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There are a variety of tree diseases that only affect a handful of species. Dutch elm disease, for example, only affects trees in the genus Ulmus.
And then there are diseases like verticillium wilt. It has been documented to infect more than 400 plant species worldwide, making it one of the more wide-ranging plant pathogens homeowners may encounter.
Unfortunately, several of the trees susceptible to verticillium wilt are common landscape species in Michigan. So, we’ll explain everything you need to know about this potentially deadly plant pathogen, including the symptoms it causes, the trees that are at risk, and what homeowners can do about it.
What Is Verticillium Wilt?
Verticillium wilt is a vascular disease primarily caused by one of two fungi: Verticillium dahliae or Verticillium albo-atrum. Both organisms can infect trees, but Verticillium dahliae is the species that most commonly causes disease in landscape trees.
Both fungi live in the soil and tend to gain entry to trees via the root system. Once inside the tree, they colonize the vascular xylem (wood) tissue. Over time, they begin to disrupt the flow of water through the tree, leading to the wilting and branch dieback associated with the disease.
The fungi can spread via contaminated soil, infected plant material, pruning tools, and nursery stock. They can also persist in soil and infected plant tissues for extended periods.
Michigan Trees That Are Susceptible to Verticillium Wilt
As mentioned, verticillium wilt can affect a broad range of species, including a number of trees that are either native to or commonly planted in our area.
- Amur maple (Acer ginnala)
- Boxelder (Acer negundo)
- Striped maple (Acer pensylvanicum)
- Norway maple (Acer platanoides)
- Red maple (Acer rubrum)
- Silver maple (Acer saccharinum)
- Sugar maple (Acer saccharum)
- Japanese maple (Acer palmatum)
- Northern catalpa (Catalpa speciosa)
- Eastern redbud (Cercis canadensis)
- White ash (Fraxinus americana)
- Black ash (Fraxinus nigra)
- Green ash (Fraxinus pennsylvanica)
- Blue ash (Fraxinus quadrangulata)
- Black locust (Robinia pseudoacacia)
- American basswood (Tilia americana)
- Littleleaf linden (Tilia cordata)
- American elm (Ulmus americana)
- Slippery elm (Ulmus rubra)
- Chinese elm (Ulmus parvifolia)
While the trees listed above are all susceptible, maples are likely the group that’s most commonly affected by the disease.
Common Symptoms of Verticillium Wilt
Verticillium wilt can cause a range of symptoms, depending on the species affected, the health of the tree, and environmental conditions. However, some of the most common symptoms include:
- Individual branches or portions of the canopy may begin to wilt, sometimes suddenly.
- The leaves may yellow significantly or turn brown (particularly along the margins).
- The tree may shed some or all of its leaves well before autumn.
- The leaves and shoots may appear small or “stunted.”
- Individual branches in the canopy may die back.
- Green, brown, or olive-colored streaking in the sapwood beneath the bark.
- Epicormic shoots (“water sprouts”) may emerge from the trunk.
Because verticillium is a vascular disease, these issues may be isolated to one portion or side of the tree. However, some trees may display more uniform wilting, foliar discoloration, or dieback, particularly if the infection is affecting several parts of the tree.
Unfortunately, none of the symptoms above provide a positive identification of verticillium wilt (though the sapwood streaking is a strong clue). This means that samples may need to be submitted for laboratory analysis if a definitive diagnosis is required.
Verticillium Wilt in Landscape Trees: Treatment & Prevention
There’s good news and bad news for homeowners facing a tree suffering from verticillium wilt.
Starting with the bad news, verticillium wilt can’t be eradicated from an infected tree nor is it easy to eliminate it from infected soil (though this is theoretically possible).
But the good news is that verticillium wilt is not necessarily a death sentence for infected trees. With proper supportive care, some will go on to survive for years, if not decades.
In fact, there are a number of things you can do to help prevent your trees from contracting the disease and help infected specimens cope, including:
- Protect the root system. Root damage can stress trees and may facilitate infection, so protect roots from damage caused by construction, mowers, and vehicular traffic.
- Avoid unnecessary fertilization. Fertilize only when warranted by a soil analysis, as excessive fertilization encourages growth rather than helping the tree cope with the disease.
- Prune infected branches. You aren’t likely to eliminate the disease via pruning, but it will help keep the tree safe and as attractive as possible.
- Collect and dispose of tree litter. The fungi that cause verticillium wilt may be found in leaves, twigs, and other tissues, so rake tree litter up and dispose of it properly.
- Don’t reuse infected wood as mulch. Wood chips produced from trees with verticillium wilt may harbor the fungus and should not be used around susceptible plants.
- Start with disease-free nursery stock. If you install trees that are already infected with verticillium wilt, you’re likely to face challenges at some point.
- Plant replacement trees in different locations. Because the fungi that cause verticillium wilt may persist in the soil, it’s wise to install replacement trees in fresh locations.
- Remove infected trees that become hazardous. While you needn’t automatically remove trees suffering from verticillium wilt, those that pose potential risks should be assessed carefully.
