As the nations largest producer of walnut trees, Missouri has become the first state in the nation to impose a ban on the transport of walnut products from nine Western states to protect the spread of thousand cankers disease.
The Missouri Department of Agriculture has issued an emergency rule halting shipments of all walnut products from Arizona, California, Colorado, Idaho, New Mexico, Oregon, Utah and Washington, as well as in northern Mexico. The quarantine issued by the Missouri Department of Agriculture applies to walnut products from those areas, as well as from Nevada.

The ban applies to nursery stock, unprocessed lumber, logs, wood chips, mulch and other products created from walnut trees, as well as any hardwood firewood originating from or traveling through affected states.

The order imposes a ban the transport of walnut products from areas where a beetle, and newly described fungus, blamed for the thousand cankers disease has been found.

Although the disease has not been seen in Missouri, the potential cost of infestation could top $850 million over 20 years.

"As the nations leading black walnut producer, we have the most to lose from the spread of thousand cankers. It is critical that we prevent the introduction of this disease into Missouri," said Missouri Director of Agriculture Dr. Jon Hagler.

"This quarantine," Hagler said, "draws a line around our state allowing us to stop thousand cankers at the border and helps keep the infectious plant disease out of Missouri."

Thousand cankers disease is carried by the walnut twig beetle, a tiny insect that bores into walnut trees. The beetle carries a fungus that can form thousands of cankers under the bark of the host tree, destroying its ability to transport water and nutrients. Early symptoms include leaf yellowing and wilting. Walnut trees affected by thousand cankers typically die within two to three years after symptoms are discovered.

Originally found in the Arizona walnut species, thousand cankers affects many types of walnut trees to varying degrees, but is lethal to black walnut. Missouri is home to more than 55 million black walnut trees -- twice the number of any other state -- and the nations largest producer of black walnut nut meats is located in Missouri.

A recent Department of Conservation study found that the annual economic impact from a thousand cankers infestation in Missouri could exceed $135 million, including $36 million in wood products, $35 million in nut production and the loss of $65 million in landscaping and street trees.

"It seems incredible that such destruction could come from a tiny beetle, but that is the destructive nature of invasive pests," said Missouri State Entomologist Collin Wamsley, the chief insect specialist with the Department of Agriculture, who issued the emergency quarantine.

"The walnut twig beetle," Warmsley said, "is just the latest invasive pest to threaten Missouri forests and forest products producers. Whether were talking about this disease, the gypsy moth or the emerald ash borer, we must prevent people from carrying destructive insects and diseases into Missouri."