Emerald ash borer: what the agencies record

This page describes what the named sources say. It is not a diagnosis of any tree and does not say what should be done with one. Each section names its source, all read on October 9, 2026. Rules on moving ash wood are set out country by country on the emerald ash borer regulated status page, and the table in insect pests of trees compares this beetle with the other pests.

Names and origin

The Canadian Food Inspection Agency, called CFIA, gives the scientific name Agrilus planipennis and calls the beetle a highly destructive invasive pest that attacks and kills all species of ash in the genus Fraxinus. Wisconsin DNR says it is native to northeastern Asia, that it was first detected in the United States in 2002, and that it is thought to have arrived from China in the wood of shipping crates. USDA APHIS puts the first North American detection in 2002 in southeast Michigan. University of Maryland Extension says it was first introduced into Prince George's County, Maryland, in 2003 and was confirmed on ash trees on the Eastern Shore in 2015.

Hosts

All four sources name ash and no other host. APHIS says the beetle kills healthy ash trees in forests and in urban, suburban and rural settings. Wisconsin DNR says true ash species are highly vulnerable whatever the stand density, tree size or tree health. It cites researchers in Michigan and Ohio who saw ash survival fall by 30 to 50 percent over three years in infested stands in southeastern Michigan, and says models built from field observations predict that a healthy forest will have lost 98 percent of its ash by year six.

What the sources list as signs

CFIA says the beetle is small, so its pages point to signs on the tree instead: woodpecker feeding, shoots growing from the trunk, yellowing leaves and branch dieback. It adds that S-shaped lines made by larvae can be seen where bark has been removed. University of Maryland Extension says an attack typically goes undetected until symptoms show, that the upper third of the crown usually thins and dies back first, and that many shoots then rise below the dead part. It describes woodpecker chipping that exposes the paler inner bark as "blonding", and lists small D-shaped exit holes, vertical bark splits and serpentine tunnels in the cambium. APHIS lists the same S-shaped tunnels and D-shaped holes, dead branches near the top, excess branching on the trunk, vertical cracks and more woodpecker activity.

The beetle and the larva

CFIA describes the adult as metallic green on the back and emerald green underneath, 8.5 to 14.0 mm long and 3.1 to 3.4 mm wide, with a flat head and usually black kidney-shaped eyes. The larva is white and flat with bell-shaped segments and grows from 2 cm to 5 cm long. CFIA says the larva feeds on the inner bark and sapwood, making flat S-shaped galleries about 6 mm wide that fill with a fine brownish coating, and that the gallery widens as the larva grows.

Life cycle as the sources state it

APHIS says adults lay eggs in bark crevices, the larvae burrow in and feed, pupate in winter and emerge as adults in spring, and that adults live for about three weeks. CFIA says the eggs are laid on the bark of branches. University of Maryland Extension says adults begin flying in spring about the time black locust trees are flowering. On how fast trees die, CFIA says infested ash in North America generally dies after 2 to 3 years, with heavily infested trees seen to die after only 1 year. University of Maryland Extension says large ash can die within three years of infestation.

How it spreads

CFIA says it spreads most often when firewood and other infested ash wood products are moved, though it also flies, and research shows adults reaching 10 kilometers. Wisconsin DNR says the insect spreads slowly on its own and that its impact is greatly sped up when people unintentionally move it in firewood and nursery stock. It adds that larvae under the bark can last as long as two years in dead wood. For the wider topic see moving wood and firewood.

Where it is recorded

APHIS, on a page modified April 23, 2026, says it has detected infestations in 38 states and the District of Columbia. CFIA, on a page modified July 27, 2026, lists regulated areas that include the southern and middle parts of Ontario, Quebec and New Brunswick, the cities of Thunder Bay, Winnipeg and Halifax and part of Hants County, Nova Scotia, and the cities of Burnaby, New Westminster, Surrey and Vancouver in British Columbia. University of Maryland Extension, on a page updated September 4, 2026, says the beetle is well established in Maryland, and that it is no longer under federal quarantine regulations as of January 14, 2021. Wisconsin DNR says it was federally deregulated in 2021 and points to a statewide firewood rule and a Wisconsin Department of Agriculture map for local detections.

Natural enemies

Wisconsin DNR reports that a native wasp was found killing larvae at two Michigan sites, where between 24 and 56 percent of larvae were parasitized in 2008. It says forest health specialists released four species of parasitic wasps from the beetle's native range in China, that three proved cold-tolerant enough to survive Wisconsin winters, and that one species, Tetrastichus planipennisi, was recovered in seven southeastern Wisconsin counties. CFIA also has pages on wasps as biological control agents.

Reporting

CFIA asks that detections outside regulated areas be reported and links a report form. APHIS lists an online report form and a telephone line, 1-866-322-4512. The report a pest in Canada and report a pest in the United States pages cover the offices in full. Options for protecting or replacing ash are covered on the trunk injection and ash treatment page, and this page gives no product names, rates or timings.