Once a tree has Dutch elm disease, treatment becomes much more difficult as infected areas must be physically cut out of the tree using a process known as ‘tracing’. Tracing has been used as an effective treatment for Dutch elm disease that can save trees, but it’s difficult, costly to the client, and there’s no guarantee the tree won’t die anyway.
Long story short: treat trees for Dutch elm disease before they get infected.
In some cases, elms infected with Dutch elm disease can be saved, but only if the fungus is completely removed from the tree. This process has been effective for nearly thirty years but the health of the tree, the progression of the disease, and the aesthetics of what’s left of the tree after tracing must be considered before starting the process.
- Four Steps in This Dutch Elm Disease Treatment
- Dutch Elm Protection – Is There Treatment For Dutch Elm Disease
- What is Dutch Elm Disease?
- How to Detect Dutch Elm Disease
- Dutch elm disease
- Identify and diagnose Dutch elm disease
- Details of the disease
- Symptoms and diagnosis
- Our research
- Related resources
- What is Dutch elm disease?
- How does Dutch elm disease happen?
- What are some initial signs of Dutch elm disease?
- What can I do to prevent Dutch elm disease?
- What if my tree can’t be saved?
- Dutch Elm Disease in Minneapolis
- Dutch Elm Disease in St. Paul
- If you think your tree might be infected or dying, and you live in the Minneapolis and St. Paul area, give us a call at 651-484-2726.
- The cause of Dutch Elm Disease
- How Dutch Elm Disease spreads
- How Dutch Elm Disease Kills Trees
- Chemical Treatment
- Injection Procedure for Dutch Elm Disease
- Case Study
Four Steps in This Dutch Elm Disease Treatment
Step 1: Find the Fungus
- Finding the fungus in the tree is the first step to saving elms by tracing. On the branches that are ‘flagging’ (limbs with yellow, wilted leaves), use a chisel and hammer to cut exploratory windows into the bark.
- The tree responds to the Dutch elm disease fungus with a staining of the water-conducting tissue under the bark. Keep cutting windows until there is only clear wood.
- NOTE: if the staining is within 10’ (3m) of the ground, the fungus has reached the roots and the tree may not be saved with this process.
Step 2: Remove Diseased Branches
- Prune off the diseased branch where it connects to the main trunk.
- Do this for every branch showing flagging symptoms. Be sure to leave a proper branch collar when removing limbs.
Step 3: Tracing
- The Dutch elm disease fungus grows in a five to eight inch (13-20cm) wide band down to the roots. Removing the bark will kill the fungus by exposing it to air.
- Using a chainsaw or a chisel and mallet, remove a narrow strip of bark on the trunk.
- As the fungus can be up to 10 feet (3m) beyond the staining, continue to remove a strip of bark up to 10 feet (3m) past the stain.
Step 4: Post-Tracing Protection
- Tracing only removes the fungus growing in the tree. It will not defend the remaining tree from getting Dutch elm disease again.
- Protecting the remaining tree with Arbotect is an important step in protecting this tree from future Dutch elm infections.
Dutch Elm Protection – Is There Treatment For Dutch Elm Disease
Elm trees once lined city streets all across America, shading cars and sidewalks with their enormous, outstretched arms. By the 1930s, though, Dutch elm disease had arrived on our shores and began destroying these favorite trees of Main Streets everywhere. Although elms are still popular in home landscapes, American and European elms are highly susceptible to Dutch elm disease.
What is Dutch Elm Disease?
A fungal pathogen, Ophiostroma ulmi, is the cause of Dutch elm disease. This fungus is spread from tree to tree by boring beetles, making Dutch elm protection difficult at best. These tiny beetles burrow under the bark of elms and into the wood beneath, where they tunnel and lay their eggs. As they chew through the tree’s tissues, the fungal spores are rubbed off onto tunnel walls where they germinate, causing Dutch elm disease.
How to Detect Dutch Elm Disease
Signs of Dutch elm disease come on rapidly, over about a month’s time, typically in the spring when leaves are just maturing. One or more branches will be covered in yellow, wilted leaves that soon die and fall from the tree. As time goes on, the disease spreads to other branches, eventually consuming the whole tree.
Positive identification based on symptoms alone can be difficult because Dutch elm disease mimics water stress and other common disorders. However, if you cut open an affected branch or twig, it will contain a dark ring hidden in the tissues below the bark – this symptom is caused by fungal bodies clogging up the tree’s transport tissues.
