Key Arthropods and Diseases Affecting Apples

Tarnished Plant Bug  Leafminer European Apple Sawfly Mites Plum Curculio Coddling Moth 

White Apple Leaf Hopper Aphids Apple Maggot Fly Borer

Tarnished Plant Bug (TPB)

Lygus lineolaris (Palisot de Beauvois)
 

• Description: Adults are approximately 1/4 inch long, oval, and slightly flattened. They are brown in color with a white or yellow Y on the thorax. Nymphs are green in color with black spots.
• Life Cycle: Adults overwinter in protected places such as under leaf litter, stones, logs, and in cracks in tree bark. They become active in the spring and move to fruit trees as buds begin to open. They are most abundant and active in the orchard from green tip through petal fall.
• Damage: TPB feeds on buds and flower parts in the spring. Buds or flowers which have been injured will abort or fail to develop normally. Early feeding on the fruit occurs later in the season and results in depressions which deepen as the fruit grows. Egg laying punctures are deeper and are most often found on the calyx end. Feeding and ovipostition on the fruit by adults is most noticeable at harvest. Fruit which is attacked when very young may abort.
• Monitoring
• Key times for monitoring: silver tip-bloom
• Monitoring method: Sticky coated 6x8" white rectangle traps should be set out at silver tip at one per 3-5 acres, near the block periphery or two rows in from the outermost row. Place a minimum of 5 traps/block. Traps should be hung vertically from an outer branch at just below knee height. Each week, the number of TPB captures should be recorded, and that week’s captures removed from the trap.
• Action Threshold: Action threshold during tight cluster for apples that will be sold wholesale is a cumulative average of 3 TPB/trap, while the threshold for retail apples is a cumulative average of 5/trap. Action threshold during late pink for apples that will be sold wholesale is a cumulative average of 5/trap, while the action threshold for apples that will be sold retail is a cumulative average of 8/trap.
• Management:
• Cultural controls: Reduce or eliminate broadleaf weeds, especially chickweeds, dandelion and clovers, from orchard sod. Do not mow from bloom through petal fall to prevent the flying of adults into trees. Avoid the placement of orchards adjacent to alfalfa hay or strawberry fields (which house alternative hosts).
• Biological Control: TPB has many natural enemies, including other true bugs, ladybird beetles, spiders, and parasitic wasps. These biological controls may lower TPB numbers, but are not able to achieve complete control of the insect.
• Chemical: See New England Apple Pest Management Guide

To Tarnished Plant Bug Images

Back to Top

Back to Index

Leafminers (LM)

Apple Blotch Leafminer

Phyllonorycter crataegella (Clemens)

Spotted Tentiform Leafminer

Phyllonorycter blancardella (Fabricius)

The biology, phenology, and management of both leaf miner species are similar and are often collectively referred to as leafminers (LM).

