Isolates of Bacillus thuringiensis Berliner with Toxicity to Anopheles darlingi Root, 1926 (Diptera: Culicidae) Larvae, the Main Malaria Vector in Brazil.

Bacillus thuringiensis Berliner 1911 has high effectiveness against important mosquito vectors of human pathogens; however, there are few studies on the selection of Brazilian isolates of B. thuringiensis with activity against Anopheles darlingi Root, 1926, the main transmitter of human malaria parasites in the Amazon region. The present study sought to select native isolates of B. thuringiensis acquired from soil samples from three Brazilian biomes, with pathogenicity to An. darlingi larvae under laboratory conditions. Fifteen isolates of B. thuringiensis from the Maranhão Entomopathogenic Bacilli Bank, Brazil, were used, selected for their high larvicidal activity against Aedes aegypti Linnaeus, 1962, in a previous trial. A selective bioassay was performed with 15 isolates, of which thirteen (86.6%) were effective against An. darlingi and were subsequently used in quantitative bioassays. Considering the observations at 24, 48, and 72 hours, the most toxic isolates were BtMA-689 and BtMA-690, for which the lowest values of LC50 and LC90 were achieved across the three reading intervals. However, six isolates (BtMA-681, BtMA-1114, BtMA-687, BtMA-690, BtMA-703, and BtMA-750) caused mortality rates similar to the standard strain Bti T14 001, for which no statistically significant differences were detected. The study confirms new Brazilian isolates of B. thuringiensis with larvicidal activity against An. darlingi, which can be used in the manufacture of specific by-products containing these insects.