Red Leaf Spot
Phyllosticta cotoneastri
13 host plants · Fungal
Last updated
This profile synthesizes data from multiple published sources. Expert field review is in progress.
You'll see red leaf spot as red-colored lesions on foliage during cool, wet conditions. This fungal disease spreads by spores. Remove infected leaves and improve air circulation. Avoid overhead watering and reduce leaf wetness. Apply fungicides preventively if disease pressure is high. These leaf-spotting diseases are most active in cool, wet conditions. Remove infected foliage and improve air circulation Early detection and prompt management of symptoms help limit disease spread.
Leaf spot and blotch diseases are primarily cosmetic on established plants, though repeated years of heavy infection can weaken them. Rake up and remove fallen leaves to reduce the spore load going into the next season. Avoid overhead watering that splashes spores from the ground onto lower leaves. If the problem is severe, protective fungicide sprays during spring leaf emergence can help, but sanitation does more than chemistry for most leaf spots.
Quick Reference
Management
Spring (March-May) during leaf emergence; fall (September-November) when temperatures cool and humidity rises. Young foliage most susceptible.
Spring and fall; cool wet conditions (55-65°F) with 10+ hours continuous leaf wetness. Multiple rain events drive successive infection cycles.
Cultural Controls
- Remove and destroy infected leaves. Leaves may be composted if completely decayed before spring. Make use of any practice that encourages decomposition of fallen leaves prior to spring bud break, such as mowing or flailing. Apply urea to leaves after leaf fall in autumn to enhance decomposition of fallen leaves.
- Rake and destroy leaves in fall. Grow other, more resistant species of Crataegus.