What are those black spots on my house?
Artillery or shotgun fungus
Have you ever wondered what those small black dots that you find around your home? The ones that feel like a raised brail bump all around your walls, windows and gutters. It is the result of a wood decay fungus called artillery fungus or sometimes called shotgun fungus.
Types of wood rot *
As wood mulch ages and gets wet and dries over and over again it begins to rot. There are a few types of rotting wood mainly white rot, soft rot and brown rot. Lets look at each and what causes each one in more detail.
Brown Rot
Brown rot also sometimes mistaken for dry rot is where hemicellulose and cellulose that form the wood structure is broken down by hydrogen peroxide. Because the hydrogen peroxide that is produced moves thru the wood it causes all the wood to become brown and fracture.
Soft Rot
Soft rot fungus breaks down the cellulose in the wood somewhat like brown rot. Soft rot uses fixed nitrogen to feed off of which can be easily taken from the wood or environment to grow and infect the wood. Soft rot can grow in areas of the country that are to hot, cold or wet for brown or white rot to grow.
White Rot
White rot is a fungus notorious for breaking down the organic polymers or lignin* in the wood. It changes the texture of the wood causing it to become moist, stringy and spongy.
Artillery Fungus *
Artillery fungus is a white wood rot that comes from the decay of wood when it stays moist over long periods of time. Wood mulch in our homes landscaping beds is always on a cycle of getting moist from morning dew, rain, and even sprinklers that water our lawns. Over time the constant wet and dry causes the wood mulch to break down and decay leaving an opening for fungus to grow. The fungus grows and these small bowl shaped pods develop in the mulch. When they mature and dry just enough they explode shooting this sticky substance well to well over 20 feet in all directions. This is a very small fungus at just .1 inches across it looks much like birds nest fungus except by the way they spread there spores. Birds nest fungus shown below spread there spores when rain hits the cups and splashes the spores a short distance around the fungus area. Artillery uses its own forces to propel the sticky tar like spore far from the original fungus site. This tar like dot is easy to take off when it first appears but as it dries becomes more and more difficult to the point of almost impossible to remove. Even if you scrape it off with your fingernail there is still a residue that remains.
What can we do about it?
The best way to handle it is by trying to prevent it from ever becoming a problem in the first place. Yearly topping off of wood mulch can help reduce the rotting or if found replacing the mulch entirely to stop rotting from overtaking the mulch bed. There is always taking the wood mulch out and putting in rock or rubber mulch solves the problem all together. If you happen to see black dots forming on your house, gutters, or car they can be taken off more easily when they are fresh. If they dry and harden then just short of burning the house down they are hard to remove.
- References. Information taken about different types of fungus from the following web sites.
http://amerimulch.com/the-dreaded-artillery-fungus/