Environmentally Safe Moss Prevention for Asphalt Roofs - Ask Extension
We own a small family owned Pacific Northwest roof cleaning business and would like to eliminate or at least reduce the amount of zinc we apply to roo...
Knowledgebase
Environmentally Safe Moss Prevention for Asphalt Roofs #934734
Asked June 08, 2026, 7:28 PM EDT
We own a small family owned Pacific Northwest roof cleaning business and would like to eliminate or at least reduce the amount of zinc we apply to roofs after we clean them to delay the return of moss growth. We have read that zinc is harmful to marine life and that it can inhibit a salmon's sense of smell, making it more difficult to return to spawn. What alternatives can you suggest that are safe for asphalt shingles - and also, if possible, for plants and animals. THanks!
Multnomah County Oregon
Expert Response
Potassium salts of fatty acids: These soap-based biodegradable products kill moss by penetrating the cell walls and changing the membranes so that the cells leak and the moss dies. These products are noncorrosive and pose minimal risk to humans and animals. Avoid overspraying on adjacent plants, and rinse any plants that are accidentally treated. Thoroughly rinse any tools or equipment used to
apply these chemicals.
Have a look at this publication (even for
asphalt): https://extension.oregonstate.edu/catalog/pnw-733-care-maintenance-wood-shingle-shake-roofs
