Dutch Elm Disease is a devastating fungal infection that has caused the loss of millions of elm trees across the U.S. Known for its ability to rapidly kill these majestic trees, Dutch Elm Disease poses a significant threat to urban and suburban landscapes. Given the severity of this disease and its rapid progression in trees inflicted by it, homeowners need to recognize its symptoms and learn the appropriate steps necessary to save elm trees affected by it.

What is Dutch Elm Disease?

Dutch Elm Disease is caused by a fungal pathogen called Ophiostoma ulmi (and a more aggressive strain, Ophiostoma novo-ulmi). The disease rapidly attacks the vascular system of elm trees, blocking the flow of water and nutrients, which eventually leads to the tree’s death. It was first identified in the Netherlands in the 1920s, hence the name “Dutch Elm Disease.” Since its discovery, the disease has spread globally, devastating elm populations not only throughout North America, but in Europe, and beyond.

Symptoms of Dutch Elm Disease

One of the first signs of Dutch Elm Disease is wilting and yellowing of the leaves. This is usually most noticeable at the top of the tree or in individual branches. As the disease progresses, the affected leaves may become dry, crispy, and eventually fall off. If you observe the following symptoms, it’s crucial to take action quickly:

• Wilting and Yellowing of Leaves: The first sign of infection is often wilting or browning leaves, particularly in the upper branches. The leaves may also exhibit a “V-shaped” pattern of necrosis (dead tissue), particularly along the edges.
• Branch Dieback: The disease typically begins in one part of the tree, causing branches to die back. You might notice that certain branches appear dead or struggling, while the rest of the tree still seems healthy.
• Discolored Wood: If you cut into the bark, you may observe dark streaks in the wood beneath the surface. This is a telltale sign of infection caused by the fungus.
• Rapid Decline: Once the fungus has infected the tree, the decline can be swift. Trees can die within weeks or months after infection, making the disease particularly destructive.

How Does Dutch Elm Disease Spread?

Dutch Elm Disease spreads primarily through two vectors: elm bark beetles and root grafts:

Elm Bark Beetles: The primary method of transmission is through the elm bark beetle, which feeds on the bark of infected trees. These beetles carry the fungal spores from one tree to another, usually in the spring and summer months. When the beetles bore into the bark of a tree, they introduce the fungus into the vascular system, where it spreads and clogs the tree’s water-conducting tissues.

Signs of Beetle Activity: If you notice the presence of small beetle holes in the bark or an increase in beetle populations around your trees, it’s essential to monitor your elms for symptoms of Dutch Elm Disease.

Root Grafts: Elms that are planted close together may form root grafts, where the roots of two or more trees become physically connected. If one tree is infected with Dutch Elm Disease, the fungus can travel through the root system to neighboring trees. This method of spread is slower but still a significant risk, and is especially common in urban areas with closely planted elms.

What Are the Risks of Dutch Elm Disease?

Dutch Elm Disease can have devastating effects on your landscape. Elm trees are highly valued for their broad canopy, shade, and beauty, but they are particularly susceptible to the disease. The risks include:

• Rapid Tree Death: Dutch Elm Disease can kill an elm tree within one to two years, leaving an unsightly, dead tree in your yard. In some cases, trees can die in as little as a few weeks if the infection is severe.
• Loss of Shade and Aesthetic Value: Elm trees are known for their large, spreading canopies that provide shade, aesthetic beauty, and habitat for wildlife. Losing these trees can significantly alter the landscape, especially in urban settings.
• Spread to Other Trees: Dutch Elm Disease can spread quickly, especially in areas where multiple elms are planted close together. A single infected tree can lead to the loss of many others in a neighborhood or park.
• Increased Pest Activity: As the disease progresses, weakened trees may become more susceptible to secondary pest attacks, including other insect infestations or fungal diseases. These additional stresses can further harm the tree and accelerate its decline.

How to Prevent and Manage Dutch Elm Disease

While Dutch Elm Disease is a serious threat, there are steps you can take to protect your trees and manage the disease if it appears.

1. Monitor Your Trees Regularly:

Regularly inspect your elm trees for signs of Dutch Elm Disease, especially during the warmer months when elm bark beetles are most active. Early detection is key to preventing the spread of the disease.

2. Control the Beetle Population:

One of the most effective ways to prevent Dutch Elm Disease is to control the population of elm bark beetles. There are several methods to do this:

• Traps: You can use beetle traps designed to attract and capture elm bark beetles.
• Insecticides: Insecticides can be applied to affected trees to kill beetles and prevent further spread. Timing is critical, as these should be applied when beetles are most active, typically in spring. As these can be powerful, it’s best to work with a certified arborist to ensure you’re using the correct insecticide and applying it in the most effective way.
• Remove Infected Wood: If you spot any dead or dying trees, immediately remove them and dispose of the wood. This helps prevent beetles from using the infected wood to lay eggs. Again, a certified arborist can be an invaluable resource.

3. Prune Dead or Infected Branches:

If you detect symptoms of Dutch Elm Disease in your tree, prune and remove infected branches immediately. Always sterilize your pruning tools between cuts to avoid spreading the disease. If the infection is isolated, removing affected branches can sometimes help preserve the overall health of the tree.

4. Fungicide Treatment:

Fungicide treatments may be available in some areas to protect healthy trees or to treat mild infections. Consult an arborist to determine if this is a viable option for your tree. Fungicides can help slow the spread of the disease, though they are not always a permanent solution. As with using insecticides, it’s important to use the correct fungicides in the most appropriate way to minimize their impact on bees, which have been negatively affected by a wide variety of chemicals.

5. Plant Resistant Varieties:

Some elm species have been bred to resist Dutch Elm Disease. If you’re planning to plant new elms, look for resistant varieties, such as the Princeton Elm or Accolade Elm. These varieties have been developed to withstand the disease and are much less likely to succumb to infection.

6. Root Graft Management:

If your trees are planted close together, avoid planting additional elms in areas where root grafts may form. Root grafts can lead to the spread of the disease even if the beetles are controlled.

Do You Think You’re Dealing with Dutch Elm Disease? We’re Here to Help!

Dutch Elm Disease can quickly kill infected trees, so early detection and decisive, proactive measures can help protect your elms. If you suspect your tree is infected, it’s essential to consult with a certified arborist to assess the situation and determine the best course of action. With vigilance and proper care, you can reduce the impact of Dutch Elm Disease on your trees and preserve the beauty of your landscape for years to come.

Our certified arborists and plant care specialists are experts in homeowners protect and care for their trees, shrubs and ornamental plants for your landscaping. They have extensive experience in diagnosing and combatting Dutch Elm Disease and can save trees afflicted with this deadly threat. If you think your elm tree or trees may have Dutch Elm Disease, contact us today! We’re here to help!