Chapter 2 -- Apple Insects And Diseases In The Southeast

Insect And Mite Pests Of Apples

Ths chapter describes the physical appearance and life histories of arthropod pests of apple in the Southeast. It covers the damage caused by each pest and the principles involved in control, including major natural enemies.

Fruit Pests

Fruit pests have the potential to cause significant economic losses in apple production. Even slightly damaged fruit reduces market value. While biological control is important for a few fruit pests, most fruit pests can be best controlled by monitoring and insecticidal spray programs.

Aphids

Aphids of several species are pests of apples in the Southeast. The rosy apple aphid, wooly apple aphid, and the complex of green apple aphid and spirea aphid are all common to southeastern apples. Rosy apple aphids are fruit and foliar pests, green aphids are foliar pests, and wooly aphids injure apple roots. In many years, injury from aphids is slight, but some species have considerable damage potential.

Rosy Apple Aphid

The rosy apple aphid, Dysaphis plantaginea (Passerini), is the most destructive aphid pest of apple in the Southeast. Apple is its preferred host, although rosy apple aphids may also feed on pear. During the hot summer months, rosy apple aphids feed on plantain.

Description

The rosy apple aphid's appearance changes with host and season. On apple, rosy apple aphids are generally wingless and have a slight purplish to rosy body color that is somewhat obscured by a waxy coating (Figure 2.1). The fall and spring winged adults, which migrate to and from apple, are brownish green with a black head and thorax and transparent wings. The overwintering eggs are glossy black.

Damage

Feeding of the rosy apple aphid early in the season causes injury to fruit, leaves, and stems. Fruit feeding is the greatest concern. It results in small fruit that is somewhat hard and knotty. Feeding on new shoots produces curled, twisted growth (Figure 2.2). Greatest injury usually occurs during cool springs, when conditions allow aphids to increase more rapidly than their enemies.

Life History

ŚRosy apple aphids overwinter as eggs on apple. Eggs are attached to the bark of twigs and branches on all parts of the tree but especially in hidden crevices and depressions. Eggs begin to hatch around bud break. The young aphids, or nymphs, which hatch from the eggs are all females and are called "stem mothers" since they are the mothers of the season's brood.

Young aphids initially feed on the outside of leaf buds and fruit clusters. They then work their way down inside of opening clusters to feed. Their feeding causes leaves to curl, and more importantly, it causes misshapen, undersized fruit.

The stem mothers mature and, without mating, give birth to living nymphs. Several generations are produced on apple before winged aphids appear and migrate from apple to plantain. The migration to plantain is usually completed by late June. Winged aphids produce wingless individuals, which feed and reproduce on plantain until fall. In the fall, winged females fly back to apple and give birth to true egg-laying females. Males develop a little later. They fly back to apple to mate with females which then lay overwintering eggs. Eggs hatch the following spring.

Control

Insecticides applied with the delayed dormant oil application have historically been used for control of rosy aphids. However, control is best accomplished from the tight cluster to the pink stage. Aphid infestations that develop following bloom should be promptly controlled with curative treatments. Biological control of the rosy apple aphid is important since the aphid is preyed upon by many natural enemies, including lady beetles, syrphid flies, and aphid lions. However, biological controls alone usually do not provide satisfactory control. Greatest injury usually occurs during cool springs when conditions allow aphids to increase more rapidly than their enemies.

Tarnished Plant Bug

The tarnished plant bug, Lygus lineolaris (Palisot de Beauvois), is a sporadic, but occasionally serious, pest of fruit buds and fruit in early spring. Tarnished plant bugs have numerous hosts and feed on many species of trees and herbaceous plants. Orchard floor management is important in dealing with plant bugs because they are attracted to weedy orchards with early season bloom in the orchard floor.

Description

Adult tarnished plant bugs (Figure 2.3) are a brassy brown color. They are generally marked with black, white, and yellow. Color and markings are variable. Adults are about 1/4 inch long, less than half as broad, flattened, and oval in outline. The nymphs and eggs are seldom seen in apple orchards.

Damage

Adult tarnished plant bugs feed on the developing fruit buds and young fruits. They inject a salivary toxin that is highly injurious to plant tissue. Plant bug feeding causes the developing fruits to become deformed or catfaced (Figure 2.4). Fruit with sunken areas of more or less conical-shaped and corky tissue at the bottom indicate tarnished plant bug damage.

Life History

Tarnished plant bugs overwinter as adults. They are active with the first warm days of spring. Tarnished plant bugs are most abundant on apple trees just before, during, and after apple bloom. Adults feed on the developing fruit buds and young fruits. There are several generations of the tarnished plant bug annually. Comparatively little reproduction occurs on fruit trees.

Control

Protecting fruit from tarnished plant bug injury is challenging. Feeding may occur during bloom when no insecticides can be applied because of the risk of bee kill and poor fruit set. Insecticides should be sprayed around pre-pink and again at petal fall. As noted earlier, elimination of blooming orchard weeds before apples break bud will help reduce plant but pressure.

Green Fruitworms

Green fruitworms of several species are sporadic, but sometimes damaging, pests of apple. Larvae occur just before, during, or just after bloom. They are more troublesome in years with long bloom periods. Late blooming varieties are more often injured by green fruitworms because timely petal fall sprays are sometimes missed on these varieties.

Description

Green fruitworm moths are brown or grayish brown; their wingspans are from 1 1/2 to 1 3/4 inches. Larvae are pale, apple green, and usually marked with white or yellowish bands along either side of the body and down the back (Figure 2.5). When larvae are full©grown, they are about 1 1/2 inches long.

Damage

After petal fall, young apples have large holes which have been chewed in the sides. At harvest the misshapen fruit are covered with sunken corky tissue.

Life History

All the green fruitworm species common to apple have similar seasonal cycles and inflict similar early season damage to buds, foliage, and fruit. Moths lay eggs which hatch as fruit buds turn green. Young larvae feed on the newly opening buds, often consuming most of the buds in a cluster. Older larvae eat large holes in the sides of immature fruit in addition to feeding on new foliage. Larvae mature and pupate in the ground in May. Overwintering occurs as pupae or adults.

Control

Since feeding activity begins before bloom, insecticides may be required when buds develop 1/2 inch of new growth (green tissue) and again at petal fall.

Codling Moth

The codling moth, Laspeyresia pomonella (L), is one of the most serious fruit feeding apple pests in the world. Apple is the codling mtoh's preferred host. Larvae are internal fruit feeders. Codling moths feed on apples, pear, quince, peach, plum, and cherry, but in the Southeast they are primarily apple and pear pests.

Description

The full-grown codling moth larva has a brown head, a pinkish white body, and is about 3/4 inch long (Figure 2.6). Adult codling moths are about 1/2 inch long. The male and female are similar in appearance. Moths have a grayish, striped appearance. Chocolate brown patches at the base of the wings contain copper-colored scales near the inside wing tip (Figure 2.7). Codling moth eggs are white, flattened, pancake shaped, and about 1/25 inch in diameter. They are laid singly. One or 2 days prior to hatching, the dark head capsule of the larva can be seen.

