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What is Artillery Fungus?

Updated: May 12, 2023



The fungi Sphaerobolus (sphere throwing) stellatus (star shaped) is more commonly known as "cannonball fungus", "sphere thrower", "artillery fungus", and "shotgun fungus". Its name comes from its ability to shoot spore-filled projectiles (called peridioles or glebal masses) as part of the transmission phase of its reproduction cycle.



 

Sphaerobolus stellatus -- The Artillery Fungus


The Latin name “Sphaerobolus” means sphere thrower and “stellatus” refers to the star-shaped receptacle left after the sphere has been ejected.


The image on the right depicts various angles and parts of the artillery fungus' life cycle:


- the 3mm black ball is a projectile called a peridiole and is filled with microscopic fungal spores the will grow new artillery fungus if it lands on an appropriate host.


- there are several layers surrounding the peridiole.


- when the temperature, humidity, and weather are right, the layers will open, slowly exposing the peridiole while preparing for launch.


- the fungus is phototropic which means it grows toward, and subsequently aims at, the light which increases the survival chances of its projectile offspring.


 

Sphaerobolus stellatus -- In the Garden


Artillery Fungi can be hard to spot.


Wood and wood products provide the perfect carbon-rich environment for it to grow.


This series of pictures demonstrates how small the artillery fungus is and how hard it can be to spot in one's garden or around the house. Notice the penny in the mulch.



When you zoom in, you can begin to see the tiny orangish spores growing on the wood mulch.









Up close, the fungus looks like little balls are protruding. This is what the fungus looks like after the peridiole has been fired off.






Here you can see the fungus on the left has already been fired, whereas the fungus on the right has a peridiole in the middle that is ready to be fired.







Here is an assortment of artillery fungi at different stages of development. Three of the fungi have fired, one in the upper right has not yet fired, and the one in the bottom left fired some time ago.






Here are four pictures after the firing cycle of the fungus. The lining that fires the peridiole starts to decrease in size leaving a star-shaped structure behind.


 

Videos of the Artillery Fungus firing its peridioles


Here is a 30-second clip of an artillery fungus firing.




A short video of 4 spores firing in succession.



This is a helpful 5-minute video that explains more about Sphaerobolus stellatus.


 

Artillery Fungus and Property Damage


The black and brown spores of the artillery fungus are found almost anywhere there is mulch. I see it on the siding and gutters of nearly every house I pressure wash. It can also be on vehicles, outside furniture, playsets/playgrounds, walls, fences, etc. These little dots are so strong and stubborn that 4400psi of water will not remove a single one. Some recommend using brushes and scrapers to remove them but given the amount of force required to remove them you risk damaging the surface in the process.


If you are determined to have the little black buggers gone, it would be easier to paint over or replace whatever they are adhered to.


 

How to get rid of black peridioles of the Artillery Fungus



Unfortunately, there is no way to get rid of the black and dark brown marks left by the artillery fungus. This is a wood-decaying fungus that thrives in the carbon-dense environments of dead trees and landscape mulch. With artillery fungus, an ounce of prevention is better than a pound of cure. It might be best to avoid using mulch in the first place as the little spots are impossible to get off. Or, if not having mulch is out of the question, a mulch with a greater bark percentage would reduce the amount of Artillery Fungus that could grow. To avoid the next-to-impossible-to-get-off little tarry black dots, use mulches in areas next to houses and cars that do not support the growth of this fungus. Recommended types are pine bark mulch or cedar or cypress mulch.


When it comes to pressure washing, most things can be removed, but some things can't. The peridioles of Sphaerobolus stellatus (aka: The Artillery Fungus) are one of the few things that cannot be removed.





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