Recent test results from Washington State University Puyallup Plant & Insect Diagnostic Laboratory confirmed the first case of Dutch Elm Disease (DED) in the core area of the Washington Park Arboretum.  The tree, a 45 year old Guernsey Elm (Ulmus minor ‘Sarniensis’), had been suffering from mechanical injury to the root crown and annual infestations of the Elm Leafminer, an insect that that feeds on elm leaves.  Over the past year, a significant portion of the tree began showing symptoms similar to DED.  Twig and branch samples from the tree showed dark staining in the cambium, which is a typical sign of DED.  The samples were sent to the WSU lab in Puyallup, which resulted in a positive diagnosis for DED.  The Guernsey Elm has been removed.

Management of Dutch Elm Disease will include frequent monitoring for signs and symptoms of the disease, sanitation pruning, prompt removal of severely infected trees, and root graft disruption when necessary.

For more information on Dutch Elm Disease, click here:

http://www.seattle.gov/transportation/pdf/sdot2dedbrochure.pdf

or here:

http://pnwhandbooks.org/plantdisease/elm-ulmus-spp-dutch-elm-disease