• Description: Moths are very small, light brown in color, appear shiny in flight, and have white spots that look like transverse bands when the wings are folded. The first three instars (sap feeders) are clear or pale yellow, flattened, and possess no legs. The last two instars, (tissue feeders) are darker yellow, cylindrical in shape, with thoracic legs and abdominal prolegs. Pupae are brown, elongated and cylindrical, with the future eyes, antennae, and wings of the adult visible.
• Lifecycle: Leafminers overwinter as pupae within leaf mines from the previous fall. Adults emerge in April to late May, mate, and commence egg laying. In the sap feeding stages the larvae feed just above the lower leaf surface, and in the tissue feeding stage, begin feeding just below the upper leaf surface, producing densely spotted mines. Pupation occurs in June, followed shortly by adult moth emergence. Second generation mines occur in July, with adult emergence in August. Third generation larvae, present by mid-August, pupate in the mines and overwinter, emerging the following spring. Generations may overlap due to the extended period of egg laying and long larval development.
• Damage: Densely spotted mined areas on the leaves. Heavy foliar damage can affect fruit quality and quantity indirectly, resulting in a decrease in fruit size, early ripening, premature fruit drop, and reduced fruit set the following season.
• Monitoring
• Key times for monitoring: Silver tip - mid August.
• Monitoring method: Sticky red visual traps should be stapled to tree trunks at silver tip. Place a minimum of 4 traps per 8-acre block. Beginning at petal fall, check 10 fruit cluster leaves per tree in at least 10 trees throughout the orchard for signs of mine development. In July, monitor for second generation population levels. Observe later folding fruit cluster leaves as well as leaves on the basal portion of the present seasons vegetative shoots. Again, observe 10 leaves per tree in at least 10 trees thoughout the orchard. Wing traps baited with pheromone may also be used for monitoring of LM.
• Action Threshold: Action threshold for red visual trap captures are a cumulative average of 4 LM/trap on McIntosh trees, 8 LM/trap on non-McIntosh trees during tight cluster. During late pink the action threshold is 9 LM/ trap on McIntosh trees and 21 LM/trap on non-McIntosh trees. The action threshold for leaf mine monitoring at petal fall is 7 mines/100 leaves for McIntosh trees and 14 mines/100 leaves for non-McIntosh trees. The action threshold for second generation monitoring in July is 50 mines/100 leaves for McIntosh and 100 mines/100 leaves for non-McIntosh.
• Management
• Cultural: Flail mowing of leaf litter in autumn may reduce overwintering leaf miner populations.
• Biological control: There is a complex of parasitoids which decrease populations of leafminer. The two most common are Sympiesis marylandensis and Pholetesor ornigis. Both are wasps whose larvae feed on LM larvae in the tissue feeding stage. Selecting insecticides which are least toxic to these natural enemies will enhance biological control.
• Chemical: See New England Apple Pest Management Guide

To Leafminer Images

Back to Top

Back to Index

European Apple Sawfly (EAS)

Hoplocampa testudinea (Klug)

• Description: The head, antennae, and lower body surface of the adult are light orange to yellow, the upper body is dark brown and shiny. Larva is light cream colored with a black head and rear shield.
• Lifecycle: EAS overwinter as mature larvae in an earthen cell. Larvae pupate in the spring and adults emerge during pink. The female EAS begins egg laying just after the king flower opens. After the egg hatches, the larva begins tunneling just under the surface of the fruit. Later in its development, the larva may exit the fruit and migrate to adjacent fruit, where they burrow to the core. Infested fruit fall to the ground where larvae exit the fruit and enter the soil. There is one generation per year.
• Damage: Larvae feeding just under the skin of the fruit create a ribbonlike scar on the surface of the fruit. Larval feeding inside the fruit causes the fruit to abort.
• Monitoring
• Key times for monitoring: Early pink-petal fall.
• Monitoring method: Sticky white rectangle traps should be placed at head height, on the south side of the tree, within 18" of the tree dripline. Place traps near a large group of blossoms but remove blossoms within 12" of trap. Place 1 trap/2-4 acres, with a minimum of 5 traps/block.
• Action Threshold: The action threshold for this pest is an average cumulative capture of 5/trap by petal fall in blocks receiving no pre-bloom insecticide, or average cumulative capture of 9/trap by petal fall in blocks with pre-bloom insecticide.
• Management
• Cultural: None available.
• Biological: No effective natural enemies are currently known in the U.S. This species had been introduced from Europe, and many of its natural enemies were not introduced with it.
• Chemical: See New England Apple Pest Management Guide

To European Apple Sawfly Images

Back to Top

Back to Index

Mites

European Red Mite (ERM)

Panonychus ulmi (Koch)

Two-spotted Spider Mite (TSSM)

Tetranychus urticae (Koch)

