When the appearance of a surface is brought down by the presence of lichen, action should be taken immediately to get rid of it and prevent it from growing. Instead of letting the problem grow to the point where it gets out of hand, take the necessary steps to gain control of the situation. Chemicals are easily available that can kill lichen and prevent it from returning for a significant period of time.
Brush any loose growth, dirt, or dust from the surface on which the lichen is growing.
Spray moss and algae killer spray directly on the lichen and the area directly surrounding it. Spray enough so that the entire area has been reached. Allow the spray to sit for an hour.
Spray the lichen directly with a water hose to wash away the moss and algae killer.
Apply concentrated moss and algae killer to the surface of the lichen to kill the spores and discourage growth.
Apply a new coat of concentrated moss and algae killer to the surface once per year or at the first sight of new growth.