Oak Wilt Disease

Oak wilt disease is caused by a fungus that is responsible for the deaths of many oak trees throughout Minnesota every year. It is especially concentrated around Minneapolis and St. Paul. Fortunately, oak wilt disease can be controlled if it is caught on time. The ability to control it means that the death rate of oak trees to this disease can be reduced with a little awareness and tree maintenance by a qualified Minneapolis tree service.


The Northern Pin Oak and the Northern Red Oak are both very susceptible to this disease. In red oaks, the disease is easy to detect because the affected trees wilt rapidly wilt. It only takes two to six weeks for the tree to completely wilt, which starts from the top of the crown and works its way down. The individual leaves wilt from the tips and margins to the bases with the colors going from bronze to brown. The leaves that fall are green at the base.

White oak trees have a level of susceptibility that is low to moderate. A white oak will die slowly when it is infected, which means it will die one branch at a time. This means the tree can survive for many years. The leaf color changes the same way they change in the fall.

Both red and white oaks may also show brown material plugging the outer rings of the springwood vessels and the outside wood may show brown streaks.

Managing Oak Wilt Disease

One way oak wilt disease is managed is by stopping the spread of the fungus through common root systems. There are also ways to prevent overland spread by insects, such as:

  • No pruning during the high risk period of April, May, and June. If trees are pruned or wounded during this time, the wounds need to be covered as soon as possible to prevent infection.
  • Wound covering can be done during the low risk period of July to October. Insect infestation is the main culprit during this time, but the incidence is low.
  • It is best to prune between November and March. Insect vectors and fungal pathogens are not active during this period.
  • Do not use tree climbing irons on living oak trees because this can increase the chance of infection.

Another way to manage oak wilt disease is to destroy infected red oaks that have spores on them in the spring. A professional is able to detect these trees and dispose of them properly. If the trees are not carefully removed and disposed of the right way, sap beetles can carry the spores to other trees.

High value white oaks can be treated with an injection of an effective fungicide by a qualified arborist. This can prevent further infection in a tree with less than 30% of the crown infected and can also prevent infection in healthy trees that are near infected trees.

Contact An Experienced Tree Service

Experience is the key when dealing with oak wilt disease. Fortunately, it is a disease that does not have to be the end of all oak trees. To find out more about how we can protect and treat your trees, call us at 1-800-311-3919 to obtain a free quote.