Thousand Cankers Disease

The Thousand Cankers Disease (TCD) is a relatively newly documented disease that occurs in the walnuts. It wasn’t until 2010 that the pathogen was recognized in the western United States. The disease is the consequence of massive outbreaks & large scale die offs that targets mostly walnuts, namely black walnuts. TCD in walnuts shows early yellowing leaves & foliage thinning.  As the disease progresses larger limbs are killed, in final stages the fungus may inhabit the trunk. Usually a tree dies near three years after symptoms seen in the crown of the tree.

The tree is killed by both the Geosmithia fungus and the walnut twig beetle. The climate of choice is cold, wet, and cloudy seasonal conditions. The walnut twig beetle borrows itself into the tree leaving cancers that coalesce to restrict the movement of water & nutrients. The Geosmithia fungus is physically transported on beetle after its been on surface. After the fungus spreads from within the beetle and its coalesced hoes have the tree.

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This blog post was an assignment for Societal Issues: Pesticides, Alternatives and the Environment (PLNTPTH 4597). The views expressed are those of the author and do not necessarily reflect the views of the class, Department of Plant Pathology or the instructor.