Oak Wilt
Oak wilt is a deadly fungal disease that affects oak trees, particularly red oaks. The fungus, Bretziella fagacearum, spreads through the tree’s vascular system, cutting off water flow and causing the tree to die. The disease is primarily spread by root grafts between trees and by sap-feeding beetles that carry fungal spores from infected trees to healthy ones.
How to Identify Oak Wilt
Recognizing oak wilt early can help protect your trees and stop the spread of this disease. Here are some key signs:
- Leaf Discoloration: Infected oaks, especially red oaks, will show rapid wilting and browning of leaves, starting at the top of the tree and progressing downward.
- Leaf Drop: Leaves often fall off the tree prematurely, even while they are still green, especially in the middle of the growing season.
- Vascular Streaking: If the bark is peeled away, dark streaks can often be seen in the sapwood of infected branches or trunks.
Different types of oaks show symptoms at different rates, with red oaks typically dying faster than white oaks.
How to Care for Oaks and Prevent Oak Wilt
Preventing the spread of oak wilt requires careful monitoring and management practices.
Avoid Pruning in Spring and Summer:
- Oak wilt is most commonly spread by beetles that are attracted to open wounds. Avoid pruning oaks from April through July, as fresh cuts during this time increase the risk of infection.
Proper Pruning Techniques:
- If pruning is necessary, or if a tree has been wounded, immediately paint the wounds with tree wound paint or latex paint to seal the cut and reduce the risk of attracting beetles.
Remove Infected Trees:
- Infected trees, particularly red oaks, should be removed and disposed of by burning, burying, or chipping to prevent further spread.
Disrupt Root Grafts:
- Since oak wilt spreads through root grafts, severing the roots between infected and healthy trees can help stop the disease from spreading. A certified arborist can assist with root graft disruption.
Monitor for Symptoms:
- Regularly inspect your oak trees for signs of oak wilt, especially during the growing season. Early detection is key to controlling the disease and protecting nearby trees.
Sun Prairie's Management of Oak Wilt
The City of Sun Prairie monitors for oak wilt in public spaces and is working to prevent the spread of this devastating disease. The city may remove infected trees or take measures to protect nearby oaks.