Tree fungus can be killed by pruning out infected limbs and spraying the tree with fungicide. Bordeaux mixture, which is made from copper sulfate and hydrated lime, is an effective tree fungicide.
Tree fungus grows directly on tree limbs, producing mushrooms, conks and other fungal-fruiting structures. Pruning infected limbs with a disinfected pruning saw and disposing of them away from the tree keeps the fungus from spreading. Spraying tree limbs and leaves with a combination of Bordeaux mixture and water until saturated kills the fungus. One tablespoon of Bordeaux can be mixed with 1 gallon of water. It is recommended to spray the tree again at bud swell and bloom time, especially during damp conditions.