Be taught About Dutch Elm Illness

Ophiostoma ulmi, O. novo-ulmi, O. himal-ulmi

If you wish to strike concern into the guts of any elm tree lover, point out the phrases “Dutch elm illness.”

This fungal illness is a worldwide drawback that devastates elm timber from Asia and New Zealand to Europe and throughout the pond to the Americas.

It has worn out complete populations of untamed and cultivated timber and has scared many gardeners away from planting elms. Don’t let it scare you off, although.

A horizontal photo of branches with dead leaves on a dying elm suffering from dutch elm disease. Healthy green leaves fill out the background of the photo.

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Whereas I received’t decrease how terrible this illness may be, there are methods to keep away from an infection or mitigate an infection. If it’s too late and your plant is already sick, this information might help with that, too.

In our information to rising elms, we focus on find out how to domesticate these timber in your panorama. Arising, we’ll discuss Dutch elm illness, and find out how to determine and handle an an infection.

Right here’s what I’ll cowl:

What Is Dutch Elm Illness?

Dutch elm illness, usually abbreviated to DED, is a fungal illness that impacts elms, because the identify suggests. Regardless of the identify, this illness isn’t Dutch in origin.

It seemingly originated in Asia, however it was first named within the Netherlands in 1921 when phytopathologists Bea Schwarz and Christine Buisman, below professor Johanna Westerdijk, recognized fungi within the Ophiostoma genus because the infectious brokers that trigger the illness.

A horizontal photo of healthy green leaves of an elm in the spring.

By 1930, it had been recognized in timber in Ohio and has since unfold across the US from there.

In North America, each Ophiostoma novo-ulmi and O. ulmi trigger the illness, whereas O. himal-ulmi is barely discovered within the Himalayan area. O. novo-ulmi is extra damaging and customary than the opposite species.

All species within the Ulmus and Zelkova genera are prone to this illness in various levels, however North American native species like American (U. americana), pink or slippery (U. rubra), or rock (U. thomasii) are probably the most prone to an infection.

These indigenous to Asia, comparable to Chinese language (U. parvifolia), Japanese (U. davidiana var. japonica), and Siberian (U. pumila) are typically fairly resistant.

The fungus that causes Dutch elm illness is unfold by species of elm bark beetles within the Hylurgopinus and Scolytus genera as they transfer round and feed on the timber.

Worldwide, a wide range of completely different native and invasive beetle species can unfold the illness as effectively. As an illustration, the bigger European elm bark beetle (S. scolytus) spreads the illness in Europe.

All are about an eighth of an inch lengthy, and black or brown with a shiny carapace as adults.

The grownup beetles and larvae overwinter within the tunnels they make within the wooden, or in close by wooden piles or leaf litter. As soon as the nice and cozy spring climate arrives, they climb out of their hidey-holes and begin feeding.

A horizontal photo of an elm with a branch covered with beetles feeding.

Relying on the native local weather, there may be as much as 4 generations of beetles per 12 months.

The fungal spores overwinter below the bark and in tunnels created by the elm bark beetles. These spores connect to any adults or beetle larvae throughout the tunnels and are additionally ingested as they feed.

Because the beetles transfer on to different timber, the spores are launched to beforehand wholesome specimens and the illness spreads, persevering with the cycle.

The pathogen may also be unfold between roots of timber rising shut collectively.

Often known as “root grafts,” the roots of neighboring timber of the identical species might be part of collectively, successfully sharing water and vitamins – and pathogens.

When the fungus is transmitted by this technique, it usually causes probably the most fast demise as a result of the pathogen strikes so rapidly by way of the newly-infected tree.

When the fungus finds a number tree, it invades the vascular system and reproduces within the xylem, which transports the vitamins and water from the roots all through the remainder of the plant.

The fungus causes blockages within the xylem, which ends up in demise beginning on the components of the cover furthest away from the roots.

A horizontal photo of an elm tree against a blue sky. The outer branches have dying leaves due to Dutch elm disease.

Because it strikes additional all through the plant, it causes all the plant to die.

Relying on the situation of the tree and the way aggressive the pathogen is, the tree might die in just a few weeks, or it might take years.

Younger or fast-growing specimens are extra prone to fast demise. Older timber or these rising in drier circumstances are inclined to have slower-moving infections.


If a tree is contaminated, you’ll begin to see leaves on the outer edges of the cover wilt or “flag” after which flip yellow.

Because the illness progresses, the wilted foliage will flip brown and ultimately fall from the tree. Subsequent, the leaves nearer to the inside of the cover begin turning yellow after which brown.

A horizontal photo of branches with dead leaves on a dying elm suffering from dutch elm disease.

The signs typically affect one department at a time, although closely contaminated specimens can have a number of symptomatic branches.

