximately 3/8 inch long. Pupation occurs on the tree in the damaged terminal. Adults begin to emerge on warm days in early spring and begin laying eggs in a few days. Eggs are deposited on needles, stems, developing tips or buds. After hatching, larvae first feed on needle fasicles, then bore into terminals and lateral shoot buds, and finally into stems. The larval period lasts from two to four weeks. There are usually three to four generations per year.

Insecticide spraying for tip moth control has not been a general practice, except in Christmas tree plantations, seed orchards, forest nurseries, and research and progeny tests. However, tip moth control is increasingly becoming a component of intensive short-rotation pine plantation management. Effective control requires that insecticide applications coincide with egg hatch and larvae emergence. Trapping or monitoring moth emergence to predict egg hatch and larval development is the critical element in a tip moth control program.

Figure 11. Nantucket pine tip moth
larva feeding at base of needles,
David J. Moorhead, UGA.

Figure 12. Nantucket pine tip moth damage to
pine terminal, Ron Billings, Texas Forest Service.

Figure 13. Nantucket pine tip moth on
loblolly pine needle, James A. Richmond,
USDA Forest Service.

Weevils

The snout beetles (Coleoptera: Curculionidae) are a diverse and abundant group of insects. Many weevils are important destructive pests of agricultural, horticultural and forest crops. Weevil larvae are creamy-white and legless, with brown head capsules. Adults are hard-bodied, cylindrical beetles with a pronounced “snout” that contains hardened, chewing mouth parts at the end.

The two most common species of boring pine weevils in the South are the white pine weevil, Pissodes strobi (Peck), and the deodar weevil Pissodes nemorensis Germar. Weevils in the genus Curculio attack the seeds of nut-bearing trees, most notably acorns, but several species are important pests on hickory, chestnut, and pecan. During certain years, the nut crop can be almost completely destroyed. In addition to the species listed, there are many other species of weevils that are important in forest environments.

White Pine Weevil
The white pine weevil is the most serious pest of eastern white pines in the South (Figures 14-15). This weevil can also feed on and reproduce on a variety of spruce and pine species. Adult weevils are 1/6 - ¼ inch long, brownish and marked with irregular gray-white patches. Adults overwinter in litter under the trees. The adults emerge from hibernation in the spring and begin feeding on cambial tissues of the main stems of the host plant, usually within 1 inch of the terminal bud. The female lays eggs in feeding pits on the terminals. After hatching, the larvae tunnel downward in the cambium. This feeding girdles and kills the leader. Mature larvae pupate in chambers formed in the wood. Adults emerge throughout the summer. Only one generation per year has been reported.

The first sign of white pine weevil attack is pitch flow from feeding punctures on the terminal shoots. Later the new growth appears stunted, and finally, the needles wilt and the terminal dies. Trees up to 3-4 feet tall may be killed. Dead terminals on larger trees are replaced by one or more branches of the topmost living whorl, resulting in crooked or forked stems. Management practices for the white pine weevil include: 1) mixed planting of white pines with hardwoods or planting white pines under hardwood cover; 2) planting only on soils where the hardpan is three or more feet below the surface; 3) selecting and pruning the least injured pines in preparation for later harvest; and 4) removal of less desirable pines from damaged stands. Drenching susceptible trees with pesticide sprays as

Figure 14. White pine weevil adult, E.
Bradford Walker, Vermont Dept. of
Forests, Parks, and Recreation.

Figure 15. White pine weevil
damage to terminal, E. Bradford
Walker, Vermont Dept. of
Forests, Parks, and Recreation.
adult weevils emerge from hibernation can provide some protection. Insecticide sprays are used to protect white pines grown for Christmas trees from damage.

