Differential Susceptibility of Japanese Beetle, Oriental Beetle, and European Chafer (Coleoptera: Scarabaeidae) Larvae to Five Soil Insecticides

Abstract

Efficacy of bendiocarb, chlorpyrifos, diazinon, ethoprop, and isoJenphos was evaluated against last-instar larvae of European chafer, Rhizotrogus majalis (Razoumowsky), Japanese beetle, Popillia japonica Newman, and Oriental beetle, AnOmala orientalis Water­ house, by incorporating insecticides into soil at one-half New York State recommended rates in a laboratory bioassay. Mortality was assessed at 1, 2, 3, 4, and 5 wk. The experiment was repeated three times with white grubs collected at different times and from different locations in New York. White grub species differed significantly in their response to some of the insecticides; European chafer was generally least susceptible. Diazinon provided high mor­ tality of Oriental beetle and European chafer grubs but very low mortality of Japanese beetles. Isofenphos provided generally low mortality of all three grub species, although the levels of mortality varied among species. Ethoprop provided uniform mortality of all three grub species. Results of these studies indicate the need to develop species-specific insecticide recommendations for the white grub complex.