Growth, sporulation, delta-endotoxins synthesis, and toxicity during culture of bacillus thuringiensis H14.

Growth, sporulation, synthesis of delta-endotoxins, and toxicity against the larvae of Aedes aegypti and Culex pipiens were studied during fermentation of Bacillus thuringiensis H14 in a 20-L fermentor. Measurements of optical density and dielectric permittivity for biomass determination suggest a highly promising technique for on-line evaluation of sporulation. The synthesis of 65-, 25- and 130-kDa proteins started at 16, 18, and 23 h, respectively.

An easy field method for estimating the abundance of culicid larval instars.

A new method is proposed that avoids manual counting of mosquito larvae in order to estimate larval abundance in the field. This method is based on the visual comparison between abundance, in a standardized sampling tray (called an abacus), with 5 (abacus 5) or 10 (abacus 10) diagrammatically prepared abundance classes. Accuracy under laboratory and field conditions and individual bias have been evaluated and both abaci provide a reliable estimation of abundance in both conditions.

Residual activity of Bacillus thuringiensis serovars medellin and jegathesan on Culex pipiens and Aedes aegypti larvae.

Bacillus thuringiensis serovar medellin strain 163-131 and Bacillus thuringiensis serovar jegathesan (B.t.jeg.

Resistance to Bacillus sphaericus involves different mechanisms in Culex pipiens (Diptera:Culicidae) larvae.

Field Culex pipiens pipiens (L.) mosquitoes that were collected after a control failure with Spherimos in southern France developed high resistance (> 10,000-fold) to Bacillus sphaericus crystal toxin after < 8 generations of laboratory selection. We show that this resistance is encoded by a single major recessive gene on linkage group I at 22.