Wood-Boring Beetles: A Pain In The Ash

North Carolina forests may soon be under threat by an intruder the size of a thumbnail. The Animal and Plant Health Inspection Service recently issued a quarantine in all counties for a non-native beetle that has the Forest Service bracing for major infections here in the Piedmont within the next few years. 

The emerald ash borer is a small green beetle that arrived in the U.S. from Asia about fifteen years ago. Etymologists believe the larvae came undetected, embedded in solid wood packing material used on cargo ships.

Highly adept at locating ash trees, the beetles lay eggs in its bark. Their larvae hatch within one week and bore into the tree itself, feeding on tissue that brings vital nutrients to branches and leaves. Since first being discovered in the Smoky Mountains three years ago, the beetle has spread rapidly eastward in North Carolina.

Watauga County Extension Director Jim Hamilton says it's due to arrive in the Triad by 2019, and the damage will be very noticeable—especially among the ornamental ash trees typically found lining neighborhood streets.

Isolating the ash borers in western North Carolina, has been more of a challenge.

"Because we don't have a huge number of urban population centers," he says. "Ash trees are found in our native woods, but you know aren't necessarily common in the landscape."

Preemptive treatments include injecting insecticides toward the bottom of the trunks of healthy ash trees. In the mountains around Boone, pheromone traps are being used to locate beetles and monitor their movement. Once they're discovered, tiny, parasitic wasps have been released in the infected areas. The imported wasps are harmless to humans, but they lay their eggs inside the emerald ash borer larvae, eventually killing them. 

Hamilton acknowledges that this method is often a difficult balancing act.

"You need to find a predator of an insect pest that really only focuses on that pest," he says. "Therefore you don't run the risk of introducing yet another invasive insect that might cause damage in some other ways."

Detecting and identifying invasive species in a timely manner requires the full force and support of funding for the state agencies that are charged with protecting the environment against these pests, according to Hamilton. 

He adds, "When you cut funding for the agencies that do the research in helping to stop these invasive pests, then there's a greater risk."