Various levels of cross-resistance to Bacillus sphaericus strains in Culex pipiens (Diptera: Culicidae) colonies resistant to B. sphaericus strain 2362.
We studied the cross-resistance to three highly toxic Bacillus sphaericus strains, IAB-59 (serotype H6), IAB-881 (serotype H3), and IAB-872 (serotype H48), of four colonies of the Culex pipiens complex resistant to B. sphaericus 2362 and 1593, both of which are serotype H5a5b strains. Two field-selected highly resistant colonies originating from India (KOCHI, 17,000-fold resistance) and France (SPHAE, 23,000-fold resistance) and a highly resistant laboratory-selected colony from California (GeoR, 36,000-fold resistance) showed strong cross-resistance to strains IAB-881 and IAB-872 but significantly weaker cross-resistance to IAB-59 (3- to 43-fold resistance). In contrast, a laboratory-selected California colony with low-level resistance (JRMM-R, 5-fold resistance) displayed similar levels of resistance (5- to 10-fold) to all of the B. sphaericus strains tested. Thus, among the mosquitocidal strains of B. sphaericus we identified a strain, IAB-59, which was toxic to several Culex colonies that were highly resistant to commercial strains 2362 and 1593. Our analysis also indicated that strain IAB-59 may possess other larvicidal factors. These results could have important implications for the development of resistance management strategies for area-wide mosquito control programs based on the use of B. sphaericus preparations.
Nielsen-LeRoux
C
C
Bactéries Entomopathogènes, Institut Pasteur, 75724 Paris Cedex 15, France.
Rao
D R
DR
Murphy
J R
JR
Carron
A
A
Mani
T R
TR
Hamon
S
S
Mulla
M S
MS
D000818:Animals; D001407:Bacillus / Q000145:classification / Q000378:metabolism*; D001427:Bacterial Toxins / Q000378:metabolism / Q000633:toxicity*; D003465:Culex / Q000187:drug effects / Q000382:microbiology* / Q000502:physiology; D007305:Insecticide Resistance; D007814:Larva / Q000187:drug effects; D010572:Pest Control, Biological
D001427:Bacterial Toxins