Damage

Codling moth larvae injure fruit in two ways. Theyc ause wormy apples and, less often, apple stings. Wormy apples are ruined by internal larval feeding. Stings are down-grading blemishes on the apple surface, the injury left by young larvae that are poisoned before they burrow far below the apple's skin.

Life History

In the Southeast, the codling moth has a spring moth flight, which is followed by two full field generations and a partial third. The codling moth passes the winter as a full-grown larva in a thick silken cocoon. In early to midspring, the larvae pupate.

Codling moth adults begin to emerge around petal fall. The spring flight is extended, sometimes persisting into mid-June. Peak spring emergence generally occurs in mid-May. In some years, moth emergence has no distinct peak, only several lesser periods.

Eggs are laid primarily on leaves near the fruit. Hatched larvae burrow into fruit at the calyx or through the side of the apple. They either feed briefly on the flesh just beneath the skin's surface or burrow directly to the center of the fruit, where they feed on the seeds.

Codling moth larvae appear to be cannibalistic; usually only one larva completes development in a given fruit. Mature larvae leave fruit and seek out tree trunks to spin cocoons and pupate. Moth emergence for the overwintered generation lasts for 4 to 6 weeks and often overlaps with moth emergence of the first field generation. The peak emergence of first field generation moths occurs around the first of July in North Carolina.

Second generationon larvae are active from July to around the first of August. Moth emergence peaks again in mid to late August. Overlapping of moth generations is common. Some second and most third generation larvae seek out cocooning sites to overwinter.

Control

Insecticidal sprays are directed against the moth, egg, or newly hatched larva. Once a larva is established inside an apple, it is immune to insecticidal sprays.

Successful codling moth control depends on control of the spring moth flight. Insecticides should be applied to coincide with moth flights. Insecticides applied at petal fall and again at first and second cover sprays are generally effective. Problems with codling moth control come from failure to have timely, effective insecticide coverage. Effective insecticide coverage is difficult because (1) adults emerge over a long period of time and (2) often there are no distinct peaks of moth emergence because of overlapping generations.

Moths migrating from nearby neglected or abandoned apple orchards generally worsen problems from codling moth and other pests. Such old orchards should be eliminated if possible.

Monitoring male moths with pheromone traps is an important IPM tool in most management schemes.

Biological control agents are significant in controlling the codling moth. Several parasites attack the egg stage. Larvae on the ground or on the tree trunks are attacked by several insect predators, birds (mainly woodpeckers), and mice.

Oriental Fruit Moth

The Oriental fruit moth, Grapholitha molesta Busck, is a pest of peach but occasionally attacks the fruit and tender terminal shoots of apple. Infestations in apples generally occur where peach and apple are growing in close proximity, although Oriental fruit moth can maintain itself in apple alone. Oriental fruit moths can cause significant economic losses in apple, especially late in the season.

Description

Oriental fruit moth larvae are pinkish white at maturity and about 1/2 inch long (Figure 2.8). Oriental fruit moth larvae are almost identical to the codling moth larvae. The reddish brown pupae are formed within a cocoon. Adult Oriental fruit moths are about 1/4 inch long. The moths are generally a dark brownish gray and have a faint pepper-and-salt appearance (Figure 2.9). They resemble the codling moth but are somewhat smaller. Eggs are laid singly and are white to amber.

Damage

Oriental fruit moth larvae are borers. On apple they may be found tunneling into fruit or succulent shoot tip growth. Earlier generations of this insect confine their attack to the succulent twig growth, which causes the tips to wither and turn brown. Tip dieback is easily detected but causes no appreciable economic loss. Orchards with tip dieback should be examined for Oriental fruit moth. If orchards are infested, controls should be applied before serious fruit infestation occurs. Sprays should be timed to control the next moth flight.

Wormy fruit produced by the Oriental fruit moth resemble those damaged by the codling moth. In both cases, a mass of dark excrement will be found at the burrow exit. However, producers can make an educated guess on which insect caused the injury by when it is found and the kind of burrow produced. Wormy fruit found earlier than expected are probably the results of the Oriental fruit moth. Tunnels that penetrate directly to the core indicate that the codling moth larva has been feeding on the seeds. Burrows of the Oriental fruit moth follow a more meandering course, and the larvae usually do not feed on the seeds.

Life History

The spring Oriental fruit moth flight is followed by two full generations and a partial third. The insect overwinters as a full-grown larva. As with the codling moth, larvae of the Oriental fruit moth are enclosed in cocoons that are attached to tree trunks or orchard debris. In early spring the insect passes through its pupal stage. The spring moth flight begins around the green tip stage. First field generation moth emergence peaks around the first of July; the second generation peaks in late August. Larvae of the third generation overwinter inside thick cocoons.

Oriental fruit moths occasionally attack apple, generally when associated with peach. Apparently they can maintain themselves on apple alone if tree vigor is sufficient to provide succulent shoot growth well into the summer and if there is uninterrupted annual fruit production.

Control

Insecticidal control of Oriental fruit moth is directed at moth flights. Because most of the spring moth flight occurs before petal fall, sprays must be applied in late June or early July during the moth flight of the first field generation. Pheromone trapping of male moths helps target moth flights.

Plum Curculio

The plum curculio, Conotrachelus nenupar (Herbst), is a sporadic pest in many southeastern apple orchards. When it does occur, however, it can be a very serious pest. Plum and peach are preferred plum curculio hosts, but it sometimes attacks apple, cherry, and blueberry.

Description

Plum curculio are weevils or snout beetles (Figure 2.10). Adults are approximately 1/4 inch long. They have a curved snout about one-third the length of the body, which projects forward and downward from the head. The body has a warty, uneven texture. Plum curculio adults are mostly brown with patches of gray or white. When disturbed, adults will characteristically fold their legs close to their bodies and remain motionless.

Plum curculio larvae are 1/3 inch long when full-grown. The body is legless, smooth, elongated, and slightly curved. The head is brown, and the body is mostly yellowish white or grayish white (Figure 2.11).

Damage

Apples attacked by plum curculio frequently suffer surface scarring and distortion from feeding and egg laying. The most important injury results from the crescent-shaped cuts (Figure 2.12) made in apples by females during egg laying. Thereafter, whether eggs hatch or not, crescent-shaped scars develop on the fruit. Infested immature apples often fall prematurely, or if they stay on the tree they may be hard, knotty, and misshapen. During mid and late summer, adult feeding also result in numerous round punctures in the skin of apples.

Life History

Adult plum curculio overwinter under trash, usually in woods adjacent to orchards. They generally begin to leave overwintering sites during bloom. Movement from overwintering sites near orchards can occur over a period of 4 to 6 weeks. Adults feed on fruit or fruit buds and mate, and the females begin to lay eggs. During egg laying, the female eats a small hole into the fruit where she deposits an egg. Then she cuts a crescent-shaped slit beneath the egg probably to create an area of dead tissue so growth of the fruit will not crush the egg.

