Too scared to eat: non-consumptive effects of predatory mites reduce plant damage by Western flower thrips larvae

Abstract: The efficacy of biological control agents is a combination of pest consumption and effects on pest behavior and fitness. We examined non-consumptive effects of predatory mites on Western flower thrips by exposing 2nd instar larval thrips, which are too large for mites to kill, to adult Amblyseius cucumeris. Larval feeding time was reduced by 30% with mites present; leaf damage was reduced by almost 40%. To determine if intimidation by mites made thrips more susceptible to soil applications of nematodes, plants infested with 2nd instar thrips were treated with the biocontrol agents in a factorial design, and adult emergence was assessed. The mere presence of mites reduced adult thrips abundance, but there was no synergistic effect with nematodes. Since only 1st instar thrips are susceptible to mite predation, non-consumptive effects of predators deserve further study for their ability to reduce the fitness of other life stages and the damage they cause.