- Worldwide distribution. On lettuce. An important disease.
- A fungus producing large spots between the veins which dry and fall out. Fruiting bodies filled with spores occur in the spots. Spread occurs in rain-splash, wind-driven rain, and in infected seed.
- Worse during periods of high rainfall when spots merge to destroy leaves and reduce quality.
- Cultural control: use certified seed; check plants in the nursery for leaf spots; use drip rather than overhead irrigation; collect debris and incorporate into soil or burn; 3-year crop rotation.
- Chemical control: use copper or mancozeb; if systemic products needed, use triazoles.