The developing plum curculio larvae feed on the flesh, core, and seeds. Immature apples infested with plum curculio larvae nearly always fall to the ground. Full-grown larvae leave the fruit and pupate in the soil. Second generation adults begin to emerge about 1 month after the larvae enter the soil. Egg laying by the second generation adults will normally begin in mid-June and continue through July. Second generation adults overwinter in debris and trash.

Control

Plum curculio infestations in apple are uncommon in the Southeast and are usually controlled by codling moth sprays, so very few orchards receive specific sprays for plum curculio. Where orchards have a history of plum curculio damage, insecticides should be applied from the petal fall through the second cover spray. If second generation control is needed, two sprays applied 14 days apart, the first in mid-June and the second in early July, may be necessary.

Apple Maggot

The apple maggot, Rhagoletis pomonella (Walsh), is a very injurious apple pest in the northeastern states and Canada. In the Southeast, it is seldom a pest in commercial orchards. At elevations near 3,000 feet, some southeastern orchards are subject to predictable apple maggot infestations. Crab apples, hawthorn, plum, pear, and cherries are also apple maggot hosts.

Description

The apple maggot adult is a fly slightly smaller than a housefly. The flies are black with white bands between segments on the abdomen, four bands on the female and three on the male. The wings are conspicuously marked with four oblique black bands (Figure 2.13). Maggots are carrot shaped, white, legless, and about 1/4 inch long when full-grown.

Damage

Maggots are sometimes called "railroad worms" because they leave brown winding trails just under the apple skin of some varieties (Figure 2.14). A decay organism associated with the burrowing maggot sometimes reduces apples to a brown rotten mass. Apples may also be pitted and dimpled with numerous tiny egg punctures.

Life History

Apple maggots overwinter inside a brown, 1/4 inch long puparium in the soil. In North Carolina, adult emergence begins in mid-June, peaks in July, and is completed by early September. Flies begin to lay eggs 8 to 10 days after emergence. After mating is completed, the females seek out fruit. Tiny, white, elongated eggs are laid under the skin of the apple through a puncture made by the female. Maggots tunnel through the apple, causing a breakdown and discoloration of the pulp. Infested apples usually drop prematurely. The full-grown maggots leave the fruit and enter the soil where they pupate. There is one generation a year.

Control

Insecticides are directed against the apple maggot flies before eggs are laid. Successful apple maggot control depends on killing the flies before eggs are deposited. With adult monitoring this is possible and practical because of the 8o to 10o day period between fly emergence and egg laying. This allows time to kill the flies before they can infest the fruit.

Leafrollers

Leafrollers of several species may be damaging to apples in the Southeast. Level of pest pressure varies considerably within the region. Leafrolling -- the foliage feeding for which this group of caterpillar is named -- is of little consequence in apple. However, fruit feeding may be quite injurious. Some areas within the region (North Carolina) experience control difficulty with some species. The leafroller complex consists primarily of tufted apple budmoth, variegated leafroller, redbanded leafroller, and obliquebanded leafroller.

Tufted Apple Budmoth and Variegated Leafroller

Tufted applle budmoth, Platynoda idaeusalis, and variegated leafroller, P. flavedana, have similar life cycles and are the most important leafroller pests in the Southeast.

Description

Pheromone monitoring of adult popualtions makes identification of adult moths important. Tufted apple budmoth adults are about 1/2 inch long, triangular-shaped, mottled gray moths, (Figure 2.15) with pronounced triangular-shaped mouthparts extending beyond the head. Tufted apple budmoths have tuft of scales on top of the wings.

Variegated leafroller moths have a more rounded, triangular shape. The are around 1/2 inch long and have elongated mouthparts that extend well beyond the head. They are reddish brown. When at rest they have a dark U-shaped line across the center of the wings (Figure 2.16).

Larvae of both species are small, light brown to tan, with chestnut brown heads, a dark shield behind the head, and a dark stripe on the back (Figure 2.17). Eggs are desposited on leaves in masses.

Damage

First generation larvae generally confine themselves to unimportant leaf feeding and leafrolling, although larger larvae of this generation can sometimes cause considerable damage. Second generation larvae often feed on fruit. Attacks generate tiny holes from early instar feeding, followed by irregular scarring of apple surfaces or areas of rot around the stem end.

Life History

These leafrollers have two generations per year. Larvae overwinter on the orchard floor. Larvae pupate and emerge as adults in late April. Eggs are laid from late May into June. First generation larvae are primarily foliage feeders, but large larvae may damage apples in July. Second generation larvae may attack fruit during August and into September.

Control

Insecticides provide the best control when they are timed 7 to 10 days after peak pheromone trap catches of first generation moths and when captures increase during the second generation. Pheromone monitoring of adult populations makes identification of adult moths important. In areas where leafrollers are resistant to traditional cover spray materials, control is more difficult. Precise timing of sprays, thorough coverage, and shortened spray intervals may be needed to control these populations.

Redbanded Leafroller

The redbanded leafroller, Argyrotaenia velutinana (Walker), is a common, but seldom injurious, pest of apple. Larvae of the redbanded leafroller feed on a wide variety of plants, including deciduous fruits, forest trees, and some herbaceous plants.

Description

Full-grown rebanded leafroller larvae are about 3/4 inch long, and the body color varies from a light yellowish green to a deep grass green (Figure 2.18). Pupae are light greenish brown when first formed but eventually change to a deeper brown. Adult rebanded leafrollers are small moths, about 1/2 inch long. The featured marking on the forewings is the reddish brown band which runs obliquely across the forewing; this marking accounts for "redbanded" in the insect's common name (Figure 2.19). Eggs are laid in masses averaging 45 eggs per mass.

Damage

Larvae of the redbanded leafroller cause injury to foliage and occasionally to fruit. Damage to foliage is generally of little economic significance. Larvae skeletonize leaves close tot he midribs from the underside, folding and webbing the leaves together. Injury to the fruit by second and more often third generation larvae can be important. Larvae seldom eat far into a fruit (Figure 2.20). Most feed on the surface beneath a white web which they spin. The larvae are secretive and normally will web down a leaf to the fruit to protect the feeding site. Other favorite spots for attack are the cavities at the calyx and stem ends and the place where two fruit touch.

Life History

In the Southeast, the spring moth flight is followed by two full and a partial third generation. The insect overwinters in the pupal stage within a folded leaf in the ground cover. The spring moth flight begins at or before the green tip stage, peaking shortly before bloom. Eggs of the first generation are laid principally on the trunk and scaffold limbs. Larvae, upon hatching, crawl up the limbs in search of food. First generation feeding is generally confined to the center of the tree, especially to tender growth on water sprouts. Eggs of subsequent generations are laid primarily on the upper surface of the leaves. Larvae feed on the foliage, and as they reach maturity, they roll or web several leaves together to form shelters. Some larvae feed on fruit under the protection of an attached leaf, and some feed at the site where two fruit are in contact. Fruit feeding by third generation larvae during September is sometimes damaging.

