Question: What can I do to identify and control oak wilt?

Answer: First, the very best way to identify oak wilt is through the Plant Disease Diagnostic Laboratory at Texas A&M. For a slight charge they can culture the organism and confirm its involvement. They recommend you send 1-1/2-inch diameter pieces 6 to 7 inches long. Choose limbs that are in stress, but not yet dead. Send them on-ice, via overnight delivery, to preserve the live organism. Contact your county Extension office or browse online for the mailing address and other specific directions and charges. Live oaks affected with oak wilt will show yellowing. Leaves will shed freely. On close inspection you’ll see that the leaf veins are reddish-brown, light green between the veins. On red oaks the leaves will wilt and die, but they will not fall from the tree. This disease is spread by root grafts and by nitidulidae sap-feeding beetles. All pruning of established live oaks and red oaks should be done during the winter dormant season, while the beetles are inactive. Seal all cut surfaces with pruning paint to prevent their entry. You should also trench between afflicted trees and other healthy adjacent trees. The trench should be 100 feet from the dying tree, and it should be 48 inches deep. You can use a labeled fungicide as long as you treat before the disease has affected more than 15 percent of the foliage. One treatment will be sufficient in most preventive programs. The Extension Service has additional information online, as will most professional arborists.

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