Deodar Weevil
The deodar weevil attacks most species of pines and many introduced cedars (Figures 16-17). These weevils cause damage by feeding on young shoots in the crowns of sapling and pole-sized trees. Both adults and larvae kill terminals and cause branch-end flagging on pole-sized and small sawlog size trees. Adults are active and lay eggs all winter. The adult weevil is about ¼ inch long, grayish-brown to dark brown with whitish spots on the wing covers. Adults are attracted to weakened, stressed or dying trees. They often breed in logging slash and trees killed by bark beetles. Adults chew holes and feed on the inner bark and wood of twigs and leading terminals. After chewing through the bark, females deposit eggs in the inner bark of host trees. Following egg hatch, the larvae feed beneath the bark much like white pine weevils, girdling and often killing the stem. Evidence of their presence is indicated by swelling of the bark over feeding areas. Pupation occurs in chip cocoons in the sapwood beneath the bark. Adults apparently become inactive (aestivate) during the summer months but appear again in the fall to feed on twigs and leading shoots. May is the month of greatest adult emergence.

Figure 16. Deodar weevil pupa in
chip cocoon, Gerald J. Lenhard, LSU.
Figure 17. Deodar weevil
adult, Gerald J. Lenhard, LSU.

Chewing Insects

This grouping, based upon USDA Forest Service Pest Trend Impact Plot System, feeds on stems and shoots but does not include the leaf-eating insects, or borers. The more important members of this group in the South are the reproduction weevils which will be covered here.

Reproduction Weevils
The pales weevil, Hylobius pales (Herbst), and the pitch-eating weevil, Pachylobius picivorus (Germar), are very destructive pests of young pines (Figures 18-20). They feed and develop on all species of pines within their range. Adult pales weevils are ¼ - 1/3 inch long with patches of yellow hairs appearing as bars across the wing covers. Pitch-eating weevils are slightly larger (1/3 - ½ inch) with yellowish spots on the wing covers. They spend the winter as adults in the soil. Overwintering adults emerge during the spring and feed on the bark of saplings and at the bases of seedlings. Most damage occurs in the spring and fall. These weevils feed at night and hide in the soil around the base of seedlings during the day. After feeding, females lay eggs on roots of recently cut, damaged or killed pines. Larvae burrow and feed on root tissue and later pupate in chip cocoons under the bark.

Figure 18. Pales weevil adult, Wayne N. Dixon,
Florida Dept. of Agriculture and Consumer Services.
Figure 19. Pitch-eating weevil adult and feeding
damage, Robert L. Anderson, USDA Forest Service.

Damage or death of pine seedlings often occurs when adults of these weevils eat patches of bark from the stems. When feeding areas overlap, the seedling is girdled. Christmas tree plantations are sometimes seriously damaged by these weevils. The most practical and economical method of controlling damage is to delay planting in areas harvested after June for at least one year. If planting cannot be delayed, chemically control reproduction weevils by root dipping seedlings in an insecticide and kaolin clay mixture, top dipping of seedlings, or over-the-top spraying of seedlings prior to lifting in the nursery or after transplanting.

Figure 20. Pitch-eating weevil adult feeding, Wayne N. Dixon, Florida Dept. of Agriculture
and Consumer Services.

Defoliating Insects

Included in this group are insects that eat leaves and needles. There is a diverse and broad array of insects that includes the many caterpillars, sawflies, leafcutting wasps, bees and ants, beetles and walkingsticks. Trees attacked by defoliators can be recognized by missing foliage and uneaten leaf parts such as veins and petioles. Additionally, many members of this group feed within a leaf, mining between the upper and lower epidermis. Defoliation reduces photosynthesis, interferes with transpiration and translocation within the tree. Light defoliation normally has little affect on the tree, but moderate-to-heavy or repeated defoliation can reduce tree vigor. The impact that defoliation has on a tree depends upon the time of the year, the tree species, tree health, and whether defoliation occurs more than one time. It is important that the manager properly identifies the organism(s) involved and clearly understands the dynamics of both the forest stand and the insect involved before any management scenario is developed and implemented. Only a few examples of the insects that make up this diverse grouping are discussed here.

