The North Carolina Forest Service has been receiving reports of scorched-looking elm trees throughout central North Carolina, from Davidson to Johnston counties. But Jim Slye, the service’s Forest Health Program head, said these trees aren't actually scorched at all.
American elm trees are being feasted on by larvae of the larger elm leaf beetle, Slye said. This native half-inch beetle has blueish-black stripes across its orange back and its larvae have a solid golden color.
“They're eating the tender part of the leaves,” Slye said. “So, they're eating everything except for the leaf veins, which are the tougher part of the leaves.”
With just the leaf veins remaining, the leaves are left with a skeleton-like appearance and turn brown, appearing similar to how trees can look after a fire.
But Slye said this process, called “skeletonization,” doesn't usually kill a tree. Affected trees tend to “bounce back” the following year.
“Don't be overly concerned, but be observant,” he said. “Look at this tree going back into next year's growing season, and be observant for the emergence of this insect again.”
However, repetitive defoliation, or loss of leaves over an extended period of time, can kill a tree, Slye said.
The beetles can be treated with insecticide outside of forest environments, but Slye said ideally, the insect’s predators, which includes birds and other insects, will keep its population under control. So it's possible this current wave may ebb next year.
Since the larger elm leaf beetle is a native insect, Slye said he's less concerned about it than some of the more invasive species, like the newer elm zigzag sawflies, which often lack natural predators.