Skip to content 
One of the most common street trees throughout the early 20th century, American elms (Ulmus americana) once dominated streets and properties across Michigan. The trees were so common that historical records suggest there were between 200,000 and half a million elms growing in Detroit alone.
But that’s no longer the case, as Dutch elm disease (DED) has killed most of our state’s native elms, resulting in millions of dollars of damage. Nevertheless, not all elms have died, and there are a few things you can do to protect any you have growing on your property.
We’ll explain everything Michigan homeowners and property managers need to know about this deadly disease and outline the treatment strategies available below.
What Is Dutch Elm Disease?
DED is caused by two different, closely related fungal pathogens:
- Ophiostoma ulmi: The first fungal species to arrive on U.S. shores, it was responsible for the first wave of DED in Michigan.
- Ophiostoma novo-ulmi: A more virulent and destructive pathogen, this species began causing widespread damage in the U.S. by the 1960s.
These fungi cause vascular disease in elm trees, which prevents the movement of water up the tree’s xylem tissue. They primarily spread through root grafting and the feeding activities of elm bark beetles, but they can also be spread by human activity, such as the transportation of elm firewood.
While the disease is not always fatal (particularly with prompt treatment), it kills most susceptible trees it infects within one to two years.
History of Dutch Elm Disease
The precise origin of DED remains unknown, but most researchers suspect that it originated in Asia, given that many Asian elm species have significant resistance to the causal fungi. We do know that it first began causing problems in Europe around 1900, and the fungus was isolated and identified by a Dutch plant pathologist in 1921.
The disease eventually spread to most of Europe and showed up on U.S. shores in 1928. It was initially found in New England, but it spread west rapidly. Elms began dying in the Detroit area by 1950, and the disease eventually colonized most of the state. Currently, DED is found throughout the range of the American elm, including most of the U.S., save for the southwestern states.
Dutch Elm Disease: Disease Transmission
DED can be transmitted in either of two ways, with each causing a slightly different disease progression.
Beetle Transmission
Elm bark beetles become contaminated with the fungal spores of O. ulmi or O. novo-ulmi by feeding on trees that are already infected. These beetles then begin feeding on the twigs of healthy elms, which allows the fungal spores to invade the tree’s xylem tissue.
Isolated elm trees are most commonly infected via this transmission route.
Root Graft Transmission
In contrast to beetle transmission, root graft transmission doesn’t involve elm bark beetles. Instead, the roots of infected elm trees form underground grafts with healthy trees, which allows the fungus to infect the healthy trees. This is how DED often spreads in street plantings or dense elm tree stands.
While both transmission routes are typically fatal, root graft transmission leads to especially rapid, systemic infections.
Dutch Elm Disease: Progression of the Disease
Ultimately, Dutch elm disease kills trees by blocking the flow of water up the trunk and branches. This is why it is often known as a vascular “wilting” disease. However, it takes some time for this to happen.
In the first few days or weeks following infection, the tree continues to appear healthy, as the fungus germinates and begins producing hyphae (rootlike filaments) and spores. Soon, the fungus produces spores that’ll travel throughout the tree’s vascular system until the hyphae begin blocking the tree’s xylem tissue.
In response to the fungal attack, the tree usually begins producing balloon-like growths known as tyloses. Normally, these are created to help block fungal spread in the tree and allow the tree to compartmentalize (“seal off”) infected tissues. But in this case, it ironically makes the problem worse and further limits water’s ability to travel through the tree.
Dutch Elm Disease Symptoms
The symptoms of DED are quite similar to many other vascular wilting diseases and include things like leaf discoloration (yellowing or browning) and premature leaf drop. In many cases, the symptoms first appear in a single branch or small portion of the canopy. This is often referred to as “flagging,” as the discolored branch appears like a differently colored flag sticking out from the tree.
As the disease progresses downward and into the trunk, symptoms will soon start to affect other branches on the tree. At this point, brown streaks in the sapwood may even be visible in branches that are cut or have their bark removed. A few weeks to months later, the entire crown will often die.
At various points in the disease’s progression, the elm may begin producing new sprouts from the base, which is another common symptom of the disease.