Treatment for Dutch elm disease requires a community-wide effort to successfully eradicate both the beetles and fungal spores they carry. A single, isolated tree may be saved by pruning out affected branches and treating bark beetles, but multiple trees affected by Dutch elm disease may require removal in the end.
Dutch elm disease is a frustrating and costly disease, but if you absolutely must have elms in your landscape, try the Asian elms – they have high levels of tolerance and resistance to the fungus.
Dutch elm disease
Identify and diagnose Dutch elm disease
Dutch elm disease is one of the most serious tree diseases in the world. It has killed over 60 million British elms in two epidemics and continues to spread today.
This page will help you to identify and diagnose Dutch elm disease and will tell you all that you need to know about its history and spread throughout Britain.
Details of the disease
- First epidemic caused by fungus Ophiostoma ulmi from the 1920s onwards
- Second and ongoing epidemic caused by the highly aggressive and related fungus O. novo-ulmi, first recognised in the 1970s
- Elm bark beetles in the genus Scolytus disseminate the fungus
- Infects all of Britain’s major elm species
- Fungus invades water conducting system of trees
Symptoms and diagnosis
- Symptoms first appear in early summer
- Clusters of leaves turn yellow and wilt
- Leaves then turn brown and fall
- Affected shoots die back from the tip
- Twigs sometimes turn down to form ‘shepherd’s crooks’
- Twigs have dark streaks in the outer wood beneath the bark, or spots or rings in cross section
Browse more pictures of disease symptoms and find out how to make a diagnosis
- We have shown that Ophiostoma ulmi and O. novo-ulmi have spread across Europe, North America and central Asia in two major migratory events.
- The two pathogens cannot coexist when their ranges overlap and O. ulmi is eliminated although transient hybrids are formed between the two species. This has allowed useful genes to be acquired by O. novo-ulmi from O. ulmi and been the driver for rapid evolutionary change.
- Ophiostoma novo-ulmi exists as two subspecies: subspecies americana and novo-ulmi. They are currently hybridising freely in Europe where they come into contact having invaded the continent in a ‘pincer movement’
- ds RNA viruses, known as d-factors, debilitate both Dutch elm disease pathogens. A recent collaboration with Scion, New Zealand, has explored the potential of these viruses to act as bio-control agents of O. novo-ulmi.
- The beetles that spread Dutch elm disease have distinct feeding preferences for certain species of elm, so even susceptible elms can sometimes escape the disease if they are not attractive to the beetles.
- The geographic origins of both elm pathogens are unknown. However, emerging evidence suggests that O. ulmi could be endemic to Japan.
- Dutch Elm disease diagnosis
- Dutch Elm disease Q&A
- Dutch Elm disease in Great Britain
- New Horizons in Dutch Elm disease control
- Resistant elms
- Science fights Dutch elm disease
What is Dutch elm disease?
Dutch elm disease (DED) is caused by a sac fungi that affects elm trees. The disease has been affecting elms in Minnesota ever since 1961. In the United States, DED is spread by bark beetles. The disease can infect all native Minnesota elm trees. Keep in mind, not all trees die from this disease.
How does Dutch elm disease happen?
Bark beetle introduce fungi to the tree. Then, the tree plugs up its xylem tissues to try and stop the fungus from spreading. This is similar to when your nose gets stuffed up when you have a cold or allergies. The plugs prevent nutrients and water from traveling up the tree, which slowly kills the tree.
What are some initial signs of Dutch elm disease?
A common sign of Dutch elm disease is when the top leaves on the top branches start to wither and fall off. You’ll notice your leaves are turning yellow or brown in the late spring or summer. Then, the rest of the crown (top of tree) will slowly lose its leaves.
Starts with a few branches
Observed in early summer
Brown streaks in sapwood
No discoloration in the inner bark
What can I do to prevent Dutch elm disease?
Pruning of weak or dying branches can be effective.
Insecticides can be somewhat effective when it comes to killing adult bark beetles.
Inject elms with fungicide. This can be expensive and it needs to be re-applied every couple of seasons.
Planting trees that are Dutch Elm disease resistant.
What if my tree can’t be saved?
An infected and dying/dead tree must be cut down and disposed of properly. Wood from the infected tree should be chipped, burned, or buried to prevent transferring of the disease.
For more about Dutch elm disease, check out these credible sources:
The U of M Garden Extension
The United States Forest Service
Dutch Elm Disease in Minneapolis
Minneapolis has an abundance of Elm trees. The beautiful trees are often found in the city’s boulevard. With the large amount of elms trees comes Dutch Elm Disease. This disease must be removed right away in order to prevent further spreading to other elm trees. If there’s a city tree near your home that has been diagnosed with DED, the city will mark it and contact you.
