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Table: Diagnosis and Control of Dutch Elm Disease
Pest Identification Host Plants Damage Symptoms
Dutch Elm Disease
Ophiostoma ulmi
Elms (American and European), Siberian and Asiatic are more resistant. Some cultivars of American elm are resistant (American Liberty Elm, Sapporo Autumn Gold, and Regal). Wilt symptoms are first present in June, but become more prevalent in July and August. Wilting leaves appear yellow and curled, and may fall from the tree. Branches showing initial wilt symptoms are called "flags". Dutch elm disease also causes a brown discoloration in the outer ring of sapwood.
Monitoring Control Options Pesticides
Wilt symptoms first appear in June, but become more prevalent in July and August. Symptoms appear as, wilting (yellowing) leaves. 'Flagging' is a good diagnostic tool. All elms should be removed and disposed of regardless of the cause of death, since dead elms provide a breeding ground for beetles. Root grafts between healthy an infected trees should be disrupted with the use of a vibratory plow. Systemic fungicides may be applied as a preventative or curative treatment (Note, trees infected through root grafting can not be cured). Resistant elms may be planted. Establish community control programs. Alamo (propoconizol)
Arbotect ( )
Description and Life History
Description: Dutch elm disease is a fungal, vascular wilt disease that causes wilting of the canopy. This disease is also associated with bark beetles (smaller European and native elm bark beetle). Fungi produce spores on aerial stalks known as synnemata and perithecia.

Life history: The fungus is dispersed from infected trees to healthy trees by insects or through root grafts. Infections occurring through bark beetle feeding usually appear on one branch in the upper canopy, while root graft infections may appear on multiple branches. Once the tree is infected, the fungus moves through the outer sapwood, causing the tree to produce tyloses and gums. These compounds plug the vascular tissue of the tree causing it to wilt. After the tree dies the fungus colonizes the outer sapwood and inner bark. Spores produced in this region, also the region where bark beetles overwinter, are picked up and transmitted by bark beetles to healthy trees in spring by bark beetles.

Overwintering: The fungus overwinters between the outer sapwood and inner bark of standing dead trees or cut elm logs.


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Last modified on March 06, 2013