Better Yields Through Science
Apple & Quince Diseases & Pests
| Disease | Symptoms, Life-cycle and Pest Management |
|---|---|
| Brown Mite | Scientific name: Bryobia rubrioculus Brown mites overwinter in the egg stage. Eggs are red and spherical but do not have a stipe rising from the top. Newly hatched brown mites have six legs and are bright red. After they molt for the first time, they turn brown, develop eight legs, and resemble the adult, only smaller. Adult brown mites are dark reddish brown, and the first pair of legs is longer than the other three pairs. Brown mites are usually the first mites to appear in spring. Brown mite is best controlled in the dormant season or early foliage season. In-season sprays are rarely justified. |
| European Red Mite | Scientific name: Panonychus ulmi European red mites overwinter as eggs; eggs hatch in spring when trees bloom. With the use of a hand lens, look for overwintering eggs in roughened bark at bases of buds and spurs on smaller branches and twigs, or in wounds, thus the importance of a dormant spray in control. They are globular and red with a slender stalk (stipe) rising from the top center and many grooves extending from top to bottom. During the growing season, eggs are laid on leaves. There are three instars before the adult stage. Immature mites are bright red, except just after molting when they appear bright green. The green color turns to red after the mites resume feeding. Adults are dark red and have six to eight white spots at the base of hairs on the back. Severe mite infestations can cause bronzing of leaves. |
| Pearleaf Blister Mite | Scientific name: Eriophyes (=Phytoptus) pyri Adult mites are very small, about the same size as rust mites, and cannot be seen without a 14 to 20X hand lens. The body is white, long and slender, striated, and with a few long hairs. Immature forms resemble adults but are smaller. Eggs are spherical and pearly white. Monitor and treat in fall or dormant season. Most of the overwintering blister mites are found beneath the outer bud scales in October and November and are readily controlled with a fall spray. The presence of any mites indicates the need for control. As the season progresses, control becomes more difficult. |
| San Jose Scale | Scientific name: Diaspidiotus (= Quadraspidiotus) perniciosus Female San Jose scales give birth to living young that emerge from under the edge of the scale covering. These tiny yellow crawlers wander in a random fashion until they find a suitable place to settle. Immediately upon settling, the crawlers insert their mouthparts into the host plant and begin feeding and secreting a white waxy material (white cap stage); eventually the waxy covering turns black and is known as the black cap stage. Later the covers turn various shades from gray to black. Infested fruit develop a reddish purple ring surrounding each spot where a scale settles. Dormant season treatments are the key to controlling this pest. |
| Black Rot and Frogeye Leaf Spot | Scientific name: Diaspidiotus (= Quadraspidiotus) perniciosus Female San Jose scales give birth to living young that emerge from under the edge of the scale covering. These tiny yellow crawlers wander in a random fashion until they find a suitable place to settle. Immediately upon settling, the crawlers insert their mouthparts into the host plant and begin feeding and secreting a white waxy material (white cap stage); eventually the waxy covering turns black and is known as the black cap stage. Later the covers turn various shades from gray to black. Infested fruit develop a reddish purple ring surrounding each spot where a scale settles. Dormant season treatments are the key to controlling this pest. |
| Green Apple Aphid | Scientific name: Aphis pomi Overwintering eggs are found on twigs of the previous season’s growth and on fruit spurs. They are identical in appearance to rosy apple aphid eggs : shiny, black, and football shaped. Newly hatched apple aphids are dark green. Mature aphids on apple foliage in spring and summer have a bright, yellow-green abdomen with darker green lateral spots. |
| Rosy Apple Aphid | Scientific name: Dysaphis plantaginea Newly hatched rosy apple aphids are dark green and are found on new growth in early spring. Mature rosy apple aphids, clustering in curled leaves or on young fruits in spring, are purplish and covered with a waxy, powdery bloom. Winged forms develop on apple trees in late spring and migrate to plantain, where they are found in summer. In fall, winged forms develop and migrate back to the apple trees. Overwintering eggs are laid on fruit spurs and shoots of the apple trees; they are shiny, black, and elongated. Examine the spurs for rosy apple aphid eggs. This can be done in conjunction with the dormant European red mite sample. Although difficult to detect, if any eggs are found, a dormant treatment is required because aphid colonies may quickly spread over the tree. Treat nonbearing trees to prevent stunting of terminal shoots. Because overwintering eggs are located on the bark, delayed dormant application will greatly reduce populations. Young trees need to be treated when terminals are infested. |
| Woolly Apple Aphid | Scientific name: Eriosoma lanigerum Woolly apple aphids infest roots, trunks, limbs, shoots, and occasionally fruit of apple trees. The bodies of these bark-feeding aphids are completely covered by masses of white, wool-like, waxy materials. This aphid is found in colonies on the aerial portions of the tree and on roots during winter. The nymphs migrate up or down the trunk of infested trees during summer and fall. |
