Verticillium wilt is caused by soil-borne fungus. It causes damage and death to maple trees if they are planted in the infected soil. According to the New Mexico State University Cooperative Extension, prevention is the best form of management for verticillium disease but infections can be managed with proper maple tree care. Recognizing the symptoms of verticillium disease is crucial to saving the maple from death.
Yellowing and dying leaves is one of the first symptoms of verticillium disease. Leaves may die throughout the tree or only be noticeable on individual branches. Yellow leaves often curl or are smaller than the healthy leaves, as their growth is stunted as the disease spreads. Leaves often drop once they yellow and die, though they may also stay on the branch.
Branches near the top of the tree usually die first. Leaves yellow and fall off, then the wood begins dying. It is more prone to wind breakage, so falling branches are a concern. Die-back continues throughout the crown, until it can eventually spread throughout the tree and kills it.
Lack of budding, new twigs and overall slow growth are also symptoms of the disease. New buds stop forming on otherwise healthy-appearing branches and new twigs and limbs no longer grow on the tree. These symptoms may affect the whole tree or only parts of it.
Verticillium fungus travels from the soil into the roots of the maple. It then travels through the sap to the rest of the tree. Infected maples have a dark ring or ark in the sapwood that is indicative of the presence of verticillium. The ring is green but may appear brown. The discoloration is not always visible in outer branches in the early stages of infection, though it is present in the trunk. Trees in the later stages of infection will show the discoloration in the branches if they are cut.