Weeping Willow Cankers

Weeping willow (Salix babylonica, family Salicaceae) thrives in moist to wet soils and is hardy in zones 4-9; that wet preference masks the fact that chronic drought or root stress makes willows unusually vulnerable to canker fungi like Cytospora, even though the species shows reliable hardiness in zone 4 where moisture is available. Because willows tolerate standing water, infections are often linked to periods of drought, heat, or physical wounding rather than constant wetness.

Cytospora species cause classic cankers: sunken, often dark lesions that may ooze resin and stop the transport of water beyond the infected area, producing progressive branch dieback. Infected tissue often shows a sharp margin where healthy wood gives way to sunken, discolored bark; that margin and exudation are the fastest way to separate canker from general decline.

Timing matters: active infections and visible dieback usually become clear after warm, dry spells or when a tree has been wounded. For intervention and slower spread, we recommend dormancy pruning and sanitation; the dormant season concentrates cuts when fungal activity is lowest and lets you inspect cambial margins more clearly. Growers who adjust watering to match seasonal shifts see faster recovery in other stress-prone trees, and the same approach helps Salix babylonica.