OneStop | Directories | Search U of M 

CUES: Center for Urban Ecology and Sustainability

Table: Diagnosis and Control of Oak Wilt
Pest Identification Host Plants Damage Symptoms
Oak Wilt
Ceratocystis fagacearum
Oak trees. The red and black oak families are the most susceptible, while the white oak family is more resistant. Leaves of infected trees turn dull green to bronze, working from the margin inward. In the white oak family leaves are slower to discolor. Discolored leaves may drop shortly after changing color. Symptoms usually start near the top of the tree and work downward. Trees in the white oak family tend to have randomly scattered branches wilting, while trees in the red and black oak family tend to have all of the branches wilting. Vascular discoloration may be observed in the outer sapwood of white oaks, but is rarely observed in oaks from the red and black oak families. Oaks from the red and black oak families may die in 2 to 3 weeks, while the more resistant white oak family can live for one or more years.
Monitoring Control Options Pesticides
Beginning in June and continuing through August, oak trees should be monitored for wilting. Monitor how many branches are wilting, what type of oak, and how fast the tree is wilting. Examine the sapwood of oaks in the white oak family for vascular streaking. Disrupt the root to root grafting with the use of a vibratory plow. Avoid pruning oak trees from April 15th to July 1st (the time when the Nitidulid beetles are active). If trees are wounded or pruned during this time paint the wounds as soon as possible. Trees in the white oak family may be systemically injected to protect or cure them from new infections. Infected oaks in the red and black oak families should be removed and properly handled, since these trees may produce fungal mats in the spring. Alamo (propoconizol)
Description and Life History
Description: Oak wilt is a fungal, vascular wilt disease that causes wilting of the canopy. This disease is also associated with sap-feeding insects (nitidulid beetles). Fungi produce spores on fungal mats beneath the bark.

Life history: The fungus is dispersed from infected trees to healthy trees by insects or through root grafts. Once the tree is infected the fungus moves through the outer sapwood causing the tree to produce gums and tyloses. These compounds plug the vascular tissue of the tree causing it to wilt. Fungal mats form between the outer bark and sapwood after the tree dies. Pressure pads cause the bark to crack open and the fruity odor of the fungal mat attracts insects. These insects (family Nitidulidae) are usually active from late April through June.

Overwintering: The fungus overwinters in infected wood of the tree.


Back to Diseases of Deciduous Trees or Oak Wilt


(C) Regents of the University of Minnesota. All rights reserved.
The University of Minnesota is an equal opportunity educator and employer.

Contact U of M | Privacy
Last modified on March 07, 2013