Chestnut Blight

If you grow chestnut trees in Western Washington, watch for orange-brown bark discoloration and small orange pustules erupting through the bark surface on stems and branches. These pustules are the fungus fruiting bodies. Beneath the bark you'll find fan-shaped buff-colored mycelial mats, and the cankers girdle branches and trunks, killing everything beyond the infection point. Once a canker forms, it expands rapidly and will eventually girdle major stems.

Chestnut blight devastated American chestnuts across the country decades ago, so this disease deserves serious attention if you're growing chestnuts in the region. Avoid wounding trees, as the fungus enters through fresh damage. Remove infected branches and stems as soon as you spot them to prevent further spread. Plant resistant species like Chinese chestnut whenever possible, since they tolerate infection better than American or European varieties. Sanitize pruning tools between cuts to avoid spreading spores from one tree to another.