• Description: The adult ERM is dark red or brownish red, with bristles on the top of the abdomen. The ERM egg is small, oval, and bright red. The ERM nymph is light orange and darkens as it feeds. TSSM are pale green or straw colored, with two dark spots on the back. When high populations of TSSM are present, they may construct webbing on the under surface of the leaf.
• Lifecycle: ERM overwinter as eggs, usually found in cracks and crevices on the bark, close to the main trunk and branches. Eggs will begin to hatch around the tight cluster stage of apple. As eggs hatch, nymphs move from twigs to developing foliage and begin feeding. Nymphs mature, mate, and lay the first generation of eggs. There may be 6-8 generations of European red mite each year. TSSM overwinter as adult females under bark or on weeds beneath the tree. TSSM are able to be dispersed by wind or air currents.
• Damage: Feeding by mites results in leaf injury referred to as bronzing. This leaf injury may result in reduced photosynthesis and a reduction in the nitrogen content of the trees. Prolonged feeding may result in a reduction in shoots growth, fruit bud set, and fruit quality.
• Monitoring
• Key times for monitoring: Petal fall-late summer.
• Monitoring method: Leaves for motile mites from May through August.
• Action Thresholds:

1. Koehler,G.W. ed. 2000. Mite Pests. Pages 43-46 in: 2000-2001 New England Apple Pest Managment Guide.Cooperative Extension Universities of Connecticut, Maine, Massachusetts, New Hampshire, Rhode Island and Vermont.

• Management
• Cultural Control: For greater control of TSSM, mow orchard grass frequently. Allowing grass to grow into trees before mowing allows for TSSM dispersal into trees.
• Biocontrol: Maintaining levels of predatory mites in the orchard sufficient to keep ERM in check is the most important means of control. Avoid pesticides that disrupt or kill predators whenever possible. Predators of the ERM include Typhlodromus pyri, Zetzellia mali, and Amblyseius fallacis. Growers may "seed" predatory mites in their orchards if the natural population is low. Growers interested in learning more about this may obtain a 4-page Fact Sheet, "Achieving Biological Control of European Red Mite in Northeast Apples: an implementation guide for growers" - Cornell IPM Bulletin 14411. See sources in this booklet for address.
• Chemical: See New England Apple Pest Management Guide

Toxicity to T. Pyri Chart¹

2. Breth, Nyrop, and Kovach. 1998. Acheiving biological control of European Red Mite in Northeast apples: An implementation guide for growers. New York State Publication. Number 215.

To Mite Images

Back to Top

Back to Index

Plum Curculio (PC)

Conotrachelus nenuphar(Herbst)

• Description: Weevils, about 1/4 inch long, are variegated gray, brown, and black with white or silvery specks. There are four humps on the back, the middle two being the most conspicuous. A distinguishing long curved "snout" protrudes from the head. Adults will feign death and drop to the ground when disturbed. Larvae are legless, whitish, bow-shaped, and have a well-defined brown head capsule.
• Life Cycle: Adults overwinter under ground debris, often adjacent to but not in the apple orchard. They are usually seen in the orchard when blossoms begin to open. New individuals from outside sources may continue to migrate into the orchard for a month to six weeks. Activity in the orchard usually peaks at 12-14 days after petal fall. Egg laying begins once fruit forms. The female creates a small cavity beneath the fruit surface with her mouth parts, then turns and deposits an egg in the cavity. She then turns again and creates a crescent shaped cut around and beneath the cavity containing the egg. This cut releases the pressure from the growing fruit. Egg laying continues for about 6 weeks after petal fall. After the eggs hatch, the larvae bore into the fruit, eating irregular cavities. Fruit which are attacked tend to drop prematurely. The larvae mature, exit the fruit, and enter the soil. The pupal stage lasts for two weeks, and the adult remains in the soil for about 5 days before emerging. New adults appear in the orchard in mid-to-late July and continue emerging and feed on fruit until late September. They then migrate to their overwintering sites.
• Damage: Adults feed on flower parts and foliage in the early spring. Egg laying creates a crescent shaped oviposition mark. Feeding on the fruit may also occur, noticeable at harvest as irregular russeting areas or small circular holes. Larval feeding results in internal breakdown and possible premature fruit drop. Plum Curculio are capable of 100% fruit damage if unchecked.
• Monitoring
• Key times for monitoring: From bloom until end of migration into the orchard.
• Monitoring method: Visually inspect for fresh feeding or egglaying activity beginning at bloom. Inspect daily until damage is seen. Examine at least 10 fruits per tree on 1 tree per 3-5 acres, on the perimeter of the orchard. Movement into the orchard is often initiated by daytime temperatures of 60° F or higher for three consecutive days or 75° F for two days.
• Action Threshold: Any detected PC injury to the fruit. Use DD model to determine timing of last spray. See New England Apple Pest Management Guide for details.
• Management
• Cultural: There are few effective biological or cultural controls for PC. Winter prune to open up canopy in order to enhance spray coverage.
• Biological Control: Several species of wasps parasitize the eggs and larvae of plum curculio. Some fungi also kill larvae. Predators such as ants, lacewings, and ground beetles also attack the plum curculio. These organisms are not usually sufficient to regulate populations of plum curculio in commercial orchards, however.
• Chemical: See New England Apple Pest Management Guide

