See:
Poplar (Populus spp.) - Canker
Willow (Salix spp.) - Twig Blight (Scab)
Cause Several different fungi have been found associated with cankers on willow samples sent to the OSU Plant Clinic including Cytospora, Phomopsis and Colletotricum.
There have been many different Cytospora spp. reported on willow in the US. Although the disease is found on many hosts, the fungi responsible may be host specific. Isolates from aspen or cottonwood were not pathogenic on alder, ash, elm or willow but were able to infect each other. These fungi enter trees through wounds such as those caused by winter injury. Weakened trees are more susceptible.
Symptoms
Cytospora - Concentric rings may appear and show the regular advance of this fungus through the branch of some willows. Dark bumps which are fruiting bodies of the fungus (pycnidia) may appear in the damaged tissue.
Cultural control
- Keep trees in good vigor and avoid wounding.
- Remove and destroy dead or severely cankered branches.
Chemical control Make applications in fall after leaves drop to protect leaf scars.
- Badge X2 at 1.5 to 2 lb/A. Group M1 fungicide. 48-hr reentry. O
- Bordeaux 8-8-100. Group M1 fungicide. O
- CuPRO 5000 at 1.5 to 5 lb/A but only up to 2 lb/A when new growth is present. Group M1 fungicide. 48-hr reentry.
- Junction at 1.5 to 3.5 lb/A. Group M1 + M3 fungicide. 48-hr reentry.
Reference Kepley, J. B. and Jacobi, W. R. 2000. Pathogenicity of Cytospora fungi on six hardwood species. Arboriculture & Urban Forestry (AUF), 26:326-333.