Once Your Tree Has Been Diagnosed
A tree that has been diagnosed with Dutch Elm Disease must be removed or treated. If you want to care for the tree yourself, you must obtain a free permit and pay for the treatment. (Minneapolis won’t pay to treat public trees.) If you don’t want to treat the tree, it must be removed. The city will contact their preferred contractor (usually Precision) to properly remove the tree. Precision will expertly remove the tree without harming any of the surrounding area. The chopped up tree will be hauled to a recycling facility to be made into wood chips. (Wood chips don’t spread DED.)
Once the tree has been removed, the city will measure and mark the stump for removal and grinding. Precision will grind the stump so the city can plant a new tree in its place. Keep in mind that the tree will be added to a replacement list, so it may take a while before a replacement tree is planted.
Dutch Elm Disease in St. Paul
Dutch Elm Disease is no stranger to St. Paul trees. The disease has been killing St. Paul elm trees since the 1960s. Tree inspectors examine elm trees every summer; St. Paul requires infected trees to be removed within 20 business days of notification. A letter will be sent to you in the mail.
If you want to treat the public city tree instead of removing it, you must get a free permit and hire a licensed tree care company (like Precision) to treat the tree. The treatment usually costs around $600 and must be treated for the next two to three years.
Minneapolis and St. Paul both recommend that you use a company that is ISA certified. Precision is proud to be a member of the ISA and TCIA. .
The cause of Dutch Elm Disease
Dutch elm disease is caused by an aggressive fungus (Ophiostoma-ulmi) that kills elms regardless of their health. It is a tree disease and remains active as long as there are susceptible trees. The fungus invades the water transporting vessels and produces toxins which cause the tree to react defensively to block the advance of the fungus. The combination of the toxins and the defense mechanisms of the tree prevent the flow of water, which causes wilting and tree death.
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How Dutch Elm Disease spreads
There are two ways this fungus is spread.
1 ) Female elm bark beetles lay their eggs beneath the bark of dead or dying elm trees. If the elm is infected with Dutch elm disease the newly hatched beetles will emerge from the tree carrying the deadly fungus on their bodies. As the beetles fly to healthy trees to feed, they spread the disease.
- 2-3 generations of elm bark beetles hatch each year
- Thousands of beetles may hatch from a single tree
2 ) Dutch elm disease may also spread when roots from two or more trees grow together. When elms grow in close proximity to each other, their roots can come into contact and graft together. This common root system provides the fungus with a pathway to spread through an entire group of healthy elms very quickly.
- To protect trees, Rainbow Treecare uses a machine to cut a trench in the ground between elm trees.
- This prevents their roots from growing together, eliminating the possibility of transmitting disease via the roots.
Due to proactive measures such as sanitation and prevention treatments, cities such as Minneapolis, Edina, Richfield, Minnetonka, St. Louis Park and Bloomington are still home to large inventories of American elm trees. In fact, the Twin Cities boasts one of the largest American elm populations in the country.
To properly manage Dutch elm disease, four steps are generally required.
- Identify the disease by the “flagging”, or wilting of leaves typically located at the ends of isolated branches in the canopy. The disease moves down the limb and then into the mainstem.
- Remove infected branches from trees (if identified in time) or remove entire trees immediately, in order to halt further spread of the disease throughout the neighborhood.
- Isolate infected trees from nearby healthy trees by soil trenching, which prevents spread of the disease via root grafting.
- Protect valuable remaining elms with the use of approved Dutch elm disease fungicide, Arbotect 20-S.
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Contact the Experts
Dutch Elm Disease Prevention and treatment. Take action to protect your elm trees from Dutch Elm Disease with “do it yourself” tree injection! DED is one of the most destructive shade tree diseases in North America and has been killing Elms since 1928 when the invasive species arrived on logs imported from the Netherlands. The disease has since spread killing a large percentage of all the elms in North America. However there are areas of central and western Canada with large elm populations that are DED free. Substantial eradication and preservation programs have been pursued which are protecting valued urban trees with focused and continued effort. This map shows the original native distribution of the American Elm.
How Dutch Elm Disease Kills Trees
Dutch Elm Disease is a tree affliction caused by a fungus that clogs up the vascular system of elm trees, restricting flow of sap, and usually killing the tree within one to three years of infection. The fungus is transmitted from tree to tree by interconnected root systems and by elm bark beetles.
