Occurrence of Corynespora cassiicola isolates resistant to pyribencarb on eggplant in Kochi Prefecture, Japan

Ninety-nine Corynespora cassiicola isolates were collected from eggplant fields in Kochi Prefecture, Japan, in 2020–2023, and their sensitivity to pyribencarb was investigated. Sequence analysis of the cytochrome b gene revealed that 68 strains harbored the G143A substitution mutation. Inoculation tests using potted eggplants showed that pyribencarb had a weaker effect on strains harboring G143A. Sensitivity to pyribencarb was assessed by culturing mycelial homogenates of isolates on PDA medium containing 10 or 100 µg/ml azoxystrobin. The proportion of resistant isolates collected in 2022 and 2023 was significantly higher than that collected in 2020 and 2021.