Potential of azadirachtin for managing black cutworms and Japanese beetle grubs in turf

Botanical insecticides have potential for managing insect pests with low hazard to humans and the environment. Azadirachtin, a limonoid extracted from the seeds of the neem tree, Azadirachta indica (Meliaceae), acts as an insect growth regulator and antifeedant against many crop pests. We evaluated two commercial azadirachtin formulations, Azatrol EC and Azatin XL (1.2 and 3.0%, respectively) against two important turfgrass pests: black cutworms [BCW], Agrotis ipsilon, and Japanese beetle [JB], Popillia japonica. Feeding on azadirachtin-sprayed creeping bentgrass caused molting disorders and death of early-instar BCW, and slowed feeding and stunted the growth of late instars. Azadirachtin also showed systemic activity against early instar BCW fed bentgrass treated via a root soak, and some deterrence of late instars in the field. Application to Kentucky bluegrass, followed by irrigation, killed 2nd-instar JB at 5 times label rate, but label rates did not provide control in the greenhouse or field. Azadirachtin residues in turf did not deter egg-laying by JB. This work indicates that azadirachtin will suppress BCW if applied when early instars are present, but probably will not effectively control late instars or root-feeding grubs.