Others have said it s a fungus from mulch.
Black spots on siding.
I am getting small dark spots on windows and the white siding of my house.
Those annoying black spots that creep up your siding or splash along the side of your car may not be mud spatters but artillery fungus.
Also known as artillery or cannonball fungus sphaerobolus it uses internal water pressure to forcefully fire its spores similar to seeds up to 20 feet away the fungus sets its sights on bright areas so that means it will aim for any pale surface that reflects light such as the siding on your house.
Some tell us it s from spiders.
We have thousands of tiny black spots pin head size all over the siding of our house.
What is artillery fungus.
The spots are about the size of the head of a pin and appear to be black or dark brown in color.
Vinyl siding is very popular due to its durability and simple maintenance.
The only way i have found to remove them thus far is by scraping the windows with a razor blade.
The photo at above left shows green algae on vinyl siding.
Algae may also look black or brown as may some molds.
It s hard to see shotgun fungus itself because it s only 2 millimeters wide.
We have these small black spots that look like specks of tar all over our white vinyl siding of our house.
Artillery fungus is a wood dwelling fungus commonly found in mulch.
It is sphaerobolus a common fungus that sticks firmly to light or white colored surfaces and resembles spots of tar.
I have tried to remove these spots with mineral spirits without success.
Click to enlarge any image small gray or darker round spots on siding that are about 1 16 in individual diameter particularly if the spots are slightly raised may be artillery fungus a mold spore.
It goes all the way up to my second story windows and is even under my soffit and on my gutters.
It s on the porch my windows but it is worse on the siding.
The black tar like spots that are all over your vinyl siding are more than likely a fungus called sphaerobolus stellatus better known as artillery or shotgun fungus although it s most often found on the east coast it can grow anywhere and especially thrives in areas that have cool damp springs or rainy fall weather conditions.
Dirt and insect secretion stains however can adhere to vinyl siding attracting molds mildews and algae.
If you notice lots of tiny black or dark brown spots developing on your siding above a landscaped area of your yard as seen below it is most likely artillery otherwise known as shotgun fungus.