Sub-Lethal Effects of Bifenthrin and Imidacloprid on Megacephala carolina carolina L. (Coleoptera: Carabidae) in Turfgrass

SIMPLE SUMMARY: Tiger beetles are important predators in turfgrass in Georgia, USA. Many insecticides are sprayed on turfgrass to manage pests. Among them, bifenthrin and imidacloprid are the most commonly used insecticides in turfgrass. These insecticides may harm beneficial insects or the behavior of tiger beetles in turfgrass. Therefore, the objective was to determine whether lower doses of bifenthrin and imidacloprid would alter the normal hunting behavior of larvae and adult tiger beetles. Lower doses of bifenthrin altered the normal hunting behavior of larvae and adult tiger beetles. However, lower doses of imidacloprid did not alter the larval behavior. These results suggest that not all insecticides are equally harmful to the beneficial insects in turfgrass. Turfgrass managers should carefully inspect the presence of tiger beetle holes before spraying insecticides on turfgrass. ABSTRACT: The tiger beetle, Megacephala carolina carolina L. (Coleoptera: Carabidae), is a common predator in turfgrass and ornamental landscapes in Georgia, USA. Among insecticides used in turfgrass to control foliar and root-feeding insect pests, bifenthrin and imidacloprid are routinely used. It was unclear whether sub-lethal doses of bifenthrin and imidacloprid could cause nontarget effects on larvae and M. carolina carolina adults. Thus, the objective was to determine the sub-lethal effects of bifenthrin and imidacloprid on larvae and M. carolina carolina adults. The results show that M. carolina carolina larvae actively hunt for passing prey by waiting at the hole of the tunnel during the day and nighttime. This larval behavior was affected by sub-lethal doses (up to 25% of full label rate) of bifenthrin but not of imidacloprid. The walking behavior of adult M. carolina carolina was also altered when exposed to sub-lethal doses of bifenthrin as they traveled further distances at greater velocities than the nontreated control. The results imply that turfgrass managers should avoid treating lawns where tiger beetles have actively colonized.