Abstract
Sensitivity of Corynespora cassicola, causal agent of Corynespora target spot of tomato, isolated from tomato plants in Okayama Prefecture in 2000 and 2001 to thiophanate-methyl (T) and diethofencarb (D) was investigated using a minimum inhibitory cocentration (MIC) method and bioassay. Of 250 isolates of C. cassicola isolated from tomato fields, 188 isolates were highly resistant to T, with the MIC more than 1600 ppm, and three isolates were highly resistant to both T and D. In bioassay tests, T and D had no effect on disease after inoculation with highly resistant isolates. This report is the first on the occurrence of C. cassicola resistant to both T and D.
