Authored by Andrea Ashby, Assistant Director, NCDA&CS
The N.C. Department of Agriculture and Consumer Services is fighting the spread of three major invasive insect species primarily harming ash, black walnut and redbay trees in the state. The threat is real and only just beginning to be seen in the state as these pests spread.
“In many cases, long-distance movement of firewood may be encouraging the spread of emerald ash borer, walnut twig beetle and the redbay ambrosia beetle into previously uninfected areas,” said Alonso Suazo, entomologist with the Plant Industry Division’s Protection Section. “We are continually trying to get the message out that it is always best to use firewood local to the area and leave any unused wood behind.”
The emerald ash borer, first identified in the state in 2013, was probably introduced to the U.S. from Asia in wood packaging materials, such as crates, pallets, or dunnage used in cargo shipments. As of summer 2014, the borer had been detected in Granville, Person, Warren and Vance counties.
All four native ash species – pumpkin, Carolina, green and white – are susceptible to attack by the borer. That means an estimated 2.5 million ash trees in the state are at risk. Damage caused by emerald ash borers may kill trees within three to five years of initial infestation.
Adult beetles are metallic green, ½-inch long and 1/8-inch wide, and are active in North Carolina from late spring through mid-summer. Larvae can be found underneath the bark throughout the year. The natural flight of the beetles is five to seven miles per year, but rapid spread has been attributed mostly to the movement of firewood, Suazo said.
Another pest, the walnut twig beetle, carries the fungus Geosmithia morbida. This fungus causes thousand cankers disease, which threatens North Carolina’s native black walnut trees. After infestation, a tree dies within two to three years. Walnut twig beetle was first found in the eastern U.S. in 2010 and was detected in Haywood County in fall 2012. Black walnut is valued for its wood, nuts and ornamental features. It is also important for wildlife, as its nuts provide food for birds, squirrels and other small mammals.
Symptoms of thousand cankers disease include a thinning canopy and branches sprouting from the tree trunk. Small holes where the beetles have entered and exited the bark may be seen if closely inspected, and small oval or round cankers may be seen if a very thin layer of the bark is removed or scraped.
Lastly, North Carolina’s Coastal Plain is threatened by the spread of the redbay ambrosia beetle. This beetle, like the emerald ash borer, is native to Asia. It carries a fungus that causes a disease known as laurel wilt, which was detected in Bladen County in 2011. The disease has since been discovered in Brunswick, Columbus, New Hanover, Pender and Sampson counties. The N.C. Forest Service has been surveying affected areas to determine the extent of the disease. Trees and shrubs susceptible to laurel wilt include redbay and swampbay, as well as spicebush, sassafras, pondspice and pondberry. As of 2014, laurel wilt has only affected redbay in North Carolina. Infected redbay trees display wilted reddish-brown leaves and black staining in the outer sapwood, which can be seen after removing the outer bark. Movement of infested firewood may also move this beetle into new areas.
“The public can help us combat these pests in two ways,” Suazo said. “First, don’t move firewood; the risk isn’t worth it. And secondly, contact your county forest ranger if you see evidence of damage from these pests. It’s important that we know if these pests are on the move in other counties.”
Hardwood-firewood quarantines are in place in Haywood, as well as Granville, Person, Warren and Vance counties due to the presence of walnut twig beetle and emerald ash borer, respectively.
An N.C. Forest Service county ranger can provide tree pest identification assistance and land management advice. Residents can find county contacts at the following link: http://ncforestservice.gov/Contacts/contacts_main.htm. Local rangers may refer potentially infested trees to other NCDA&CS specialists.
You can also report the location and descriptions of potentially infested trees to department staff at 1-800-206-9333 or via email at [email protected]. You can also visit us on Facebook to upload an image, location and contact information at http://www.facebook.com/NCDAforestpestoutreach.