Effect of the method of transition to organic on naturally occurring soil-dwelling entomopathogenic fungi

The continually growing demand for organic products exceeds supply, creating opportunities for farmers. However, conventional farmers need to know the consequences of their management practices on the likelihood of successful conversion to organic production. We are currently examining the interaction between soil disturbance and initial cover crop type and management on weed populations, soil quality, and economic performance during the three-year transition to organic production in a feed grain rotation in central Pennsylvania. Our experiment includes four systems comprised of a factorial combination of two levels of primary tillage (full vs. minimum) and two types of initial cover crop (perennial sod/legume vs. annual cereal grain/legume). Over a three-year transition period the cropping sequence consists of an initial cover crop, followed by soybean, and finally, maize. Here, we discuss the impact of these treatments on naturally occurring entomopathogenic fungi (EPF), indicators of the ability of the soil to resist outbreaks of insect pests. We detected EPF by bioassay of soil samples collected four times during each field season and examined the relationship between EPF and biotic and abiotic soil characteristics. We detected three species of EPF: Metarhizium anisopliae, Beauvaria bassiana, and Paecilomyces fumosoroseus. EPF were favored in systems that minimized tillage and utilized a sod-forming timothy/red clover cover crop mixture. Greater detection of EPF occurred during the initial cover crop than during soybean or maize production. The presence of EPF was positively associated with soil moisture and the concentration of permanganate oxidizable carbon in soil. This study will inform farmers of the impacts of management practices on soil function, specifically conservation biological control.