Verticillium wilt is a deadly fungal disease that can linger in your soil for years and potentially kill your trees, shrubs, and fruit plants. With no cure, knowing how to identify the disease early and prevent its spread is crucial to keeping your trees healthy and alive in southeastern Pennsylvania.
In this article, we will look at verticillium wilt, explain its causes, symptoms, and the damage it does, as well as provide tips on what to do when you notice verticillium wilt in your trees.
PRO TIP: Want to learn more about common diseases the trees in Montgomery and Bucks County face? Check out our previous articles on the topic:
Key Takeaways
- Verticillium wilt is an often fatal fungal disease with no cure that targets shrubs, trees, and other plants.
- The Verticillium fungi survive in tiny resting structures called microsclerotia in the soil before infecting tree roots. The fungi constrict the flow of water throughout the tree.
- Symptoms include wilting, yellowing leaves, branch dieback, and black streaks under the bark.
- Common trees affected by verticillium wilt include maples, elms, smoketrees, ash, and magnolia.
- Prevention methods include keeping trees healthy, planting resistant species, properly disposing of infected material, avoiding spreading infected soil to new locations, and sterilizing pruning tools.
A maple tree displaying streaks under the bark that indicate verticillium wilt. Photo courtesy of William Jacobi, Colorado State University, Bugwood.org.
Verticillium Wilt: The Basics
The fungus Verticillium dahliae, along with other fungi in the Verticillium family (most notably Verticillium albo-atrum), causes verticillium wilt as well as other fungi in the Verticillium family (most notably Verticillium albo-atrum). These fungi live in the soil and can affect trees, shrubs, vines, fruit plants, vegetable plants, and herbaceous ornamentals. Controlling the disease can be difficult because it affects over 300 species of plants in the United States. These fungi live in the soil and can affect trees, shrubs, vines, fruit plants, vegetable plants, and herbaceous ornamentals. Controlling the disease can be difficult because it affects over 300 species of plants in the United States.
The Spread of Verticillium Wilt
Initial infection occurs in the soil where the Verticillium fungus lives. The fungal organism that causes the disease can lie dormant in the soil for years until it detects roots. They survive by producing microsclerotia, tiny resting structures that look like seeds on the ground. The fungus infects the roots, typically entering through open wounds that may occur while a tree’s roots grow.
The fungus then moves into the xylem (the water-conducting tissue of a tree) and blocks the movement of water throughout the plant. This will lead to the tree displaying symptoms of the disease and eventually dying if it is susceptible to verticillium wilt.
Once the disease takes hold, it will produce microsclerotia on dead plant material, such as the stems, leaves, and roots, allowing it to overwinter and survive for several seasons in the soil and on the tree. The wind can then carry infected leaves to new hosts. Verticillium wilt can also spread between neighboring trees when healthy and diseased roots are in contact.
Symptoms of Verticillium Wilt
Verticillium wilt is difficult to identify, as the external symptoms may be acute, and it’s nearly impossible to distinguish internal symptoms. The only way to prove your tree has verticillium wilt is to submit a sample for laboratory tests.
Common symptoms to watch out for that may indicate your tree is dealing with verticillium wilt include:
- Wilting of the entire plant (the plant may display worse symptoms in the heat and return to an unwilted state when the weather is cool or wet)
- Yellowing leaves
- Shriveling leaves
- Branch dieback
- Brown or black streaks under the bark (streaks may be green in maples and magnolias, while ash trees will show no streaking at all)
- Discolored sapwood in the recent annual rings
Trees infected with verticillium wilt will likely eventually die.
A silver maple tree displaying symptoms of verticillium wilt. Silver maples are one of many trees susceptible to this disease. Photo courtesy of William Jacobi, Colorado State University, Bugwood.org.
Common Trees Affected by Verticillium Wilt
Some common trees that are most susceptible to verticillium wilt include:
- Maples
- Elms
- Smoketrees
- Ash
- Tulip Poplar
- Redbud
- Kentucky coffee tree
- Magnolias
Some plants have displayed resistance to verticillium wilt, including:
- Apple
- Crabapple
- Beech
- Birch
- Boxwood
- Dogwood
- Hackberry
- Hickory
- Sweetgum
- Pear
- Linden
- Walnut
Managing Verticillium Wilt
There is no cure for verticillium wilt, making prevention vital to keeping your trees healthy.
Tree removal is often necessary when verticillium wilt is present.
Preventing Verticillium Wilt
Some of the standard practices we recommend to prevent the spread of verticillium wilt to your trees include:
- Keep trees healthy and unstressed: A healthy and unstressed tree can better resist disease and may allow a tree to better compartmentalize verticillium wilt. Provide water during dry spells, fertilizer when a soil test indicates a deficiency, and place mulch around your tree.
- Avoid spreading infected soil: The Verticillium fungus can live in soil for years, so avoid moving the soil from place to place via tools or dirty shoes. Also, avoid using the soil for other applications.
- Do not plant susceptible species: If your tree or shrub dies from verticillium wilt and you remove it, the fungus will still exist in the soil. Consider replacing your tree with a resistant species or cultivar instead of using the same tree.
- Properly dispose of infected material: If you have a tree with verticillium wilt, carefully dispose of any infected material, including branches and leaves. Do not use wood chips from trees with verticillium wilt for mulch, as the fungus may survive on the chips. The University of Michigan Extension reports that the fungus can survive up to a year in mulch made from infected trees.
- Sterilize pruning tools: Pruning dead or infected branches is always a good idea; just be sure to sterilize your pruning tools after each cut to lower the risk of spreading the disease to other sections of the tree or other plants on your property.
Treatment of Verticillium Wilt
The Penn State University Extension reports that research indicates benzimidazole fungicides may kill some populations of Verticillium. This is not a cure and will not work for all trees, meaning prevention is often the best course of action.
Researchers for the university also report that a licensed pesticide applicator can fumigate infested soil to reduce the population of Verticillium in soil. However, fumigation will not eliminate the population.
Clauser Tree Care Can Help You Care for Your Sick Trees
If you believe your trees are dealing with an infection of verticillium wilt or any other disease in Bucks and Montgomery counties, fast action is critical. Verticillium wilt has no cure, and removing the infected tree and cleaning up all debris may be the only way to protect the rest of your trees.
At Clauser Tree Care, we can determine what is ailing your tree and provide you with recommendations for treatment. If you have sick trees, don’t wait! Call us at 215-542-8291 or request a free quote online today.
