Screening of mosquitocidal Bacillus thuringiensis from Southern Viet Nam

Abstract

The purpose of this study was to screen for mosquitocidal Bacillus thuringiensis (B. thuringiensis) from southern Vietnam. From 47 samples including leaf, wood and soil collected from different localities in southern Vietnam, based on morphological characteristic and crystal proteins formation, nine B. thuringiensis species were obtained. Soil was found as the most productive sample type since 77% of B. thuringiensis strains were isolated from soil sample. Toxicity tests were conducted on larvae of Aedes aegypti (A. aegypti) and Anopheles dirus (An. dirus). Five B. thuringiensis isolates were found to be highly toxic to mosquitoes larvae since they could kill over 50% of the tested larvae. Among these strains, B. thuringiensis HM1 was particularly interesting due to having ability to kill A. aegypti and An. dirus at low 50% lethal dose concentration (LC50) (6.13 µg/ml and 12.5 µg/ml, respectively). LC50 of this strain was comparable with that of commercial strains. This result suggested that B. thuringienisis HM1 has a high potential for production of B. thuringiensis mosquitocidal product to control mosquito in southern Vietnam.

Key word: Aedes aegypti, Anopheles dirus, Bacillus thuringiensis, parasporal crystal, mosquitoes, spore-crystal mixture, 50% lethal concentration