Effect of soybean trichome density on soybean aphid and its natural enemies

Since the arrival of soybean aphid, Aphis glycines, Matsumura, (Hemiptera: Aphididae) in North America, outbreaks are managed with broad-spectrum insecticides. However, genes conferring antibiotic resistance to A. glycines (i.e. Rag genes) occur in soybean germplasm and can prevent aphid outbreaks in North America. Soybean pubescence or trichome density is not a component of Rag-based resistance, but has historically contributed to the management of potato leafhopper, Empoasca fabae, Harris, (Hemiptera: Cicadellidae). However, there is limited documentation of the impact of trichomes on A. glycines in North America. Our objective was to determine if varying trichome density limits A. glycines population growth in both lab and field settings. We hypothesize that trichomes interfere with both A. glycines and their associated natural enemies. In the lab, we compared the impact of trichomes on A. glycines using 10 soybean isolines with varying levels of trichome density as well as an aphid-susceptible (i.e., positive control) and an aphid-resistant (i.e., negative control containing Rag1 + Rag2). To determine the impact of trichome density on the biocontrol of A. glycines, we compared aphid population growth on caged and uncaged plants from these isolines within a field setting. To date, we observed no impact of soybean trichomes on A. glycines population growth in a laboratory setting. However, within a rainfall simulator, we observed more aphids removed from glaborous than pubescent varieties after a rain event.  Currently, our field experiment is not completed. We will discuss if trichome density interfered with A. glycines’ predation, reducing the biocontrol of this pest within the field.