Emerald Ash Borer in New Hampshire: What to Do With Your Ash Tree

Last checked: August 6, 2026  •  Pest status from NHBugs; town list updated September 24, 2025

Where This Stands in August 2026

Emerald ash borer was first found in New Hampshire in Concord in March 2013. NHBugs — the pest site run jointly by UNH Cooperative Extension, the Division of Forests and Lands and the Department of Agriculture, Markets and Food — has kept the town list ever since. For the six towns this site covers it reads: Amherst 2017, Hollis 2018, Nashua 2019, and Hudson, Merrimack and Litchfield in 2020. That page was last updated September 24, 2025; we read it as of August 2026.

You will see 2014 in print — a Granite Geek column in the Concord Monitor on August 3, 2026 puts the arrival there. Every state and Extension source says March 2013.

There are three moves available with an ash here: treat it and keep treating it, take it down now, or take it down later at a higher price. The thresholds that sort those are published and specific, and almost nobody selling tree work quotes them.

Where the Beetle Actually Is

NHBugs publishes detections town by town, and as of that September 24, 2025 update the list reaches Berlin, Gorham, Jefferson, Randolph and Lancaster, each detected in 2024. What it does not publish is a statewide total, so there is no total here either.

• Amherst — 2017. Earliest of the six towns here.
• Hollis — 2018.
• Nashua — 2019.
• Hudson, Merrimack and Litchfield — 2020.
• Source: NHBugs, NH Towns With EAB Infestations, updated September 24, 2025; read as of August 2026.

The Quarantine Everyone Gets Wrong

Most of what is written about EAB quarantines describes rules that no longer exist, and there were two. The federal domestic quarantine — USDA's rule on moving ash material out of infested areas — was removed effective January 14, 2021. New Hampshire's own in-state quarantine on ash logs, chips, nursery stock and hardwood firewood was eliminated by the Department of Agriculture, Markets and Food in 2018; the UNH Extension notice went up in October 2018 and gives no precise effective date, so this page gives none either. NHBugs states the position now in one sentence: "Movement of ash wood and ash wood products is no longer regulated within New Hampshire." What is still in force is a firewood rule, and it is not an ash rule.

• Out-of-state firewood is prohibited from New Hampshire unless it is labeled as certified heat-treated — 140°F (60°C) for 60 minutes. In place since July 2011. (NHBugs, as of August 2026.)
• Ash moves freely inside the state — but NHBugs still recommends keeping ash firewood within about five miles of where it was cut, or seasoning it on site at least a year first. That is a recommendation, not a law, and it is not written here as one.

Is It Ash, and Is It Infested?

Most pages hand you a confident field key here — branching pattern, exit-hole shape, what the wood looks like under the bark. There isn't one on this page, because the New Hampshire sources behind it do not publish one and a key we invented would be worth nothing to you. What is published is the threshold that decides what happens next, and it is measured in crown dieback rather than in beetles. New Hampshire's guidance is that ash with greater than 50% crown dieback, or dead, should be removed rather than treated; past that point the tree can no longer move an insecticide around effectively (NHBugs, Using Insecticides, as of August 2026). The Purdue Landscape Report, in a January 22, 2019 piece on removal timing, draws the line earlier: under 30% canopy loss, treat; over 30%, plan the removal. For the identification itself, NHBugs takes homeowner reports through its own reporting form, and an ISA Certified Arborist — voluntary here, and the credential worth asking about — can put a written assessment in your hand.

Treat or Remove, and What Treatment Commits You To

New Hampshire's guidance is permissive, and the wording carries the weight. NHBugs says that when you find yourself within ten miles of an EAB outbreak and have ash you want to save, consider starting semiannual treatments of systemic products. Consider — not must. Every town here sits well inside that window, so the decision is live for every ash in the service area; that is not the same as saying treat.

• The chemistry. NHBugs describes emamectin benzoate, delivered by trunk injection, as giving better killing power over a longer period than the other active ingredients. It does not say how long, so no duration appears here.
• The commitment. Treatment protects a tree; it does not cure it. Keeping an ash alive means re-treating on a cycle for as long as you own the house. Stop, and the beetle is still in the neighborhood.
• The comparison. The only cost framing with a state agency behind it is exactly that — a comparison. NHBugs: "Removals of mature urban landscape trees can cost several thousand dollars compared to several hundred dollars for pesticide treatments."

Why the Same Tree Costs More in Two Years

Removal is several thousand once. Treatment is several hundred repeatedly, and never converts into a tree that stops needing it. Which way that falls depends partly on how long you plan to be in the house — and partly on the fact that the removal itself gets harder. Ash killed by emerald ash borer does not soften the way a rotting maple does; it goes brittle. The Purdue Landscape Report (January 22, 2019) states that ash killed by EAB "become extremely brittle and break easily as they decline," and, more usefully for timing, that structural integrity "can begin to decline even when trees are mostly green and have two thirds of the canopy still intact." Dead ash then does something genuinely dangerous: it stays hard. Writing in TCI Magazine on July 1, 2023, an ISA Certified Arborist described EAB-killed ash as brittle but hard — it sounds solid under the pre-climb sounding test that would warn a climber off a rotten tree, and the guidance there is not to climb ash in that condition at all, but to work it from an aerial lift. A live ash with most of its canopy is a climbing job; the same tree dead is a lift-or-crane job. No sourced dollar figure for that gap exists, and none is invented here — but the direction runs one way. A 2018 UNH Cooperative Extension article in the New Hampshire Municipal Association's Town & City describes the pattern that catches towns out: about seven years after a first detection only around 10% of ash are dead, and over the following five years 80% die. Nashua's detection year was 2019.

The One License New Hampshire Does Issue

Cutting a tree down in New Hampshire takes no state licence at all — the trade carries no exam, no credential and no insurance requirement written into law. UNH Cooperative Extension is unambiguous about what a certification is and is not: "Certification is not required by the State of New Hampshire but it does indicate that the arborist has a high degree of knowledge." Injection and spray work is the exception. RSA 430:33: "No person shall engage in the commercial application of pesticides ... without possessing a valid certificate of registration issued by the division," with competency shown by examination and proof of financial responsibility, and a $60 commercial application registration (statutory text effective July 1, 2025; checked as of August 2026). UNH Extension gives its reach: "anyone applying pesticides on property that they do not own, as part of their business or not, must be certified (licensed) as a commercial pesticide applicator" — paid or not, general-use product or not. So on your own ash: the person who cuts it down needs no state credential, and the person who injects it does. NHBugs gives (603) 271-3550, the NH Division of Pesticide Control, as the number for finding an applicator in your area. This is general information about New Hampshire law, not legal advice; these citations were checked as of August 2026.

Ask About an Ash Tree

Leaning, dropping limbs, dead down one side, too close to the wires — whatever the tree is up to, put it here and one insured local crew rings back to set up a look.

First name *

Last name *

Phone *

This is the number the crew rings back on — give the one you answer outside.

Email * City/Town * Select your town Nashua Hudson Merrimack Amherst Hollis Litchfield Other nearby What is the tree doing? Send the Details

* Required. By submitting, you agree that your details may be passed to one independent, insured local tree contractor, who will call you back about the tree. See our privacy policy.

Tree already down, or resting on something it shouldn't be? The phone is faster — (603) 506-4389.

What Else Ends Up on the Same Work Order

Removal is one line on a longer list: the pruning, the stump, the brush pile, and the back lot nobody has touched in thirty years.