Abundance of the soil entomopathogenic fungus Metarhizium anisopliae sensu lato in agricultural field and forest soils in Japan

Metarhizium anisopliae sensu lato is a facultative entomopathogenic, soil-inhabiting fungus that has been used for biological control of soil-dwelling arthropod pests. However, little is known about the density of M. anisopliae sensu lato in forest soils and the difference in the density among different habitat types and geographical origins. In this study, we determined the density of this fungus in soil samples collected from forest and agricultural fields in Japan by plating method with semi-selective agar medium and analyzed its associations with the habitat types and latitudes of the collecting sites. Mean and mode density of 211 soil samples were 9.4 × 10 ² CFUs/g soil and 1.0 × 10 ³ -1.0 × 10 ⁴ CFUs/g soil, respectively, which were comparable to the levels previously reported in other countries. The density in forest soil was not significantly different from that of the other habitat types, despite previous studies that concluded M. anisopliae sensu lato to be less abundant in forest soil based on occurrence determined by insect bait method. The latitude was also not significantly associated with the density. This study revealed higher abundance of M. anisopliae sensu lato in forest soil than the original expectation.