| Scab | Pathogen: Venturia inaequalis Superficial, velvety dark-olive-to-black spots on fruits and leaves are the initial symptoms of apple scab. These fruit spots become scab like with age and tissues may become misshapen. The fungus survives in dead leaves on the ground. Primary spores are discharged during spring rains and infect young leaves and fruits during prolonged moisture. Secondary spores may spread disease from established infections on trees. As a rule, this disease requires yearly treatments. As plant parts mature and the weather gets warmer, susceptibility to this disease decreases, but pinpoint scab can occur during extended periods of moisture during summer. The main objective in scab management is the reduction or prevention of primary infections in spring. Extensive primary infections result in poor fruit set and make scab control during the season more difficult. If primary infections are successfully controlled, secondary infections will not be serious. The key to success in scab control is exact timing and full coverage so the Lime sulfur can eradicate the spores. Scab control is often part of a combination treatment aimed at other diseases and insect control so timing is extremely important. The key to successfully controlling scab is to apply early and thoroughly to protect new growth. The first susceptible tissues exposed in opening cluster buds are the tips of the leaves and sepals. The most critical period for scab development is from the breaking of the cluster buds until leaves are fully expanded, thus the Delayed Dormant spray is vital to control and generally leads to cleaner fruit and a minimum of later applications. This is followed by sprays at pre-pink, pink, calyx and first cover. Fungicide protection is especially critical from shuck split to 5 weeks post bloom. Sprays should be applied every 10 to 14 days until about a month before harvest. During the month before harvest sprays applied for brown rot control will help reduce late-season scab infections on the fruit, twigs, and leaves. |
| Powdery Mildew | Pathogen: Podosphaera leucotricha Powdery mildew is distinguished by superficial, white powdery growth on leaves and shoots that results in the stunting and distortion of young growth. Infected fruit are stunted and russetted, and fruit set may be reduced. The fungus overwinters in terminal buds that are white, flattened, and pointed. Disease development is favored by warm days and cool, moist nights. Thus, the post harvest treatment is important for good management of the fungus. Preferred spring application is at pre-pink and pink bud. Treat immediately if mildew is found on shoots or leaves on inner scaffolds. If powdery mildew continues to be a problem in the orchard, apply additional treatments as needed. |
| Sooty Blotch | Scientific name: Gloeodes pomigena Sooty blotch appears as greenish irregular blotches or patches on the fruit surface. Individual blotches can grow together to form larger infected areas. Sooty blotch fungus is common in the Eastern U.S. but rare in the West. Fruit may be infected by heavy spore dissemination on twigs of various wild trees. On apples, clusters of short dark hyphae make a thallus on the cuticle and this appears as a sooty brow or black blotch ¼ inch in diameter. Numerous spots may completely cover the apple. The disease develops in rainy summer weather when nighttime temperatures and overall humidity remains high. It infects fruit from after petal fall through late summer. |
| Apple Blotch | Pathogen: Phyllosticta solitaria Blotch can infect the fruit, leaves, and twigs of apple and crabapple trees. Leaf spots occur on the veins, midribs, and petioles (leaf stems) as long, narrow, slightly sunken, light-colored lesions. These contain several dark dots–the fruiting structures (pycnidia) of the fungus. When petiole infections are numerous, leaves might drop off. New shoot infections look similar to petiole infections at first, except that they are longer and more visible. They occur at the juncture of the petiole with the shoot (node) or between the nodes. Once the lesion is established, it might continue to enlarge for 3 or 4 years, becoming noticeably larger than the diameter of the normal limb. In this manner, the organism causing apple blotch establishes itself in the tree. Fruit infections vary in size from small, dark spots to large blotches that can cover much of the fruit surface. Edges of the larger lesions are irregularly lobed with many radiating projections. Large lesions often cause the fruit to crack. The fungus overwinters in twig and limb cankers. The first infections in spring occur at about petal fall on leaves, young fruit, and new shoot growth and are caused by spores oozing from the cankers. Secondary infections from spores produced in the pycnidia can occur until late summer. Frequent rains and temperatures above 75°F favor the disease. Since the disease characteristically occurs annually, control measures should be applied each year. There are two lines of remedial procedure: the removal of the cankered twigs and the protection of the susceptible parts by spraying. Spraying must be done before inoculation takes place; this occurs within a month after the petals fall. First application, three weeks after the blossoms drop. Second application should be made two to four weeks after the first. A third application is recommended ten weeks after the petals fall. Fall clean up spray and dormant sprays can help reduce overwintering spores. |
| Fly Speck | Scientific name: Microthyriella rubi Similar to Sooty blotch, Fly speck fungus is common in the Eastern U.S. but rare in the West. Flyspeck appears as groups of small, shiny, black dots on the fruit surface. Fruit may be infected by heavy spore dissemination on twigs of various wild trees. The disease develops in rainy summer weather when nighttime temperatures and overall humidity remains high. It infects fruit from after petal fall through late summer. |
| Oystershell Scale | Scientific Name: Lepidosaphes ulmi The oyster shell scale belongs to a group of insects called the armored scales. There is one or two generations of oystershell scale each season. Oystershell scale feeding weakens the plant. Damage consists of small, dark brown scales cluster on bark or on fruit. Scales overwinter as fertilized females with 40-150 egg masses under their scale. Eggs hatch in late spring, approximately two to three weeks after bloom, and young crawlers emerge. Crawlers are small white with six legs, moving to an appropriate site where to begin feeding. They insert their mouthparts into the plant, begin to suck sap and soon molt. From this point on, they will remain in the same spot for the rest of their lives. After a few hours of feeding, the scale begins to form. Mating occurs and females die shortly after they lay their last eggs. Crawlers spread through orchards by wind, birds’ feet, workers’ clothing and on farm equipment. Use lime sulfur during late dormancy just before bud break when scales have only a thin wax covering. Delaying application until green tissue is present often results in poor scale control, because scales have produced a larger protective wax coating making complete coverage of the insect more difficult. |