Gypsy Moth
When it is present, the European gypsy moth, Lymantria dispar (Linneaus), is one of the most destructive hardwood forest pests (Figures 21-23). A native of Europe, the gypsy moth was accidentally introduced into the U.S. in New England in the late 1800s and has gradually spread into at least 17 eastern states, as well as into other parts of the U.S. and Canada. The generally infested area now includes all of the northeastern states and portions of West Virginia, Virginia, Michigan and Ohio.

Between 1982 and 1996 in the U.S., gypsy moth defoliation ranged from less than 1 to more than 8 million acres per year. Female European gypsy moths are incapable of flight but are prolific egg layers. Females lay eggs in masses in trees and on lawnmowers, outdoor furniture, mobile homes, recreational vehicles, firewood, building materials, doghouses, and other items left outdoors. New gypsy moth infestations occur through inadvertent transport of egg masses and pupae. Local infestations can spread as small larvae move from one site to another on air currents for distances of a few feet

Figure 21. Gypsy moth larva, James
A. Copony, Virginia Dept. of Forestry.
to several miles.

Figure 22. Gypsy moth females and egg
masses, John H. Ghent, USDA Forest Service.
Figure 23. Gypsy moth defoliation,
Mark Robinson, USDA Forest Service.

The female gypsy moth is heavy bodied, almost white with a wingspan of about 2 inches. The male is dark brown, with blackish bands across the forewings, and has a wingspread of about 1 ½ inches. Full-grown larvae are from 1 ½ to 2 ½ inches long. Older larvae have yellow markings on the head, a brownish-gray body with tufts of hair on each segment, and a double row of five pairs of blue spots followed by a double row of six pairs of red spots on the back. Moths are harmless, but the caterpillars from which they develop are voracious leaf feeders of forest, shade, ornamental and fruit trees and shrubs. Large numbers of caterpillars can completely defoliate an area. A single defoliation can kill some softwoods, but it usually takes two or more defoliations to kill hardwoods. Large infestations contain millions of caterpillars and can degrade aesthetic and recreational values of forests, parks and wooded homesites. The number of trees killed as a direct result of gypsy moth defoliation is relatively small, but many trees are weakened and become susceptible to secondary attack by other insects or plant diseases.

A U.S. Department of Agriculture Federal Domestic Quarantine (7CFR 301.45 gypsy moth) regulates transport of firewood, lumber, and many other outdoor items from infested areas to non-infested areas to prevent or reduce the likelihood of gypsy moth transport. A nationwide, cooperative state-federal monitoring program based on the use of large numbers of pheromone traps continues to monitor for accidental introductions of gypsy moths. The pheromone traps are effective in capturing the highly mobile adult males and are a good tool to monitor low-level gypsy moth populations. Control of newly developed “spots” detected by this monitoring program in southern states in recent years has been effective. Without this regulatory action, the gypsy moth would undoubtably infest an area much larger than the current areas.

Despite the quarantine efforts, isolated infestations of gypsy moth have occurred in the southeast in North Carolina, Tennessee, Arkansas, and Georgia. As these isolated infestations were found, comprehensive eradication projects, as mandated by federal law, have been undertaken.

During the past 80 years, many people have tried to control gypsy moth populations by introducing parasites into infested areas with limited success. Ongoing research on the use of viral and fungal diseases show promise for controlling the gypsy moth. In particular, a fungus introduced on several occasions over the last 80 or so years, appears to have increased in virulence or otherwise become widespread and extremely effective on reducing gypsy moth populations in recent years. This

fungus, Entomophaga maimaga, has been reported to have significantly reduced gypsy moth populations in much of New England and Pennsylvania. We can only hope that the impact of this fungus continues to increase.

Aerial spray programs of an approved insecticide are still an important component of gypsy moth control programs in infested areas (Figure 24). Large acreages of forests and urban ornamental trees in infested areas are treated aerially with chemical and biological insecticides each year to reduce potential damage by this pest.

Figure 24. Spraying Bt. by helicopter
for gypsy moth, G. Keith Douce, UGA.

