The aphids create yellowish-red, angular blotches on leaflet surfaces between veins. Blotches may start out one-quarter of an inch and grow, even when aphid leaves.
Blotches die and turn brown, caused by a toxin injected by the aphid as it feeds.
Only a few damaged areas can cause a leaf to drop. Feeding typically begins in the center of the tree canopy and moves outwards. Early defoliation by this pest can affect the nut crop for that yea and the nut set in the subsequent year. It also makes the tree more susceptible to winter injury. The black pecan aphid is the only black aphid that attacks pecan foliage.