Oklahoma Agriculture Blog

Oklahoma’s Official Agricultural Information Site

Quarantine Placed to Protect Oklahoma’s Walnut Trees

Posted by arthur1234 on August 30, 2010

A walnut branch from an infected tree. Photo provided by Tennessee Dept. of Agriculture

The Oklahoma Department of Agriculture, Food, and Forestry has issued an emergency quarantine on the importation of all walnut (Juglans spp.) and other regulated articles originating in areas infested with Thousand Cankers Disease (TCD) of walnut.

The insect-fungal pest complex that is lethal to walnut trees has been detected in at least 8 western states and recently confirmed in eastern Tennessee. The western states include Arizona, California, Colorado, Idaho, Nevada, New Mexico, Oregon, Utah and Washington.

The quarantine prevents movement from infested areas of nursery stock, unprocessed lumber, logs, wood chips, mulch, firewood, and other products created from walnut trees. It does not include nut products. Oklahoma joins Missouri, Kansas, Nebraska, and Michigan in establishing the TCD quarantine.

TCD is spread by the walnut twig beetle, a tiny insect that bores holes into walnut trees. The beetle carries a fungus that forms thousands of cankers under the bark of the host tree and kills a tree within 2-3 years after initial infection. Early symptoms include leaf yellowing, wilting, and tree crown thinning which are symptoms often confused with other pests and environmental factors.

Black walnut trees have been reported in nearly every county of Oklahoma, according to the ODAFF Forestry Services Division. Foresters said if TCD were to spread to our state and the region of native black walnut trees it will cause negative economic, ecological, and sociological effects.

Because control options are not known at this time, preventing the movement of walnut from infested areas into Oklahoma is the primary means of limiting the spread of TCD. The quarantine will restrict movement of walnut from known infested states and protect the black walnut in Oklahoma and its native range in eastern states.

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