Marssonina leaf and twig spot
Marssonina spp.
14 host plants · Fungal
Last updated
This profile contains verified disease data from extension databases. Regional field notes and expert review are in progress.
Willow or oak shows leaf spotting and twig damage from Marssonina fungi living in fallen leaves and dead twigs. Prune and destroy infected twigs, sanitize tools, and rake fallen leaves in fall to reduce overwintering inoculum. Disease pressure decreases with good sanitation.
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 and early summer (April-June) during active growth. Peak: late April through May. Young foliage and new twigs most susceptible.
Spring cool wet conditions (55-65°F) with 8+ hours continuous leaf wetness. Rain-splash primary dispersal. Marssonina spp. favor cool maritime climates.
Cultural Controls
- Prune and destroy infected twigs if practical.
- Disinfect pruning tools after use.
- Rake and destroy any fallen leaves from beneath willow trees, particularly in the fall, to reduce reinfection risk.