Bonide Copper Fungicide 16oz. Copper fungicide/Bactericides are useful against many different plant diseases. Please read the label and use carefully. COPPER FUNGICIDE is 10% Copper Octanoate (copper Soap), 90% inerts.Â Labeled for fruits, nuts, vegetables and ornamentals. Effective for peach leaf curl, rust, black spot, fruit rot, powdery mildew, late blight and other diseases. Most uses .5 to 2 oz mixed to 1 gallon water. 16 oz. Concentrate. Ship wt 3#.