Control

Insecticidal control for the larval stage is most effective when insecticidal sprays are applied shortly after the peak of adult emergence, thereby killing not only moths but eggs and newly hatched larvae. Sprays applied during the late June or early July moth flight are also usually effective. Pheromone traps can be used to monitor adult activity. Biological control plays an important role in maintaining populations of the redbanded leafroller at low levels.

Obliquebanded Leafroller

The obliquebanded leafroller, Choristoneura rosaceana (Harris), is a widely distributed insect throughout the United States and Canada. It is not considered a major pest of apple in the Southeast, but where high populations occur, it can cause significant damage. In some northern states, populations have developed resistance to pesticides and can no longer be controlled by standard programs. The obliquebanded leafroller feeds on a vareity of plants in the Rosaceae family as well as many other deciduous trees.

Description

Adult leafrollers are tan or brown (Figure 2.21). The front wing is crossed by alternating light and dark bands. Female moths are larger and more distinctly marked than males, which are attracted to pheromone traps.

Flattened, overlapping masses of eggs are laid on apple trees. The color and appearance resemble those of the redbanded leafroller, but the egg masses are larger.

Larvae are green with head capsules which vary from black to brown (Figure 2.22). The thoracic shield (area immediately behind the head) also varies from black to green brown.

Damage

In the spring, foliage feeding can be severe if populations are high. Larvae may attack several leaves or flower buds, webbing them together to form tubelike feeding chambers. This feeding can result in reduced leaf area and growth in young, nonbearing trees. Fruit feeding by the obliquebanded leafroller is similar to feeding by the redbanded leafroller, but feeding scars are usually much deeper.

Life History

Partially grown larvae pass the winter in densely spun cocoons or hibernacula, usually in bark crevices or under bark scales. When bud open in the spring, the larvae become active and bore into the opening buds. As the foliage unfolds from the buds, larvae may web leaves together to construct a tubelike feeding chamber. As larvae mature, each will construct another tubular structure from a single large leaf, within which it will pupate. Adult moths will appear 10 to 12 days later.

The moths of this spring generation are usually present by mid-May in the Southeast, a little later at higher elevations. Eggs are deposited on apple limbs and trunks within a few days, and first generation larvae hatch 10 to 12 days later. The larvae may feed on either fruit or foliage until they mature near the end of June.

Moths of the second generation usually occur by mid-July. Second generation larvae feed primarily on foliage until they are almost half-grown. In higher elevations and in the more northerly areas of the Southeast, these larvae spin the hibernacula in which they pass the winter. In the more southerly portions of the region, these larvae may mature, and a third generation will occur. This third generation will comprise the overwintering generation.

Control

Pheromone traps can be used to detect the flight of moths as they occur. Applications of effective insecticides can then be timed to coincide with the late flight period when eggs have begun to hatch. Sprays applied during pink for control of the rosy apple aphid can be effective in reducing damage caused by overwintered larvae. Biological control agents also play an important part in management of this species.

Foliar Pests

Foliar pests have less potential to rapidly inflict crop injury than pests which attack fruit. However, foliar injury is often cumulative, and infestations that last too long can be quite injurious. Careful monitoring, using treatment thresholds, and selecting the corrent pesticide when treatments are required will improve the producer's ability to manage these pests.

Green Apple Aphid and Spirea Aphid

Green apple aphid, Aphis pomi (DeGeer), and spirea aphid, Aphis spiraecola Patch, are similar in appearance and behavior. Management for both species is the same. Hosts of green apple aphids include apple, pear, quince, and hawthorne. These aphids may be abundant and troublesome during the spring and early summer months. They are most abundant on young trees, water sprouts, and vigorous terminals. When abundant, they curl elaves and foul both leaves and fruit with honeydew. Unlike rosy apple aphids, these species remain on apple year-round.

Description

Wingless aphids are a uniform green, except for the head which is pale brown. Wings of the winged aphid are transparent (Figure 2.23). Eggs are glossy black and o difficult to distinguish from eggs of the rosy apple aphid.

Damage

Aphids such sap from leaves particularly near the growing tips. Heavy aphid feeding can cause curling and discoloration of developing foliage. Young trees may suffer reduced growth. The most extensive problems occur when high aphid populations develop on terminals and watersrouts and the area beneath is covered with honeydew. A sooty-mold fungus often develops on the honeydew, discoloring the fruit and adversely affecting its quality. Aphids' feeding on immature apples results in stunted and deformed apples; their feeding on mature fruit produces russeted apples.

Life History

Green apple aphids overwinter as eggs on the bark of the previous season's growth usually on rough areas, such as leaf and pruning scars, spurs, or terminals. Eggs begin to hatch around silver tip. These early spring nymphs, all females, are known as stem mothers. Stem mothers mature and feed on the opening buds and developing leaves then give "birth" to living nymphs without mating (parthenogenesis). These nymphs feed, mature, and produce living nymphs. Generation follows generation in this manner.

Winged aphids (alates) soon appear, and for the remainder of the summer the population consists of winged and wingless parthenogenetic females that produce living nymphs. The winged aphids fly to other apples or other host plants and reproduce. In the fall, winged aphids produce nymphs that develop into true sexual forms. After mating with males, females lay the overwintering eggs, which hatch the following spring.

Control

Lady beetles, syrphid flies, and aphid lions are important biological control agents in helping to maintain aphid populations below economically damaging levels. Insecticidal control may sometimes be necessary, particularly on young trees.

Spotted Tentiform Leafminer

The spotted tentiform leafminer, Lithocollectis blancardella Fab., feeds inside apple leaves throughout the growing season. Resistance to commonly used organophosphate insecticides has led to increased problems with this pest throughout much of the southeastern United States.

Description

Adult spotted tentiform leafminer moths are 1/8 inch long. They are brown with white transverse stripes margined with black (Figure 2.24). The minute eggs are not easily seen. Full-grown larvae are yellowish and 1/8 inch long when mature.

Damage

Spotted tentiform leafminers injure apple leaves by internal feeding or "mining." Each mature mine reduces the leaf's green tissue by about 5 percent. Mines buckle the leaf like a small tent (Figure 2.25), hence the name spotted tentiform leafminer. Excessive mining combinted with drought, mite injury, or foliar diseases may be quite damaging. Mines remain visible after the leafminer has emerged or been killed by sprays. To determine if mines are active, it is necessary to open them and observe for larvae.

