Selective toxicity of halofenozide to exotic white grubs (Coleoptera : Scarabaeidae)

Field populations of Japanese beetle, Popillia japonica Newman; European ch afer, Rhizotrogus (Amphimallon) majalis (Razoumowsky); oriental beetle, Exo mala orientalis (Water-house); and Asiatic garden beetle, Maladera castanea (Arrow),were exposed to the ecdysone agonist halofenozide in turf plots. I n mixed-species larval populations, a higher dosage of halofenozide (1.7-2. 2 kg [AI]/ha) was required to give significant suppression of European chaf er than was required to control Japanese and oriental beetles (1.1 kg [AI] /ha). In other experiments, halofenozide (1.1-1.7 kg [AI]/ha) reduced Japan ese beetle and oriental beetle populations by 75-98%. These data confirm pr edictions of selectivity based on previous laboratory studies. Asiatic gard en beetle survival in the field was 40-50% higher in plots treated with hal ofenozide than in untreated plots. Dosage effects were compared for Europea n chafer and Asiatic garden beetle 3rd instars in the laboratory; Asiatic g arden beetles were insensitive to halofenozide at all tested dosages. Asiat ic garden beetle and European chafer may increase in relative importance wh ere halofenozide is used against mixed populations of exotic scarabs.