MDA details new Emerald Ash Borer finds, quarantine rules, treatment options and how to report sightings

Jonathan Austis, the Emerald Ash Borer technical assistance coordinator in the Minnesota Department of Agriculture (MDA) Plant Protection Division, reviewed recent detections of Emerald Ash Borer (EAB) in Minnesota, described how to identify the pest and its damage, summarized quarantine rules that limit movement of ash material and hardwood firewood, and outlined management options for homeowners and communities.

Austis said the briefing was prompted by new detections: “We’re having this meeting due to the recent detections of EAB in Kanabec County and then, new parts of Cass and Isanti Counties.” He emphasized that early detection and reporting improve MDA’s ability to respond and that the agency posts an interactive EAB status map on its website.

Why this matters: Minnesota has an outsized ash resource that makes the state vulnerable. Austis told attendees Minnesota has roughly a billion ash trees — more than any other contiguous state — and that in many communities ash can compose one in five, and in parts of northern and western communities one in two or three, of street and yard trees. Because EAB populations build slowly and then often cause rapid mortality, many communities face synchronized tree losses that create safety hazards and large removal costs.

What to look for: Austis gave four diagnostic signs he called most reliable. The single most diagnostic sign is an S-shaped feeding gallery under the bark. He said, “If you find those s shaped, tunneling galleries in an ash tree, you know it’s emerald ash borer.” Other useful indicators are a larva with two tail spines (urogomphi), the iridescent green adult beetle with a reddish abdomen, and a D-shaped exit hole. He also recommended looking for woodpecker damage and bark ‘blonding’ in the mid-to-upper canopy — dime-sized shallow holes and pale patches — which often appears before trunk symptoms.

Life cycle and timing: Austis described EAB’s adult flight period as roughly late May through September in Minnesota, with life cycles of one or two years depending on latitude and infestation density. He said a female typically lays 60–90 eggs (about 70 on average) and explained that immature larvae can remain under bark for more than a year, which is why moving cut wood long distances risks spreading the pest.

Quarantine and regulated materials: MDA enforces two quarantine types. An internal state quarantine restricts movement of regulated articles (all ash material, any EAB life stage, mulch and all hardwood firewood) between infested and non-infested counties; an external quarantine limits import from out of state and Canada without a compliance agreement. Austis said compliance options include chipping or grinding to particles less than about 1 inch in two dimensions, debarking, composting, or heat treatment by certified dealers. He recommended buying heat-treated, MDA-certified firewood locally: certified firewood bears an MDA shield label and can move freely.

Management choices: For yard and community trees, Austis said the practical options are removal or insecticide treatment. Treatments include professional trunk injections (commonly emamectin benzoate, effective for about two years) and homeowner soil drench products (e.g., imidacloprid, dinotefuran) that generally require annual reapplication. He advised that trees with more than roughly 30 percent canopy decline are poor treatment candidates, and that communities within about 10 miles of known infestations should consider starting treatments on high-value trees.

Costs and community planning: In the Q&A Austis provided cost guidance: homeowner trunk-injection treatment averages about $10 per diameter inch (he illustrated this as about $150 every two years for a 15-inch tree), while communities that do treatments in-house can sometimes reduce per-inch costs below $5. He encouraged communities to build ash inventories and management plans and noted that Minnesota DNR Community Forestry grants and other rounds (including a relief grant last fall) have helped fund inventories, removals and replacements but that grant eligibility varies by round.

Reporting and contacts: Austis urged people to document suspected infestations with photos showing the specific damage (woodpecker holes, galleries, larvae or beetles) and detailed locations (address or coordinates) and to report via MDA’s online “Report a Pest” form, email or voicemail. He offered to share slides and the recorded webinar via the MDA EAB web page and provided contact information for follow-up. For regulatory or business-specific questions about moving regulated articles, he referred attendees to MDA regulatory specialist Danielle DeVito and said he would share her contact information.

Next steps: MDA will continue updating its interactive status map as detections occur and urged communities to check the map frequently, prepare management plans, and avoid moving firewood long distances. The recorded briefing and slides will be posted on the MDA Emerald Ash Borer web page.