To Plum Curculiio Images

Back to Top

Back to Index

Codling Moth (CM)

Cydia pomonella (L.)

• Description: Moths, ½ inch long, are gray-brown, and have a coppery area at the tip of each wing. Larvae are light pink, with a brown head capsule.
• Lifecycle - CM overwinter as mature larvae in cocoons under tree bark, in ground cover, and in other sheltered areas. The larvae pupate in mid-spring. Adults emerge around petal fall and continue to emerge for 6 weeks. Peak emergence is usually 10 to 14 days after first emergence. This generation of CM mates and lays eggs on leaves and developing fruit. When the eggs hatch, the larvae seek out fruit and chew through the skin, burrowing into the fruit. When development is complete, larvae crawl out of the fruit and drop to the orchard floor. Larvae from this generation may enter hibernation, or pupate and emerge as a second generation of adults in August.
• Damage: Larvae may cause "stings", which damage only the surface flesh of the fruit. Deep inner tunneling results in internal breakdown and possible abortion of the fruit.
• Monitoring
• Key time for monitoring: Bloom through harvest.
• Monitoring Method: At bloom, place a sticky wing trap with female codling moth pheromone trap at eye level near the periphery of the tree, with 1 trap in the center of each block. Change the pheromone every 3-4 weeks and trap bottom as necessary. Traps should be inspected daily until the first male moth capture.
• Action Threshold: From the first adult CM trap catch, calculate degree days to first insecticide spray (250-350 DD base 50). For second generation CM, calculate DD from first adult catch to time of insecticide spray (1260-1370 base 50). See the New England Apple Pest Management Guide for details.
• Management
• Cultural: None.
• Biological control: While there are predators and parasites which feed on codling moth, these biological controls do not sufficiently control this insect in commercial orchards. Mating disruption through the use of pheromones has been tried in some orchards and can be an effective management option for some growers.
• Chemical: See New England Apple Pest Management Guide

