College of Agriculture & Natural Resources

• Bitter pit and cork spot

  Small, green to purplish to light brown, slightly sunken lesions appear on the surface of mature fruit. Individual lesions on the fruit surface are dry and do not extend deep into the fruit; however, cutting into the fruit can reveal numerous internal lesions.

• Apple anthracnose

  Branch lesions first appear as small, circular spots that are purple or red when wet. As lesions enlarge, they become elliptical, sunken and turn orange to brown. A distinct margin develops between healthy and diseased tissue, which eventually causes the bark to crack around the infected area.

• Dock sawfly

  The adult is bluish black with red legs. The larva is a smooth velvety green worm with white legs and a dark head.

• Climbing cutworms

  Adults are dark brown or grayish colored moths. Larvae tend to be smooth caterpillars with few hairs, brown or black head capsules, and bodies a dull gray-brown background color with stripes, spots, or dark brown, black, yellow or white splotches.

• Forest tent caterpillar

  Adults are reddish brown with two brown, transverse-parallel bands. Masses of shiny black eggs are laid in a ring around twigs. Larvae have long silky hairs on their body and a row of elongated spots along the back.

• Pearleaf blister mite

  The adults are very small and cannot be seen without a 15X hand lens; the body is white and elongate oval in shape, like a tiny sausage.

• Variegated leafroller

  Adult is grayish magenta with dark brown bands on the middle and end of the forewing. Larvae are pale green with yellowish green heads.

• Oystershell scale

  The adult female remains immobile under a small brown scale in the shape of an oyster shell attached to the bark of branches. The white and oval eggs are laid inside the scale and crawlers emerge in the spring during the petal fall stage of apple.

• Pear psylla

  Adults resemble very small cicadas and can be reddish brown or tan to light brown. Smaller, wingless nymphs are yellow with red eyes, flat and oval in shape, and develop within a clear honeydew drop.

• Gypsy moth

  The adult male is brownish and marked with blackish zigzag lines. The adult female is whitish with brown transverse zigzag stripes and does not fly. The masses of oval and yellow eggs are laid on the trunk of trees and covered with hair left by the female.

• Phytoseiid mites

  A dark mark in the form of an "H" sometimes appears within their body. This mark is red when they feed on European red mites and yellow when they feed on twospotted spider mites. They move very rapidly on the leaves.

• Crown gall

  Infected trees are often stunted and produce small, chlorotic leaves. Spherical to elongated swellings along the roots or on the trunk just above the soil line is the primary symptom.

• Roundheaded appletree borer

  Adult has a hard, elongated body, with white and brown longitudinal stripes and long antennae. The larva is a fleshy, cream-colored legless grub with a dark brown head, blackish mandibles.

• Potato leafhopper

  All leafhopper species feed on the undersides of leaves, puncturing cells and sucking out the contents. In general, juice grape (labrusca) varieties are much more tolerant of leafhoppers than hybrid or vinifera varieties.

• Pear slug (Pear sawfly)

  The adult looks similar to a small, black-bodied wasp with the ventral side and legs yellow in color. The larva is small, fleshy, dark green to orange, slug-like, and slime-covered, with the front part of the body enlarged.

• Redhumped caterpillar

  The adult is a grayish brown moth. The larva is yellow with a red head and is lined longitudinally with orangish, black, and white stripes.

• Woolly apple aphid

  The colonies of reddish brown adults and nymphs produce waxy secretions, which resemble small tufts of wool or cotton batting. The aphids are without cornicles, possessing only abdominal pores.

• Mucor Rot

  Infected tissue appears light brown, soft, and watery. The infection usually develops at wound sites, at the calyx end, or at the stem end of the fruit.

• Snowy tree cricket

  Adult somewhat resembles a field cricket, but is pale green in color and has a longer, more slender body and smaller head. Antennae are much longer than the body; males have stiff veins in their flat wings.

• Silver leaf

  Silvering of the foliage is the characteristic symptom. At first, silvering may be associated with only one or two major branches, but eventually the entire tree becomes silvery in appearance. When infection is severe the leaves may curl upward.