Verticillium-Resistant Trees for Your Michigan Property
Though it won’t help address existing verticillium wilt infections, there is one other key strategy for avoiding the disease: opting for species that are resistant to the disease.
A few of the best choices for Michigan properties include:
- Balsam fir (Abies balsamea)
- Paper birch (Betula papyrifera)
- Yellow birch (Betula alleghaniensis)
- American beech (Fagus grandifolia)
- Shagbark hickory (Carya ovata)
- Bitternut hickory (Carya cordiformis)
- Honeylocust (Gleditsia triacanthos)
- Tamarack (Larix laricina)
- American hophornbeam (Ostrya virginiana)
- White spruce (Picea glauca)
- Black spruce (Picea mariana)
- Norway spruce (Picea abies)
- Jack pine (Pinus banksiana)
- Red pine (Pinus resinosa)
- Eastern white pine (Pinus strobus)
- American sycamore (Platanus occidentalis)
- White oak (Quercus alba)
- Bur oak (Quercus macrocarpa)
- Eastern arborvitae (Thuja occidentalis)
- Black walnut (Juglans nigra)
By choosing any of these species, you’ll still be able to enjoy all of the benefits the trees provide, while greatly reducing the risk posed by verticillium wilt.
Verticillium Wilt in Michigan Trees: FAQ
It’s normal to have questions about any tree disease that may affect your property, including verticillium wilt. We’ll try to help you better understand this pathogen by answering some of the most common questions our clients have below.
Can a tree recover from verticillium wilt?
Trees usually don’t completely rid themselves of the pathogen that causes verticillium wilt, but with good supportive care, many will survive — often for many years.
Will verticillium wilt kill my tree?
It is possible. Though verticillium isn’t the guaranteed death sentence that some other pathogens are, it certainly can kill susceptible trees. This is particularly true for trees that are already stressed.
How quickly does verticillium wilt kill a tree?
Verticillium wilt usually doesn’t kill trees especially quickly, though it is difficult to predict exactly how long a given tree will survive after contracting the disease. Some trees survive for years — even decades — after contracting the disease, while other trees may die in a matter of months.
Can verticillium wilt spread from one tree to another?
Yes. The fungi that cause verticillium wilt may spread via contaminated soil, infected plant material, pruning tools, or nursery stock.
How can I tell if my tree actually has verticillium wilt?
While there are a number of clues that can point to a verticillium wilt infection, such as streaks in the sapwood, sudden wilting of a branch, and premature leaf drop, positive identification usually requires a laboratory diagnosis.
Can I plant another tree where a tree with verticillium wilt died?
Because the fungi that cause verticillium wilt can persist in the soil for some time, it’s generally not a good idea, unless the new tree is a resistant species.
Is there a fungicide that treats verticillium wilt?
Unfortunately, no. There is no fungicide that reliably eliminates verticillium wilt from a tree.
Expert Tree Care Is Only a Click or Call Away
If you’re concerned that one or more of your trees are suffering from verticillium wilt, you’ll likely need expert guidance to give them the best chance of surviving and potentially limit the pathogen’s spread.
The plant health care experts at Longtree Tree Service can certainly help with that. There may not be a magic cure for verticillium wilt, but there are often things our arborists can do to help.
Contact us today to arrange for a free onsite evaluation.
Sources and References
- Arboriculture & Urban Forestry (ISA) – “Verticillium Wilt of Landscape Trees”
Peer-reviewed review by Larry D. Smith of Verticillium wilt in landscape trees, discussing the causal fungi (Verticillium dahliae and V. albo-atrum), host symptoms, and control measures.
https://auf.isa-arbor.com/content/5/9/193 - MSU Extension – “Verticillium Wilt”
Extension factsheet on Verticillium wilt (Verticillium dahliae), covering the soil-borne fungus’s host range, the wilting and vascular streaking it causes in maple and other susceptible trees, and management through tree vigor and pruning.
https://www.canr.msu.edu/resources/verticillium_wilt - MSU Extension – “Verticillium Wilt Refresher”
Extension news article revisiting the diagnosis of Verticillium wilt, distinguishing it from other dieback causes, and reinforcing the cultural management options available since no cure exists.
https://www.canr.msu.edu/news/verticillium_wilt_refresher - UW-Madison Division of Extension – “Verticillium Wilt of Trees and Shrubs”
Extension guide to identifying Verticillium wilt across woody hosts, understanding the vascular discoloration and branch dieback it produces, and managing affected plantings.
https://hort.extension.wisc.edu/articles/verticillium-wilt-of-trees-and-shrubs/ - Morton Arboretum – “Verticillium Wilt”
Arboretum plant-care resource describing Verticillium wilt symptoms, susceptible and resistant tree species, and care practices to support infected trees.
https://mortonarb.org/plant-and-protect/tree-plant-care/plant-care-resources/verticillium-wilt/ - Wageningen University – “Verticillium Wilt in Trees: Detection, Prediction and Disease Management”
Doctoral thesis by J.C. Goud investigating the detection, disease-risk prediction, and management of Verticillium dahliae wilt in trees, including soil inoculum assessment for nursery and landscape plantings.
https://edepot.wur.nl/121445
