Eastern Forest Threat Center - Thousand Cankers Disease

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Branch cankers around beetle galleries

Branch cankers around beetle galleries

Ned Tisserat, Colorado State University, Bugwood.org

Thousand Cankers Disease
Geosmithia sp.

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).

Keywords: fungus, walnut twig beetle, Pityophthorus juglandis, walnut, Juglans species, cankers, bark beetle galleries

Distribution Map Distribution Source Image

Threat Description

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 recogniction and description of the disease. TCD has since been confirmed in several western states (PDF, Pennsylvania Department of Agriculture) and also been found in black walnut's native range in the states of Tennessee, Virginia, and Pennsylvania.