Oak wilt is Wisconsin’s most destructive oak disease, killing thousands of healthy trees annually.
Start the year off by pruning your trees to protect them from harmful pests that emerge after the thaw.
It is ideal to prune trees in the winter since branch damage or weak branch structure is more visible and because pests that cause harmful tree diseases are inactive in cold temperatures. One such disease is oak wilt, a fatal disease that spreads through tiny sap-feeding beetles attracted to open wounds on trees.
“What’s encouraging about oak wilt is that preventing and slowing its spread takes only the most basic measures,” said Paul Cigan, DNR Forest Health Specialist.
The WDNR encourages Wisconsin residents to only prune trees in winter. Pruning oaks during April through July places them at the greatest risk for oak wilt infection and should be avoided when possible.
It also suggests keeping firewood transport local and reporting oaks with sudden, mid-to-late summer leaf drop immediately to a certified professional.
Prune young trees to establish a central trunk, proper trunk taper and good branch structure and spacing. Prune older trees to remove dead or hazardous limbs. In addition, it’s recommended to prune landscape trees throughout their lifetime to maintain strong structure and remove dead wood.