Experimental formulations to mitigate effects of sunlight on germination and growth of the Canadian isolate of the entomopathogen Metarhizium anisopliae - A candidate biological control agent

The entomopathogen Metarhizium anisopliae including M. anisopliae var. anisopliae S54 has been developed and used as an insect control agent in integrated pest control programs. The efficacy may be reduced by exposure to sunlight. This study determined the effects of formulation components on potential detrimental effects of exposure to natural sunlight on the conidial germination rate of M. anisopliae var. anisopliae strain "S54," an isolate originally found in Canadian soil, in different oil carriers. Mycelia growth, number of colony-forming units, and the germination rate of conidia of M. anisopliae var. anisopliae S54 were assessed after exposure in 11 mixtures, including horticultural oil, mineral oil, safflower oil, canola oil, sunflower oil, Silwet (X-77), and Tween 80. After exposure to natural sunlight, the strains mixed with vegetable and mineral oil carriers demonstrated some sunlight intolerance. Exposure to natural sunlight delayed the germination of surviving conidia in all 11 oil formulations, but germination was greater after 48 h of incubation than after 24 h. In conclusion, formulation in oil improves the efficacy of this fungus and may extend the application of species with lipophilic conidia in agricultural environments that have limited natural light. The tested formulations are compatible with this candidate biopesticide agent and offer some protection from environmental factors that affect germination and growth.