Sawflies
Several species of sawflies (Hymenoptera: various families) can be serious defoliators of conifers in both forest and plantation stands. Sawfly adults are small broad-waisted wasps. Larvae resemble caterpillars but are usually without hairs and have five or more pairs of fleshy prolegs under their abdomen (caterpillars normally have four or fewer pairs). Larvae of the more commonly found sawflies vary from 2/3 to 1 ¼ inches long, are usually greenish to dusky gray, and have conspicuous stripes or spots. Outbreaks occur periodically, sometimes over large areas, and can result in loss of tree growth and sometimes tree mortality.

Redheaded Pine Sawfly
The redheaded pine sawfly, Neodiprion lecontei (Fitch), is one of the more commonly found and most destructive sawflies in the Southeast (Figure 25-26). Red headed pine sawfly larvae are usually found on trees from 1-15 feet tall, where they feed gregariously on old and new needles and on tender shoots of these young trees. Full-grown, redheaded pine sawfly larvae are about ¾ to 1 ¼ inches in length; have a reddish head capsule and a yellowish-white body marked with six rows of black spots. Many times a naturally occuring virus causes collapse of an infestation. Occasionally, controls are warranted during heavy population peaks. Depending upon the size of the infestation, these treatments may be applied aerially or by ground equipment.

Figure 25. Redheaded pine sawfly
larvae, Gerald J. Lenhard, LSU.

Figure 26. Redheaded pine sawfly adult female oviposition, James McGraw, NC State University.

Pine webworm
The pine webworm, Tetralopha robustella Zeller, may become a problem in pine plantations (Figure 27). The adult moth has about a ¾-inch wingspan. The basal part of the forewing is purple-black, the central part grayish, and the outer part blackish. Full-grown larvae are yellowish brown, with two dark brown longitudinal stripes on each side and are about ¾ inch long. Pine webworms overwinter as pupae in the soil. Adults emerge in late spring to early summer and deposit eggs on the needles. Young larvae mine needles, while older larvae live in silken tubes that extend through webs of globular masses of brown, coarse frass. These webbing masses enclose the needles upon which the larvae feed. At first, the webbing masses may be only one or two inches long. The webbing mass may contain several larvae and increases in size as the larvae mature. Seedlings up to two feet tall can be completely

Figure 27. Pine webworm
damage, Robert L. Anderson,
USDA Forest Service.
defoliated. Infestations on larger trees can cause partial defoliation resulting in loss of growth and poor tree appearance.

Usually no controls are necessary unless extremely heavy populations are encountered or individual specimen trees are involved. Individual infestations can be destroyed by hand. If controls are required, the larvae are easily controlled by labeled insecticides, but good spray coverage and pressure are needed to penetrate the webs.

Fall webworm
The fall webworm, Hyphantria cunea (Drury), can have two or more generations per year. Webworms enclose leaves and small branches in their light gray, silken webs (Figures 28-29). Fall webworm is known to feed on more that 100 species of forest and shade trees. In the eastern U.S., pecan, walnut, American elm, hickory, fruit trees, and some maples are preferred hosts. The moth is white with dark wing spots and has a wingspan of between 1.4-1.7 inches. Though the webs are unsightly, damage to most trees is considered to be insignificant and is usually of only minor economic importance as a forest pest. However, in areas where heavy defoliation occurs, including in pecan production areas, control measures may be needed.

Figure 28. Fall webworm larva, James
B. Hanson, USDA Forest Service.
Figure 29. Fall webworm webbing,
Ron Billings, Texas Forest Service.

Oakworms
The three common species of oakworm found in the South are the orangestriped, Anisota senatoria

(J.E. Smith); the pinkstriped, A. virginiensis (Drury); and the spiny, A. stigma (Fabricius). Oakworms occur throughout the eastern U.S., are voracious feeders, and when abundant quickly strip trees of their foliage. However, since defoliation usually occurs late in the summer or into the fall, their economic impact is relatively minor. Orangestriped oakworm larvae are black with eight narrow yellow stripes; pinkstriped oakworms are greenish-brown with four pink stripes; and the spiny oakworm is tawny with pinkish short spines. Larvae have a distinctive pair of long, curved “horns” on the dorsum behind the head.

