Abstract
A novel technique to measure the virulence of an entomopathogenic fungus, Beauveria bassiana by exposing tarsi of adults to dry conidia was developed to evaluate effectiveness of nonwoven fabric strip formulation of this fungus for controlling adults of the Japanese pine sawyer, Monochamus alternatus. To regulate inoculum density without suspending conidia in water, conidia were killed by heating at 100°C for 1 h and a step dilution series of conidia was prepared by mixing dead conidia with live conidia at different ratios. The conidial mixtures were attached to tarsi of CO2-anesthetized adults with a fine hairbrush. The 50% lethal doses determined by this method on 14 d were 5.5×106 conidia/individual for aged adults and 1.9×106 conidia/individual for young adults, and on 30 d were 2.8×105 conidia/individual for aged adults and 2.4×104 conidia/individual for young adults. The number of conidia produced on a nonwoven fabric strip was 3.5×108 conidia/cm2, and 8.5×105 conidia/individual were attached to adult beetles which walked on the strip. Based on these results, the validity of a biological control method for M. alternatus to prevent vectoring of the pine wilt disease is discussed.
