Serious Threat to Black Walnut Trees in the Denver Area


Black Walnut Beetle Deadly Fungus CarrierSince its entry into Colorado in 2003, Thousand Canker Disease effects Black Walnut trees. The Thousand Canker Disease is caused by a fungus carried by the Walnut Twig Beetle. In the process of tunneling into the tree, the beetles transmit the Geosmitha fungus into the phloem tissue which transports nutrients and the fungus throughout the tree. Affected trees have yellowing leafs, thinning upper tree crowns, and dying limbs.

Thousand Cankers Disease Carrier Walnut Twig Beetle
Another symptom of this disease, although much less obvious, is the appearance of thousands of dark brown/black stains (cankers) in the cracks of the bark of the tree. Regrettably, no current treatments are highly effective in stopping the disease. However, homeowners with black walnut trees are injecting the trunk with fungicides and insecticides in order to eliminate both the beetle and fungus. A second method is to use soil applications of insecticides before the disease is well-established. Still, many trees die within three years of the first noticeable symptoms. If you discover that one of your trees is infected with TCD, prompt tree removal, followed by burning or burying the tree, is the best way to prevent its spread.

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