Life History

The leafminer overwinters as a pupa inside apple leaves on the orchard floor. Adult emergence begins around the 1/2-inch green stage and continues through bloom. Females lay approximately 25 eggs singly on leaves. They hatch in 6 to 10 days. Larvae go through two stages: sap feeding and tissue feeding. Sap-feeding larvae are very small; they pierce plant cells and feed on sap. Tissue-feeding larvae are larger, have well-developed mouthparts, and feed directly on tissue inside leaves. A complete generation requires 35 to 55 days. Leafminers feed in orchards from early spring until leaves drop in the fall.

Control

Well-timed pre-bloom sprays should provide control of the first two generations of spotted tentiform leafminer. When necessary, post-bloom control is directed at sap-feeding larvae. Larval control requires precise timing to target the sap-feeding stage. Larval control also requires use of carbamate insecticides, which are quite damaging to mite predators. These complications strongly favor pre-bloom control strategies.

White Apple Leafhopper

The white apple leafhopper, Typhlocube pomaria McAtee, is an increasingly troublesome pest in southeastern apples. Problems from this previously innocuous insect point to the development of resistance to standard cover spray insecticides. Growers should monitor for leafhopper nymphs starting at petal fall.

Damage

The white apple leafhopper is a leaf feeder and does not directly attack the druit. As sap is sucked from the leaves, green tissue is destroyed, causing leaves to become speckled or mottled with white spots. Besides injuring leaves, leafhoppers deposit numerous small spots of excrement on fruit, potentially reducing its quality.

Description and Life History

White apple leafhoppers overwinter as eggs in the bark of 1- to 5-year-old wood. Eggs begin hatching at pink. Young leafhoppers are tiny, whitish green, and wingless and are usually found on the underside of older leaves. They move quickly, going sideways or forward. Adults are greenish white and 1/3 inch long (Figure 2.26). They fly readily when disturbed. Aduls develop in June and are active for several weeks. During this period, they lay eggs in the petiole and veins of leaves. The eggs begin to hatch during June. Leafhoppers feed in the orchard into the fall. Overwintering eggs are laid in young wood during September and early October.

Control

Young leafhoppers are much easier to control than adults. Effective control of the first brood may prevent high populations of the second. The first brood is also a better target since the hatch is fairly synchronous and leafhoppers at this age are vulnerable to insecticides. Use of the insecticide carbaryl as an apple thinner often provides excellent control of this pest.

White apple leafhopper control generally requires use of carbamate insecticides. These materials are detrimental to mite predators, and their use can lead to mite outbreaks. Monitor leafminer numbers, and if control is necessary try to treat early in the season before mite predator numbers build up. Thorough coverage of upper and lower leaf surfaces is necessary for effective control.

European Red Mite

The European red mite, Panonychus ulmi (Koch), is the most common and important plant-feeding mite found on apple foliage in the Southeast. This mite occurs on many deciduous fruits and ornamentals but is most injurious to apple.

Description

Adult female European red mites are bright to brownish red with an elliptical body (Figure 2.27). Adult females are not much larger than the period at the end of this sentence. Females have four rows of curved spines on their backs, each spine borne on a whitish tubercle. These spines can be seen with a hand lens. The overwintering eggs are bright red, spherically shaped and have a distinct white stalk about as long as the diameter of the egg (Figure 2.28). This white stalk can be seen only under magnification. Summer eggs are translucent.

Damage

European red mites feed on leaves. Sevee mite injury produces browning and loss of color in the leaves (Figure 2.29), commonly referred to as bronzing. Extensive foliage injury may reduce the quality and quantity of fruit and the following year's return bloom.

The extent of mite injury is influenced by numerous factors: (1) time of the growing season when injury occurs, (2) duration of feeding when injury occurs, (3) vigor and tree cultivar, (4) crop load, and (5) weather conditions. Excessive foliage injury early in a growing season (May and June) is most detrimental to the trees. Injury at this time may result in excessive fruit drop, and it may reduce return bloom. Midseason (July) injury is less detrimental but with other stress may result in fruit drop, reduced fruit color, and reduced effectiveness of growth regulating sprays.

Life History

European red mites overwinter as eggs on twigs and smaller branches of trees. Eggs begin to hatch just before bloom. The mites crawl to the leaves and suck the plant juices. After mating, females lay approximately one fertilized egg per day. These eggs develop into male and female mites. Females do not have to mate to lay eggs, but eggs from unmated females only develop into males. Eggs hatch into a six-legged larval stage. The larvae then pass through an eight-legged protonymph and deutonymph stage before becoming adults.

Ordinarily, populations of the European red mite build up slowly during the spring, but under favorable summer conditions they can increase to unacceptably high populations. Hot, dry weather is favorable to populations increases of this mite. Nine or more generations may develop per year.

Control

Mite management emphasizes orchard floor management, scouting of pest and beneficial populations, consideration of other stresses on the trees, and prudent use of chemicals. Chemicals should be chosen for effectiveness, selective toxicity, and lowest toxicity to natural enemies. Also important is alternation of materials, application of the minimum effective dosage of chemicals, and proper timing of sprays.

Natural enemies of plant-feeding mites are very important in the management of these mite populations. Commonly, two predatory mites, Ambelacious fallacis and Zetzellia mali, and the predaceous lady beetle, Stethorus punctum, feed on plant-feeding mites. The size of predator populations can be determined only by careful examination of an orchard. A hand lens is needed to observe the predaceous mites. The larval and adult stages of the lady beetle can be seen with the naked eye.

European red mites are generally the primary source of food for predators, so a cyclic development of mites and predators can be expected. European red mites and mite predators are generally uncommon during April or May. Populations of European red mites may increase rapidly during the warm weather of late May, June, or July. Predators respond to this increased food supply. However, the length of time required for predators to control the mite population varies considerably.

If plant-feeding mite numbers are above threshold, and predator levels are too low to provide control, it may be necessary to apply a selective miticide to help improve the balance in favor of the predators. Avoid use of nonselective miticides at this time. Even though non-selective miticides may give good control of pest mites, they also kill the predators. This may lead to a rapid rebound of pest mites and season-long problems.

If the predator population increases sufficiently, the European red mite population willd ecline and remain at a low enough level so that the damage they inflict is acceptable. Frequent observation of mites and predators and of the relative changes occurring in populations helps to determine if a spray is needed and when to spray. Regular mite sampling is essential because repeated sampling allows the producer to follow population trends.

Twospotted Spider Mite

The twospotted spider mite, Tetranychus urticae Koch, is a sporadic problem in southeastern apple orchards. Economically damaging populations generally develop during the latter part of the season. Unlike the European red mite, which feeds only on deciduous plants, the twospotted spider mite feeds on a very wide variety of hosts including garden, greenhouse, nursery, and ornamental platns and weeds.

Description

The adult female twospotted spider mite's summer color pattern varies, but most are greenish yellow with a prominent dark spot on each side near the middle of the body (Figure 2.30). These spots may enlarge to cover most of each side of the body as the mite feeds. The body is somewhat egg shaped and broadest toward the head region. Adult females are not much larger thant he period at the end of this sentence. The eggs are spherically shaped and shiny; their color varies from light or clear to pale green.

