Dothiorella wilt

Infects

American and Siberian elm trees

Symptoms

Disease symptoms may first appear in mid to late June. Leaves will begin to wilt, curl and turn yellow in color, often on one branch.

As the disease progresses, wilting will gradually spread to other limbs. Eventually dieback will occur in some of the stems. Death may occur in larger trees in 2 to 5 years.

When the bark is peeled back, the vascular tissue will have a diffuse streaky brown color. The bark of smaller branches will shrivel and have a reddish hue.

Note: In general, the disease's outward appearance is similar to Dutch elm disease and Verticillium Wilt. Testing in a laboratory setting is necessary for proper diagnosis.

Cause

Dothiorella wilt is caused by a fungus that overwintes in infected tissue.

In the spring, fungal spores can spread by wind, rain, insects and/or non-sterilized pruning equipment.

Cure

If caught early enough, dothiorella wilt can be controlled by pruning and destroying the affected branches.

IPM Toolkit

Preventive tools

• Watering and fertilizing will aid in the tree's ability to resist this disease.
• Sterilize your pruning equipment with methanol (gas line antifreeze) between cuts or a 50:50 bleach water solution.

Physical tools

• Pruning of affected wood is an effective control method. Diseased wood should be pruned back a minimum of 30 to 60cm from the last visual discoloration in the wood. Pruning may have to occur several times before all the diseased wood is removed.
• Immediately burn any diseased wood or take it to be buried in a local landfill.

Biological tools

• Not applicable

Chemical tools

• Not applicable