Steinernema scarabaei, an entomopathogenic nematode for control of the European chafer

Abstract

Abstract A new entomopathogenic nematode species, Steinernema scarabaei , was evaluated for efficacy against two white grub species, the European chafer, Rhizotrogus majalis , and the Japanese beetle, Popillia japonica , in laboratory, greenhouse, and field trials. In laboratory assays, S. scarabaei caused greater mortality than Heterorhabditis bacteriophora . S. scarabaei was highly virulent with an LC 50 of 5.5–6.0 and 5.7 infective juveniles (IJs) per third-instar larva in R. majalis and P. japonica , respectively. In a greenhouse trial, S. scarabaei provided greater mortality of R. majalis at all application rates (0.156–1.25 × 10 9 IJs/ha) than Steinernema glaseri and H. bacteriophora (both at 1.25 × 10 9 IJs/ha). Combination of imidacloprid and S. scarabaei resulted in an antagonistic interaction. In a fall field trial, S. scarabaei provided 88 and 75% control of R. majalis at 2.5 × 10 9 and 10 9 IJs/ha, respectively, and 54% control of P. japonica at 10 9 IJs/ha; H. bacteriophora had no effect on mortality of either white grub species. In a spring field trial, unusually cool temperatures impeded nematode activity. Against R. majalis , S. scarabaei provided moderate control (56–59%), whereas Heterorhabditis marelatus provided no control. Mortality of P. japonica was moderate (49–66%) in both S. scarabaei and H. marelatus treatments. Overwinter persistence of S. scarabaei activity was demonstrated in a spring assay of soil from fall treated plots in which nematode infection was absent from control plots and present in treated plots.