Avoidance behavior of adult whiteflies (Bemisia argentifolii) to predatory beetles on cucumber and its implication in pest management

Prey are known to change their activity level and/or habitat use to reduce their risk of mortality from predators. These non-consumptive predator effects on prey behaviors can substantially influence pest population dynamics and thus should be considered in biological control programs. In this study, we asked how the use of biological control agents might affect host plant use patterns by herbivorous pests in greenhouse environments. Specifically, we determined whether adult whiteflies, Bemisia argentifolii (Hemiptera: Aleyrodidae), on cucumber alter their within- and between-plant distributions in response to the presence of predatory beetles, Delphastus catalinae (Coleoptera: Coccinellidae). Within a leaf-disc we found that the presence of the predatory beetles on the leaf-disc delayed the settling of adult whiteflies on the leaf compared to a leaf-disc with no predator. Within a plant adult whiteflies avoided the predatory beetles that primarily inhabited the lower stratum of cucumber plants and moved faster upward in the plant canopy compared to plants with no predators. Among plants we found that when the predatory beetles were introduced into a spatially aggregated whitefly population, more adult whiteflies dispersed to surrounding plants compared to when no predators were introduced. This suggests that the use of the predators can entail a trade-off between benefits that arise from killing pests (i.e., immature whiteflies) and costs from elevating dispersal of pests (i.e., adult whiteflies) across habitats. Our results show that the non-consumptive effects of natural enemies, along with their consumption on pests, should be considered in designing and implementing biological control programs.