Aerial Application of the Pyrethroid Deltamethrin for Grasshopper (Orthoptera: Acrididae) Control

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Abstract
Field trials were conducted to determine deposition of deltamethrin applied to pastures by aircraft, and resulting effectiveness in controlling grasshoppers. Residue analysis indicated that 73% of 7.2 g (AI)/ha deltamethrin applied was deposited on vegetation and litter. Sampling via sweep net indicated considerably higher rates of control than did estimates of density based on trap catches 1 day after application, although both methods indicated a 65% reduction in grasshopper density after 4 days. The bias in sweep-net samples is due to reduced activity just after spraying. Contrary to earlier reports, efficacy of deltamethrin was unrelated to age distribution, species composition, or grasshopper movement. Estimates of mortality based on independent toxicological experiments in the laboratory agreed with field results, given the deposition measured at time of spraying.