Verticillium wilt of trees: what the extension services record
What the University of Wisconsin-Madison, UC Statewide IPM and The Morton Arboretum say about Verticillium wilt: the soil fungus, the trees named as hosts, acute and chronic symptoms, the sapwood streaking and how the fungus lives in the soil.
Checked against the sources at the bottom of this page on October 9, 2026. Rules, fees and pay change: the source has the last word.
This page describes what the named sources say. It is not a diagnosis of any tree and does not say what should be done with one. None of the three pages read lists Verticillium wilt as regulated or notifiable. Each section names its source, all read on October 9, 2026. The full list of diseases is on the tree diseases page.
Cause and name
The Morton Arboretum says the disease is caused by a soil-borne fungus, Verticillium dahliae, and that a second species, Verticillium albo-atrum, is a less common cause. The University of Wisconsin-Madison Plant Disease Diagnostics Clinic names the same two fungi as the main causes and calls them common in Wisconsin soils, and in the roots, branches and leaves of infected plants. The Arboretum calls it a disease of the xylem, the water-conducting tissue. Wisconsin says the fungi enter through the roots and grow in the xylem, and that the blocked water movement is what leads to wilting.
Hosts the sources name
The Arboretum describes a serious disease that injures and eventually kills trees, shrubs, ground covers, vines, fruits, vegetables and herbaceous ornamentals. For woody plants it names maple, smoke-tree, catalpa and magnolia as commonly infected. Wisconsin calls it typically fatal and says the trees most commonly and severely affected in that state are maple and ash. It also lists barberry, catalpa, elm, lilac, linden, smoke-tree and redbud as susceptible. UC Statewide IPM lists herbaceous hosts such as dahlia, gerbera, marigold, peony, snapdragon and vinca, and shows a maple with foliage damaged by the disease.
| Source | Woody hosts named | Plants named as resistant, immune or not known to be susceptible |
|---|---|---|
| University of Wisconsin-Madison | Maple and ash most; also barberry, catalpa, elm, lilac, linden, smoke-tree, redbud | Adapted from a textbook: apple, aspen, azalea, beech, birch, butternut, crabapple, dogwood, flowering quince, ginkgo, hackberry, hawthorn, hickory, holly, honeylocust, katsura tree, mountain-ash, oak, pear, poplar, sweetgum, sycamore, walnut, willow. Conifers such as pines, spruces and firs appear immune. |
| The Morton Arboretum | Maple, smoke-tree, catalpa, magnolia, among others | Not known to be susceptible: arborvitae, bald cypress, beech, birch, boxwood, crabapple, ginkgo, hackberry, hawthorn, hazelnut, hickory, holly, honey locust, hornbeam, ironwood, Katsura tree, mulberry, oak, pine, serviceberry, spruce, sweetgum, walnut, willow, yew |
| UC Statewide IPM | Maple pictured; the page lists mainly herbaceous hosts | Not published on the page |
The two lists are not the same. Beech, birch, ginkgo, oak, sweetgum, walnut and willow are among those on both, while the Arboretum alone lists, for example, boxwood and yew and Wisconsin alone lists, for example, poplar, pear and sycamore. Each list is stated for its own region and source.
Symptoms as the sources state them
Wisconsin gives the first signs as individual branches that suddenly wilt and die, on one side of the tree or scattered through it. UC Statewide IPM says woody plants are often affected first on one side or in scattered parts of the canopy, with leaves yellowing first at the margins and between the veins, then turning tan or brown. It names browning of older leaves while younger leaves stay green as characteristic. It says infection usually happens in cool conditions but damage may not show until warm weather, when plants are more stressed.
The Arboretum splits the external symptoms in two. Acute symptoms are seen in mid-season, often on scattered branches: leaf colour changes (red, brown or yellow depending on the host), wilting, defoliation and stem dieback, with leaf margins sometimes turning brown and scorched. Chronic symptoms are usually seen early in the growing season and come from sapwood that died in earlier years: slow growth, sparse or small foliage, leaf scorch, abnormally heavy seed crops and branch dieback.
Streaking under the bark
Both Wisconsin and the Arboretum describe streaks in the sapwood when bark is peeled from an affected branch. The Arboretum says the discolouration is brown in most woody plants and green in maples and magnolias, and that ash shows no streaking. Wisconsin agrees that streaking is common in maple and redbud and often not visible in ash and lilac. The Arboretum warns that streaking helps identify the disease but does not guarantee it, because other factors or diseases can also discolour sapwood.
How the fungus lives and moves
The Arboretum says the fungus lives in the soil as small resting structures that can stay dormant for years. When roots of a susceptible plant grow nearby, it germinates and infects them. Healthy roots can be infected, but damaged roots are more vulnerable, and the fungus can enter through wounds or natural openings. The xylem is blocked by the fungus and also by gums the plant makes to stop it. The fungus forms resting structures in the dead tissue, and that tissue can re-infect the soil. The Arboretum says the disease is difficult to control because it persists in soil for long periods even with no host plant present.
Wisconsin says leaves that fall from symptomatic trees, and mulches made from infected trees or of unknown composition, are potential sources of the fungus. Both Wisconsin and the Arboretum say the disease can be carried on pruning tools.
Laboratory confirmation
The Arboretum says only laboratory examination can positively diagnose the disease, and names the University of Illinois Plant Clinic as one that confirms it. Wisconsin points to its own Plant Disease Diagnostics Clinic and says very few diseases can accurately be told by eye. The directory lists the plant disease and insect diagnostic labs in the United States.
Outcome and what the sources say about management
Wisconsin says infected trees and shrubs cannot be cured and will likely die eventually. The Arboretum says a precise diagnosis does not save the tree, and that no chemical control is known. UC Statewide IPM names sanitation and resistant plants as the primary strategies. This page gives no treatment steps. None of the pages names a regulation, quarantine or report line.
Related reading
Another fungus that blocks a tree from the roots is on the Armillaria root rot page, and the oak wilt page covers a vascular wilt of oaks.