Blumeriella jaapii
Overview
- Can be a significant problem when inoculum builds on cherries grown in humid climates
- Lack of control can cause premature leaf drop and declined winter hardiness
- Sweet cherry generally less susceptible to cherry leaf spot than tart cherry, when it can become severe!
Symptoms
- Primarily appears on leaves as small reddish-purple spots, may coalesce and cause leaf yellowing
- Infected leaves eventually fall off, resulting in poor fruit quality, complete defoliation by late summer, and winter hardiness issues including tree death of young trees
- Good pictures of cherry leaf spot on MSU Fruit Pest and Beneficial Search
Disease cycle
- Overwinters on leaves on orchard floor (think apple scab)
- Spores discharged, ideal temperature 60 to 85 F., triggered by rain, beginning at bloom to 6 weeks after petal fall
- Very similar to apple scab, varying hours of leaf wetness, depending on temperature, required for infection
- Continued spread by conidia on infected leaves continues with wetting
Management
- Sanitation by removal/chopping/decomposition of leaf litter should help, as well as good season-to-season control
- Otherwise, fungicide applications beginning at petal fall (or first leaves) and continuing every 7 to 10 days until harvest, followed by 2 post-harvest applications
- Tart cherries require more aggressive fungicide application schedule (including post-harvest) than sweet cherry, particularly during wet seasons