Metabolites of Metarhizium anisopliae against Malaria Vectors and Non Target Organisms

Abstract

Vector borne diseases are affecting millions of people annually. Entomopathogenic fungi toxicity on malaria vectors increase mortality rates, and are less effective on nontarget organisms, thus representing a control measure that could be used in integrated programmes. Before metabolites of entomopathogenic fungi can be integrated into control programmes, an effective delivery system must be developed. In the laboratory, Metarhizium anisopliae were cultured in complete broth media. All instars of Anopheles stephensi and aquatic non-target organisms were passively treated with culture metabolites by different concentrations. The mortality values were subjected by probit analysis for a period of 24, 48 and 72 hours, respectively. Fugal filtrated metabolites significantly increased mortality in the exposed larvae of malaria mosquitoes and had a less adverse effect on nontarget organisms. The highest LC 99 (663.77 ppm) values were observed in fourth instars of A. stephensi and found lowest LC 99 (254.09 ppm) values in first instars. First instars tolerated applications better than other instars. A positive correlation was found between concentrations of fungal filtrate and percentages mortalities for the all instars of malaria vector. All nontarget organisms were not found susceptible at lower concentrations. Our study marks the first to use of extracellular secondary metabolites of entomopathogenic fungus against all instars of A. stephensi and nontarget organisms. The good biological stability of extracellular metabolites makes this a promising alternative to mycelium and conidial based larvicides. It could be regarded as fungal –based natural larvicides for the use of vector control strategy.