To Coddling Moth Images

Back to Top

Back to Index

White Apple Leafhopper

Typhlocyba pomaria McAtee

• Description: White apple leafhopper adults are faintly yellow with a reddish orange tinge to the head and thorax, about 1/8 inch long, and hold their wings over their backs when resting. The eggs are white, and the nymphs are pale white for the first two instars, and white to yellow for the last three instars.
• Lifecycle: White apple leafhopper overwinters as an egg under the bark of twigs. Eggs begin to hatch during bloom, and usually complete hatching by petal fall. The nymphs then move to the underside of a leaf in order to develop. Once mature, females mate and may lay as many as 50-60 eggs. The total life span of the white apple leafhopper is five to six weeks. There are two generations per year.
• Damage: White apple leafhoppers cause stippling and mottling of the leaf. Their honeydew can cause fruit spotting or speckling. They are a nuisance to orchard workers if they occur in large numbers, and can act as a disease vector.
• Monitoring
• Key times for monitoring: Petal fall – August.
• Monitoring method: Counts should be made on 20 leaves/tree on 5 trees/block for nymphs and adults.
• Action Threshold: If the average count of WALH exceeds 25 on 100 leaves, control should be considered.
• Management
• Cultural: None.
• Biological: WALH may be attacked by an egg parasite, Anagrus epos Girault. It both overwinters inside the egg and attacks the eggs during the summer. Nymphs of the WALH may be attacked by predatory mirids. In order to enhance biological control, choose pesticides which have low toxicity to these biological control agents when possible.
• Chemical: See New England Apple Pest Management Guide

To White Apple Leafhopper Images

Back to Top

Back to Index

Aphids

Green Apple Aphid (GAA)

Aphis pomi De Geer

Spirea aphid

Aphis spiraecola Patch

Spirea aphids resemble GAA, the chief difference between them being that spirea activity may extend later into the summer, and the spirea aphid may have a somewhat different susceptibility to specific insecticides.

• Description: GAA adults are yellowish green to green with black cornicles at the end of the abdomen. They are generally present in early to mid summer.
• Lifecycle: GAA overwinter as eggs on water sprouts and twigs. Eggs hatch in spring between silver tip and half inch green. Nymphs feed on foliage as they mature. Adults give birth to living young without mating. In the summer winged individuals appear and may migrate to other host plants, as light winds can carry them many miles. In the fall, GAA produce males and females, mate, and the females deposit eggs. GAA can produce 10-15 generations per year.
• Damage: GAA aphids suck sap from apple trees. Large populations may cause leaf curl. Large excretions of honeydew provide a media for the growth of black sooty-mold fungus.
• Monitoring
• Key times for monitoring: Monitor mid-to-late June-August.
• Monitoring Method: Monitor for GAA weekly beginning in mid to late June when colonies are readily apparent, and continue to monitor through August. Populations can be monitored by inspecting 10 foliage terminals (not waterspouts)/tree on 1 tree/3-5 acres. Presence of aphids and predators should be noted (see biological control section below). A predator:prey ratio of 1:5 should suppress aphid populations. (If for every 5 terminals which have aphids, one of those terminals has a predator, this level should effectively suppress aphid populations). Examine 15 apples on 3 trees/acre for the presence of aphids and/or honeydew. If at any time, greater than 10% of fruit have aphids and/or honeydew, control is recommended.
• Action Thresholds: More than 50% of vegetative terminals are infested and predators are present on less than 10% of the infested terminals, or 10% of the fruit have honeydew or aphids.
• Management
• Cultural: Maintain proper nutrition in the orchard in order to discourage succulent growth. Prune in such a way as to avoid encouraging the tree to produce water sprouts.
• Biological: Many natural predators provide control of aphids. Predators of aphids include chrysopid (green lacewing) larvae, syrphid and cecidomyiid fly larvae, ladybird beetle adults and larvae, and many others. Choose an insecticide that will allow for significant predator survival.
• Chemical: See New England Apple Pest Management Guide

To Aphid Images

Back to Top

Back to Index

Apple Maggot Fly (AMF)

Rhagoletis pomonella (Walsh)