Eastern tent caterpillar
The eastern tent caterpillar, Malascoma americanum (F.), is primarily an aesthetic problem (Figures 30-31). Species of the genus Prunus are preferred hosts, with black cherry being the preferred non-cultivated host. Full-grown larvae are between 2 to 2 ½ inches in length, have black heads and long light-brown body hairs. The back has a light stripe bordered on each side with yellowish-brown and black wavy lines. The sides are marked with blue and black spots. Eastern tent caterpillar overwinter as eggs in shiny, dark brown masses around small limbs on host trees. Eggs hatch in early spring, and the larvae begin to construct a tent and enlarge the structure as they feed and grow. Chemical controls are usually not justified. Defoliated trees normally refoliate and suffer only minor growth loss.

Figure 30. Eastern tent caterpillar
larvae, Gerald J. Lenhard, LSU.

Figure 31. Eastern tent caterpillar
tent in tree branches, Robert L.
Anderson, USDA Forest Service.

There are numerous other defoliating insects that will not be covered here.

Sucking Insects

This group of insects has piercing-sucking mouthparts which they use to pierce plant tissues and suck sap from the plant. Insects in this group that attack trees are in the Orders Homoptera and Heteroptera. In addition to these insects, many species of mites in the Class Arachnida: Order Acari also feed on plants. Only a few species of sucking insects kill forest trees directly. Among the observable symptoms of feeding by sucking insects are 1) discoloration of needles or leaves, 2) curled foliage, 3) honeydew and sooty mold on leaves, stems, twigs and other materials, 4) fine silk webbing on the needles and leaves, 5) premature leaf drop, 6) branch mortality, 7) oviposition scars made by cicadas and treehoppers, and 8) galls. In addition to their direct feeding damage, some sucking insects are vectors of plant diseases. Many of these insects are individually quite small and are frequently transported on nursery stock. As before, we will only discuss a few of the major forest pest species that make up this complex group.

Scale insects
A number of species of these small sucking insects are important in forest environments (Figure 32). Adult females lack wings, may not have legs, and are saclike with no definite body segmentation. Adult males are more insect in appearance, usually with one pair of wings and with a definite head, thorax and abdomen. Most scale insects produce a waxy substance that covers the body either as a shield-like structure or as a coating on the body surface. Natural dispersion is usually by windborne, first instar “crawlers” that are equipped with legs and can be quite mobile. In most cases, instars other than

Figure 32. Pine needle scale infestation
on foliage, James B. Hanson, USDA
Forest Service.
crawlers are generally sessile (do not move). The small size and cryptic appearance of many scale insects has greatly helped disperse many scales inadvertently as contaminants on plants transported during commerce. Scale insects damage plants by inserting their sucking mouthparts in plant tissue and ingesting large amounts of plant sap. Scale insects also excrete large amounts of honeydew which serves as a substrate for the growth of sooty mold. Plant deformation and toxin injury are produced by some species of scale insects. Natural enemies are frequently important in regulating scale insect populations. Scale insects occasionally become a problem in pine seed orchards where other pesticide applications have eliminated or reduced natural predator and parasite populations. Important groups of scale insects in forestry include mealy bugs, soft scales, armored scales and Kermes scales.

The scale life stage most susceptible to chemical control is the first instar crawler stage. During this part of their life cycle, there is little or no waxy covering on the body. Attempts to control scale insects during other life stages are greatly hampered by the waxy covering on the insect’s body and are often not very successful. To achieve control, monitor crawler emergence and time control efforts accordingly.

Aphids
Aphids are common pests on trees throughout the South. All southern pines are subject to aphid attack. They are soft-bodied, usually wingless insects less than 1/8 inch long. They may be pink, brown, black, whitish or greenish. The rate of development and reproduction of aphids is very rapid, producing many generations each year.

