Artillery Fungus: Identification and Prevention

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artillery fungus

You may be worried about the tiny black spots that appear in your car, the leaves of ornamental plants, siding, downspouts, soffits, and windows. This is Artillery Fungus.

You may mistake Artillery fungus or Sphaerobulus Stellatus as tar, scale insects, or insect excrement.

The dark spots are about 1 to 2 mm in diameter and slightly raised in globular.

However,  coating of the spot is actually brown and darkens with age.

When they open, the center tends to be while, finely granular, and gummy.

It is important to note that often mulch is the cause of artillery fungus in your backyard or ln.

It forcefully ejects its mature spores high up in the air, leaving pesky stains.

Keep on reading about the causes, treatment, and prevention of artillery fungus.

Artillery Fungus

Artillery fungus or Sphaerobulus Stellatus looks like dark spots that are about 1 to 2 mm in diameter and slightly raised to globular.

However,  coating of the spot is actually brown and tends to darken with age.

Moreover, when the scrape opens, the center is off-while, finely granular, and gummy.

The black spots are masses of mature spores that fruit the body of the fungus expels.

This fungus is a relative of the bird’s nest fungus and is commonly popular as Artillery fungus.

The spherical fruiting body is approximately 2mm in diameter.

artillery fungus 2

It produces spores internally, and when they mature, the fruiting body splits open forming a cup-like structure.

The round mass of spores or glebal mass is about 1mm in diameter and rests in liquid at the bottom of the cup.

After about 5 hours of opening, the glebal mss catapulted into the air.

According to estimates, this discharge mechanism generates about 1/10.000hp and can throw the mass up to 6 meters.

Upon contact, the sticky coating adheres to the mass of any surface it touches.

Furthermore, it is important to note that the fruiting body is strongly phototropic and glebal mass is generally shot towards the strongest sources of light.

If you are unsure if artillery fungus exists in your home or landscape, you can inspect the spots with a magnifying glass.

The spores of artillery fungus are globe-shaped and when you scratch the outer coating, you will see a whitish, finely granular, gummy-like center.

Description of Artillery Fungus

Sphaerobolus stellatus is the most common species and is common on wood and much around the world.

Basidiocarps that grow in groups are about 1 to 3 mm in diameter, roughly spherical or ovoid in shape.

The outer wall consists of different layers, including a gelatinous layer.

When mature, the exoperdium or outermost layers split into several lovers to expose the single, reddish black to a dark periodical or spore casting about 1mm in diameter.

Moreover, this outer spore casing forcibly ejects leaving evaginated endoperidium.

Spores tend to develop inside the spore casing and are about 6 to 10 x 4 to 6 micrometers.

these are elliptical to oblong in shape, thick-walled, and hyaline and intermix with irregularly shaped cells: gemmae.

It is important to note that these species have a cosmopolitan distribution and you can find them on dung, decaying wood, landscaping mulch, or vegetative litter.

Mechanism of Spore Discharge

The peridium which consists of six distinct layers forms two cups at maturity.

The three layers form an outer cup, two forms the inner cup, and one layer tends to dissolve to create the fluid that bathes the glebal.

After splitting of the layers, the gleba, enzymatic conversion of glycogen to glucose tends to increase the internal osmotic pressure and turgidity of palisade cells in the inner peridial cup.

Moreover, analysis of glebal carbohydrates reveals that there is an increase in glucose, mannitol, and trehalose before glebal discharge.

This can account for an increase in osmotic pressure.

Glebal discharge often occurs 5 to 6 hours after the apex splits and in S. stellatus, the peridiole shoots off an audible pop.

Thus, leaving a remnant looking like a miniature earth start.

This species is phototropic, and the nearest source of direct or reflected sunlight will be the target for glebal discharge.

Furthermore, the spores tend to remain viable for a number of years, while gemmae can also germinate.

Causes of Artillery Fungus

Landscape mulch consists of hardwood shreds or chips which provide a nice cover in landscape beds.

It holds moisture for the plantings and adds beauty to the exterior of your home.

However, it can also provide a food source or breeding ground for the growth of fungus.

