Protect Ash Trees: Don’t Move Firewood!


Emerald ash borer. Photo by Pennsylvania Dept. of Conservation & Natural Resources,
Emerald ash borer. Photo by Pennsylvania Dept. of Conservation & Natural Resources,

Emerald ash borer was recently detected in Georgia, making it the 21st state invaded by the non-native pest that attacks all members of the ash genera. First found in Michigan in 2002, the insect has since spread south (and north into Canada), mainly on wood moved long distances.

The number one strategy for preventing further spread of the emerald ash borer? “Don’t move firewood,” says Paul Merten, entomologist with U.S. Forest Service Forest Health Protection unit. “Emerald ash borer larvae tunnel into trees underneath the bark, and cutting a tree into firewood does not kill them. They can emerge as adult beetles ready to infest healthy trees.” To protect forests from the emerald ash borer and other invasive exotic forest pests:

 Emerald ash borers only attack ash trees. Learn how to identify ash, and watch for the following signs of infestation:

Firewood infested with emerald ash borer. Photo by Troy Kimoto, courtesy of
  • Jagged holes from woodpeckers feeding on larvae
  • Cessation of terminal growth
  • Crown dieback
  • Small leafy branches sprouting from the trunk

Merten and his colleagues are working with land managers to monitor public lands in Tennessee, Virginia, Kentucky, and North Carolina. They use several methods to detect emerald ash borers including trap trees, hanging traps with attractants, and biosurveillance. To make trap trees, they girdle living ashes, causing the trees to emit chemical distress signals that attract wood-boring insects. After a few months, scientists cut the trap trees down, peel off the bark, and look for emerald ash borers beneath the bark.

Girdled trap tree. Photo by Pennsylvania Dept. of Conservation & Natural Resources Forestry Archive, courtesy of

Purple triangular traps are also used to detect emerald ash borers. These sticky traps are placed in high risk ash trees, and if the bugs are around, they’re drawn to the trap by its color and a chemical attractant. Once the beetles make contact with the trap, they become stuck to its surface.

Another way of determining whether ash borers are in the neighborhood involves a technique called biosurveillance, in this case monitoring nest entrances of a native wasp, Cerceris fumipennis. Females of the species hunt for beetles in the buprestid family, which includes emerald ash borers. Once a beetle is captured, the wasp paralyzes it and carries it to a subterranean nest before laying an egg on the hapless beetle. When the egg hatches, the wasp larvae eat the living but paralyzed beetle. The entrance to this macabre nursery can be monitored for emerald ash borers.

Merten and his colleagues have been monitoring wasp nests located on baseball fields across North Carolina. That’s a typical place to find colonies,” says Merten. The wasps like sunny open fields with sandy compacted soils.” Merten and other researchers will be watching the wasps this year for signs of beetles on the move.  

“There’s been some pushback on the ‘don’t move firewood’ message,” says Merten. But if everyone is more mindful of their part of the problem, we could really slow the spread of pests like the emerald ash borer and help protect our forests.”

For more information, contact Paul Merten at

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