ABSTRACT
Three Bacillus sphaericus H-5a5b strains designated Ghar.l & 10 Ghar. 2 & 20 and Ghar . 3 & 30 were evaluated against Culex mosquitoes in simulated
and natural breeding sites . Broth suspensions of all strains at 1.5 x io to io6 cells I ml gave 89 - 97 % and 97 - 100 % mortality in field - collected C. pipiens larvae exposed outdoors ( 1.5 L buckets ) for 2 and 4 days respectively . Further testing of strain Ghar . 2 & 20 at io - 10 cells I ml against larval populations of the same species breeding in 25 L dishes showed
94.2 - 100 % control within 2 days . All strains at 2 x 1O4 - I0 cells I ml also exhibited excellent control ( 94 - in two days ) of a mixed population of C. wiiviuatus and C. anlennatus breeding in 1 - m2 plastic - bottomed ponds . Generally , larval control persisted for 7 - 14 days Application of strain Ghar. 2 & 20 at l0 cells I ml to cesspools and Ghar. 3 & 30 at lO cells I ml to a ditch produced 98.2 % and 94.5 % of C. pipiens larvae within 3 days, respectively. Primary powders of strains Ghar. 2 & 20 and Ghar . 3 & 30 at 12 - 24 mg I liter provided 92.2 - 100 % control of G. wuviliatus and C. aluennazus larvae breeding in 10 liter dishes.
