Susceptibility of Field Populations of Anopheles sinensis (Diptera: Culicidae) to Bacillus thuringiensis subsp. israelensis

Abstract

The susceptibility of Anopheles sinensis to Bacillus thuringiensis subsp. israelensis (Bti) was evaluated through exposure to varying concentrations of Bti. Mosquitoes were collected from five field populations of southern and central China (Zhongshan, Hengxian, Wuchang, Xinzhou, and Ruichang) and compared with a standard laboratory strain. The LC₅₀ values were 146.4, 50.4, 57.9, 50.0, 41.6 and 24.6 ng/mL, respectively. Differences in susceptibility to Bti ranging from 1.7 to 5.9-fold compared with the laboratory strain. The Zhongshan strain had the greatest resistance. At low doses, Bti displayed residual effects. Peak mortality occurred from the first to the fourth day. Exposure to low doses increased the duration of larval development and decreased the duration of pupal development, indicating that low doses of Bti have a sublethal effect on their hosts.

Keywords:

• Bacillus thuringiensis subsp. israelensis
• Anopheles sinensis
• susceptibility
• field population
• sublethal concentration

Acknowledgments

We would like to thank Dr Trevor Jackson for the critical review and careful modification of the manuscript, and are grateful to Dr Dave Saville for assistance in statistical analyses, and Dr Mark Goettel and two anonymous referees for providing valuable comments that improved the manuscript. This research received financial support from the UNDP/World Bank/WHO Special Program for Research and Training in Tropical Disease to Hongyu.