Evaluation of liquid Bacillus thuringiensis var. israelensis products for control of Australian Aedes arbovirus vectors

Laboratory bioassay studies were conducted in southeast Queensland, Austral ia,: on the efficacy of Teknar (R), VectoBac (R) 12AS, and Cybate (R) (acti ve ingredient: 1,200 international toxic units Bacillus thuringiensis var, israelensis [Bti]) against 3rd instars of the arbovirus vectors Aedes aegyp ti. Ae. notoscriptus, Ae. vigilax, and Ae. camptorhynchus. Probit analyses were then used to determine LD,, (median lethal dose), LD95, and lethal dos e ratios (LDR). Aedes aegypti and Ae. notoscriptus, both container-habitat species, tolerated the highest Bti concentrations compared with saltmarsh A e. vigilax and Ae. camptorhynchus. For example, the LDR for Ae. vigilax ver sus Ae. notoscriptus exposed to Cybate was 0.14 (95% confidence limit [CL] 0.03-0.61). Similarly, the Cybate LDR for Ae. camptorhynchus versus Ae. not oscriptus was 0.22 (95% CL 0.07-0.70). Teknar produced similar results with an LDR of 0.21 (95% CL 0.04-1.10) for Aedes vigilax versus Aedes notoscrip tus. Differences in product efficacy were found when tested against the 2 c ontainer-breeding species. Cybate was less effective than Teknar with LDRs of 1.55 (95% CL 0.65-3.67) and 1.87 (95% CL 0.68-5.15) for Aedes aegypti an d Ae. notoscriptus, respectively. The significant differences in susceptibi lity between mosquito species and varying efficacy between products highlig ht the importance of evaluating concentration-response data prior to contra cting with distributors of mosquito control products. This information is c rucial to resistance management strategies.