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Thousand cankers disease

TCD is a disease complex native to the western United States and primarily affects black walnut Juglans nigra. This disease is the result of the combined activity of a fungus (Geosmithia morbida) and the walnut twig beetle (Pityophthorus juglandis).

Fungal spores are carried and introduced into the tree by adult beetles during gallery construction. Subsequent canker development in the inner bark disrupts the flow of nutrients throughout the tree. Widespread mortality of black walnut since 2001 in Colorado led to the recognition and description of the disease. TCD has since been confirmed in several western states (Pennsylvania Department of Agriculture) and also been found in black walnut’s native range in the states of Tennessee, Virginia, and Pennsylvania.