Utility ofBacillus sphaericusin controllingCulex tritaeniorhynchusbreeding

Abstract

Freeze-dried powder preparation of a streptomycin-resistant (Str) mutant of Bacillus sphaericus B.42 was applied against Culex tritaeniorhynchus larvae breeding in paper factory effluent. Whether applied as single, double or triple sprays on days 0, 1 and 2, respectively, a complete control of larvae was observed only until day 7 post application. Though the applied strain of B. sphaericus persisted (in the sprayed pits) at least until 91 days, as evident from larval resurgence, the sprayed B. sphaericus did not recycle in paper factory effluent. Whenever the heat-resistant spore counts dropped below approx. 600/ml, a build-up in larval population was observed. The Str mutant strain of B. sphaericus used in the present study seems to be an effective biocide capable of persisting and controlling C. tritaeniorhynchus larvae breeding in such a highly polluted water habitat as paper factory effluent.