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

Field populations of Japanese beetle, Popillia japonica Newman; European chafer, Rhizotrogus (Amphimallon) majalis (Razoumowsky); oriental beetle, Exomala orientalis (Water-house); and Asiatic garden beetle, Maladera castanea (Arrow), were exposed to the ecdysone agonist halofenozide in turf plots. In mixed-species larval populations, a higher dosage of halofenozide (1.7-2.2 kg [AI]/ha) was required to give significant suppression of European chafer 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 Japanese beetle and oriental beetle populations by 75-98%. These data confirm predictions of selectivity based on previous laboratory studies. Asiatic garden beetle survival in the field was 40-50% higher in plots treated with halofenozide than in untreated plots. Dosage effects were compared for European chafer and Asiatic garden beetle 3rd instars in the laboratory; Asiatic garden beetles were insensitive to halofenozide at all tested dosages. Asiatic garden beetle and European chafer may increase in relative importance where halofenozide is used against mixed populations of exotic scarabs.