Threat of Infection and Threat-Avoidance Behavior in the Predator Dicyphus hesperus Feeding on Whitefly Nymphs Infected with an Entomopathogen

The nature and severity of intraguild interactions between predators and entomopathogens will be determined, in part, by a combination of threat of infection, and avoidance of that threat by the predator. We determined the threat of infection posed by the entomopathogen, Paecilomyces fumosoroseus (as PFR-97 (TM)) to the generalist predator, Dicyphus hesperus. We then asked if D. hesperus displays behavioral avoidance of infection while foraging for whitefly nymphs at different stages of infection by the pathogen. When exposed to leaf surfaces treated with the pathogen, 28% of adult female predators died due to infection. Consumption of Ephestia kuehniella eggs by surviving predators over 6 d was significantly reduced, suggesting effects of a sublethal infection. Whitefly nymphs that had been treated with P. fumosoroseus 3 d prior were acceptable as prey to D. hesperus but whitefly nymphs that had been treated with P. fumosoroseus 5 days prior were not. When foraging for whitefly nymphs, adult D. hesperus females rejected infected nymphs 96% of the time, compared to 39% of non-infected nymphs. Paecilomyces fumosoroseus therefore presents a measurable threat to D. hesperus through mortality and reduced prey consumption. Dicyphus hesperus does not avoid initial contact with infected prey but does not feed on such prey. The mechanism underlying these rejections could be due to either avoidance of infection or rejection of prey already consumed by the infectious agent. These results suggest that predation by D. hesperus foraging among infected whitefly nymphs under greenhouse or natural conditions could be reduced through a combination of pathogenicity and reduced efficiency of foraging.