The dispersal and persistence of Beauveria bassiana and Metarhizium anisopliae following application in soybean fields as kaolin dust and sprays of soybean oil formulations were investigated. Fungal dispersion was evaluated from a centrally-treated area by sampling leaflets on eight transects at 20-m intervals in concentric rings up to 100 m from the central area. Density of colony-forming units (CFU) per unit leaf area was determined by washing the soybean leaflets in water containing Tween 80, and plating the aqueous suspensions on an oatmeal-dodine semi-selective agar medium. Spatial dispersal of B. bassiana in soybean field was significantly higher when conidia were applied as an oil formulation compared with a kaolin dust formulation. No significant differences were observed in M. anisopliae CFU number between sprayed or dusted plots. Oil-based formulations favor the dispersal of B. bassiana in soybean crops, but not the dispersal of M. anisopliae. Kaolin-based formulations are not suitable for B. bassiana or M. anisopliae dispersal.
entomopathogens; epizootiology; fungi; insect; persistence
