Pruning: DO NOT PRUNE during the warm season; trimming is a major cause of oak wilt infections in Michigan today. If oaks need to be pruned, the dormant period is best - November through February. If storm damage occurs during the warm season, clean-prune the branch 1-2 feet below any visible injury and seal with a pruning paint. Repair of storm damage should occur as quickly as possible-optimally within hours or within a couple of days of the damage.
Storm damage which has occurred during the dormant (winter) months is not of particular concern for oak wilt. Nevertheless, winter storm damage should be repaired during the winter months and not during the warm season. It is not advised to use pruning paints during winter storm repair.
Except for emergency situations, cessation of pruning during the warm season, is probably our most effective tool for preventing oak wilt at this time. Compared to Dutch Elm Disease, in which elm bark beetles can easily transmit the fungus from diseased trees to healthy trees, the oak wilt insect vector is inefficient at transmitting the oak wilt fungus when no wounds on oaks are present.
Additionally, have enough space between oak trees, especially those in the Red Oak family, so that root grafts are unlikely will limit the speed of Oak Wilt spreading through a planting.
Oak in the Red Oak family typically die within one season. Oaks in the White Oak family die more slowly...perhaps five years. Oak in the Live Oak family are intermediate in resistance.