Dutch elm disease (DED) is a fatal disease of elm (Ulmus sp.) caused by the fungus Ophiostoma novo-ulmi. Introduced to the United States in the 1930’s the disease has killed millions of elm trees and remains a key focus for urban foresters throughout the country.

The fungus can be spread by root graft transmission but is most commonly vectored from diseased trees to healthy trees by the European elm bark beetle and the native elm bark beetle.

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Dutch elm disease symptoms begin to develop 4-6 weeks after infection. The first noticeable symptom that results from the fungal occupation of the water conducting vessels is wilting or “flagging” of one or more branches, usually starting at the branch tip. Leaves on infected branches turn dull green to yellow, curl, and become dry and brittle. As the infection spreads the wood beneath the bark displays a brown discoloration.

Using leaf symptoms alone to determine where the leading edge of the infection is does not work.  To determine where the leading edge of the fungal infection is, the arborist must peel back the outer bark and examine the sapwood for staining.

 
Susceptible Hosts (*denotes most susceptible)
  * American (white) elm U. americana
  * Red (slippery) elm  U. rubra
  * Rock elm   U. thomasii
  * Winged Elm   U. alata
  Cedar elm   U. crassifolia
  Siberian elm   U. pumila
  Chinese elm   U. parvifolia

Symptoms
• “Flagging” of one or more branches, usually starting at the branch tip.

• Leaves on infected branches turn dull green to yellow, curl, and become dry and brittle

• Beetle galleries beneath bark

• Sapwood discoloration on infected branches and trunk

Signs
• None visible without magnification

Distinguish from Look-alikes

• Wilt from physiological drought will be even throughout canopy, DED will often flag individual branches

• Broken branches in canopy can appear similar to DED. Use binoculars to determine.

Treatment

Dutch Elm Disease spreads overland by Elm Bark Beetles and below ground by root grafts.  The elm bark beetle feeds in the 2 -4 year old branches of healthy elms.  If the beetle is carrying the disease spores on its body, it introduces the fungus at that time.  Thus, the purpose of Arbotect macro infusion is to evenly and completely cover all the 2 -4 year old branches with enough fungicide to keep the fungus from being able to grow.  Arbotect is diluted and macro-infused with high volumes of water to ensure complete and even distribution of the fungicide in the crown of each tree.

• Arbotect protects elm trees for 3 growing seasons from Dutch elm disease using the Rainbow macro-infusion system. 

• Arbotect DOES NOT protect Elms from root graft infections and Arbotect DOES NOT SAVE DISEASED elms with out pruning out the infection.

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