Branch cankers around beetle galleries
Ned Tisserat, Colorado State University, Bugwood.org
Thousand Cankers Disease
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
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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.