Evaluating a Naturally Occurring Baculovirus for Extended Biological Control of the Black Cutworm (Lepidoptera: Noctuidae) in Golf Course Habitats

Golf courses are a potential market for microbial insecticides, but how intensive management of such sites interacts with efficacy of entomopathogens is poorly known. We evaluated Agrotis ipsilon nucleopolyhedrovirus (AgipMNPV) for suppressing black cutworms, Agrotis ipsilon Hufnagel (Lepidoptera: Noctuidae), in turf representative of golf course habitats and on whole tees under actual play. In independent trials on sand- or soil-based putting greens and surrounds, or fairway-height creeping bentgrass (Agrostis stolonifera L.), <= 1-wk-old AgipMNPV residues (10 X 108 occlusion bodies [OBs] per m(2)) typically gave 50-60% lethal infection of introduced third instars. In most cases, however, there was no residual control beyond 2-4 wk. Spraying fairway-height bentgrass with AgipMNPV alone (10 x 10(9) OBs per m(2)) gave 90, 85, and 7% infection of second instars introduced 4 d, 3 wk, or 5 wk later, but adjuvants (optical brightener, lignin, or both) intended to synergize and protect the virus from UV degradation did not extend infectivity. Fresh (<1-wk-old) AgipMNPV residues killed 76-86% of neonates hatching from eggs on tees under play, but levels of control plummeted within a few weeks. Three species of braconids, an encyrtid Copidosoma bakeri (Howard), and a tachinid, Bonnetia comta (Fallen) collectively killed 24-31% of larvae recovered from those tees. AgipMNPV seems better suited for targeted control of early instars than for season-long control. Golf turf is a severe environment for baculoviruses so several applications per growing season would probably be needed to maintain high enough titers on grass foliage to effectively control caterpillar pests.