Although the DED is widspread and aggressive, many large elm trees remain uninfected, and there are measures you can take to protect them. If you still have large live elm trees on your property, you do not have to sit by and wait for your precious old elm trees to die. You can easily treat against infection and death of trees by DED using trunk injection of the fungicide Propiconazole 14.3 using reloadable Chemjet® Tree Injectors.
Elm trees can be treated using the fungicide Propiconazole 14.3 to protect from infection by DED. This is easily conducted using Chemjet® Tree Injectors to inject the fungicide propiconazole into small drilled holes at multiple locations around the base of the tree. The chemical is then carried throughout the tree, from up to the leaves down to the roots, effectively inoculating the tree from infection by DED for a limited time. According to the labeled instructions for Propiconazole 14.3 injecting with the treatment rate described in the injection procedures detailed below will provide 24 to 36 months of control. This would protect from root graft infection from adjacent infected trees and also infection from fungus brought in by elm bark beetles with tree injections every two or three years.
With the relatively simple implementation of tree injection using the inexpensive Chemjet Tree Injectors, it is feasible to inject and protect many more elm trees. This brings to reality an economical option of DIY injecting all of the healthy elm trees on your woodlot to inhibit expansion of the disease to your trees.
It takes a few minutes to a few hours for the chemical to go in the tree. If you have one or two trees to treat you could get by with five Chemjets (re-use them as you drill around the tree) and a quart of Propiconazole 14.3. If you have many trees you will need 20 or more Chemjets and you can buy Propiconazole 14.3 more economically by the gallon.
Get Chemjet Tree Injectors online here: chemjettreeinjector.com/products/
Get Propiconazole 14.3 online here: domyownpestcontrol.com
Treating for Dutch Elm Disease is easy and relatively cheap! The fungicide costs about $0.25 per 10 ml injector dose and Chemjets cost about $13 each and can be reused for years.
Injection Procedure for Dutch Elm Disease
This injection procedure for DED is Adapted from the Chemjet® manufacturer suggested procedure , the Label Instructions for Propiconazole 14.3, and this report.
- Confirm with a qualified Arborist, or Biologist that this procedure is appropriate for your tree. You may not have a Dutch Elm Disease risk or there may be other circumstances that would cause this procedure to be inappropriate. Also confirm that you are able to follow the label instructions on the fungicide that you are using. There is always the risk that this procedure may harm your tree, or that your tree is already diseased or infested and the chemical injection will be of no benefit.
- Only inject trees that have green leaves indicating there is transpiration and sap circulation.
- Only inject trees after a good rain or after substantial watering. Do not inject trees during drought conditions.
- Plan for use of one Chemjet® injector every three inches around the circumference of the tree.
- Put on rubber gloves and safety goggles for use during mixing and all injection work.
- Disinfect Chemjet® injector and drill bit by washing and scrubbing in diluted bleach solution or Lysol disinfectant solution. Pull disinfectant solution through the nozzle filling the injector several times. Rinse inside and out with clean water.
- Prepare 50/50 solution of the fungicide Propiconazole 14.3 Use distilled or filtered water.
- Drill the first three holes at three inch intervals around tree at 45 degree angle downward no more than 1.25 inch deep. Only use a 11/64 drill bit. Drilling more than three holes may heat up the bit and scorch the wood which will inhibit injection.
- Pull the chemical mix into the injector until full at 20 ml and lock the handle back while twisting.
- Insert into recently drilled hole. Push into place and seal (don’t twist because the nozzle may break off).
- Using both hands, hold the Chemjet® in place and then twist and release the red plunger so that injection begins. If there is leakage push the nozzle in harder to seal. Repeat for remaining two holes.
- After all chemical is in tree, pull injector straight out of hole. If chemical starts oozing back out of open hole, replace Chemjet® and leave there for another half hour or use a plug.
- Repeat with three more holes, going around tree.
- If an injector is taking chemical slowly, leave it in place and move on. It could take up to 24 hours.
- IMPORTANT: Disinfect drill bit and all Chemjets (inside and out) before using on any other tree per step 6. Disinfect your hands and put on new rubber gloves to avoid potential for transferring diseases to next tree.
- Take Care of your Chemjet Tree Injectors after the work is done (or during long term work at least once per week) so they keep working smoothly by disassembling, washing all parts with hot soapy water, rinse and air dry, then lubricate the nozzle barrel and rubber plunger washer with silicone lube or vegetable oil before reassembly.
