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ISSUE 11 July 10, 2003

DUTCH ELM DISEASE

We’ve had several samples submitted for culture of the Dutch Elm Disease (DED) pathogen, Ceratocystis ulmi. This is a wilt disease of American elms that will move rapidly to destroy whole trees. Symptoms become apparent as sections of the canopy wilt, turn yellow, and possibly turn brown fairly quickly. These symptoms should become evident presently as a tree’s demand for water increases with temperature and the advancing season. One way to assess potential DED in a tree is to peel back the bark and look for brown streaking on the wood just under the bark. This is also a characteristic symptom of the disease.

If you are concerned about DED in an elm, we can confirm the presence of the pathogen, indicating a need for tree removal. To provide the most reliable and accurate diagnosis of this disease requires taking care when sampling the tree. Select a branch from the yellowing area of the tree’s canopy. Take one that is about an inch in diameter or larger, but no smaller than the diameter of a fat pen. We only need 6-8 inches of that branch section but more is fine. Leave the bark intact on the sample. Cultures will take about a week to complete and there is a $30 fee for this service; however if you send in multiple samples in one package, the fee is reduced to $25/sample. Scouting for infected these trees, efficient and timely removal, and other sanitation practices are the best management strategy.

The following web sites contain more detailed information and color pictures of the disease:

http://www.na.fs.fed.us/spfo/pubs/howtos/ht_ded/ht_ded.htm

http://www.ext.nodak.edu/extpubs/plantsci/trees/pp324w.htm

Cheryl Biller
NDSU Plant Diagnostician
diaglab@ndsuext.nodak.edu


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