Evaluating toxicity of extracted destruxin from metarhizium anisopliae against citrus leafminer, Phyllocnistis citrella

Abstract

Problem statement: The fungus, Metarhizium anisopliae (Metschnikoff) Sorokin produces some cyclic peptide toxins, destruxins, which exhibit a variety of insecticidal actions. Citrus leafminer, Phyllocnistis citrella Stainton, is a major pest of young citrus trees; therefore its effective and safe control is a important issue. Approach: Five isolates of M. anisopliae were inoculated in Potato Dextrose Broth (PDB) mediums. Destruxin was extracted by adding chloroform. Citrus leafminer was bioassayed by using the leaves containing early stages larvae and the data were recorded after 1, 2, 3 and 4 days after treatment. Results: The range of mortality was between 30-65% based on the endpoint data. The minimum of three days to achieve 50% mortality was proved by probit analysis of time-mortality responses. The 10, 15 and 20 fold dilutions of extracted destruxins from isolates cause 17.2-48.5, 9.4-37.5 and 0-26.5%, respectively. Conclusion: Bioassay of destruxin by using citrus leafminer larvae shows its acceptable effect of destruxin. By considering biology of this species and calculated LT50s, destruxin seems to be an effectiveness component of IPM programs. The 10, 15 and 20 fold dilutions of extracted destruxin have a reduced amount of mortality, but in some cases it can balance the expensive production process of microbial agents and their efficacy. © 2010 Science Publications.