Where it came from
Northeastern Asia: China, Korea, Japan, Mongolia, and the Russian Far East.
How it got here
Arrived in wood packing material in shipping crates and was discovered killing ash trees near Detroit in 2002, though it had probably been there since the early 1990s. It was found in New York in 2009 and on Long Island in 2018, spreading largely in firewood.
What it does to the ecosystem
Larvae tunnel serpentine galleries under the bark that cut off water and nutrient flow; an infested ash dies in two to four years. It kills more than 99 percent of the ash trees it reaches, removing an entire genus from forests and taking with it the dozens of insects that depend only on ash.
What it costs
The most destructive forest pest in North American history by dollar value: tens of millions of trees dead and tens of billions of dollars in removal, replacement, and lost property value. Municipalities on Long Island are removing street ash trees now.
Don’t confuse it with
- Six-spotted tiger beetle and native metallic wood-borers. The tiger beetle is bright green but larger, runs on bare ground, and has white spots. Emerald ash borer is slender, bullet-shaped, half an inch long, and found only on ash.
How to identify it
Metallic green beetle half an inch long; D-shaped exit holes in ash bark, S-shaped galleries under bark, thinning crowns, and woodpecker damage.
What to do
Do not move firewood. Valuable ash trees can be protected with systemic treatments by a certified arborist. Report new finds.
On Long Island
Confirmed in both counties since 2018. If you have a healthy ash you want to keep, a certified arborist can protect it with trunk injections every two to three years. Never move firewood.
Worth knowing
- The D-shaped exit hole is the diagnostic sign: flat on one side, curved on the other, about an eighth of an inch across.
- Woodpeckers strip infested ash bark to reach the larvae, leaving pale patches called blonding that you can spot from the road.
- Tiny parasitoid wasps from Asia have been released across New York as biological control and are establishing.
