Just a quick update here. If you have had problems with black pecan aphids (BPA) and/or anticipate having problems with them in certain blocks that are vulnerable to their infestation, spraying gibberellic acid (Pro Gibb 4%, ProGibb LV Plus) at this time of the season is an option. Gibberellic acid is a plant growth regulator that prevents damage from black pecan aphid feeding, and inhibits BPA establishment in the orchard.
Three applications should be made at 2-week intervals, beginning in mid-July, applying 10 oz (or 5 oz of ProGibb LV Plus) each time.
When black aphid nymphs are feeding on leaves, it causes leaf chlorosis (yellowing/browning of the leaves). Spraying gibberellic acid before this injury occurs will prevent the injury from manifesting in spite of black aphid feeding. Preventing this injury from occurring will inhibit establishment of BPA on treated trees. If leaf yellowing has already occurred, spraying giberrellic acid will not make the leaves green again.
It is important to note that spraying gibberellic acid will not kill the black pecan aphids, yellow and blackmargined aphids.