Emerald ash borer is a small metallic green beetle from Asia that bores into ash trees. NYS DEC says it feeds on every native ash species in New York, and that most infested trees die within 2 to 4 years. It was first found in the state in 2009, and FOX 5 reported in September 2026 that DEC now has it confirmed in every county but Hamilton and Lewis.
How it reached Long Island
The East End find came first. In January 2019, Cornell Cooperative Extension of Suffolk County found larvae in an infested ash in Southold. By 2021, CBS New York reported DEC had found it in about 80 trees around Selden, that a street in Nesconset had lost eight ash trees, and that the Town of Smithtown was checking about 50,000 street trees. In Nassau, Patch reported in 2022 that the Village of Garden City expected to take down hundreds of ash trees, possibly close to 1,000, and plant two smaller trees for each one removed.
Signs in your own tree
You will rarely see the beetle itself. DEC lists what it leaves behind:
- Thinning at the top. Dieback starts in the top third of the canopy and moves down until the tree is bare. Leaves turn yellow and brown.
- Pale, scraped bark. Woodpeckers strip the outer bark to get at the larvae, leaving light patches that DEC calls “blonding.”
- D-shaped holes. Adults chew a small D-shaped exit hole as they come out of the bark.
- Winding tunnels. Under split or loose bark you can see S-shaped larval galleries packed with sawdust.
- Vertical splits in the bark.
- Sprouts coming out of the trunk and roots, often with leaves bigger than normal.
Adults come out in late May and are most common in June and July.
Treat it, or take it down
Treatment. DEC says landowners may consider treating their ash trees with insecticide. Dan Gilrein, an entomologist with Cornell Cooperative Extension of Suffolk County, told 27east that there are effective treatments that generally work well to protect ash trees before they are infested, and suggested getting your tree looked at by someone qualified. A DEC forester put the other side plainly to Patch: once you see the tree start to decline, it is unfortunately too late. An ISA Certified Arborist can tell you which side of that line your tree is on.
Removal. DEC says an infested tree does not have to come down unless it could fall onto a building or a road, and that it has no program to help private owners pay for removal. Waiting on a dead ash near the house tends to cost more, not less. Jones Tree and Plant Care in Smithtown says dead or compromised trees, including ash hit by emerald ash borer, are unpredictable to cut and take longer, which shows up in the price. And Miguel’s Tree Service says an emergency removal typically costs 50 to 100 percent more than a planned one, so a dead ash is cheaper to take down before a storm does it for you. Tree removal covers permits and what the quote should include.
What to do with the wood
New York limits moving firewood of any species to within 50 miles of where it was grown, and DEC says most long-distance spread of the beetle has been traced to ash firewood and nursery trees. When the Southold find was announced, DEC asked that wood from infested ash be left or used on site, or chipped to less than an inch in at least two dimensions. Ask the crew to chip it or leave it rather than haul it away whole.
Reporting
Because it is now confirmed across nearly all of New York, DEC only asks for new reports from a few upstate counties. On Long Island, questions can go to DEC’s Forest Health line at 1-866-640-0652.