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Dutch Elm Disease

Symtoms & Diagnosis

Symptoms

The first evidence of Dutch Elm disease is wilting or "flagging" in one or more of the branches, usually starting in the outer portion of the crown. Leaves on the infected branches turn dull green to yellow and curl, finally becoming dry, brittle, and brown. The symptoms progress down the limb and eventually throughout the entire tree. Trees infected through root grafts can die very rapidly, while trees infected via the feeding of bark beetles can take 1 - 3 years to die. Another symptom of the disease is the discoloration of the water conducting vessels. This is easily seen by peeling the bark off infected wood, revealing the brownish staining.

This elm has the beginning stage of Dutch Elm disease

	Symptoms involve wilting leaves that start in a small area and expand

(click images to view a magnified version)

Diagnosis

Understanding the Dutch elm fungus and how it grows makes diagnosing this disease easier. A few key distinctions will help in accurately making sure that you are in fact dealing with this dreaded disease.

Leaves on infected trees are almost always curled or wilted looking, and often drop off. Leaves that are flat and shiny are common in the late summer and are usually caused by branch senescence.
The disease symptoms progress as the fungus grows in the tree. Thus, there is a pattern of leaf death outside the tree that reflects the fungus growth inside the tree. Remember that the initial infection grows downward in a narrow band until it has reached the roots. It then spreads sideways and grows back up the rest of the tree. See the Technical Description of Dutch elm disease for more information.
Check under the bark close to where there are external leaf symptoms. Dutch elm disease always causes the water conducting vessels to turn a dark brown. Finding this discoloration along with wilting leaves is a very good indicator that Dutch elm disease is present. Use a chisel and a hammer to open a hole in the bark to check for the discoloration.
Trees in the spring can die rapidly – causing the appearance that the Dutch elm disease is moving very quickly. What is happening in reality is the fungus was in the tree from last summer, the tree grew new tissue over the top of the infected wood, and then the fungus colonized the newly formed wood causing rapid dieback. Infections that happen in the current year can be seen reflected in leaf dieback as the fungus grows.
If you are unsure if your elm has Dutch elm disease– you can take samples and send them to a lab for confirmation. See sending samples to a lab for diagnosis.

Another symptom of Dutch elm disease is discolored brown to black wood under the bark. Healthy elm wood is white

The fungus grows downward to the roots. After reaching the root area, it spreads sideways and moves back up the tree.

Tree Health Issues

Bacterial Leaf Scorch

Chlorosis

Dutch Elm Disease

	Technical Description
	Symptoms & Diagnosis
	Managing the Disease
	Root Graft Disruption
	Arbotect vs. Alamo
	Protect with Arbotect
	Arbotect MSDS
	Arbotect Label
	Saving Infected Elms
	Marketing Literature
	Research
	Library & Downloads