Green Roof Mold, Direct Afternoon Sun

[Fixmattshouse]

I have read the threads on roof mold and none seem to cover my situation. I have light green moldy growth in large raised splotches a few feet wide/ long on my asphalt shingle roof subject to direct late afternoon sunlight without interference from trees or branches. It actually looks bird droppings but would take a Rodan-sized creature to make the deposits I have. My questions: What is it? How do I get rid of it?

[tomh]

I have experienced similar growth on my roof, and we have sun most of the year in California. Its algae or moss and is controlled by zinc sulfate. Moss-Out is an example of a product available at nursuries or home improvement stores that contain zinc. Zinc is toxic to the algae or mold. The growth will be killed within several weeks of application. You may need to do some cleaning to remove the residue. Annual application, or installation of zinc strips at the ridge will keep the problem from recurring.

[bravey]

Sounds like you may have moss or lichen.

Moss typically grows on the north face of walls and roofs and has a soft, fuzzy texture. It’s color is often dark to mid green.

Lichen typically grows in thicher, raised patches and can tolerate direct sunshine. The color tends to be a mottled tan/rust/brown but I have seen dark green. Its texture is more course. Lichen is a kind of primitive plant species composed of strands of alga linked with roots and branches of a fungus. Lichen can grow almost anywhere, from moist bark to arctic rocks.

Lichen and moss can be controlled somewhat by running a 4″ strip of galvanized sheet metal along the ridge of your roof. As the weather oxidizes the sheet metal, run-off containing zinc washes the roof and inhibits lichen and moss growth. You can see this effect where plumbing vents penetrate the roof and the downhill surfaces are stained slightly white and are devoid of lichen or moss. I have heard that copper wire works as well, but I have no experience with this method. The sheet metal must be securely fastened or it will blow away in a srong wind. This method is slow acting but is effective for 10 to 15 years.

Regards

[Giddaymate]

Hi Matt. Bravey is spot on with saying it is Lichen. I found a great site for you to visit that explains why it can grow in full sunlight and how it can also grow in cold climates http://www.bugs.bio.usyd.edu.au/Mycology/Plant_Interactions/Lichen/lichenBiology.shtml . Regards Noelene

[Fixmattshouse]

Tks to tomh, bravey, giddaymate for help with my question of roof mold. After visiting the http://www.bugs.bio.usyd.edu.au/Mycology/Plant_Interactions/Lichen/lichenBiology.shtml site, it sure looks like what I have is Lichen and your educated responses tell me that Zinc is in my future. I will post results of corrective measures as I try them over the next few weeks. Also, I noticed some of my neighbors have the same problem. Because my lawn usually wins the Spring Yellow Flower Puffball prize, I will share your insights with them and hopefully begin my rehabilitation as a contributing member of the community.

Tks again…Matt

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