Effect of temperature on toxicity of two bioinsecticides spherix (Bacillus sphaericus) and bactoculicide (Bacillus thuringiensis) against larvae of four vector mosquitoes.

Two bioinsecticide preparations, viz. Spherix (Bacillus sphaericus) and Bactoculicide (Bacillus thuringiensis H-14), were tested in the laboratory against larvae of Anopheles culicifacies, Anopheles stephensi, Culex quinquefasciatus and Aedes aegypti at different temperatures. The LCs50 of Spherix against III instar larvae of these species at 27 +/- 2 degrees C were 2.0, 0.19, 0.05 and > 40 mg/litre, respectively and those of Bactoculicide were 0.32, 0.16, 0.06 and 0.03 mg/litre, respectively. The toxicity of two bioinsecticides, especially Spherix, varied to a great extent when the tests were repeated at 21 +/- 2 degrees C and 31 +/- 2 degrees C. At 21 +/- 2 degrees C, Spherix was almost non-toxic against larvae of An. culicifacies and An. stephensi (LC50 > 10 mg/l) but at 31 +/- 2 degrees C the bioinsecticide was highly toxic against An. culicifacies (LC50 = 0.48 mg/litre) and An. stephensi (LC50 = 0.04 mg/litre). A similar effect of the temperature was also observed with Bactoculicide.