Isolation and Use of Bacillus thuringiensis for the Production of Bio-Insecticide in Control of Mosquito Larvae

Abstract

Bacillus thuringiensis is a widely studied bacterium and it is known for its use in pest management. It is selectively active on pests and less likely to cause resistance; hence it is considered a suitable replacement to chemical pesticides. The study assessed the potential of Bacillus thuringiensis in controlling mosquito larvae. Bacillus thuringiensis isolates selected were tested against secondary stage larvae of mosquito. Thirty-six larvae (6 each) were transferred into each test tubes (7 x 9) cm with 30ml sterile distilled water. The stock suspension of cultures of Bacillus thuringiensis in broth was diluted to 107, 106, 10 5, 104, 103 and 102 in sterile water, following the McFarland standard method for microbial load count. The test tubes were kept at room temperature, larval mortality was observed over time within 24hrs. The results showed that all mosquito larvae died at the 107 and 106 dilutions but at dilutions 105, 104 and 103 though affecting mosquito larvae, it was highly dependent on time because there was a decrease in concentration. The study showed that B. thuringiensis is safe for use in aquatic environments, including drinking-water reservoirs, for the control of mosquito, black fly and nuisance insect larvae. The products should contain the ICPs and be free from other microorganisms and biologically active metabolites.