Marssonina leaf and twig spot

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.