Here is a video
For information on how to treat other tree diseases and pests check out the links below:
Buy Chemjet Tree Injectors Now
How Chemjet Works
Oak Wilt Disease and Treatment
Dutch Elm Disease Treatment
Save Your Trees from Oak Wilt
Save your trees from Pine Bark Beetle
Case Study: Microinjection to Protect Trees from Oak Wilt
Emerald Ash Borer Treatment
Hemlock Woolly Adelgid Treatment
Sudden Oak Death Treatment
Asian Longhorned Beetle Treatment
Plugs for Tree Injection Holes
Chemjet Tips and Ideas
Video: Injecting for Oak Wilt
Video: Chemjet use in Australia
Find an Arborist
Logical Result LLC is a North American Distributor for Chemjet Tree Injectors. We have also posted a few links to some products that will refer you to other suppliers. If you click the links provided for the linked suppliers to purchase items, we may receive a referral commission as an affiliate of the sellers at no cost to you.
The Science of Matching the Tool to the Job
During our 40 years of Dutch elm disease experience we have evaluated every treatment option under the sun. Macro-injections, micro-injections, soil applied treatments, even bark sprays as well as a number of different fungicide formulations.
We have a 99.5% success rate preventing elms from infection by this disease. Understanding just a few key distinctions about the biology of the disease and the physiology of the tree helps explain why macro-injection and Arbotect® are the tools we use.
Micro-injection utilizes small volumes of water and fewer injection sites. Research has shown micro-injections to be very effective for insecticides, miticides, and antibiotics but not with fungicides for vascular wilts.
Macro-injectionuses high volumes of water, allowing for even and complete coverage of the treatment throughout the canopy. This is critical for vascular wilts like Dutch elm disease.
Compare these conclusions with the recommendations provided by other tree injection device manufacturers.
1. THE RIGHT EQUIPMENT
In the case of preventative treatments for Dutch elm disease, it is vital that every single twig in the canopy receives an ample amount of the treatment. This is because the elm bark beetles that spread the deadly fungus are feeding in the 2-3 year old branches at the very top of the tree. Missing even a small percent of those branches greatly increases the tree’s chance of infection.
CONCLUSION: Only Macro-Injection provides enough solution to effectively cover the entire canopy.
2. EVEN AND COMPLETE COVERAGE
Fungicides do not exhibit much lateral movement inside the xylem; the treatments go fairly straight up. Getting even and complete distribution is critical for successfully protecting the tree.
CONCLUSION: Only a higher number of injection sites applied with even pressure can ensure complete canopy coverage.
3. THE RIGHT FORMULATION
Protection from this deadly disease is a lifelong commitment for the tree, thus it is imperative that the tree have enough time between treatment to compartmentalize the injection wounds. Research shows Arbotect® moves into new xylem tissue, protecting new twigs for up to 3 years. Propiconazole lasts in the tree just 8 months and does not move into new tissue. CONCLUSION: Only Arbotect® will protect the tree for multiple seasons, allowing enough time to compartmentalize the wounds from previous treatments
Cost of Treatment Options for Dutch Elm Disease Protection
WHAT ARE THE COSTS OF AN ANNUAL TREATMENT OR A 3-SEASON TREATMENT OVER TIME? Scientific research has shown two treatments are effective for protecting elm trees from Dutch elm disease. This research shows that one treatment, Arbotect, is effective for 2.5-3 seasons of protection, whereas the other treatment, Alamo, is effective for just one season. Both of these treatments are applied by Macro-Infusion, a process where a large volume of solution is injected into the tree by drilling a series of holes into the root flares. Let’s compare how the costs of the service and the impacts on the tree add up over time:
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Everything we recommend starts with a protocol that includes proper diagnosis and the full suite of management options. You can check out our library of diagnostic guides.
Figure 1. Three American elms in severe decline caused by Dutch elm disease.
Introduced into America near Cleveland in the 1930s, this disease still kills mature elms today. Dutch elm disease occurs throughout the natural range of American elms, and is found in virtually all the continental United States except the desert Southwest. Historically speaking, it is known as “Dutch” elm disease because the first extensive research was done by pioneering Dutch women.
American elm trees once dominated our urban landscapes as beautiful shade trees. Now, due to DED, they are no longer prominent. In fact, American elms are virtually absent in most communities today, with the exception of lone “survivors.” Some communities have made extensive attempts to save their elm trees, such as Washington, D.C., and Syracuse, New York, but more often than not the costs of managing DED on a city-wide scale prohibit the development of successful management programs. In nature both American and slippery elms can still be seen in locales where the environmental conditions are suitable for natural elm regeneration, such as in riparian environments.
