Efficacy and persistence of Bacillus sphaericus, Bacillus thuringiensis var. israelensis, and methoprene against Culiseta incidens (Diptera: Culicidae) in tires.
The efficacy and persistence of Bacillus sphaericus (2362) was compared at three dosage rates in tires that continually contained cadavers of Culiseta incidens (Thomson) versus tires with all dead larvae removed. At treatment rates of 3.75 and 7.5 ppm, the continual presence of cadavers in the tire water resulted in higher mortality rates. At the 15 ppm treatment rate, mortality rates were similar in tires with or without cadavers. Mortality rates increased in all tires 4-6 wk after treatment, suggesting an amplification of the pathogen. The mortality rate did not exceed 90% for greater than 2 wk in any of the tires. At a second site, the efficacy of B. sphaericus, Bacillus thuringiensis var. israelensis, and methoprene was evaluated against C. incidens in tires exposed to full sunlight versus shaded tires. In shaded tires inoculated with B. sphaericus (15 ppm) and B. thuringiensis var. israelensis (15 ppm), mortality exceeded 90% for 5 and 2 wk, and 50% for 10 and 4 wk, for the two bacteria, respectively. Larvae were adequately controlled (greater than 75% mortality) in the sunny tires for approximately 1 wk. The insect growth regulator, methoprene (applied at 2.5 ppm), inhibited the emergence of approximately 90% of the larvae present at the time of treatment, but not of larvae subsequently introduced into either the sunny or shaded tires.
Kramer
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Contra Costa Mosquito Abatement District, Concord, California 94520.
D000818:Animals; D001407:Bacillus; D001413:Bacillus thuringiensis; D009033:Culicidae; D008726:Methoprene; D010572:Pest Control, Biological; D013472:Sunlight; D014867:Water
D014867:Water; D008726:Methoprene