Toxicity of insecticides for control of freshwater Culex annulirostris (Diptera : Culicidae) to the nontarget shrimp, Caradina indistincta (Decapoda : Atyidae)

Laboratory evaluations were conducted in southeastern Queensland, Australia , to determine the toxicities of two organophosphate compounds (temephos an d pirimiphos-methyl), an insect growth regulator (s-methoprene), and an ent omopathogenic bacterium (Bacillus thuringiensis variety israelensis de Barj ac [B.t.i]) to Culex annulirostris (Skuse), an Australian freshwater mosqui to vector of arboviruses, and to Caradina indistincta Calman, a co-habiting nontarget shrimp species. S-methoprene and B.t.i. were safest for Cx. annu lirostris control with lethal dose ratios (LC95 nontarget/LC95 target) of 3 ,300 and 846,000, respectively. In contrast, lethal dose ratios for temepho s and pirimiphos-methyl were 0.05 and 0.00005, respectively, suggesting tha t they are environmentally unsuitable. Based on their high lethal dose rati os, s-methoprene and B.t.i. are recommended for control of larval Cx. annul irostris in Australian freshwater habitats.