Abstract: The newly occurred pepper disease，pepper leaf spot，observed in greenhouse of Liaoning
Province was studied. The pathogen was identified as Cladosporium oxysporum. The damage and
symptoms of this disease were reported. The results of the biological characteristics of the pathogen
showed that the best medium for mycelial growth was V8 juice. Pathogens can effectively use of sugar and
nitrogen sources. Sorbitol and malt extract could be used as better carbon and nitrogen sources for growth.
The optimum temperature for mycelial growth was 20 ℃ to 25 ℃. The optimum pH was 6 to 8. Light
could promote mycelial growth. The mycelia lethal temperature was 77 ℃. The optimum temperature for
conidium germination was 20 ℃ to 30 ℃. The optimum pH was 7. Light had no obvious promoting effect
on conidium germination. The conidium lethal temperature was 48 ℃.

Key words: pepper, leaf spot, Cladosporium oxysporum, biological characteristics