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U.S. Forest Service Scientists Working on Many Fronts to Slow Spread of Walnut Twig Beetles, Thousand Cankers Disease

St. PAUL, Minn, August 22, 2011 - In the woods and in the lab, scientists with the U.S. Forest Service, Northern Research Station, are working with partners in Midwestern and Northeastern states to slow the spread of the walnut twig beetle and the fungus that causes Thousand Cankers Disease (TCD). Since 2010, the disease has been identified in three eastern states: Pennsylvania, Virginia and Tennessee.

In the woods, Northern Research Station scientists are assisting with visual surveys by sampling suspicious trees in Iowa, Minnesota and Missouri. Scientists also contributed to developing guidelines and data collection protocol adopted by the Forest Service and USDA Animal and Plant Health Inspection Service / Plant Protection and Quarantine (APHIS-PPQ). These guidelines and data collection protocol are being used in visual surveys for TCD in 15 eastern states.

In the lab, researchers are examining branch samples collected from suspect trees to determine whether the walnut twig beetle or the fungus that causes TCD, Geosmithia morbida, are present. Dr. Jennifer Juzwik’s lab in St. Paul, Minn., is one of the “confirming labs” for positive finds of TCD arising from the eastern state surveys.

A research plant pathologist with the Northern Research Station, Juzwik serves on the National Steering Committee for TCD, which coordinates survey and detection, research, and outreach activities with state agencies and federal agencies.

Juzwik encourages people to check black walnuts in their yards and woodlands for unexplained dieback and signs of the disease. So far, TCD has only been detected in urban and suburban areas, but walnut plantations and natural stands may be just as susceptible. Suspect trees may be reported to the state natural resource or agricultural agency for follow-up by trained forest health personnel.

 “It’s not too late in the season to look for visible symptoms,” Juzwik said. “Finding the sick trees now is critical to protecting black walnut throughout the region.”

Symptoms of TCD include yellowing and thinning of the upper crown, followed by the death of progressively larger branches. During the final stages of the disease, large areas of foliage may rapidly wilt. Trees often are killed within three years after initial symptoms are noted. A checklist of TCD symptoms can be found on the Tennessee Department of Agriculture’s website:http://www.tn.gov/agriculture/regulatory/tcdchecklist.shtml

Juzwik and other Northern Research Station scientists are engaged in research aimed at understanding and managing TCD. Projects include researching the genetics of the TCD fungus to determine its origin and methods of causing cankers; screening elite selections of black walnut for resistance to TCD; and investigating whether other insects carry the canker pathogen as well as what other tree pathogens the walnut twig beetle may carry.

Northern Research Station scientists are collaborating with university researchers to test “trap trees,” or girdled black walnut, as an early detection technique for the beetle and the TCD fungus.

The mission of the U.S. Forest Service is to sustain the health, diversity, and productivity of the nation’s forests and grasslands to meet the needs of present and future generations. The agency manages 193 million acres of public land, provides assistance to state and private landowners, and maintains the largest forestry research organization in the world. The mission of the Forest Service’s Northern Research Station is to improve people’s lives and help sustain the natural resources in the Northeast and Midwest through leading-edge science and effective information delivery.

The U.S. Forest Service is an agency of the U.S. Department of Agriculture, a mission of sustaining the health, diversity and productivity of the nation’s forests and grasslands to meet the needs of present and future generations. The mission of the Forest Service's Northern Research Station is to improve people’s lives and help sustain the natural resources in the Northeast and Midwest through leading-edge science and effective information delivery.

The U.S. Forest Service manages 193 million acres of public land, provides assistance to state and private landowners, and maintains the largest forestry research organization in the world. Public lands the Forest Service manages contribute more than $13 billion to the economy each year through visitor spending alone. Those same lands provide 20 percent of the nation’s clean water supply, a value estimated at $7.2 billion per year. The agency has either a direct or indirect role in stewardship of about 80 percent of the 850 million forested acres within the U.S., of which 100 million acres are urban forests where most Americans live. For more information, visit www.fs.usda.gov/.

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Last modified: August 22, 2011