Issue 11

The First Enemy of American Chestnut

In the early to mid-1800s, the American chestnut got its first shock from Phytophthora cinnamomi, an exotic root-borne fungus. Called ink disease because it turns roots black, P. cinnamomi reduced the range of the American chestnut by eliminating it from lower elevations. The disease causes root rot and persists in wet clay or compacted soils. Globally, P. cinnamomi causes economic and ecologic damage to forest, ornamental, and crop trees, including avocado and walnut.

According to SRS research forester Stacy Clark, one question being posed in nursery production of chestnut seedlings relates to the best fertilization and irrigation protocols to limit the growth of fungal pathogens such as ink disease. Field studies have shown that American chestnut seedlings planted in soils contaminated with P. cinnamomi have little to no chance of survival.