Efficacy of a new formulation of Bacillus thuringiensis var israelensis (Bti) in laboratory and field conditions of Kumaun foothills of Uttaranchal, India.

Efficacy of a new Bti formulation was tested in the laboratory and small scale field trials against mosquito larvae were carried out from March to June, 2001 in different breeding habitats of Kumaun foothill region of Nainital and Udham Singh Nagar districts, Uttaranchal state, India. Laboratory tests revealed increased efficacy against Culex quinquefasciatus (LC50 = 0.035 mg/L) followed by Aedes aegypti (LC50 = 0.0628 mg/L), An. culicifacies sp A (LC50 = 0.184mg/L) and An. stephensi (LC50 - 0.2216mg/L). Results of field trials revealed 100% mortality of mosquito larvae after treatment with Bti @ 0.5 gm/m2 surface area. The impact was similar on different mosquito species breeding in different habitats. However, repeated treatments were required due to reappearance of larvae in the breeding habitats within a week. No side effects of Bti was observed during field trial on non- target organisms (NTOs). Environmental disturbances and man made problems affected the spray impact of Bti.