What Are These Tiny Black Spots on My Siding?

Have you noticed tiny black dots on your siding, windows, trim, gutters, or even vehicles parked near your home?

You may be dealing with artillery fungus, sometimes called shotgun fungus.

Artillery fungus commonly grows in hardwood mulch and gets its name from the way it spreads. When conditions are right, it launches tiny spore masses into the air. Those spores can travel surprising distances and stick firmly to nearby surfaces.

The result is often hundreds, or even thousands, of small black dots appearing on:

• Siding
• Windows
• Doors and trim
• Gutters
• Painted surfaces
• Vehicles parked nearby

The frustrating part is that these spots are not dirt, algae, or mildew.

Each black dot is a sticky spore mass that attaches itself to the surface. Once it sticks, it can be extremely difficult to remove.

Why Is Artillery Fungus So Hard to Remove?

Unlike algae or mildew, artillery fungus usually cannot simply be washed away.

Once the spores bond to a surface, they often require individual removal using specialized cleaners, plastic scrapers, careful hand labor, or a combination of methods. Even then, complete removal is not always guaranteed.

In some cases, trying to remove the spots aggressively can risk damaging the surface underneath.

The longer the spores remain, the harder they typically become to remove.

Can Pressure Washing Remove Artillery Fungus?

Usually, no.

This is one of those situations where more pressure is not the answer.

Excessive pressure can damage siding, paint, window seals, trim, and other exterior surfaces long before it removes well-attached artillery fungus spores. That is why proper identification matters before any cleaning method is used.

What Causes Artillery Fungus?

The most common source is hardwood mulch, especially mulch that stays damp and shaded for long periods of time.

Not every mulch bed develops artillery fungus, but certain conditions can make it more likely, including:

• Damp mulch
• Heavy shade
• Poor airflow
• Mulch placed close to siding
• Older decomposing hardwood mulch

The problem often starts in the landscape, but it shows up on the house.

Can Artillery Fungus Be Prevented?

There is no guaranteed prevention method, but there are steps that may help reduce future outbreaks.

Homeowners can consider reducing excessive moisture, replacing infected mulch, improving airflow around the home, and using alternative ground cover materials near the house.

Early detection is important. The sooner artillery fungus is identified, the better the chances of successful removal.

The Bottom Line

After more than 26 years in exterior cleaning, artillery fungus remains one of the most challenging issues homeowners face.

It is small, stubborn, and often misunderstood. Many people assume the spots are dirt, algae, mildew, or something that can be blasted away with pressure. Unfortunately, artillery fungus does not work that way.

If you have noticed tiny black spots on your siding, windows, gutters, trim, or nearby vehicles that will not wash off, artillery fungus may be the culprit.

Cornwell Exterior Cleaning provides professional exterior cleaning services in Natchez, MS and surrounding areas. If you are unsure what is on your home, we can take a look and help identify the right cleaning approach.