The potential of Beauveria bassiana inoculum formulated into a polymeric matrix for a microbial control of spruce bark beetle

Two local strains of Beauveria bassiana originally isolated fromnaturally infected spruce bark beetles in Slovakia were tested for their virulence to Ips typographus (IT) and for their compatibility with a polymeric matrix composed of low-molecular polyethylene. Conidia could be homogenously immobilized in the low-molecular polyethylene matrix with no adverse effect on their viability and infectivity. At constant temperature (25 degrees C), viability of immobilized conidial decreased only by 1-2% after 7 or 14 days when compared with non-formulated conidia. In field conditions, viability of conidia formulated in the matrix was even significantly higher than non-formulated conidia 35 days after their application in traps. Conidia incorporated into the polymeric matrix were infective to IT adults in laboratory bioassays. Mean values of LC50 for native conidia (0.72-2.05x10(6) conidiaml(-1)) and conidia immobilized in the polymeric matrix (0.64-1.03x10(5) conidiamm(-2)) demonstrated high virulence. The efficacy of the local strains was significantly higher than that of B.bassiana strains from mycoinsecticides (Boverol((R)), Botanigard((R)) ES and Naturalis-L-(R)). Results showed potential of this polymeric material for its use in microbial control of IT when mixed with conidia of B.bassiana.