Laboratory and Field Evaluation of Isofenphos for Scarabaeid Grub (Coleoptera: Scarabaeidae) Control in Turfgrass

Abstract

Isofenphos (1-methylethyl 2-[[ethoxy[(1-methylethyl)amino]phosphinothioyl]-oxy]benzoate) was equally effective on cyclodiene-resistant and susceptible 1st-in star European chafer, Rhizolrogus majalis (Razoumowsky). Japanese beetle, Popillia japonica Newman, 1st instars were more susceptible than the European chafer. On 3rd-instar European chafers, initial action of isofenphos was slower than diazinon but eventually surpassed the latter, especially at lower temperatures. Isofenphos at rates of 1.7 to 2.2 kg of AI/ha applied during April and May or midsummer were highly effective in controlling European chafer, Japanese beetle, and Oriental beetle, Anomala orientalis Waterhouse, grubs during late summer and fall. Second-year residues of isofenphos were present in sufficient quantities to produce significant grub mortality in some cases. In the above-ground vegetation, isofenphos residues of the 6E formulation were initially higher than with the 5G formulation, but both were nearly dissipated by 15 weeks. Soil residues in the 0- to 1.3-cm depth were 2.5 to 10 times greater than in the 1.3- to 3.8-cm depth during the first 15 weeks.