Abstract
We tested 977 strains of Botrytis cinerea, isolated from eggplants and tomatoes between 2002 and 2006 in Mie Prefecture, for their sensitivity to mepanipyrim. In the in vitro assays using the FGA-paper disc method, the MIC values for 974 strains were 3 ppm, whereas three strains collected from a greenhouse in 2005 had MIC values >3 ppm. In an in vivo assay using cucumber to determine whether the three strains were resistant to mepanipyrim, mepanipyrim gave 100% control of the sensitive strains at 100 ppm but had poor efficacy against the three strains and a resistant strain isolated from Europe. Therefore, the strains were confirmed to be resistant to mepanipyrim. This is the first report of mepanipyrim-resistant strains of B. cinerea in Japan. The practical dosage of mepanipyrim WP had excellent efficacy against resistant strains to mepanipyrim in the field trial. However, the rate of resistant strains significantly increased in the area treated with mepanipyrim compared with the nontreated area.