Life History Twospotted spider mites overwinter as orange-colored females. In apple orchards the overwintering females congregate under debris on the orchard floor or bark scales at the base of trees. During the spring the twospotted spider mite feeds on vegetation, especially vetch and other legumes underneath the trees. As these orchard floor hosts dry out with the arrival of hot weather, twospotted spider mites move into apple trees. Hot, dry weather is favorable to population increases of this mite. The twospotted spider mite passes through the same developmental stages as does the European red mite.

Control

Refer to sections of European red mite for management.

Japanese Beetle and Green June Beetle

The Japanese beetle, Popillia japonica Newman, and the green June beetle, Cotinis nitida L., are locally abundant foliage-feeding beetles that are sometimes damaging.

Description

Adult Japanese beetles are metallic green with a reddish brown wing cover and a series of small white spots along the sides and near the tip of the abdomen (Figure 2.31). Beetles measure about 5/8 inch long. Larvae feed in the soil on grass roots.

Adult green June beetles are velvety green. They are nearly 1 inch long, robust, and somewhat flattened. The margins of the body are bronze to yellow (Figure 2.32). Larvae feed in the soil on grass roots.

Damage

Foliage of apple plants may be injured by adult Japanese beetles and green June beetles. Adults attack the fruit by chewing irregular holes in it, and in some cases the fruit is nearly devoured. Apple foliage is skeletonized so that all the leaf tissue between the veins is removed. Orchard grass is occasionally killed by the larvae feeding on the roots.

Life History

The Japanese beetle overwinters as a larva or grub about 1/2 inch long, buried in the soil. In the Southeast larval growth is completed during June. Larvae pupate in the soil, and adults emerge in greatest numbers in July. Adult beetles can be seen flying, feeding, and mating on warm sunny days. Mated females lay their white spherical eggs 2 to 6 inches deep in the soil. There is normally one generation per year.

Green June e beetles also overwinter in the soil. Adult emergence occurs during July and August. Green June beetles are often most abundant a few weeks before and during harvest. There is one generation per year.

Control

Protection of fruit and foliage from attack by Japanese beetles and green June beetles requires killing adult beetles in the orchard. Adults are strong fliers, and seemingly continuous or successive invasions may occur, especially following soaking rains. Orchards near pastures fertilized with chicken litter often suffer more severe Japanese beetle or green June beetle problems. If an orchard has a history of problems with either of these beetles, use insecticides before the beetles become too abundant because aggregations of beetles tend to attract other beetles from afar.

Pests of Stems, Shoots, and Roots

Pests of stems, shoots, and roots can cause a variety of problems. The damage occurs when these pests remove nutrients from the tree, causing a general lack of vigor, thin foliage, limb death, and reduced yields. Good cultural practices are extremely important in control of these pests. These practices include selecting healthy rootstock, pruning, fertilizing, irrigating, and resting orchard land. Other control practices include monitoring and spraying.

San Jose Scale

The San Jose scale, Quadraspidiotus perniciosus (Comstock), attacks a wide range of trees and shrubs in addition to apple. Scale insects are difficult to detect until damaging populations occur. Many times this insect is not detected until damage begins to appear on the fruit at harvest. Once populations reach such levels, control is often difficult and expensive.

Description

Mature female scales are about 1/10 inch in diameter. Color varies from nearly white for young scales to dark gray for mature females. Females have a distinct black spot in the center of the scale. Male scales are oblong with a black spot near one end and are much smaller than the female. The active immature stage (crawler) is lemon yellow and about 1/100 inch long (Figure 2.33).

Damage

All stages remove sap from the tree. Low populations do not cause any noticeable damage to the tree. However, populations can build to high numbers in a very short time. Large numbers of scales can completely cover the bark of individual limbs. The area around the feeding site turns a characteristic purplish red color (Figure 2.34). This can be easily observed on tender new growth. If a thin cut is made just under the scales on older limbs, the discolored area is easily seen. Prolonged attack will cause the bark to split and crack. Eventually the branch or entire tree will die if the scales are not controlled. When populations are high, crawlers may migrate from the fruit spurs onto the fruit. At harvest the fruit will have the distinct "measles" spots on the surface. When the scale is removed from the fruit, a light-colored bull's eye is evident.

Life History

San Jose scale overwinters as immature blackcap scales. Feeding resumes in early spring, and scales reach maturity during bloom. Adult males are tiny, gnatlike insects that fly about the tree in search of females. The females remain beneath the scale cover where mating takes place about petal fall. Unlike most scales, San Jose scale females produce live crawlers instead of eggs. Each female produces about 400 young over a 6-week period. The crawlers move around for a few hours before settling down and inserting their mouthparts into the bark. The scale cover is secreted shortly after the crawlers settle down. Males require about 25 days to reach maturity while females require about 31 days.

There are four generations of San Jose scale each year. The first-brood crawlers appear in May. Second-brood crawlers are present during late June and early July. The third-brood crawlers are active during mid-August and fourth-brood crawlers from September until frost. Because of the long life span of mature females, crawlers may be present during much of the growing season after early May.

Control

There are two methods of monitoring population development: monitor either adult male emergence or crawler emergence. Pheromone traps are available for monitoring adult male emergence. Traps should be placed in trees with active populations of San Jose scale at the pink stage. Capture of adult males will aid in timing the first sprays.

Crawler emergence can be monitored in the following way. Wrap black electrician's tape around infested branches at each end of the infested area. Coat the tape with a thin film of petroleum jelly. Check the tape at least twice a week. When crawlers begin to emerge, they will migrate onto the tape and become stuck in the petroleum jelly. This makes it relatively easy to detect their emergence. Apply an insecticide when you detect the first crawlers.

Insecticides known to be effective against scale crawlers should be used whenever crawlers are active, particularly against crawlers of the first two broods. If males are detected during petal fall, insecticidal sprays will help to reduce numbers and prevent mating. An oil or an oil plus insecticide spray during the dormant or delayed dormant period will combat scale populations. On the other hand, use of pyrethroids and certain carbamate insecticides on a regular basis will aggravate scale problems.

Often, San Jose scale populations will first appear in areas of the tree that do not receive thorough spray coverage. Coverage is the secret to successful management of this pest. Large trees with rough bark make it even more difficult to obtain good coverage. Proper pruning to maintain an open tree canopy makes it much easier to achieve thorough spray coverage. Heavily infested branches with splitting bark are best removed.

Wooly Apple Aphid

The wooly apple aphid, Eriosoma lanigerum (Hausmann), is found on apple, pear, hawthorn, mountain ash, and elm. Alternate hosts outside the orchard make management of this pest difficult.

Description

Young nymphs have a dark purple body covered with powdery grayish wax. Larger nymphs and adults vary from dark purple to a rosy color and are nearly covered by a wooly mass of long wax filaments (Figure 2.35). Adults and nymphs have needlelike mouthparts which are inserted into the bark where they feed on the sap.

