Emerald Ash Borers Invade Southeastern Forests


Adult emerald ash borer. Photo by Leah Bauer, courtesy of Bugwood.org.

The emerald ash borer is one of the most destructive forest pests introduced to North America in recent years. Adult beetles merely nibble on the leaves of native ash trees, but their larvae burrow through the inner bark of the tree, leaving a trail of snaky galleries that permanently scar the tree and make it unable to transport nutrients. Infested ash trees essentially starve to death, often in as little as 3 to 5 years.

First identified in 2002 in Michigan, the beetle came from Asia and eastern Russia, probably accidentally introduced to the United States in 1996. Since then, it has killed tens of millions of ash trees across the United States and Canada. Recently emerald ash borers invaded forests in Virginia, Kentucky and Tennessee, and were first detected in the Great Smoky Mountains National Park in 2011. Paul Merten, an entomologist with U.S. Forest Service Forest Health Protection unit confirmed an infestation in the Greenbrier area of the Park in fall of 2012.

“Park Service tree climbers were getting ready to climb up the trees to look for signs of emerald ash borers, but we decided to check the tree trunks first,” says Merten. “I peeled off a section of an ash trees outer bark and saw that the inner bark was riddled with S-shaped galleries left by emerald ash borer larvae. It looked like the infestation was several years old.”   

However, not all suspected outbreaks are that clear cut. “Five counties on the Virginia and North Carolina border are infested, but emerald ash borers have not been found in North Carolina,” says Merten. “Last fall we heard about a stand of declining and dying ash trees on public lands in North Carolina. When I saw the trees, I thought we had an emerald ash borer infestation on our hands. So I peeled up a section of bark, expecting to find their galleries, but there was nothing. We didn’t find galleries on any of the trees. It was very surprising.”   

Larva in gallery. Photo by James W. Smith, courtesy of Bugwood.org.

Further sampling in this area will be a priority in the coming year, especially in May and June when, if present, adult emerald ash borers would be active.  

Its not uncommon for emerald ash borer infestations to take years to detect. As Merten explains, “Most of the beetle’s life is spent underneath tree bark. A lot of times, we don’t know they’re in the area until ash trees start declining or dying.”

Scientists are working on ways to detect emerald ash borers sooner, so that land managers and land owners have time to protect ecologically and culturally valuable trees with insecticides or biological control agents.

Since emerald ash borers are discreet hitchhikers, hiding in or underneath wood bark, the best way to protect trees is to stop moving firewood. When firewood or nursery stock is moved from place to place, emerald ash borers may be riding along, getting a free ride to new locales.

Read more about emerald ash borer.

For more information, contact Paul Merten at pmerten@fs.fed.us

Access the latest publications by SRS scientists.


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