In 2002 and 2003, sensitivity to thiophanate-methyl (TM) of Fusarium spp. and Microdochium nivale, causal agents of Fusarium head blight, isolated from wheat in Aomori Prefecture was tested in vitro. Five of 74 isolates in 2002 and 1 of 361 isolates in 2003 were identified as F. culmorum and were highly resistant to TM and had a minimum inhibitory concentration higher than 1600 ppm. In inoculation tests in 2005, TM did not control disease after when wheat plants were inoculated with TM-resistant isolates of F. culmorum. This report is the first on the occurrence of benzimidazole resistance in F. culmorum.
