Hydrogen peroxide and fungicides are common treatments that combat tree fungus. Keeping a tree healthy with regular maintenance also combats tree fungus, by preventing it from growing.
The 3 percent hydrogen peroxide solution that is available at most drug and discount stores is an organic treatment that kills fungus, and it is generally harmless to trees. Hydrogen peroxide treats fungal diseases that include powdery mildew, rot and wilt. The weekly treatment process involves spraying the foliage of the infected tree until the hydrogen peroxide is dripping from the underside of the leaves.
Types of tree fungicides include copper, lime sulfur, oil and captan. Brands of fungicide include Safer and Green cure.