Survival of Yersinia entomophaga MH96 in a pasture ecosystem and effects on pest and non-target invertebrate populations

Yersinia entomophaga MH96 (Ye MH96) has shown activity against the pasture pest porina (Wiseana spp. larvae) in laboratory bioassays. In this field trial Ye MH96 was applied to pasture as three separate formulations. The presence of viable Ye MH96 was detected in soil for 112 days following application but the number of bacteria decreased rapidly following heavy rainfall 4 days after treatment. Porina numbers were reduced by all formulations of Ye MH96 at 5 and 17 weeks (34-40% and 61-72%) and by fenitrothion, an insecticide used to control porina (93% and 96% respectively). Other non-target Lepidoptera were also reduced by Ye MH96. No effects of Ye MH96 were observed on the earthworms, Aporrectodea caliginosa and Lumbricus rubellus, the pasture pest Listronotus bonariensis or pasture inhabiting Staphylinidae. The survival of Ye MH96 for long enough to affect the target insect, despite the heavy rain, suggests that a microbial alternative to conventional insecticide management of porina may be possible.