Individual and combined effects of <i>Bacillus thuringiensis</i> var. <i>israelensis</i>, temephos and <i>Leptolegnia chapmanii</i> on the larval mortality of <i>Aedes aegypti</i>

Abstract

Larvicidal effects of interaction between <i>Bacillus thuringiensis</i> var. <i>israelensis</i> (<i>Bti</i>), temephos and <i>Leptolegnia chapmanii</i> zoospores on larvae of <i>Aedes aegypti</i> were determined under laboratory and seminatural conditions. In laboratory bioassays, two concentrations of <i>Bti</i> (0.012, 0.027 ppm), two of temephos (0.00035, 0.001 ppm), and a single concentration of <i>L. chapmanii</i> zoospores (6.1 × 10⁴ zoospores ml⁻¹) were evaluated. Trials under field-like conditions were performed in a single container and then placed either in the shade or in direct exposure to sunlight. We evaluated concentrations of <i>Bti</i> and temephos at 3-fold those normally used in laboratory tests: 0.09 and 0.003 ppm, respectively, plus 1.8 × 10⁵ zoospores ml⁻¹ of <i>L. chapmanii</i>. The combined effect of sublethal concentrations of <i>Bti</i>, temephos, and <i>L. chapmanii</i> zoospores thus indicated that this fungus is not inhibited by the larvicides and also demonstrated the synergistic effect of the action of <i>L. chapmanii</i> when used together with <i>Bti</i> and temephos.