Common Diseases of Weeping Willow Trees and Their Management

Introduction

Willows (Salix) are beloved for their dramatic elegance, often found along waterways but adaptable to many sites. They thrive in full sun and all soil types, sometimes helping prevent erosion. However, several diseases can damage leaves, wood, and even kill the tree.

Willow Scab

Caused by Fusicladium saliciperdum. Favored by damp, wet weather. Irregular brown spots appear on leaf veins and midribs, turning olive-green as spores form. Young leaves are especially vulnerable; severely infected leaves dry and drop. Fungus spreads to twigs, causing dark cankers and dieback. Treat with copper fungicide per label. Prevention: prune dead twigs, rake and burn fallen leaves.

Crown Gall

Bacterial disease causing tumor-like galls on roots, stems, and sometimes branches. Small, round, light-colored knots enlarge and multiply, eventually girdling roots/stems. Leaves discolor, dieback increases, growth stunts. Galls invite secondary infections. No cure—remove and destroy infected trees.

Cytospora Canker

Various Cytospora fungi attack stressed or weakened trees. Fungus grows in bark and wood. Symptoms: yellow, black, or brownish-orange discolored bark areas; pimple-like black cankers that ooze orange, thread-like spores in moist conditions. Inner wood may appear reddish-brown. Dead bark persists for years. Control by maintaining tree health: avoid lawn-equipment wounds. Remove infected branches with clean cuts. Clean fresh wounds by removing diseased tissue; on old wounds, remove loose bark. Do not apply dressings—allow to dry.