Pseudocercosporella capsellae (teleomorph: Mycosphaerella capsellae)
White leaf spot occurs on turnips, Chinese cabbage, Chinese mustard, cabbage and broccoli, and infrequently on cauliflower. Oval lesions with gray, brown or nearly white centers and dark margins form on cotyledons, leaves and petioles. When lesions are numerous, affected foliage may turn yellow and senesce.
Conditions for Disease Development
This fungus may be seed-borne and overwinters in volunteer plants or perennial weeds. The ascospores are spread by wind and rain. Disease development is generally favored when air temperatures are cool [13-18°C (55-64°F)] and moisture is abundant.
Eradicate cruciferous weeds and volunteers. Cultivate to help promote good soil drainage, and implement crop rotation to non-host species.