You can prevent oak wilt by painting fresh pruning wounds immediately after you cut the branch. Spray right away so the beetles don’t get there first! Cover the entire wound with a thin coating of black spray paint. The commercial pruning paints, also called “tree wound dressing,” are a petroleum base product, and are very toxic to trees, especially on fresh wounds. They are thick like auto body undercoating. People tend to apply a thick protective application with the thought that more is better. When it dries and cracks, insects hide in behind this thick coating application, causing damaging infections. It is best to buy an inexpensive black spray paint at your local hardware store or Wal Mart for about $1.00. A light application is sufficient and will allow the wound to cure properly as nature intended. A thin coat of spray paint seals wounds so spores can't stick to the sap and germinate. The purpose here is to stop the molecular evaporation of oak sap, that attracts the beetle. Everything between insects and trees is chemical and that rings like a loud dinner bell for the insects.