Damage

Wooly apple aphid can infest apple trees aboveground. There they feed on new growth around pruning cuts and other injuries and on leaf axils on sprouts. Feeding around wounds prevents the bark from healing properly. Feeding on new growth can produce gall-like swellings on the small branches. Aboveground infestations, especially on older trees, produce relatively little damage.

The most seriuos damage occurs from colonies that feed on the roots and underground parts of the trunk. Underground feeding often produces large knots on the roots (Figure 2.36). Trees heavily infested underground often develop a short fibrous root system and have yellowish foliage. Young trees that are heavily infested can be easily uprooted.

Life History

Wooly apple aphids overwinter either as eggs or as immature nymphs. The nymphs are found on the roots of apple trees. Where elms are present, adult females deposit eggs in cracks and crevices of the bark. The eggs hatch in the spring. These wingless stem mothers give birth to daughters. Two generations are produced on elm where the aphids feed on buds and young leaves. Feeding on elm leaves causes leaves to curl into a rosette.

The third generation has wings and migrates to apple and other hosts. Repeated generations are then produced on apple. Some nymphs may migrate downward when populations are high. They reach the roots at the base of the tree where the soil has been loosened by swaying of the tree. Organic matter, root suckers, stones, and soil cracks are other avenues of entrance to the root system. Reproduction may be continuous in the underground colonies.

In the fall, winged females are produced in both the aerial and underground colonies. These females migrate back to elm trees where they give birth to both males and females. These aphids are wingless. A short time after mating, the female inserts a single egg in a rough area of the elm bark. This egg is almost as large as she is.

Wooly apple aphids can spread during the nymph stage. They can be dispersed by the wind, birds, or other insects that may come in contact with a colony. Young nymphs are most abundant in spring and fall. Aerial colonies are not a good indicator of root infestations. A tree may have aerial infestations and never develop root infestations of the wooly apple aphid.

Control

Careful selection of insecticides is important in managing wooly apple aphids. Some of the carbamate insecticides and the pyrethroid insecticides may increase problems with the wooly apple aphid by killing naturally occurring parasites. When aerial colonies are detected, an application of a good aphicide will provide control. There is no control for the underground colonies. Some of the Malling-Merton series of rootstocks are resistant to wooly apple aphids. These rootstocks should be used where possible to reduce problems from this pest. Nursery stock may also have infestations. Trees should be inspected prior to planting, and infested trees refused.

Dogwood Borer

The dogwood borer, Synanthedon scitula (Harris), is the larva of a small clearwing moth with infests burr knots.

Description

The adult moths bear a striking resemblance to small wasps. They have a black-and-yellow color pattern with clear wings. The wingspan is about 1 inch. The yellow band on the fourth abdominal segment is much wider on the female than on the male (Figure 2.37). The larvae vary from white to a light pink (Figure 2.38). The larval head capsule is dark brown. Mature larvae are about 1/2 inch long.

Damage

Dogwood borer larvae feed almost exclusively within burr knots on apple trees. Burr knots are aggregations of partially developed root initials that usually occur in clusters at or below the graft union. The Malling and Malling-Merton series of rootstocks have a tendency to produce burr knots.

The first indication of a dogwood borer infestation is an accumulation of reddish brown sawdustlike material, known as frass, on the surface of the burr knot. At times, golden brown pupal cases may be found protruding from the burr knot. This is a sign of adult emergence.

Feeding within the burr knot does not harm the tree directly. It may produce an entry for disease organisms but otherwise causes little or no damage. Occasionally, the larvae may begin to feed under the bark outside the area of the burr knot. This can girdle the tree and cause death. In most cases continuous infestation by dogwood borer larvae for several years may cause a slow decline of the tree and reduced yields.

Life History

Dogwood borers overwinter as nearly mature larvae. A cocoonlike hibernaculum, in which the larva remains during the winter, is formed inside the feeding gallery. In the spring the larva feeds for a short time and then spins a silken cocoon, which is covered with frass, just below the surface of the burr knot. Adults emerge about 25 days later. Adults may be present from May through July. Mating takes place a short time after the adults emerge from the cocoons. The female lays eggs on or near burr knots. Previously infested burr knots are favored oviposition sites. The eggs hatch in 8 to 9 days, and the larvae enter the burr knot.

Control

Pheromone traps can be used to monitor adult emergence. Traps should be placed about 4 feet above the ground. Placement much higher or lower will significantly reduce trap catches.

Burr knots can be controlled with plant growth regulators such as NAA. This is not desirable in most situations since it will force the dogwood borer larvae to feed under the bark at the margins of the burr knot. Other borers may also attack at the site of a dead burr knot. Of the Malling and Malling-Merton rootstocks, only MM 111 shows any indication of resistance to dogwood borer attack.

White latex paint applied to the lower trunk before egg laying begins will reduce infestation levels significantly. Proper planting to avoid production of burr knots below the graft union will prevent infestations from becoming established.

Trunk sprays with residual insecticides will help control dogwood borers. Generally, a single application at peak emergence will provide adequate control. A low pressure application that thoroughly wets all surfaces of the lower trunk and the burr knots is needed to ensure good control.

Periodical Cicada

Only portions of the southeastern apple-producing region experience significant threat form the periodical cicada, Magicicada septemdecin (L.), which spends most of its 17-year life underground.

Description

Adults are large flying insects about 1 1/2 inches long (Figure 2.39). The body is mostly black while the egs, legs and wing veins are orange-red. Wings are clear except for the distinct veins. Nymphs, which live in the soil, are light brown and resemble adults, but lack wings.

Damage

The most serious damage is a result of female egg laying. The female slices the small branches with her sawlike egg-laying apparatus and then inserts the eggs in the slits (Figure 2.40). Egg laying severely weakens branches. These branches usually break off in the wind. When populations of periodical cicadas are high, nearly all the smaller branch tips will break off. This is especially serious in young trees which may even be killed. Loss of scaffold limbs during the early years of development may affect productivity for the life of the tree.

Nymphs also have the potential to damage trees. Nymphs enter the soil after hatching and feed on the roots with their needlelike mouthparts. This removes nutrients from the tree. When hundreds of thousands of nymphs feed on the root system for 13 to 17 years, a tree will most likely be damaged.

Life History

Adults emerge in May once every 13 to 17 years, depending on the particular brood that is present in an area. The males produce a shrill, earsplitting whine that some people have likened to a flying saucer in science fiction movies. Females are attracted to the singing males. About 10 days after the males begin to sing, the females begin laying eggs. A single female produces as many as 400 eggs. She deposits the eggs in slits in 40 to 50 pencil-sized branches. Egg laying continues for about 30 days; then the adults die, and silence returns to the area.