Beneath the tree, it should begin to seem like fall arrived early, with brown, fallen leaves scattered concerning the place.

When you peel away a number of the bark of the symptomatic branches, you’ll usually see brown, grey, blue, or tan splotches or streaking beneath within the sapwood. When you take a cross-section of an contaminated department, you’ll see a hoop of discoloration.

You too can typically see the white fungal spores in addition to proof of beetle feeding tunnels and frass below the bark.

A close up of the bark of a trunk peeled back to reveal feeding from invasive beetles.

This all begins taking place in spring or early summer season, however it’s not exceptional for the signs to seem at any time of 12 months.

Signs are typically noticeable in spring as a result of because the tree places out new progress, it’s actively shifting vitamins and water – and the fungus – all through its vascular system.

In the summertime, wooden progress slows, and so the infectious agent strikes extra slowly.

To make sure the signs you might be seeing are on account of DED, you possibly can take a pattern of a symptomatic department to your native extension workplace, the specialists there’ll be capable to let you know for positive.

Natural Management Strategies

Addressing Dutch elm illness requires a multi-pronged strategy and it’s not simple.

In lots of circumstances, the tree is destined for the chipper as there may be little to do within the case of a extreme an infection.

That mentioned, catch it early and you’ve got a number of choices for therapy. You’ll additionally must take steps to regulate the beetles.

Develop Resistant Varieties

There aren’t any two methods about it: this illness is unhealthy information. One of the best ways to keep away from it’s to plant resistant cultivars. The necessary phrase right here is “resistant” as there aren’t any elms which are fully immune.

The Asiatic cultivars and hybrids Accolade™,‘Cathedral,’ Commendation™, Danada Appeal™, ‘Discovery,’ ‘Sapporo Autumn Gold,’ ‘Triumph,’ and ‘City,’ are extremely resistant.

A square photo of an Accolade Elm specimen.


Nature Hills Nursery carries the beautiful Accolade™ (U. davidiana var. japonica ‘Morton’). It’s fast-growing, tolerates drought and air pollution, and barely contracts DED.

When you desire American hybrids and cultivars, which are usually bigger and have extra distinctive leaves, search for ‘American Liberty,’ ‘Homestead,’ ‘Independence,’ ‘New Concord,’ ‘Princeton,’ Prairie Expedition®, ‘St. Croix,’ and ‘Valley Forge.’ These are extra resistant than different American sorts.

U. americana ‘Lewis & Clark,’ generally referred to as Prairie Expedition®, has a stunning umbrella-like form and doesn’t flinch at air pollution or DED.

A close up square image of a Prairie Expedition elm growing by the side of a river.

Prairie Expedition®

Quick Rising Timber carries this adaptable plant in four- to five- or five- to six-foot-tall sizes.

Remember that you’ll want to fastidiously and persistently prune American sorts for the primary decade or so after planting to maintain them wholesome and promote resistance to DED.

Take away any useless, diseased, or dying branches and prune any codominant branches – these which are rising shut collectively in parallel.

A horizontal photo of a large elm tree being pruned by a gardener.

Weeping elms are sometimes extra resistant as a result of the beetles that unfold the illness aren’t good acrobats.

They don’t like being the other way up, so they often keep away from timber with drooping branches.

Lastly, you might contemplate selecting up and shifting to the southwestern states the place there may be at the moment no indicators of the illness!


Assuming you catch the issue earlier than the signs prolong past just a few branches, you possibly can doubtlessly save the tree by way of some cautious pruning.

If greater than 10 p.c of the tree is symptomatic, this technique received’t work.

A horizontal photo of a gardener with red boots and a shovel digging around a tree.

For every symptomatic department, lower it off no less than six ft beneath the diseased space. When you make the lower and also you see discolored wooden, lower one other six ft down.

If greater than half of your tree is symptomatic, you’ll must eliminate it. I do know it hurts, however the contaminated specimen is performing as a number to beetles that may unfold the illness to different specimens. It received’t recuperate and it is best to lower it down. Burn and bury or chip the wooden.

When you’ve got timber which are rising very shut collectively, dig a trench between them to stop the roots from one coming involved with these of the opposite. This fashion, if one turns into contaminated, it received’t routinely unfold the illness to the tree close by.

Dig a trench no less than 40 inches deep and a foot huge across the tree simply past the drip line. Consider it as a moat to thwart marauding pathogens.

When you dig the ditch, place metallic lining or fill it with cement earlier than protecting with soil.

Use sticky bands to catch the beetles as they transfer up the trunks of prone timber.

Catchmaster Sticky Bands

You can also make your personal or purchase Catchmaster sticky bands in rolls of 30 ft, accessible by way of Amazon.

