Abstract
BackgroundThe 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.MethodIsolation 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.ResultsThe 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 LC50 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, LC50 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.ConclusionFindings 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.
Highlights
In vector control programme, there is increased usage of same or different types of chemical insecticide for vector control which synthetic chemical pesticide, insect growth regulators and chemical repellent cause environmental pollution, affect non-target organisms and mosquito species get insecticide resistance capacity [1]
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
Many extracellular crude metabolites isolated from different fungi species such as, Metarhizium sp., Beauveria sp., Tolypocladium sp., F. oxysporum, Lagenidium giganteum have been tested for larvicidal potential on major mosquito species [4,5,6, 9,10,11,12,13]
Summary
There is increased usage of same or different types of chemical insecticide for vector control which synthetic chemical pesticide, insect growth regulators and chemical repellent cause environmental pollution, affect non-target organisms and mosquito species get insecticide resistance capacity [1]. The entomopathogenic fungus contain enormous amount of secondary metabolites with high toxicity to larvae, pupae and adult mosquito species as confirmed by Vivekanandhan and others [4,5,6]. Many studies have reported interesting research results on the toxicity of fungi crude metabolites extracts of Beauveria bassiana, Fusarium oxysporum, Metarhizium anisopliae on larvae, pupae and adult of mosquito vector species [4,5,6, 8]. Artemia nauplii are bisexual organisms in salt water environment. These species are adaptability in high salinity and temperatures range from 5–30 ̊C. 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
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