Larvicidal Efficacy of Locally Available Plant Species in Sri Lanka for the Development of Potential Larvicidal Agents Against Aedes aegypti L

The Aedes aegypti mosquito transmits diseases such as dengue, Zika, and chikungunya, prompting the need for safe and effective larvicidal agents. Traditional insecticides pose risks, prompting the exploration of sustainable alternatives like local plants with bioactive compounds. This study evaluates the efficacy of these plants against Aedes aegypti larvae, aiming to develop new larvicidal agents. A larvicidal bioassay methodology recommended by the WHO was adopted. Following the initial screening of 32 plant species, those exhibiting promising larvicidal effects were selected for the follow-up studies using storable dried powder. A series of larvicidal bioassays was conducted to determine the effectiveness. Eight different concentrations derived from the dried powder of the most promising plants were tested to determine the effective concentration for mosquito controlling at their natural breeding sites. The egg hatching and survival rate of Aedes aegypti second instar larvae was monitored at each concentration. Out of 15 samples identified as potential larvicides against Aedes, 13 were leaf crude extracts. The time taken for the 100% mortality varied from 5 and 138 minutes. Positive retesting with the larvicidal bioassay was conducted for nine selected plant leaf crude extracts that demonstrated mortality within 60 minutes. The overall results showed that clover leaf powder was the most promising treatment for controlling dengue mosquito breeding. It inhibits larvae development by over 80% at a concentration of 0.01g/ml and can be recommended for application in water-holding containers where Aedes mosquitoes are likely to breed.