Fungal leaf spots
Phyllosticta sp. and Dothiorella candollei (formerly Macrophoma candollei)
5 host plants
Last updated
Oakleaf hydrangea shows small necrotic leaf spots by mid to late summer. Phyllosticta and Dothiorella species cause minor spotting, usually noticed in midsummer. Avoid overhead watering, space plants for air flow, and clean up fallen leaves. Healthy plants tolerate small numbers of spots; fungicide rarely needed in home landscapes.
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
Leaf spot diseases are usually noticed in midsummer to early fall.
Cultural Controls
- Avoid overhead watering.
- Space plants and prune to improve air circulation.
- Use good sanitation.
- Remove and destroy or dispose of diseased plant materials.
- Clean up fallen leaves and debris beneath plants.
- Do not compost diseased materials.