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
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