The effectiveness of biological mosquito larvicide: Bacteria (Bacillus thuringiensis israelensis) embedded in Silica Granules
Milagros M Greif
Mosquitoes are very tiny insects but the impact they brought to humans and society is very huge. An application technique for the control of mosquito larvae under tropical conditions was conducted in Cebu City, Philippines. The study used a bacterium, Bacillus thuringiensis israelensis embedded in silica granules under laboratory conditions. Five concentrations were prepared in range finding and 4 concentrations in definitive range finding tests. Each of the concentration was tested with 25 3rd and early 4th instar larvae of Aedes aegypti. Results obtained from the test have very effective residual effects against the larvae of mosquitoes. The efficacy varies according to the concentrations applied to the mosquito larvae. The high mortality rate of mosquito larvae is associated numerically with higher concentration of the larvicide (1.6 grams) and the low mortality rate of mosquito larvae is associated numerically with lower concentration (0.4 grams) after one (1) hour application of the larvicide. This means that even, with lower level of product concentration of the larvicide, the mortality rates among mosquito larvae are still high with the lowest rate of 93% after 1 hour of exposure to the biological mosquito larvicide. Further, there is a significant increase in the number of dead mosquito larvae after 2 hours of treatment. It implies that the toxicity level of the larvicide is still there even after 2 hours of treatment. However, 1.2 g concentration is proven to be effective and achieved 100% mortality after 2 hours of application to the mosquito larvae.