Abundance of Entomopathogenic Fungi in Leaf Litter and Soil Layers in Forested Habitats in Poland

SIMPLE SUMMARY: The soil environment is an important reservoir for a wide variety of entomopathogenic fungi that can suppress insect populations, including agricultural and forestry pests. This research aims to investigate the species composition and density of entomopathogenic fungi (EPF) in the leaf litter and at different soil depths in different types of forests during different seasons (spring, autumn). The current study describes the density of four different genera of entomopathogenic fungi in forest soils and leaf litter. The densities of EPF were usually higher in leaf litter than soil, and Beauveria spp. were the most prevalent fungi among leaf litter and soil samples compared to other entomopathogenic fungi. This research will give new insights into our understanding of EPF diversity and composition in forests. ABSTRACT: This study aims to determine the species composition and density of colony-forming units (CFU) of entomopathogenic fungi (EPF) in leaf litter at different depths of the top layer of forest soils depending on the type of forest (coniferous, deciduous and mixed forest), and the date of sampling (spring, autumn). In each type of forest, leaf litter and soil were collected using a soil stick from four depths of soil: 0–5, 5–10, 10–15 and 15–20 cm. Entomopathogenic fungi were isolated by a soil or litter dilution plating method on a selective medium. Four fungal genera were found: Beauveria spp., Cordyceps spp., Metarhizium spp., and Lecanicillium spp. The density of EPF was usually higher in leaf litter than in the layers of soil below, and the most frequently isolated species from both environments were Beauveria spp. among soil samples from all forest types; Beauveria spp. were most abundant in the top layer (0–5 cm), and their density of CFUs gradually decreased deeper into the soil profile.