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| Black aphid | Black aphid damage |
BLACK APHID
The black pecan aphid is much more destructive than the yellow aphid species. Three black pecan aphids per compound leaf can cause severe leaf damage and defoliation. Like the yellow aphids, the black pecan aphid feeds on the undersides of leaves and occurs throughout the pecan growing region of Texas.
Damage: While feeding, the black pecan aphid injects a toxin that causes the leaf tissue between major veins to turn bright yellow. These damaged areas, up to 1/4 inch across, turn brown and die. Infested leaves soon fall. Premature defoliation reduces nut fill and the following year's production.
Biology: The black pecan aphid is pear-shaped. Nymphs are dark olive-green while adults, which may be winged, are black. Like the yellow aphids, all summer forms are females that reproduce without mating. Male and female forms appear in the fall and females deposit eggs which overwinter on branches.
Densities often are very low until August or September, when infestations often increase rapidly.
Control: Monitor the orchard frequently for black pecan aphids and their characteristic leaf injury. Since these aphids feed singly and can be damaging in low numbers, examine leaves closely. Pecan varieties differ in their susceptibility to black pecan aphid injury. Consider the ex- tent of leaf damage and aphid numbers. In general, treat when black pecan aphids average more than three per com- pound leaf. In most cases, black pecan aphids are not as difficult to control with insecticides as are the yellow aphids. Natural enemies are important in maintaining low numbers of black pecan aphids.