Experimental formulations of Bacillus sphaericus for the control of anopheline and culicine larvae

Abstract

Four experimental formulations of Bacillus sphaericus Neide (2362 isolate) were evaluated for larvicidal activity against culicine and anopheline larvae in several natural and artificial habitats. A granular formulation (5% primary powder) was tested against natural populations of mosquitoes in two simulated habitats in Florida and in maturing and reflooded rice fields in Louisiana. Larvae of Culex quinquefasciatus Say were reduced by 97 and 99% after application of the granules at the rate of 10 kg/ha to polluted tanks and 2.5 kg/ha to sod-lined potholes, respectively. Anopheline and Psorophora columbiae (Dyar and Knab) larvae were reduced by 68 and 92-100%, respectively, after application of 5 kg granules/ha to rice fields. A flowable concentrate (12.8% primary powder) applied to unpolluted and organically enriched habitats in Florida at 0.25 kg/ha reduced populations of Culex spp. by 93-100% and 99%, respectively. Sustained-release briquets (5% primary powder) applied at the rate of one half briquet/1.8 m2 sod-lined potholes reduced larval populations of Cx. quinquefasciatus by 88-95% for up to 2 weeks in open sunlight. Sustained-release pellets (30% primary powder) applied to small woodland pools in Memphis, TN at the rate of four pellets/pool virtually eliminated larval populations of Cx. restuans Theobald for over 8 days. Variable persistance of larvicidal activity was noted for the other treatments depending on the formulation, target species and habitat. © 1988 Society for Industrial Microbiology.