Oak Wilt is becoming an increasing problem throughout the State and kills off a large number of oaks every year. Even though oak wilt is active in a large area of Minnesota, effective management techniques exist.
Oak wilt in a healthy tree will begin wilting the canopy. This usually starts at the top of the tree and spreads downward. The tree then sheds leaves, which will begin individually wilting at the edges and spread towards the midrib of the leaf or at the leaf tip and wilt towards the stem. A discoloration or streaking of the wood just below the bark may also be present.
In Red Oaks, the deterioration process can take as little as 4 weeks. In White Oaks, the disease may come back every year but death of the tree could take up to 5 years or longer after the initial symptoms appear.
Healthy oak trees are usually infected by the fungus's ability to move underground through the roots of nearby trees that have grafted together. In general, trees more than 50 feet apart are less likely to be infected through grafted roots. Sap beetles also transport the disease above ground by moving from an infected tree to a healthy one.
Stopping the spread of oak wilt is possible. Breaking root connections between closely spaced oaks will reduce the chance of the disease spreading from infected trees to nearby healthy ones. This takes a specialized piece of equipment and can be difficult to achieve. This is way preventing infection in the first place is the recommended best management practice.
Even though the nice weather makes you want to head outside and work on your property, you should avoiding pruning and wounding healthy oaks in the spring and summer. Between April and July, oak trees are at a much higher risk of infection by sap beetles who are attracted to fresh wounds in the bark of oak trees and may be carrying the fungus. Oak trees should be assessed for storm damage and any wound should immediately be sealed with a water-based paint of another type of plant sealer.
Other techniques to stop the spread of oak wilt include; avoid moving firewood from known infected areas, timely removal and disposal of infected trees, and the use of fungicide when necessary. Many times multiple approaches are necessary to slow or eradicate the problem. Meeting with a local tree care providers can help create a management plan that will be effective on your property.
If you have more questions or are concerned about Oak Trees in your area, contact a local professional to inquire about what can be done on your property. Early detection is still the best method of control.