Utilization of Coconut Milk and Cane Sugar to Grow Indigenous Entomopathogenic Bacillus thuringiensis for Controlling Aedesaegypti Larvae

Abstract

Bacillus thuringiensis is bacteria utilised to control Aedes aegypti larvae for many years. However, there is no B. thuringiensis commercial products are commercially available in Indonesia. Therefore, development of B. thuringiensis-based biolarvicide using indigenous strain and local medium is very important. The aim of the study were to evaluate growth and toxicity of Mataram indigenous Bacillus thuringiensis isolate when grown on coconut milk and cane sugar as natural culture. Mataram indigenous B. thuringiensis isolate (namely Bt-TP2B) was grown in liquid medium consisted of coconut milk and cane sugar in 4 ratios (1:1; 1:3; 1:5 and 1:7) for 7x24 hours. Cell, endospore, and parasporal crystal (toxin protein) concentration were measured every 24 hours for 7x24 hours. Toxicity of the cultures was evaluated against 3rd instar of A. aegypti larvae. This study showed that the highest cell, endospore and toxin protein crystal concentration was shown by B. thuringiensis grown in ratio of 1:7, which were 2.20x107 cell/mL, 2.09x107 endospore/mL and 9.85x106 crystal/mL, repectively. The highest toxicity against 3rd instar A. aegypti larvae was shown by B. thuringiensis grown in ratio of 1:7 which was 90-100% (in 3-day observation). From this study It was concluded that natural medium consisted of coconut milk and cane sugar can be used to grow B. thuringiensis and to stimulate toxicity against 3rd instar of A. aegypti larvae.