Roof Doctor, Inc. uses two methods for moss control. The first is simply an application bleach water, and the second, used for tougher moss growth, is the application of zinc sulfate. Zinc sulfate is a combination of sulfur and zinc. It is an herbicide typically used for moss control. The toxicity of zinc sulfate depends on the amount of zinc in the product. Zinc is an essential mineral for human, animal, and plant nutrition. Zinc can be found naturally in the environment, foods, and water. How does zinc sulfate work? Zinc binds to proteins or organic acids in plants. In high concentrations, it affects the growth of moss and other plants, and damages the cells causing them to turn yellow. Once the moss completely dies off, it will deteriorate and no longer be present on your roof.