Laboratory and Field Evaluation of the Efficacy of Four Insecticides for Aedes vigilax (Diptera: Culicidae) and Toxicity to the Nontarget Shrimp Leander tenuicornis (Decapoda: Palaemonidae)

Abstract

Laboratory and field evaluations were conducted in southeastern Queensland, Australia, to determine the toxicities of 2 organophosphate compounds (temephos and pirimiphos-methyl), an insect growth regulator (s-methoprene), and Bacillus thuringiensis variety israelensis de Barjac (Bti) to Aedes vigilax (Skuse), an Australian saltmarsh mosquito vector of Ross River virus. The toxicity of these compounds to Leander tenuicornis Say, a cohabiting nontarget shrimp species, was also assessed. s-Methoprene and Bti were found to be the most selective for Ae. vigilax, with selectivity ratios (LC95 nontarget/LC95 target) of 255,000 and 38,000, respectively. In contrast, selectivity ratios of 13 and 0.01 were calculated for temephos and pirimiphos-methyl, respectively. As predicted by the laboratory studies, the field applications of s-methoprene and Bti were highly effective against Ae. vigilax, while not affecting L. tenuicornis survival. In contrast, although temephos and pirimiphos-methyl were both effective against Ae. vigilax, these products also killed 100% of caged L. tenuicornis. s-Methoprene and Bti did not affect water quality, whereas temephos and pirimiphos-methyl significantly influenced pH and turbidity. Accordingly, based on the high selectivity ratios, excellent field efficacy, and lack of influence on abiotic water characteristics, s-methoprene and Bti were ideal for insecticide control of Ae. vigilax in Australian saltmarsh pools.