Larvicidal toxicity of Metarhizium anisopliae metabolites against three mosquito species and non-targeting organisms

Background The fungal toxin acts as effective, low-cost chemical substances for pest control worldwide and also an alternative to synthetic insecticides. This study assessed the larvicidal potential of Metarhizium anisopliae fungi derived metabolites against Aedes aegypti , Anopheles stephensi , Culex quinquefasciatus and non-targeted organisms at 24hr post treatment. Method Isolation of entomopathogenic fungi M . anisopliae from natural traps confirmed by using 18s rDNA biotechnological tools. Crude extracts from M . anisopliae solvent extraction and their secondary metabolites were bio-assayed following WHO standard procedures against Ae . aegypti , An . stephensi and Cx . quinquefasciatus , Artemia nauplii , Eudrilus eugeniae , and Solanum lycopersicum after 24 hr exposure. Histopathological analysis of E . eugeniae treated with fungi metabolites toxicity compared to those treated with Monocrotophos after 24hrpost-treatment. M . anisopliae metabolites were characterized using GC-MS and FT-IR analysis. Results The larvicidal activity was recorded in highest concentration of 75μg/ml, with 85%, 97% and 89% mortality in Ae . aegypti , An . stephensi and Cx . quinquefasciatus respectively. M . anisopliae metabolites produced LC 50 values in Ae . aegypti , 59.83μg/ml, in An . stephensi , 50.16μg/ml and in Cx . quinquefasciatus , 51.15μg/ml respectively. M . anisopliae metabolites produced lower toxic effects on A . nauplii , LC 50 values were, 54.96μg/ml respectively. Bio-indicator toxicity results show 18% and 58% mortality was recorded in E . eugeniae and A . nauplii and also there is no phytotoxicity that was observed on S . lycopersicum L. under semi-field condition. E . eugeniae histopathological studies shows fungal metabolites showed lower sub-lethal effects compared to synthetic chemical pesticide at 24hrs of the treatment. The GC-MS and FT-IR analysis identified five major components of active ingredients. Conclusion Findings of this study indicate that, M . anisopliae ethyl acetate derived secondary metabolites are effective against larvae of Ae . aegypti , An . stephensi and Cx . quinquefasciatus mosquito species, lower toxicity effects were observed on non-target organisms such as, Artemia nauplii , Eudrilus eugeniae as well as, no toxicity effect were observed on Solanum lycopersicum . Further research should be conducted in laboratory for separation of single pure molecule and be tested semifield conditions.