Ontario residents are being urged to avoid pruning oak trees during the no-pruning season, which runs from now until November. Pruning or damaging oak trees during this period makes them more susceptible to oak wilt disease, an invasive condition caused by the fungus Bretziella fagacearum. Oak wilt disrupts the movement of water and nutrients through oak trees, causing their leaves to wilt, turn brown, and fall prematurely. Over time, the tree may lose all of its leaves. While all oak trees are at risk, red oaks are especially vulnerable, often dying within 2 to 6 weeks after infection. Oak trees are an important part of Ontario’s environment, economy, and communities. They enhance property values, reduce energy costs, help prevent soil erosion, and provide critical habitat for wildlife.