Disclosed are compositions and methods of treating oak wilt, decline, or other fungus-induced diseases of trees. A mixture is applied to the root system comprising sulfur and pentachloronitrobenzene or pentachlorophenol as its active ingredients, and optionally other ingredients such as a wetting agent, nitrogen, an insecticide, and a nutrient source. It is preferable to simultaneously treat the bark and crown of the tree with a composition which includes a fungicide and an insecticide. Other ingredients, such as a wetting agent or a fungicide/nutrient, can also be present in the Bark & Crown Composition.
