D3044: Direct and indirect effects of entomopathogenic fungi on generalist predators of whiteflies

Generalist arthropod predators have historically contributed to the suppression of arthropod pests in many agroecosystems. In addition, work with entomopathogenic fungi (EPF) have uncovered encouraging results for induced pest control. However, the direct (survivorship) and indirect (prey consumption) effects of using EPF in conjunction with generalist arthropod predators is unresolved. Here we test the hypotheses that EPF exposure level and EPF strain differentially influence survivorship and prey consumption of common predatory arthropods. Our study evaluates two entomopathogenic fungi and their direct and indirect effects on two common predators of the sweetpotato whitefly, Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae). Using a cotton leaf as our standardized unit, we exposed predators (Hippodamia convergens, and Geocoris punctipes) to two commercially available EPF strains, Cordyceps javanica Apopka-97 and Beauveria bassiana GHA strain at two exposure levels, including 24h (single exposure) and one week- continuous exposure (newly sprayed whitefly nymph provided daily). Predators were introduced into cages containing a cotton leaf with either EPF-infected or uninfected whitefly nymphs and monitored for survivorship and predation levels on whiteflies over a seven-day period. Hippodamia convergens survivorship was not significantly affected by exposure to EPF-infected whitefly nymphs. However, significantly higher mortality was observed for G. punctipes provided with EPF-infected nymphs. Furthermore, both H. convergens and G. punticipes consumed fewer whiteflies infected with the Apopka-97 strain. Combined, our results suggest exposure level and EPF strain specific effects on predator species, through both direct effects (survivorship of G.punctipes) and indirect effects of reduced feeding on EPF-infected prey.