Cucumber scab caused by Cladosporium cucumerinum in Korea.
During 1994-96, cucumber scab caused serious losses in plastic film house blocks in Goisan and Ansung, Korea Republic. C. cucumerinum was isolated from the diseased cucumbers and shown to be the causal agent using Koch's postulates. When C. cucumerinum was inoculated on cucumber plants, sunken or dark brown spots appeared on leaves, stems, and fruits. The lesions were usually covered with dark grey mould. Most of infected fruits were covered with a gummy substance which had leaked from the lesion. The colonies were greenish black and pale brown, and erect conidiophores of 5.0-6.7 µm grew up on the medium. Conidia were oval to fusiform, pale brown, and 0-2 septate. Conidial size was variable and ranged from 4.5 to 17.9×2.8-8.4 µm. The optimum temperature for mycelial growth and conidial formation of the pathogen on PDA medium was c. 20°C and the optimum pH ranged from 4.0 to 8.0.