Bad News. The black streaks that form on your roof shingles are bacteria feeding on the limestone filler of those asphalt shingles. Worse yet it's highly contagious. You probably have seen in on a few of your neighbors houses as well. Good news. Your roof can be cleaned. In order to preserve the integrity of your roofing shingles Island Cleaning Service uses a safe effective procedure recommended by your shingle manufacturer to remove the streaks, lichen, and moss feasting on your house. No power washer or any other mechanical means will be used in the treatment of your roof.