Aphids suck plant juices from the tender, succulent parts of plants. Heavy feeding causes stunting of terminal buds, and needles become distorted or stunted. Often the first sign of attack is the presence of many aphids on the branches. They excrete sweet, sticky honeydew which may attract many ants. A fungus, sooty mold frequently develops on the honeydew and the branch or entire tree may appear black. Automobiles parked under heavily infested trees will frequently be covered with this sticky honeydew.

Chemical control of aphids is generally not economically justified except in cases of very high value or aesthetically important cases, such as Christmas tree plantations or nursery stock. Aphids can be controlled by an application of labeled insecticides when necessary.


Balsam Woolly Adelgid
The balsam woolly adelgid was accidentally introduced into the U.S. from Europe around 1900 (Figures 33-34). It has become a serious pest of natural Fraser fir stands in the southern Appalachians and thus causes considerable damage to the Fraser fir Christmas tree industry. The impact of this adelgid has been severe. Complete stand mortality, severe timber losses and reduced tree growth have been

observed. This insect has killed millions of board feet of true fir timber in North America. Adults are blackish purple, roughly spherical in shape, and about 1/32 inch in length. The insect produces a covering of white wax threads on the surface of the tree’s bole, limbs and buds. In the South, there are two to three generations of the adelgid per year. Orange-colored eggs are produced and remain under the adult’s body until hatching. The newly hatched “crawler” is the only stage of the adelgid that is mobile. When the crawler begins feeding, it transforms into a first instar nymph and becomes stationary. During the feeding process, the host tree is stimulated to produce abnormal wood that reduces the trees ability to translocate food and water. A heavily infested tree may die within 2 to 7 years. Chemical controls can be quite effective but are extremely costly and are usually limited to high value trees.

Figure 33. Balsam woolly
adelgid infestation, USDA
Forest Service Archives.

Figure 34. Balsam woolly adelgid
infestation, USDA Forest Service Archives.
Figure 35. Sycamore
lace bug adults.

Lace Bugs
Lace bugs, Corythucha spp., feed on the leaves of many tree species (Figure 35). Both the adults and nymphs feed on leaves, often resulting in chlorotic flecks or tiny chlorotic spots on the upper leaf surface. In addition to the presence of numerous nymphs and adults, the underside of leaves upon which lace bugs are feeding usually has numerous cast nymphal skins and numerous small black “frass spots” and black fungus. Heavily infested trees may be partially or fully defoliated, especially in dry weather. There may be several generations per year, and all life stages reside on the leaves of the host tree. Both the nymphs and the adults feed by inserting their mouthparts into the leaf tissue and sucking plant juices. Nymphs are dark-colored and covered with spines. Adults have broad, transparent, lacelike wing-covers. The adults are flattened and are about ¼ inch in length. Natural enemies are usually effective in controlling populations. Chemical controls are usually only used on high value shade and ornamental trees.

Spider Mites
Spider mites are found throughout the South (Figure 36). A number of species are important pests of ornamentals and shade trees, as well as many other plants. Spider mites are less than ½ inches in length, and, depending upon the species, vary in color from yellowish, greenish, orangish, and reddish to red. Major symptoms of spider mite damage are silk webbing, cast skins, active mites, and discolored yellowish foliage. Spider mites spin very fine silk webbing as they move about. There are several generations of mites per year. During high infestations, infested foliage may be discolored, disfigured, or killed.

Insects in Seed Orchards and Forest Nurseries

High value, intensively managed sites, such as seed orchards and forest nurseries, require aggressive forest

Figure 36. Spider mite damage,
Robert L. Anderson, USDA
Forest Service.
insect control programs. A number of insects that are normally not considered economic forest pests can be quite damaging in seed orchards and forest nurseries. Pheromone traps are often used to monitor insect populations in these sites. Some of the major seed and cone insect pests are the southern pine coneworms, pine seedbugs, various sawflies and thrips.

