Effect of different Bacillus thuringiensis strains on the longevity of Africanized honey bee

Abstract

The aim of this study was to assess the effects of three strains of Bacillus thuringiensis (Bt) on the longevity of workers of Africanized honey bee. Solutions at a concentration of 3 × 108 spores.mL-1 (dosage) were prepared for each strain of Bt (IPS 82, BR 81, and BR 147). Three bioassays were performed as follows: spraying on the bees, contact with the sprayed surface, and candy paste incorporated with Bt. The bees of the Bt bioassay were submitted to histological analysis of the mesenteron. The longevity of workers was assessed from one to 120 hours using different ranges. It was found that the bees that were exposed to the strain of Bt IPS 82, in the spraying test, exhibited a reduced longevity. In the contact test, the BR 147 strain reduced the longevity of the bees. In the food test, in turn, the three studied strains reduced the longevity of the bees as follows: Bt IPS 82: 64.5 hours; Bt BR 81: 64.5 hours; and Bt BR 147: 60.0 hours. The Bt BR 81 strain was considered the most selective of the evaluated strains on Apis mellifera, reducing the longevity of this bee only when it came into contact by the method of ingestion.