We applied Zinc sulfate to this roof which had a lot of moss growing on the composition shingles. Zinc sulfate is heavily regulated by the US Department of Agriculture as it is a pesticide for controlling moss growth. In Oregon it is required by law that anyone applying zinc sulfate to control moss as a business must be registered with the US Department of Agriculture. Violators can face a fine of up to $10,000.
Zinc Sulfate and the environment
Zinc sulfate is a white powdery substance that can be applied wet in a solution form or dry to control moss. When applied at the correct ratio it provides excellent moss control results. Applications can last 1 – 3 years depending on the seasonal weather patterns and the vegetation around the treated area. After the application it usually takes about a month or so for visible change to occur to the moss. After the moss is dead the roots will start to loosen and dislodge from the singles. Some species of moss cling more than others and may require physical removal to completely remove the moss. About 95% of the time the moss can be blown away after the first year.