Imidacloprid disrupts the movement of scarab larvae through soil microcosms

Synthetic insecticides and biological control agents can influence the behavior of taxa from major soil insect complexes and thereby the outcome of interventions against root-feeding pest species. Non-lethal rates of neonicotinoid insecticides have diverse deleterious effects on target insects, yet little is known about how soil insects detect and orient to insecticides or other soil-borne antagonists. Herein we use a non-destructive radiographic technique to reveal that imidacloprid influences the movement of European chafer larvae through soil microcosms. Results from a series of experiments with different combinations of soil-incorporated imidacloprid and germinating grass seed show that this insecticide functions in a concentration-dependent fashion as a contact-arrestant to disrupt movement. The implications of these finding are discussed with respect to other sublethal effects attributed to neonicotinoids and to the potential for chemical-biological synergisms as an approach for white grub control.