Net Tisserat, Colorado State University; bugwood.orgA cutaway of a canker shows the walnut twig beetle tunnels.Ohio State University has warned landowners to be on the lookout for thousand cankers disease, which affects most species of walnut trees.
In the East, researchers are most concerned about black walnuts, according to a news release.
The trees provide lumber and edible nuts.
In the West, they're concerned about English walnuts, which are grown mainly in California for their nut meats, and black walnuts.
Thousand cankers is caused by the fungus, Geosmithia morbida.
The small walnut twig beetle spreads the fungus from infected trees to healthy trees.
Initially, leaves of infected trees may turn yellow and drop.
If you look carefully, you may see small exit holes caused by the beetles and small lesions, or cankers, on the branches.
Eventually the tree dies.
Ohio landowners who suspect the disease should call the Ohio Department of Agriculture at (614) 728-6400.
For more information about the disease and beetle, visit www.thousandcankers.com.
The website provides a drop-down menu with updates for every state.