The fungus is often found in wood chip mulch.

artillery fungus 1

However, you can also find decaying fallen trees and other rotting wood as well as animal dung.

It tends to need sunlight and moisture for growth.

Moreover, artillery fungus mainly occurs in cool spring and fall weather in a temperature range between 50 and 70 degrees Fahrenheit.

The fruiting bodies will not develop in weather that is above 78 degrees.

Strategies to Contol Artillery Fungus

It is important to note that prevention and avoidance are the major strategies to control this fungus.

This is because chemicals are ineffective against this type of fungus.

Moreover, you will need to remove or disturb the wood chips or bark mulch with a rake to disperse the fungus and dislodge the fruiting bodies.

This will help to dry out the much by increasing air circulation and creating conditions that are less favorable for the growth of fungus.

It is important to note that periodically overlaying with fresh much can also help.

Thereby reducing the light which is important for periodiole discharge.


However, when overlaying, it is important to avoid making the mulch layer that is too thick.

While making sure to select mulch that contains at least 85% back.

Avoid mulches that contain a high concentration of wood as wood chips are a better source of carbon than mulches that consist of bark.

All types of wood mulches can support the growth of this type of fungus, and research is currently in progress to find if one type of mulch is more frequently associated with this fungus than any other type.

Another way to minimize this issue in your landscape is to use an alternative form of mulch.

These include:

  • black plastic
  • stone
  • pea gravel
  • marble chips

Other Strategies

Furthermore, sphaerobolus can occasionally be a problem in plants that you grow in containers when bark or wood products are components of potting soil.

Experts suggest that composting the bark or wood products before using them can help to reduce the ability of the artillery fungus to colonize the wood or back.

This will promote the growth of beneficial organisms that are antagonistic to it.

You will need to remove peridioles from the affected surfaces with stiff water from a hose.

Or you will need to scrub them with a wet cloth or stiff brush before they dry.

In most cases, however, it is not practical and removal is often done after peridioles dries out.

When this is the case, it is difficult to remove them and you will physically need to scrub and scrape them off the surface.

Moreover, when the glebal masses are on glass surfaces, you can easily scrape them off with a razor blade.

However, you need to be careful when removing the hardened masses from other surfaces as the removal itself can damage the substrate.

Extensive staining can remain after removing the fungus.

As the brown spots or peridioles of the fungus can remain in the air for more than 10 years, they can serve as a means to spread the fungus.

As a result, you need to take care when scraping off the affected surface.

The peridioles will not grow on house siding or inert substrates like concrete or sidewalks.

However, if they fall into mulch or another suitable organic substrate, they will germinate and re-infest these substrates.

A trap or similar item can help, you will need to place it under the area you are scraping to catch the fungal structures as they drop in order to keep them from re-infesting.

Preventing Artillery Fungus

In order to prevent artillery fungus from growing, it is best to prevent it in the first place.

You can use bark mulch or cedar mulch instead, as they tend to be resistant to artillery fungus.

However, experts do not recommend using redwood mulch or cypress mulch for sustainability reasons as native forests have been depleted by timbering.

Moreover, artillery fungus will not grow in dry weather conditions, thus, if you have a small yard, stirring up the mulch regularly can help to keep it dry.

removing mulch

If you, however, have an ongoing problem it is best to remove the affected mulch and start from scratch with new, more resistant mulch.

Also, if you have old mulch with the artillery fungus in place, then cover it with a new layer of mulch.

But it is important to note that the fix is temporary, as the fruiting bodies will reemerge.

Dispose of all the contaminated mulch safely in the trash and do not compost it or dump it in your yard, as the fungus can spread.

Another alternative is to use a non-organic material to cover unplanted areas like using stone or gravel.

Final Thoughts

The presence of persistent, small, brown spots on cars, house siding, plants, and other surfaces can indicate the presence of artillery fungus. It other grows on wood, bark chips, dying and decaying wood, and dung.

This type of fungus can be a nuisance to your plants. However, you cannot use fungicides to remove it as they are ineffective on it. removal is your only option. Removing black spots within two to three weeks after they appear ineffective for their removal. The longer the stain remains, the more difficult it will be to clean the surface.

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