Coneworms
Several species of coneworms (Dioryctria spp.) are highly injurious to seeds and cones of conifers (Figures 37-38). These insects infest all commercially significant pines as well as spruce, fir, hemlock, and cypress. The southern pine coneworm (D. amatella) infests cones, male flowers, shoots, and fusiform rust cankers on a variety of southern pines. Adults have a wingspan of about 1 and 1/8 inches. The forewing is dark brown with contrasting white patches in zigzag lines running across the wings. Mature larvae are brownish to purplish above, pale whitish to greenish below and about one inch long. This species is frequently reported to cause heavy cone losses to southern pines.

Figure 37. Southern Pine Coneworm larva, adult,
and damage, R. Scott Cameron, International Paper.
Figure 38. Webbing coneworm adult,
Larry R. Barber, USDA Forest Service.

The Heteroptera, the true bugs, contains two families that are significant pests of a number of conifer species. The coreid bugs (Coreidae) and the stink bugs (Pentatomidae) feed on the ovules and seeds of pines and conifers.

Leaffooted Bugs
Leaffooted bugs in the family Coreidae genus Leptoglossus are important pests of loblolly and shortleaf pines (Figure 39). Both the nymphs and adults are reddish-brown to gray and have long legs with a laterally expanded “leaflike” tibia on the hind leg. The adults are 2/3 - ¾ inches in length and have distinctive whitish marks across the wings.

There are several generations produced each year. Nymphs and adults have piercing-sucking mouthparts that

Figure 39. Leaffooted pine seed bug
adult, R. Scott Cameron, International Paper.
they insert into the conelets or cones to penetrate and feed upon the developing ovules and seeds. Attacked cones show no external damage symptoms, but damage to seed can be severe.

Stink Bugs
Stink bugs in the family Pentatomidae emit a disagreeable odor when they are disturbed. The shieldbacked pine seed bug, Tetyra bipunctate (Herrich-Schaffer), is an important pest in southern pine seed orchards. The adults and nymphs are oval and have a humpbacked appearance. The adults are about 2/3 inch in length and are gray-brown to reddish-brown in color. There is only one generation per year. Nymphs and adults both have piercing-sucking mouthparts which they insert into cones to penetrate the seeds (Figure 40). Most of the

Figure 40. Stink bug nymph, John
H. Ghent, USDA Forest Service.
damage occurs in late summer and fall, which results in poor seed viability and low yields of sound seeds.

A number of insecticides are specifically labeled for and are used in seed orchards and forest nurseries. Ground-based hydraulic sprayers, airblast sprayers (mistblowers), and handheld compressed-air sprayers can be used to apply pesticides. Aerial applications are made with both helicopter and fixed-wing aircraft, equipped with either conventional or by ultra-low volume equipment.

Gallmakers
When feeding on plant tissues, many insects and mites inject or secrete a substance into the plant that causes the plant to grow abnormal “galls” (Figure 41). Galls may be found on leaves, buds, stems, or roots. Plant galls are caused by a number of different animal and disease organisms, but the majority are caused by insects and mites. The greatest majority of galls are produced by cynipid wasps (Family Cynipidae), gall midges (Family Ceccidomyiidae), and eriophyid mites (Class Arachnida: Order Acari: Family Eriophyidae). However, other wasps,

Figure 41. Typical oak gall, Robert L.
Anderson, USDA Forest Service.
mites, flies, beetles, homopterans, and lepidopterans also produce galls. Each species of insect or mite produces a characteristic gall on a certain part of a specific plant. The host involved, the location, and the shape of the gall produced are extremely useful in identification of the causing species, since the actual organism itself is small or may have already vacated the gall.

Insect and mite galls are not considered economically important in forest stands. Gall makers are considered important pests on certain ornamental trees and shrubs and on some Christmas trees. Usually controls are not needed for gall makers but may be desired in some situations such as Christmas tree plantations and ornamental plantings.

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The University of Georgia - Warnell School of Forestry and Natural Resources and
College of Agricultural and Environmental Sciences - Dept. of Entomology
Last updated on Wednesday, October 21, 2015 at 12:06 PM
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