Field evaluation of a previously untested strain of biolarvicide (Bacillus thuringiensis israelensis H14) for mosquito control in an urban area of Orissa, India

A previously untested strain of Bacillus thuringiensis israelensis (Bti) serotype H14 (ID No. VCRC B 17) has been evaluated under field conditions in an urban area of Rourkela city, India for its impact on the larval density of different mosquito species in a variety of habitats. The persistence of the biolarvicide used in an aqueous solution varied in different habitats. The lowest field application rate of 0.5 ml/m(2) remained effective for about 10-12 days and provided 80-100% reduction in larval abundance of anopheline species, including Anopheles culicifacies breeding in unpolluted water bodies. However, in stagnant polluted waters in drains and cesspools supporting culicine breeding, the biocide at the same rate persists for 5-6 days only. An application rate of 1 ml/m(2) to stagnant drains and cesspools, resulted in 84- 100% reduction in the larval population of Culex quinquefasciatus over a period of 2 wk. Based on the field observations, an operational dose of 0.5 ml/m(2) at fortnightly intervals is suggested for clean water sources Supporting anopheline breeding. However, to control breeding of culicine mosquitoes in stagnant and polluted waters, an operational dose of 1 ml/m(2) at fortnightly intervals is required. The study showed that Bti scrotype H14 (VCRC B17) is a suitable biolarvicide that can be used against different mosquitoes in different types of urban habitats.