Dutch Elm Disease Treatments
Fortunately, there are a few effective treatment strategies homeowners and property managers in Michigan can employ to protect their trees. These include:
- Preventative Fungicide Treatments: There are two common fungicides — Arbotect® 20-S and Alamo® — used to protect healthy elms from DED. They’re administered as trunk or root flare injections and provide one to three years of protection.
- Reactive Fungicide Treatments: Both of the fungicides used to protect trees from DED can be used to treat trees that have already become infected. However, the efficacy depends heavily on how early the disease is detected, and they’ll never completely “cure” a tree already suffering from DED.
- Sanitation Pruning: In some cases, the removal of infected or dead branches serves as an important component of an overall DED prevention or treatment program. This is usually carried out in conjunction with fungicide injections or macro infusions.
- Root Graft Disruption: DED transmission via root grafts can be more difficult to treat with fungicides, so root graft disruption — essentially involving the trenching of a narrow strip between neighboring elms — is often included in an overall treatment strategy.
Dutch Elm Disease Susceptibility and Resistance: Species & Cultivars
It is important to note that DED does not affect all trees equally; some species, varieties, and cultivars are susceptible to the disease, while others are at least partially resistant.
Species Susceptible to Dutch Elm Disease
DED appears to target elm trees in the genus Ulmus exclusively. For example, it does not appear to affect the closely related zelkova trees, such as the Japanese zelkova (Zelkova serrata).
Among the elms, it is typically most problematic for North American natives. The American, September (U. serotina), and slippery elm (U. rubra) are a few of the most susceptible species, though cedar (U. crassifolia) and winged elms (U. alata) are also susceptible. However, the disease often progresses more slowly and is less likely to be fatal for these species than the American elm.
Species, Hybrids, and Cultivars Resistant to Dutch Elm Disease
While many “wild type” North American elms are highly susceptible to DED, a few American elm cultivars display varying amounts of resistance to the disease. These include the following:
- ‘Princeton’: A cultivar first created in 1922, this is one of the most commonly planted American elm cultivars.
- ‘Prairie Expedition’: Dating back to 2004, this cultivar was created by North Dakota State University.
- ‘New Harmony’: A cultivar created in 1995 by the Maryland Agricultural Research Service, loved for its great form.
- ‘Valley Forge’: Also created by the Maryland Agricultural Research Service in 1995, this form has strong resistance.
- ‘St. Croix’: First found in 1997, this form was commercially released in 2009 by the University of Minnesota.
In contrast to most North American elms, most Asian elm species — including the lacebark (U. parvifolia), Japanese (U. davidiana var. japonica), and Siberian elm (U. pumila) — are largely resistant to the disease. This has led to the development of many hybrids, which combine the growth form and physical traits of the American elm with the disease resistance of Asian species.
A few of the most noteworthy DED-resistant hybrids include:
- ‘Accolade’: First released in 2005, this hybrid is made by crossing Siberian elms with Japanese elms.
- ‘Triumph’: Another Japanese-Siberian elm hybrid, this cultivar dates back to 1980.
- ‘Morton Stalwart’: A hybrid created in 2003 by crossing the Siberian elm with the European field elm (U. minor).
These are only a few of the most popular DED-resistant hybrids and cultivars. If you’re interested in installing new elms on your property, contact the arborists at Longtree Tree Service to discuss the best options for your property.
Protecting Your Trees from Dutch Elm Disease: Key Steps
There are several things homeowners and property managers can do to give their elms the best chance of survival in the face of DED.
- Monitor your trees closely for signs of “flagging” or foliar discoloration between April and August.
- Avoid storing elm firewood on your property.
- Prune trees during the dormant season to avoid attracting elm bark beetles.
- Address root grafts, if present, to prevent the disease from spreading.
- Have an ISA-certified arborist provide preventative trunk or root flare injections to protect your trees.
Fortunately, these are all pretty simple steps that are easy to put into action.
Dutch Elm Disease in Michigan: FAQ
Still have questions about DED or how it may affect your trees? We’ve rounded up a few of the most common ones our customers have and answered them below.
What are the first signs of Dutch elm disease?
Leaf discoloration is often the first sign of DED. Initially, the discoloration is often limited to a single branch (“flagging”) or portion of the canopy. However, it will usually spread to the rest of the crown in the coming weeks or months.
Is Dutch elm disease still a problem?
