Field Efficacy and Persistence of Entomogenous Nematodes in the Management of White Grubs (Coleoptera: Scarabaeidae) in Turf and Pasture

Abstract

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 [AIl/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.