Survival outcome of Aedes (Stegomyia) aegypti larvae exposed to varying dilutions of Bacillus thuringiensis var. israelensis (Bti) sero 14 spores.

Abstract

The larvicidal action of Bacillus thuringiensis var. israelensis (Bti) Sero 14 spores was tested against Aedes (Stegomyia) aegypti fourth instar (L4) larvae, the primary vector of dengue fever in the Philippines. Treatments of Bti spore concentrations (1 mg/mL to 1 x 10-5 mg/mL) and distilled water (negative control) were prepared for two groups (with and without Purina feeds) to determine survival outcomes of L4 Aedes (Stegomyia) aegypti larvae. Life Tables Analysis with Wilcoxon (Gehan) Statistic pairwise comparison determined that Bti spore concentrations of 1 mg/mL, 1 x 10-1 mg/mL, and 1 x 10-2 mg/mL were lethal to Aedes (Stegomyia) larvae within 1.5 days compared to spore concentrations of 1 x 10-3 mg/mL, 1 x 10-4 mg/mL, 1 x 10-5 mg/mL, and negative control (p=0.001) for both groups. Pupal and adult emergence cases were only observed in larvae administered with Purina feeds and Bti Sero 14 spore concentrations of 1 x 10-4 mg/mL and 1 x 10-5 mg/mL. Thus, the spores of the Philippine Bti Sero 14 strain can be further explored as a biological control agent against larval Aedes (Stegomyia).