Dutch Elm Disease in Montana: Symptoms, Spread and What to Do

Is Dutch elm disease really in Montana?

Yes. Montana State University Extension includes it in its guide to tree and shrub problems in the state, listing American elm and European elm as hosts. MSU Extension in Roosevelt County has reported elms in the town of Culbertson testing positive through the Schutter Diagnostic Lab in Bozeman. In Great Falls, a 2026 news report quoted the city forester saying the disease has been spreading there since the first reported cases in 1987, and described the city asking residents to watch for symptoms.

Those are the Montana cases we could confirm from sources loaded on 11 October 2026. We did not find a statewide map or count, so we are not going to guess at one. The practical reading is that any American elm in a Montana town should be watched.

Does the City of Missoula have a Dutch elm disease program?

We looked for one and did not find a dedicated program described on the City of Missoula's Urban Forestry pages or in its 2015 Urban Forest Master Management Plan. If you need a definite answer for a boulevard elm, the City's Urban Forestry Division is the place to ask.

What the City's documents do show is useful background. In the plan's street tree inventory, Siberian elm made up 5.6 percent of Missoula's street trees, and the species tables in its appendix list 1,157 Siberian elms against 26 American elms. The City's 2026 approved street tree list includes elms chosen for resistance, describing 'Valley Forge' American elm as a Dutch elm disease resistant cultivar, 'Accolade' as a resistant hybrid and 'Sapporo Autumn Gold' as highly resistant. The plan also uses Dutch elm disease as its example of why no single species should dominate a city's streets.

What are the first symptoms?

MSU Extension describes it this way: starting in summer, leaves on infected branches in the upper canopy curl, wilt and turn grayish-green or yellow. Arborists call that flagging, because one branch stands out against a green crown. As the disease moves, neighboring branches follow and major dieback shows. Drought stress can make symptoms develop faster.

The confirming sign is under the bark. Peel a wilting branch and the wood shows distinct brown streaks running lengthwise. North Dakota State University Extension, which has dealt with the disease in every county of that state, cautions that other diseases and disorders also cause wilting in elms and that a lab test is the only way to be certain. In Montana, samples go to the Schutter Diagnostic Lab through your county Extension office.

How does it get from one elm to the next?

Two ways. The first is elm bark beetles. MSU explains that the beetles breed under the bark of dying or dead elms, including diseased ones. The fungus grows in their galleries, the spores stick to the new adults, and those adults fly to healthy elms to feed, carrying the fungus into the water-conducting wood. The Roosevelt County Extension page notes that most emerging beetles feed on healthy elms within 1,000 to 1,500 feet of where they hatched, though wind can carry them much farther.

The second is root grafts. Elms growing close together, within about 50 feet according to that same page, fuse roots over the years, and the fungus moves through the shared plumbing. NDSU says root-graft infections progress much faster, often wilting the lower branches first in spring and killing the tree that same summer or fall.

Which elms are most at risk?

American elm is the most susceptible and Siberian elm the most resistant, according to NDSU, which also stresses that no elm species is totally resistant. That is some reassurance for the Missoula and Bitterroot valleys, where the common elm is the tough, weedy Siberian elm found along alleys, ditches and old fence lines.

Resistant does not mean harmless. The Roosevelt County Extension page points out that dead and dying Siberian elm wood breeds the beetles just as American elm does. A half-dead Siberian elm on your fence line may be a breeding site for the beetles that threaten somebody's American elm down the block.

When should elms be pruned?

In the cold months. NDSU says pruning to remove infections should be done from November through March. The Roosevelt County Extension page explains the reason: adult beetles begin emerging about the middle of May and keep emerging through the warm months. Routine elm work therefore belongs in the dormant season, which matches the general advice in our Montana tree pruning calendar and our dormant pruning service.

The exception is a branch that is actually flagging. MSU Extension says to start scouting the upper canopy in mid-June, and to prune out and destroy symptomatic branches immediately, checking the wood for streaking. NDSU adds that the cut needs to be at least 8 to 10 feet below the symptoms, in wood with no discoloration, and that the tree should be watched closely afterward because it is hard to be sure everything was removed. Disinfect tools between cuts. MSU gives 70 percent ethyl alcohol or a household disinfectant spray, and NDSU a 15 to 20 percent bleach solution.

Can a confirmed tree be saved?

Sometimes, if it is caught in a single branch. Beyond that the realistic answer is usually no. The Roosevelt County Extension page says there is no way to eliminate the disease once it begins, and that control aims to spread the losses over a long period.

For healthy, high-value elms, MSU notes that fungicide injections are an option. NDSU describes them as injected into the root flare by a trained tree care professional, more effective as prevention than as a cure, lasting up to about three years, and unable to stop root-graft infections. It also warns that repeated injections can damage a tree. We do not want to promise a treatment in a guide, so ask us about it when we look at the tree.

What happens to a tree that has it?

It should come down promptly. The Extension sources recommend removal within two to three weeks of confirmation, because the chance of root-graft spread grows with every week an infected tree stands. Where a neighboring elm is close, NDSU describes trenching to sever root grafts as an option when less than a quarter of the diseased crown is affected. Removal of a declining elm near a house or wires is the kind of work described on our hazard tree removal page.

Then the wood has to be dealt with. NDSU lists burning, burying, chipping or debarking. The one thing not to do is stack it. The Roosevelt County page says protected firewood piles are where the beetles best survive the winter, and that a few elm logs kept by one household can undo sanitation for several blocks. Our guide to firewood and wood chips after tree removal covers what can be kept.

Who is responsible for a boulevard elm?

In Missoula, the City says its Forestry Division oversees all activity in the right of way, that adjacent owners are responsible for caring for boulevard trees, and that all work on them requires a permit from the Urban Forestry Division. This is general information, not legal advice, and other towns have their own rules, so call your city or county before touching a street tree. Our guide to Missoula tree permits and the right of way explains the process.

For an elm on your own ground, an assessment is the first step. It is part of our tree services, and you can find related guides in the Montana Tree Guide.

Call HJ Property Care & Tree Service at (406) 215-7319 or request a tree assessment and an ISA Certified Arborist will look at the tree with you.

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