38th Annual Meeting of the Society for Invertebrate Pathology

Beauveria bassiana, Paecilomyces sp. and Metarhizium anisopliae are cosmopolitan fungi that are found in agricultural and forest soils. We report the influence of the rhizosphere of soybean, wheat, sunflower, corn, wild radish (Raphanus sativus L.) and lupine (Lupinus albus L.) on the abundance of colony forming units (CFU) of these entomopathogenic fungi. Soil samples were collected from the rhizospheres of each plant species and from soil outside of the root projection zone. Soil samples were suspended in water and a serial dilution was plated on dodine-based medium. CFUs were quantified after 15 days of incubation. The density of B. bassiana ranged from 0 to 1,442 CFU/g dry soil with greater densities in the rhizosphere than in the outer rhizosphere of all plant species, in most of the cases. The numbers of M. anisopliae CFUs did not follow a consistent pattern like B. bassiana. The numbers of Paecilomyces sp. CFUs from the rhizosphere did not differ from CFU numbers outside of the root projection zone. No differences of CFUs were found by plant species. These results suggest that chemical (root exudates) and physical (humidity, aeration) conditions near the roots can influence the prevalence of propagules of certain species of entomopathogenic fungi.