Dutch Elm Disease

• Dutch elm disease is a fungal disease caused by Ophiostoma ulmi. This disease originated in Asia but became problem throughout North America and Europe after World War I. Dutch elm disease is most prevalent in the American elm, red elm, rock elm and cedar elm and is responsible for the death of many of the naturally occurring elm trees throughout the United States.
  
  

Symptoms

• Dutch elm disease causes many symptoms in cedar elm trees. The first noticeable symptom is the yellowing of the leaves of the tree. As the disease progresses, the leaves wilt and eventually fall from the tree. Because of the way in which this fungus spreads, a section first displays symptoms and then neighboring areas are affected.
  
  Severe cases of Dutch elm disease can cause the tree to defoliate and die. For the damage to become this severe, the fungus must infect the plant for many years. The fungus that causes Dutch elm disease enters the xylem vessel of the tree, causing brown streaks to appear in the wood of the tree. You can only see this if the tree is cut down or the bark is stripped from the trunk of the infected tree.
  
  

Disease Spread

• The fungus that causes Dutch elm disease is carried from tree to tree by means of the elm bark beetle and the European elm bark beetle. These pests pick up spores of the fungus when they are feeding on the bark of the infected plant and carry the spores with them to neighboring branches and plants. Because these beetles are capable of flying up to a quarter of a mile, elms can be infected that aren't a direct neighbor of the initial host tree.
  
  

Control Methods

• Because there are no methods of correcting or reversing the damage caused by this fungus, all infected trees must be removed and destroyed to prevent the spread. If the disease is not yet present, both insecticides and fungicides have proven effective in preventing its occurrence. Apply insecticides in April that prevent the beetles that aid in the spread of this disease.
  
  A second method of control is to inject the tree with a systemic fungicide. Because of the chemicals used, a professional should do these injections. Although this is a pricey option, it is effective for up to three years.