Factors Influencing the Efficacy of Bacillus thuringiensis var. israelensis As a Biological Control Agent of Black Fly Larvae (Diptera: Simuliidae)
|Title||Factors Influencing the Efficacy of Bacillus thuringiensis var. israelensis As a Biological Control Agent of Black Fly Larvae (Diptera: Simuliidae)|
|Publication Type||Journal Article|
|Year of Publication||1981|
|Authors||Molloy, DP, Gaugler, RR, Jamnback, H|
|Journal||Journal of Economic Entomology|
In laboratory trials with Bacillus thuringiensis Berliner var. israelensis de Barjac against Simulium larvae, the following factors significantly influenced efficacy: black fly instar and species, formulation, temperature, and product manufacturer.
Mortalities were consistently higher among smaller larvae, e.g., after 15 min exposures with Bellon Laboratory primary powder at 11°C, the LC90 value for 2nd–5th instars (111 ppb) was significantly lower than for 7th instars (615 ppb). S. verecundum Stone and Jamnback larvae were significantly more susceptible than S. vittatum Zetterstedt to Bellon primary powder. In trials comparing Bellon preparations by total product weight, significantly higher mortalities were achieved with primary powder than with other preparations. No difference in efficacy, however, was evident between Bellon WP and primary powder when compared solely on the basis of the weight of their AI (Bellon wettable = 50% AI (wt/wt), while Bellon primary = 100% AI). Both the Bellon aqueous suspension and emulsion were less effective than the WP and primary powder. Results with the emulsion were erratic due to adverse effect on feeding behavior. Microscopic observation of test larvae revealed abnormal clumping of their cephalic fan rays and inhibition of normal feeding during exposure to the emulsion. Mortality among S. vittatum larvae treated at 20°C was twice that recorded at 10°C. Tests with Abbott and Bellon primary powders showed the Bellon preparation to be 3 to 4 times more toxic.