Yes, DED is still a problem, especially here in Michigan. High-value native elms should all be treated preventively to protect them from the disease, to give them the best chance of survival.
What is the cause of Dutch elm disease?
DED is caused by either of two fungal pathogens, known to biologists as Ophiostoma ulmi and Ophiostoma novo-ulmi. The former was the first to arrive on U.S. shores, but the latter is far more virulent.
How did Dutch elm disease get to America?
DED is thought to have arrived in America when European elm bark beetles arrived in a shipment of logs from the Netherlands. The beetles, which were contaminated with spores of one of the fungi that causes DED, escaped and began spreading throughout New England.
Can you save a tree from Dutch elm disease?
Treatments may prolong the lives of trees that are already suffering from the earliest stages of DED, but they are unlikely to prove effective in saving trees with advanced disease. It’s important to note that treatments do not completely cure already-infected trees; they limit the spread of the disease and often allow the trees to survive for much longer.
Are there any elm trees left in the US?
Yes, there are plenty of elm trees left in the U.S. Most living specimens are native species that aren’t as susceptible to the disease (such as winged elms), Asian species that are largely resistant to the disease, DED-resistant cultivars, or susceptible species that have received preventative treatments. Additionally, some elms manage to resprout after suffering the disease, though these new sprouts will generally succumb to the disease at a later time.
How much does it cost to treat Dutch elm disease?
DED treatment costs vary based on a variety of factors, but they generally range from about $150 to $400 per tree.
Let Longtree Tree Service Protect Your Elm Trees from DED
While DED is clearly a serious threat to elm trees in Michigan, there are things you can do to protect your trees. You may even be able to save trees that are suffering from the early signs of the disease. But prompt action is critical for enjoying any real chance of success.
Whether your elms are still healthy or you’re starting to see dieback or wilting, contact the tree-care experts at Longtree Tree Service to schedule an assessment and receive your free estimate for our plant health care services. We’ll assess your elms (or any other tree you’re concerned about) and outline the options available for protecting your trees.
Sources & References
- University of Minnesota Extension – “Dutch Elm Disease”
A plant disease profile explaining the symptoms, spread, and management of Dutch elm disease in trees.
https://extension.umn.edu/plant-diseases/dutch-elm-disease - Invasive Species.gov (U.S. Federal Government) – “Dutch Elm Disease”
A government resource describing the pathogen, ecological impacts, and control challenges of Dutch elm disease as an invasive tree disease in the U.S.
https://www.invasivespeciesinfo.gov/terrestrial/pathogens-and-diseases/dutch-elm-disease - The Morton Arboretum – “Dutch Elm Disease: Plant and Protect”
An informational resource providing guidance on identification, prevention, and care related to Dutch elm disease.
https://mortonarb.org/plant-and-protect/tree-plant-care/plant-care-resources/dutch-elm-disease/ - Michigan State University Extension – “Dutch Elm Disease”
A fact sheet from MSU Extension outlining the causes, symptoms, and management practices for Dutch elm disease.
https://www.canr.msu.edu/resources/dutch_elm_disease - Michigan State University – “Dutch Elm Disease (E308)”
An archived extension publication detailing the biology, spread, and control methods for Dutch elm disease.
https://archive.lib.msu.edu/DMC/extension_publications/e308/e308.pdf - Model D Media – “Dutch Elm Disease: How It Took Over Michigan’s Elm Population”
A journalistic article discussing the historical impact and current status of Dutch elm disease in Michigan.
https://modeldmedia.com/dutchelmdisease - Missouri Botanical Garden / MUCC – “Bringing Back the American Elm”
A conservation article presenting efforts, strategies, and species considerations for restoring American elm trees.
https://www.mucc.org/bringing-back-the-american-elm - Ohio State University Extension – “Dutch Elm Disease: Tree Pathology Factsheet”
An Ohio State fact sheet covering the identification, life cycle, and management recommendations for Dutch elm disease.
https://ohioline.osu.edu/factsheet/plpath-tree-04 - University of Minnesota Extension – “Dutch Elm Disease–Resistant Elm Trees”
An extension resource describing elm species and cultivars with resistance to Dutch elm disease for landscape planting.
https://extension.umn.edu/trees-and-shrubs/dutch-elm-disease-resistant-elm-trees
