Hoping for Empty Traps

Asheville Boy Scout helps Forest Service survey for walnut twig beetle

Boy Scout William David helps SRS scientist Bud Mayfield prepare to hang traps for the walnut twig beetle along Glenn's Creek Greenway in Asheville, North Carolina. Photo by U.S. Forest Service.
Boy Scout William David helps SRS scientist Bud Mayfield prepare to hang traps for the walnut twig beetle along Glenn’s Creek Greenway in Asheville, North Carolina. Photo by U.S. Forest Service.

Sometimes you may not really want to find what you’re looking for.

On June 11, 6th grader William David, along with his brother Bennett and mother Sherry, met U.S. Forest Service researchers Bud Mayfield and Bryan Mudder to set out traps along a greenway near the Forest Service Southern Research Station (SRS) office in Asheville, North Carolina, for the walnut twig beetle (Pityophthorus juglandis).

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Funnel trap hung in eastern black walnut trees to detect the presence of the walnut twig beetle. Photo by U.S. Forest Service.

Not yet found in Asheville, the walnut twig beetle, believed to be native to the U.S. Southwest, carries the fungus (Geosmimithis morbia) that causes thousand cankers disease. The fungus grows under the bark of walnut trees entered by the beetles and forms multiple small cankers that cut off the flow of nutrients, killing the tree in as little as three years.

Since 2010, thousand cankers disease has been found in the native range of eastern black walnut in Tennessee, Virginia, Pennsylvania, Ohio, and Maryland. Probably transported in firewood, the disease threatens millions of eastern black walnut trees of great economic and ecological value. The state of Tennessee established quarantines on the movement of walnut firewood in east Tennessee counties in 2010. So far in North Carolina, the beetle has only been detected along the Tennessee border in Haywood County.

“William is helping SRS survey for the presence of the walnut twig beetle along Glenn’s Creek Greenway, which has a large population of black walnut trees,” says Mayfield, project leader of the SRS Insects, Diseases, and Invasive Plants unit. “If the beetle does come to Asheville, we hope to detect it early.”

William helped the researchers hang black ropes on the lower branches of four walnut trees along the greenway. The ropes are used to raise and lower the two funnel traps mounted on each tree. One trap in each tree is baited with a pheromone that lures walnut twig beetles, while the other trap is baited with the pheromone plus a slow-release ethanol lure. A cup in the bottom of each funnel trap contains a small amount of non-toxic antifreeze to preserve the insects that are trapped until they’re collected.

Traps will stay in the trees through August and will be removed in September.

“If we trap a walnut twig beetle during the survey, it would be a new county record and only the second detection in North Carolina,” says Mayfield. “It would also prompt discussions about whether we should start a more extensive survey.”

The best way to prevent the spread of thousand canker disease is to not move firewood. In 2014, Mayfield and fellow researchers established that heat treatments effectively kill both the beetle and pathogen and could be used to ensure that wood coming from areas infected with thousand cankers disease does not spread it further.

For more information, email Bud Mayfield at amayfield02@fs.fed.us.

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