Trees are an excellent addition to your backyard landscaping, but there are many diseases that can kill them and ruin the look of your yard. Dutch elm disease is one of these diseases, and it can destroy your elm trees. Here are three things gardeners need to know about Dutch elm disease.

What causes Dutch elm disease?

Dutch elm disease is caused by Ophiostoma ulmi, a type of fungus. This fungus is though to be native to Asia and was accidentally introduced to the United States in a shipment of logs. Now, this fungus can be found everywhere but the deserted regions of the Southwest.

Beetles allow the fungus to spread from tree to tree. If an elm bark beetle lands on an infected tree, then lands on one of your trees, your tree could then develop Dutch elm disease. The fungus can also spread through root systems of nearby trees, so if one of your neighbors has an infected tree, your trees could be at risk.

What are the signs of Dutch elm disease?

Usually, the signs of Dutch elm disease appear in June or July. You'll notice that some of the branches on the affected trees are wilting or sagging, and the leaves will turn brown. Late-summer infections will make the leaves turn yellow and fall to the ground. If you pull a piece of bark off an infected twig, you'll see that the wood underneath is stained brown.

How can you treat affected trees?

If your trees are newly infected, an arborist may be able to save them with tracing. This is a difficult procedure, and it's not guaranteed to save your tree. First, the arborist will determine the spread of the fungus throughout the tree by chiseling small windows in the bark. If the fungus hasn't spread to within 10 feet of the ground, there's still a chance that the roots are unaffected and the tree can be saved.

If the arborist determines that the tree may be salvageable, they will remove a strip of bark from the trunk with a chainsaw or chisel. The fungus will be killed by exposure to air, so it won't be able to spread downwards past this bark-free area.

If the arborist determines that your tree can't be saved, they will need to complete tree removal. The tree will need to be burned to destroy the fungi and protect other trees in the area. 

If your elm trees have wilted branches or brown leaves, they may be afflicted with Dutch elm disease and should be evaluated by an arborist.