Dutch Elm Disease in Illinois and Indiana: What Homeowners Need to Know

Dutch Elm Disease: Still a Major Threat in Illinois and Indiana

Dutch elm disease (DED) has been killing American elms since the 1930s in North America, and it remains an active threat across the Midwest today. Illinois and Indiana — two states that once lined countless streets with majestic American elms — continue to lose trees every year. While the peak of the epidemic has passed, DED still claims thousands of elms annually across the Midwest, including in Wisconsin, Michigan, Minnesota, Iowa, Ohio, and Missouri.

Understanding DED is essential for any Midwest homeowner lucky enough to still have American elms on their property. Use our tree identification tool to confirm your elm species.

How Dutch Elm Disease Spreads

DED is caused by fungi in the genus Ophiostoma (O. ulmi and the more aggressive O. novo-ulmi). The disease spreads through two primary pathways:

• Elm bark beetles: Both the native elm bark beetle and the European elm bark beetle breed in dead and dying elm wood. Adult beetles carry fungal spores on their bodies and transmit them to healthy elms when feeding on twig crotches in the canopy. This is the primary overland transmission route.
• Root grafts: Elms growing within 25 to 50 feet of each other often have interconnected root systems. The fungus can move through these grafts from an infected tree to its neighbors, creating clusters of dying elms along streets and in parks throughout Illinois and Indiana.

Identifying Dutch Elm Disease

Watch for these symptoms, particularly from late May through August when the disease is most active:

• Flagging: Individual branches wilt and turn yellow or brown while the rest of the canopy remains green. This is often the earliest visible symptom.
• Leaf curling and wilting: Affected leaves curl, turn yellow, then brown, and may cling to the branch.
• Brown streaking in sapwood: Peeling back the bark on a symptomatic branch reveals dark brown streaks in the outer wood rings — this is the definitive field diagnostic.
• Rapid crown decline: In warm weather, an entire large elm can decline in a single season once infection is established.

Current Status in Illinois and Indiana

Both states maintain elm tree monitoring programs, but the disease remains widespread:

• In Illinois, DED is most prevalent in the northern third of the state, including the Chicago metropolitan area and communities along the Rock and Illinois Rivers. Municipal elm maintenance programs in cities like Evanston, Oak Park, and Springfield continue to remove infected trees annually.
• In Indiana, the disease is statewide, with significant impacts in Indianapolis, Fort Wayne, and South Bend. Indiana DNR estimates that over 80% of the original American elm population in the state has been lost to DED since the 1960s.

Fungicide Injection Treatment

Proactive fungicide injection can protect valuable elms:

• Thiabendazole (Arbotect) is the most widely used macro-injection treatment for DED prevention. It is injected into the root flares and distributed through the vascular system.
• Treatment must be preventive — once more than 5% of the canopy shows symptoms, fungicide injection is unlikely to save the tree.
• Injections provide approximately three years of protection and should be repeated on schedule.
• Cost ranges from $200 to $800 depending on tree size, with large legacy elms at the higher end.
• Treatment should be performed by an ISA Certified Arborist experienced in macro-injection systems.

Sanitation Is Critical

Removing dead and dying elms promptly is the most important community-wide management practice:

• Remove symptomatic trees before bark beetles can breed in them
• Debark or chip all elm wood immediately — do not store elm logs or firewood
• Municipalities in Illinois and Indiana with aggressive sanitation programs have maintained significantly lower infection rates than those without
• Sever root grafts between infected and adjacent healthy elms using a vibratory plow

Resistant Elm Cultivars

The best long-term strategy is planting disease-resistant elm varieties developed through decades of breeding:

• 'Princeton' American Elm — Excellent DED resistance with classic vase form. Hardy to zone 4. Thriving in plantings across Illinois and Indiana.
• 'Valley Forge' American Elm — Outstanding DED resistance and fast growth. Zone 4.
• 'Jefferson' American Elm — Released by the National Arboretum with strong resistance. Zone 4.
• 'Accolade' Elm (hybrid) — A Morton Arboretum introduction with DED resistance and excellent form. Very popular in the Midwest. Zone 4.
• 'Triumph' Elm (hybrid) — Strong disease resistance and vigorous growth. Zone 4.

These resistant cultivars allow Midwest communities to enjoy elms again without the devastation of DED.

Frequently Asked Questions

Are there elm trees resistant to Dutch elm disease?

Yes. Decades of breeding research at institutions like the Morton Arboretum in Illinois and the USDA have produced several American elm cultivars and hybrids with strong DED resistance. 'Princeton,' 'Valley Forge,' 'Jefferson,' 'Accolade,' and 'Triumph' are all proven performers in Midwest climates and are widely available from nurseries.

How fast does Dutch elm disease kill a tree?

In red-flagging weather (hot, dry conditions common in July and August across Illinois and Indiana), DED can kill a large American elm in a single growing season. In cooler conditions or when infection occurs late in the season, decline may take one to two years. The speed depends on where the infection enters, the tree's overall health, and whether root-graft transmission provides a massive fungal load.

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Protect your remaining elms. Find an arborist experienced in DED management through the TreeIssues directory.