A novel technique to inoculate conidia of entomopathogenic fungi and its application for investigation of susceptibility of the Japanese pine sawyer, Monochamus alternatus, to Beauveria bassiana

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 CO 2 -anesthetized adults with a fine hairbrush. The 50% lethal doses determined by this method on 14 d were 5.5ϫ10 6 conidia/individual for aged adults and 1.9ϫ10 6 conidia/individual for young adults, and on 30 d were 2.8ϫ10 5 conidia/individual for aged adults and 2.4ϫ10 4 conidia/individual for young adults. The number of conidia produced on a nonwoven fabric strip was 3.5ϫ10 8 conidia/cm 2 , and 8.5ϫ10 5 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.

Entomopathogenic fungi and insect behaviour: from unsuspecting hosts to targeted vectors

“…Although this example utilised a complex inoculation device, this is not always necessary. Shimazu (2004) found that young adult pine sawyers, Monochamus alternatus (Hope), could be inoculated with a lethal dose of B. bassiana through walking on a non-woven fabric strip that had been contaminated with the fungus at a concentration of 3.5 9 10 8 conidia cm -2 .…”

Media for conidial production of the entomopathogenic fungus, Fusarium coccophilum (Anamorphic fungi: Phialosporae)

“…A strain of Beauveria bassiana produces 3.5ϫ10 8 conidia/cm 2 on nonwoven fabric band (Shimazu, 2004) (Lee et al, 1996). Lee et al (1996) also cultured Metarhizium anisopliae on the same media and obtained 1.2ϫ10 7 -2.2ϫ10 7 conidia/cm 2 .…”

Transmission of Metarhizium brunneum conidia between male and female Anoplophora glabripennis adults

“…The conidial loads we obtained in the laboratory with the ventral surface of the beetle held against a conidial lawn could be higher than for beetles walking freely over a fungal band on a tree. In a study by Shimazu (2004), using a cerambycid similar in size to A. glabripennis, M. alternatus, the tarsi of beetles that walked on B. bassiana fungal bands became contaminated with 8.5 9 10 5 ± 4.5 9 10 5 conidia (mean ± SD), which was greater than the LD50 for deaths within 30 days, but less than the 14-day LD50.…”