SUSCEPTIBILITY OF JAPANESE-BEETLE, ORIENTAL BEETLE, AND EUROPEAN CHAFER (COLEOPTERA, SCARABAEIDAE) TO HALOFENOZIDE, AND INSECT GROWTH-REGULATOR

Japanese beetle, Popillia japonica Newman, European chafer, Rhizotrogu s (Amphimallon) majalis (Razoumowsky), and oriental beetle, Anomala or ientalis Waterhouse, were exposed to an ecdysone agonist, halofenozide , in the egg, 1st instar, and 3rd instar at 1.5, 3, 6, and 12 ppm, res pectively, in soil. Species, stage, and physiological condition of lar vae affected the response to halofenozide. Japanese beetle was the mos t sensitive, with maximal response of 1st instars at 3 ppm. First and 2nd instars were more susceptible than were 3rd instars. Sublethal exp osure of 1st-instar European chafer and 3rd-instar oriental beetle res ulted in dose-dependent accelerated development and successful molts. Field trials are needed in locations where there are mixed populations of scarabs to determine whether the species differences in susceptibi lity to halofenozide observed in this work will translate to increased relative importance of European chafer.