FIELD EFFICACY AND PERSISTENCE OF ENTOMOGENOUS NEMATODES IN THE MANAGEMENT OF WHITE GRUBS (COLEOPTERA, SCARABAEIDAE) IN TURF AND PASTURE

The entomogenous nematodes Steinernema carpocapsae (Weiser) and Heterorhabditis heliothidis (Khan, Brooks & Hirschmann) were used to control white grubs in turf and pasture. In the turf trial, nematode concentrations of 0.25, 0.5, or 1 million nematodes per m2 were evaluated. Only 12% of the grubs were killed by the nematodes at all three concentrations. In the pasture trial, nematode concentrations of 0.5 and 1.5 million per m2 were applied alone or in combination with diazinon (2.25 kg [AI]/ha). Comparisons (t tests) of the mean number of grubs recovered from each treatment area 2-4 wk after application showed significant reductions in the grub populations in both trials after certain nematode treatments. When applied at a rate of 1.5 million per m2, nematodes persisted for 8 wk after application in the pasture trial. In other tests of persistence, nematodes survived as long as 5 wk after application. Nematophagous fungi were recovered from treated areas and untreated plots; however, no significant increases in numbers of propagules occurred after application. Predaceous mite populations did significantly increase after application in one trial. Many of these mites are considered nematophagous.