Black Pecan Aphid, Melanocallis caryaefoliaeHosts: Found on pecan and hickory.
Symptoms: The first signs of feeding are bright yellow patches in the leaflets that are often rectangular in shape. These yellow areas eventually die and turn brown. The patches are caused by a toxin that the aphid introduces into the leaf tissue while feeding. Only a few damaged areas are necessary to cause the entire leaflet to drop from the tree. The damaged spot will appear and continue to develop even if an aphid is killed after feeding for only a few minutes. Because of the severity of the damage caused by the black pecan aphid, large-scale, premature defoliation can occur in orchards with heavy populations. This defoliation not only contributes to poor nut quality but also reduces return bloom in the orchard the following year.
Life Cycle: The black pecan aphid overwinters as an egg in bark crevices. The nymphs hatch in the spring, move to young foliage, and begin to feed. They mature into asexual stem mothers in about a week and begin to produce living young. These offspring in turn mature into asexual females. Many generations (15 to 30) of females are produced per year. The fall forms, wingless females and winged males, begin to appear among the nymphs in October. These forms mate and the females migrate to protected areas of the limbs and trunk and deposit their eggs in cracks.
Description: Most of the forms of the black aphid are pear-shaped, pale to dark olive green in the nymphal stages and black as adults. However, the early summer forms, which include the stem mothers and one or two generations of their offspring, are yellow-green with relatively little dark pigment. They have four rows of hairs on their bodies - two along the back and one on each lateral margin. Winged adults are jet black with transparent wings and several snow white, waxy spots on the upper surface of the body. They hold their wings tent-like over their abdomens at rest.
Control: Please contact your local county extension office for current information.
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