Dutch elm disease can be treated if recognized early. Early symptoms typically include yellowing leaves (i.e. chlorotic) on the tip of a branch and then turning brown and curling up. They are usually retained on the branch for some time (Fig. 1). These symptomatic branches are called “flags” and their appearance in an otherwise green crown is called “flagging.” As the disease progresses, more flags will appear until the whole crown becomes symptomatic (Fig. 2).
Figure 2. Recognizing leaf flagging early is crucial to preventing DED from claiming mature trees.
Figure 3. Diagnostic brown streaking just under the bark of branches of different sizes is characteristic of DED.
Figure 4. Elm bark beetle larval gallery.
Other diseases may present somewhat similar symptoms. As the name implies, the pathogen that causes elm yellows also produces yellowing (chlorosis). However, it is usually generalized, affecting the whole crown from the onset, rather than beginning with individual branches. Bacterial leaf scorch of elm produces brown lesions on the leaves surrounded by a yellow halo. It should be noted that DED can also infect healthy elms trees through root grafts with infected trees (see below), in which case the entire crown will often display symptoms at once.
Other, more diagnostic symptoms of DED include a brown to black streaking or discoloration under the outer bark of infected branches (Fig. 3). However, only a trained diagnostician can confirm the nature of the condition by conducting specific laboratory investigations.
Causal Organism and Disease Cycle
Dutch elm disease is caused by a fungal pathogen (Ophiostoma novo-ulmi or Ophiostoma ulmi) that is vectored by European (Scolytus multistriatus) and North American (Hylurgopinus rufipes) elm bark beetles. The bark beetle larvae tunneling (Fig. 4) in infected trees acquire fungal spores that are spread to new trees when they emerge as adults. The spores are introduced into healthy trees when the young beetles feed on twig crotches to complete their sexual maturation. As a result, monitoring bark beetle flights, which typically occur 1 or 2 times a year, can aid in monitoring the possible spread of DED.
Once introduced, the fungus grows within the vascular tissue where it evades host defenses. The host defenses clog the water-conducting elements, leading to the flagging symptoms and eventually death by wilting. The beetles are attracted to dying and dead elm trees to lay eggs, and the cycle begins again. Therefore, prompt removal of dead and dying trees, as well as logs of infected trees, are key steps to limiting DED spread.
Dutch elm disease is also capable of spreading via natural root grafts between systemically infected and healthy elm trees. Mechanical or chemical disruption of elm root grafts has been used to limit the spread of the disease between closely planted trees.
Management of DED utilizes a combination of early detection to enable one to use “curative” treatments (if desired or warranted) and sanitation to limit further spread. Some of the measures used in a successful management plan are:
- Plant elms trees resistant to DED if possible, such as Asiatic elms or American elm varieties that are now available commercially, such as American Liberty, Valley Forge and New Freedom.
- Maintain healthy conditions for elms, such as avoiding construction activities that might weaken the root system.
- Disrupt natural root grafts where appropriate using mechanical or chemical disruption. These procedures should only be conducted by trained and certified professional arborists.
- Plant new elm trees in a mix with other trees, and keep elms at least 60 feet apart.
- Be prepared to recognize the early symptoms of DED if they appear, and know the difference between DED symptoms and those caused by other pathogens.
- Removal of an infected limb, at least 10 feet beyond the observable limit of streaking under the bark can potentially save an infected tree.
- For healthy or early symptomatic (only one branch infected at tip) high-value trees, commercial products with the active ingredient thiabendazole (such as Arbortect-20S®) are available for application by professional arborists. In some cases, application of these products as a preventative treatment, with up to 2 to 3 years protection, may be recommended by an arborist, although there is evidence that this may not always be effective. Thus, costs and benefits should be weighed carefully before pursuing this treatment option.
- Insecticidal spray programs to control insect vector populations in combination with insect monitoring are potentially very effective at limiting disease spread, but these approaches are often unaffordable for individual homeowners and also costly for most communities or municipalities.
- In all cases in which dead and dying trees are present, sanitation is of paramount importance. This involves removal and destruction by chipping or burning of DED infected trees, which act as an inoculum source for the disease, and a home for the vectoring beetles. If elm wood cannot be destroyed, it should be stored under tarps to deny access to elm bark beetles until the bark naturally falls off the logs and branches. Alternatively, the logs and branches can be debarked mechanically, thereby depriving the beetles of the habitat necessary for completion of their life cycle.