Efficacy of Larvicides against Aedes aegypti Larvae in Laboratory Conditions in Lahore, Pakistan

Objective: Aedes aegypti is a known vector mosquito transmitting world’s deadliest disease dengue fever. Vector control by chemo and bio pesticides is popular method for control but due to resistance development in adult and larvae of Aedes aegypti, it becomes a serious threat. Present study was planned to assess the efficacy of two insecticides, Bacillus thuringiensis var iaraelensis and pyriproxyfen against Aedes aegypti larvae Bacillus thuringiensis is a bacterium that produce toxin and act as a bio pesticide.

Methods: Efficacy of Bacillus thuringiensis bioassay was done and mortality was recorded after every thirty minutes for three hours. Larvae were placed in the depression slides with a little amount of water that is sufficient for the larval movement and were examined under microscope. 20 larvaes put in 50ml water in a beaker, and added 100 µl Bacillus thuringiensis toxins, average mortality was recorded 9.50%. Efficacy of pyriproxyfen was evaluated by putting it in the 100 ml glass beakers containing 50ml of tap water and maintained at 25±1°C.

Results: Aedes aegypti larvae were also exposed to three concentrations (1ppm, 0.5ppm and 0.25ppm) of pyriproxyfen “insect growth regulator” for three weeks, and mortality rate was recorded after every 24 hours. Pyriproxyfen inhibited emergence of Aedes aegypti even at very low dose. Comparative analysis between Bacillus thuringiensis and pyriproxyfen revealed that highest mortality (13.50%) was recorded by pyriproxyfen, as compared to Bacillus thuringiensis (9.50%).

Conclusion: Pyriproxyfen is useful larvicides, especially in fields where larvae have developed resistance against other larvicides.