You also needs to take away any free mulch or wooden piles within the neighborhood to disclaim the beetles a spot to overwinter.

Lastly, pray, forged a spell, do a dance, or no matter it’s you do to try to affect the climate as a result of a late freeze will usually destroy the beetles and forestall an outbreak.


As soon as upon a time earlier than the fungus arrived in North America and invasive bark beetle species arrived on its shores, these pests had been no huge deal.

They lived in concord with the timber and did little to no injury. That’s not the case anymore.

A vertical photo of a red headed woodpecker against a gray background.

Now, we have to restrict these pests to stop the unfold of the illness.

A method to do that is to encourage woodpeckers to hang around in your yard. These birds can’t get sufficient of bark beetles. They’re like me with a cheese platter.

Different birds like these pests, too. So, arrange that suet feeder, hold a pleasant fowl feeder, and plant wild fowl favorites like sunflowers, coneflowers, elderberries, and grasses.

Parasitic wasps (Oomyzus gallerucae) and flies (Erynniopsis antennata) will kill the pupae.

You may typically buy these regionally, or you possibly can encourage them to go to your backyard by planting a number of native flowers. Some municipalities have a program in place to frequently launch these parasitoids to guard native elms.

You also needs to management ants in your backyard, since some ants eat the pupae and eggs of those helpful bugs. Attempt to keep away from utilizing broad-spectrum pesticides in your backyard as a result of it will probably kill the nice guys in addition to the unhealthy.

Natural Pesticides

Technically, you possibly can attempt utilizing pesticides to regulate the beetles, however they’re typically not efficient in the long run – and their use received’t save your tree if the illness is current within the space.

A horizontal photo of a large elm tree being pruned by a gardener.

However you need to use this along with different strategies mentioned right here to attempt to save a tree or forestall one from being contaminated.

Understand that utilizing pesticides can hurt helpful bugs, so solely spray on calm, wind-less days and solely as usually as completely obligatory.

Pesticides ought to be utilized within the fall to kill the final technology of beetles and forestall the females from laying the eggs that may hatch in spring.

Then, spray once more within the spring when the adults begin to emerge.

A vertical product photo of a bottle of Monterey Take Down Garden Spray against a white background.

Monterey Take Down Backyard Spray

Use one thing that incorporates pyrethrin like Monterey’s Take Down Backyard Spray.

Arbico Organics carries 32-ounce ready-to-use, or pint or gallon concentrates.

Higher but, apply a product containing the helpful fungus Beauveria bassiana within the spring, summer season, and fall to kill the beetles earlier than they’ll rework into adults.

These merchandise goal the pupal stage and shouldn’t be used to try to kill adults. That’s why that is extra of a preventative choice than a therapy.

A close up of the packaging of BotaniGard 22 WP isolated on a white background.

BotaniGard 22WP

BotaniGard 22WP is an effective choice, and yow will discover it accessible at Arbico Organics.

Chemical Management

There are fungicides accessible that may kill the pathogens, however provided that you apply them earlier than greater than 5 to 10 p.c of the tree is contaminated.

And after I say “you,” I imply a educated skilled who can inject the tree with the suitable fungicide on the applicable time.

A horizontal photo of a gardener spraying a plant against disease and insects. The sun is shining through the trees behind the house.

You shouldn’t attempt to inject your tree except you’ve been educated to take action, and using the suitable chemical compounds could be restricted in your space.

An knowledgeable will inject the foundation flares with the fungicide however on the similar time, you’ll must prune off all of the symptomatic branches. Fungicide therapy is just not an alternative choice to pruning.

Additionally, understand that therapy is fairly costly, so that you’d higher actually love that tree in case you resolve to go this route.

By way of pesticides to regulate the beetles, use a systemic product that incorporates imidacloprid. That is an efficient grub and beetle management that lasts for a very long time within the backyard.

Mineiro 2F is a dependable choice.

You should purchase a gallon from the Atticus Retailer by way of Amazon, then apply following the producer’s instructions as quickly because the soil may be labored in spring and once more in late Might or early June.

A Devastating Illness

It’s by no means enjoyable coping with any kind of plant illness, however Dutch elm illness is a selected problem.

It’s greatest to begin by rising resistant cultivars, however not all of us have that luxurious, whether or not we inherited an present tree or just can’t discover them in our space.

A horizontal photo of a tree in a neighborhood that is dying from Dutch elm disease.
Picture Credit score: Ward Upham, Kansas State College,

Are you seeing signs in your elm tree? What’s happening? Tell us what you’re experiencing within the feedback part beneath and we’ll do what we will to assist.

When you want a little bit assist with another tree ailments, and also you discovered this information helpful, listed here are just a few price testing subsequent:

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