The eggs hatch in 6 to 7 weeks, and the tiny white nymphs fall to the ground and burrow into the soil. Nymphs begin feeding on grass roots and eventually move to tree roots. Feeding continues for 13 or 17 years. When the transformation to the adult stage is at hand, the nymphs emerge from the soil, crawl to a tree trunk or other vertical surface, and climb several inches to several feet up. The nymphs' skin splits along the back, and the adults crawl out. In an hour or so, the wings expand, and the adults' skin hardens. When the adults first emerge, they are light colored. As they age, the normal colors appear.

Control

Several management strategies are available. If growers are planning to establish an orchard, planting should be delayed until the year after an emergence. On young trees, winter pruning should be delayed until summer. Summer pruning should begin when the cicadas quit singing but within the 4- to 6-week period after eggs are laid. Pruning at this time and destruction of the prunings will prevent most of the young nymphs form entering the soil.

Damage during the emergence period can be reduced by the use of two methods. For small orchards and backyard trees, the use of netting toenclose the trees will prevent most damage. The netting should have a 1/4-inch or finer mesh. The netting should be put in place when the first singing is heard and remain on the trees until adult activity ceases.

Where netting is not practical, pesticide sprays can be used. Several pesticide options are available, but each has specific drawbacks. For young trees in particular, one of the registered pyrethroid materials may be the best option. There are problems with mite resurgence after the use of these materials. Sprays should be applied as often as required to prevent oviposition activity. This will require scouting every 2 or 3 days. This is especially important where woods are adjacent to the orchard.

On older trees, various organophosphate insecticides alone or in combination may be a better choice than carbaryl. Carbaryl may cause unwanted fruit thinning and can cause mite resurgence. Pyrethroids are not recommended on older trees because of the mite problems associated with their use.

Even in an emergence year it is difficult to predict whether an orchard will be attacked. Diligent scouting from the time that the first males are heard singing is the best strategy to achieve control.

Flatheaded Appletree Borer

The flatheaded appletree borer, Chrysobothris femorata (Oliver), is an occasional pest of young fruit trees as well as other deciduous trees and shrubs. It is of major concern during the first 2 or 3 years after orchard establishment.

Description

Adult beetles are about 1/2 inch long and appear somewhat flattened. Their color varies from a dark metallic brown to dull gray. The wing covers appear to be finely corrugated. The body is blunt at the head and tapers to a rounded point at the posterior end (Figure2.41). The larvae are legless and have a yellow to yellowish white color. The distinctive characteristic of this borer is the broad flattened enlargement of the body immediately behind the head (Figure 2.42). Mature larvae are 1 1/2 inches long.

Damage

The larvae cause damage to trees by creating extensive galleries in the phloem of the trunk and main branches. The galleries are partially filled with powdery frass. Infested areas are often reinfested year after year. Location of active galleries is often indicated by the presence of frothy sap bleeding from cracks in the bark. The damaged areas often become depressed with splits developing in the bark. The borers usually attack the sunny side of the tree. The galleries can eventually extend around the trunk and girdle the tree.

Life History

Adult beetles begin to emerge from infested trees in late spring and continue to emerge until November. Female beetles seek out trees under stress or with damaged areas on the bark and deposit individual eggs in bark cracks or on the margins of wounds. Each female is capable of producing at least 100 eggs during her life. The larvae enter the bark after hatching and begin forming galleries. If the tree is vigorous, the larvae are often drowned by heavy sap flow. In weakened trees or in major bark wounds, the larva rapidly bores into the cambium layer and begins to form the gallery system. Development is completed in 1 year with nearly mature larvae overwintering.

Control

There is no effective chemical control for this pest. Trunk sprays for dogwood borer may give partial control. If feasible, tree wraps applied immediately after planting will prevent infestation. However, this may stimulate the development of burr knots. Maintaining tree vigor through proper fertilization and irrigation will reduce attacks by the flatheaded appletree borer.

Roundheaded Appletree Borer

The roundheaded appletree borer, Saperda candida Fab., can be a serious pest of tree crops. At one time it was the second most important pest of apples in the United States. Current pest management programs have relegated it to a minor pest although it has the potential to cause serious damage. It is more common in the Northeast but is presently in the higher elevations of Alabama, Georgia, South and North Carolinas, and Tennessee.

Description

The adult beetles are about 1 inch long and grayish white with three distinctive velvety brown stripes running the length of the body. The antennae are as long as or longer than the body. The larvae are about 1 inch long at maturity. The body is creamy yellow with a brown head. There is a rounded thickening immediately behind the head (Figure 2.43).

Damage

Larvae bore into the sapwood and move upward or downward in the trunk, depending on the time of year. The galleries are continually enlarged as the larvae feed. Mature larvae may bore an inch or more into the wood. Adults feed on the fruit, bark, and foliage. However, they usually do not cause any significant damage.

Life History

Adults begin to emerge in May. Adults live about 40 days. Unlike many borers, the roundheaded appletree borer usually selects young healthy trees for egg laying. Female beetles lay eggs in slits cut in the bark of the tree, usually near the soil line. Eggs are deposited individually between the bark and the xylem. The larvae begin to tunnel in the sapwood immediately after hatching. Larvae continue to bore in the wood for 2 to 3 years before emerging as adults.

Control

Regular orchard sprays eliminate most of the adult beetles. Trunk sprays for dogwood borer will also help control the adults before they lay eggs in the tree. There are very few natural enemies of this pest. Downy woodpeckers are one of the few predators that appear to have any effect.

Prionus Root Borers

The larval stages of the tile-horned prionus root borer, Prionus imbricornis (Linnaeus), and the broadnecked root borer, P. laticollis (Drury), feed on the roots of a wide range of hardwood trees including apple. Usually, atack by these borers is restricted to trees weakened by various stess factors. However, cases have been documented where significant tree loss occurred within 2 or 3 years after an orchard was established on recently cleared land. In these cases the prionus borers appeared to be primary attackers of the young trees.

Description

The adults are large (1 1/2 to 2 inches long), robust, reddish brown beetles with antennae about as long as their bodies. The larvae are creamy white or yellow with brown heads. Mature larvae may be as long as 4 inches (Figure 2.44).

Damage

Newly hatched larvae feed on the surface of small roots and attack progressively larger roots as they grow larger. All feeding damage is below the soil surface. Symptoms are thin foliage, premature defoliation, lack of vigor, and gradual limb-by-limb death of the tree.

Life History

Adult beetles emerge from the soil in late spring and early summer. They are often attracted to lights at night. Eggs are laid in the soil near apple trees. The larval stage may last 5 years. Mature larvae pupate in earthen cells 8 to 12 inches below the soil surface. The adults emerge from these cells and burrow to the soil surface.

Control

There is no chemical or cultural control for these borers. There is some indication that the larvae can survive for quite some time in large roots left in the soil after clearing forest land. If an apple orchard is to be planted on land that was formerly in hardwoods, complete removal of all old hardwood roots from the soil prior to planting the trees is very important. Leaving the site fallow for 1 or 2 years would be a good practice. It is also important to follow proper cultural practices to ensure that the trees are not under stress and grow properly.

Clyde S. Gorsuch