title: International indoor and outdoor evaluation of Bacillus sphaericus products: complexity of standardizing outdoor protocols.
abstract: Only one Bacillus sphaericus strain, strain 2362, is currently used commercially to control Culex larval populations. A reliable methodology, easily used, was developed to identify new strains for field application. Larvicidal activities of 3 highly mosquitocidal strains, strains C3-41, Mal, and LB24, previously selected in the laboratory, were compared with that of strain 2362 in tropical and European countries. The following steps were performed: production and titration of acetonic powders from these 4 strains on local Culex species, survey of initial and residual activity under standardized indoor and outdoor conditions, and evaluation of the efficacy of liquid formulations of the 4 strains in natural breeding sites of Culex. In indoor conditions, strain C3-41 showed the highest activity on both Culex pipiens and Culex quinquefasciatus; strain Mal was the least active. The residual activity causing 80% mortality differed from 20 to 90 days according to the strains and the country. Outdoor experiments with powders (0.02-1.6 mg/liter) were performed and the initial toxicities were similar in all cases. Residual activities were very different, from 6 to 95 days posttreatment. Liquid formulations were applied to larval habitats (from 0.1 to 10 g/m2). In tropical countries, larval recolonization in cesspits or ponds occurred after 10-35 days. In Europe, higher doses were needed in polluted water than in clear water (from 3 to 10 liter/ha) for the same control, and the time before 80% residual activity was reached was less than 9-12 days. However, in cesspits, residual activity could be observed for 12 days to 5 mo. A strain 3-5 times more active than the others in bioassays is not significantly detectable from those strains in field trials.
authors.affiliation: Institut Pasteur, Bactéries Entomopathogenes, Paris, France.
authors.forename: I
authors.initials: I
authors.lastname: Thiery
authors.forename: T
authors.initials: T
authors.lastname: Baldet
authors.forename: P
authors.initials: P
authors.lastname: Barbazan
authors.forename: N
authors.initials: N
authors.lastname: Becker
authors.forename: B
authors.initials: B
authors.lastname: Junginger
authors.forename: J P
authors.initials: JP
authors.lastname: Mas
authors.forename: C
authors.initials: C
authors.lastname: Moulinier
authors.forename: K
authors.initials: K
authors.lastname: Nepstad
authors.forename: S
authors.initials: S
authors.lastname: Orduz
authors.forename: G
authors.initials: G
authors.lastname: Sinègre
mesh_terms: D000818:Animals; D001407:Bacillus / Q000737:chemistry*; D003465:Culex; D007306:Insecticides
chemical_list: D007306:Insecticides