Management of Melanocallis caryaefoliae (black pecan aphid) via applications of exogenous gibberellic acid

Melanocallis caryaefoliae (black pecan aphid, BPA) is a principal pest in every pecan growing region within the United States. In New Mexico pecans are the highest earning crop when it comes to gross cash receipts. Therefore most growers in the state monitor and manage for BPA. This pest is a foliar feeder and resulting damage includes chlorotic/necrotic areas near feeding sites. In heavy infestations, BPA feeding will promote early leaf senescence resulting in poor nut fill, and lower yields. Applications of exogenous gibberellic acid (ProGibb LV Plus) in pecans promotes trees to have increased leaf retention and maintain green foliage. An untreated control and four rates of ProGibb were applied using a modified air blast sprayer to four blocks of five trees in 2021 and 2022. Leaves were destructively sampled weekly to quantify all aphid life stages and were then scanned to determine total chlorosis. Clip-cages were placed over a 3^rd/4^th instar BPA in the field and checked daily until molting into an adult. Clip-cages were harvested two weeks after treatment to count aphids and estimate chlorotic area. Leaf nutrient concentrations, yield, and nut quality were estimated for each tree. Early data analysis for 2022 shows total aphid populations encompassed in clip-cages having a decreasing trend in treated plots, on 9/7/22 treated plots show a decrease in aphid numbers per compound leaf when compared to control, and early analysis on leaf chlorosis shows high variability between treatments.  Consequently, ProGibb is looking more promising as a management tool.