• Description: Adult fly is slightly smaller than a common housefly. It has a white dot on its thorax and black banding in the shape of an M on its wings. The larvae resemble typical housefly maggots.
• Lifecycle: AMF overwinters in the pupal stage in the soil. Adults emerge in mid to late June, and mate. The females begin laying eggs under the skin of the apple 10 to 14 days later. The larvae then tunnel through the apple flesh, causing the apples to drop prematurely. After the fruit drops, the larvae leave the fruit and enter the soil to pupate. Most New England orchards have only one generation of AMF per year.
• Damage: Internal decay and fruit abortion caused by larval tunneling. Surface "stings" caused by oviposition are difficult to detect.
• Monitoring
• Key times for monitoring: Late June - August.
• Monitoring method: Hang a standard sticky red sphere at head height in the fruiting zone on the south side of the tree, away from leaves, near block periphery. Clean spheres as necessary. Place at 1 red sphere/2-4 acres, minimum of 5 traps/block. Several variations on the sticky red sphere, including lightweight disposable spheres, are available from IPM supply catalogs. A bait made from synthetic apple volatile may be added to the sphere. The baited spheres have been shown to be 2-4 times more effective in capturing AMF than unbaited spheres. Hang traps in late June in blocks where early ripening cultivars are grown, and in early July for non-early ripening cultivars.
• Action threshold: The action threshold is a cumulative average of 2 AMF per trap on non-baited spheres, and 5 AMF per trap on baited spheres.
• Management
• Cultural: Trapping out the AMF has been tried in some orchards, and may be an effective management tool for some growers.
• Chemical: See New England Apple Pest Management Guide

To Apple Maggot Fly Images

Back to Top

Back to Index

Borers

Dogwood borer

Synanthedon scitula (Harris)

Roundheaded apple tree borer

Saperda candida (Fabricus)

• Description: The dogwood borer adult is a black and yellow striped clear winged moth that resembles a wasp. The larva is pale pink with a brown head. Adult round-headed apple tree borers are light olive brown beetles, with two white stripes running the length of the body. The females are approximately 1 inch long, the males slightly smaller. Larvae are pale yellowish white, with a dark brown head and dark mandibles.
• Lifecycle: Dogwood borers overwinter as full-grown larvae under bark. The insect pupates in the spring and the adults emerge in June, continuing to emerge through July and often early August. Round-headed apple tree borer adults deposit eggs under bark and in small cavities in the tree trunk, near the ground. The larvae hatch, and bore into the tree, eventually reaching the heartwood. The larvae pupate and emerge as adults two to three years later.
• Damage: Dogwood borers bore into burr knots or adventitious roots just below the graft union. Insects are detectable by the presence of reddish brown frass on the surface of the bored wood. Presence of round-headed apple tree borers is detectable by sawdust casting pushed from the on the ground beneath bored tunnels.
• Monitoring
• Key times for monitoring: spring and bloom (dogwood borer). September (roundheaded apple tree borer)
• Monitoring method: Wing pheromone traps may be used for monitoring adult male emergence of dogwood borer. Traps should be installed during bloom. Traps may be baited with either dogwood borer pheromone or lilac borer pheromone. Research in Virginia has shown that traps baited with the lilac borer pheromone are actually more effective at catching dogwood borer than traps baited with the dogwood borer pheromone. Traps should be hung at four feet above the ground. Height of trap placement is critical - deviations may drastically reduce trap capture. Traps for dogwood may also capture other borers, as these traps are not very species specific. There are currently no action thresholds for dogwood borer. In the spring, check under tree guards for active infestations of dogwood borer. If burr knots on the tree are noticed, they should be examined for the presence of the protruding pupal skins of the dogwood borer. To monitor for the presence of round headed apple tree borer, look for reddish sawdust-like castings at the base of the tree and darkened areas in the bark in September.
• Management
• Cultural: Keep trees healthy. It has been found that regularly watered and fertilized trees are able to maintain vigor and are less susceptible to borer injury, while stressed trees are more susceptible to borer attack. Select rootstocks with a lower propensity for burr knots. Keep the area around the trunk weed-free and do not mulch around tree trunks. Use wire mesh rather than solid plastic mouseguards. Apply white latex paint to the trunk area to deter egg laying. Severely attacked trees should be removed. Monitor for round-headed borer presence in September. If presence of round-headed borer is noticed, a small length of wire can be inserted into tunnels to kill larvae.
• Chemical: See New England Apple Pest Management Guide

To Borer Images

Back to Top

Back to Index