Evaluation of a Controlled-Release Silicate Formulation of Temephos Against Aedes Aegypti Larvae in the Laboratory and Psorophora Columbiae Larvae (Diptera: Culicidae) in Rice Field Plots1

Abstract

A controlled-release silicate formulation of temephos was tested for its effectiveness and longevity in controlling Aedes aegypti larvae in the laboratory and Psorophora columbiae larvae in rice field plots. Treatments were based on a theoretical total release of active ingredients. Laboratory bioassays resulted in ≥80% larval mortality up to 80 days at the 0.19-ppm treatment, 122 days at the 0.38-ppm treatment, and 150 days at the 0.76-ppm treatment. Field bioassays resulted in ≥80% larval mortality up to 7 days at the 0.38-ppm treatment, 50 days at the 1.92-ppm treatment, and 71 days at the 3.83-ppm treatment. Temephos residues recovered from water of field plots reached their highest concentration in all plots on day 2 post-treatment and averaged 0.050, 0.283, and 0.761 ppm in the plots treated at 0.38, 1.92, and 3.83 ppm, respectively. Residues (>0.001 ppm) were not detected after 2 days in the 0.38-ppm treatment, after 8 days in the 1.92-ppm treatment, or after 10 days in the 3.83-ppm treatment.