Thanks for the question.

The black material that you are observing is a mass of mature fungal spores ejected from Sphaerobolus stellatus, also known as an artillery fungus. These masses are called peridioles.

Regarding your question, as you have discovered once attached the peridioles stick stubbornly. The black spots can be very difficult to remove. Right now (May 2025) the spore contents may or may not have been dispersed. You could just leave these spots as is and with time they may slowly fade. I don’t know when you first discovered these peridioles but with continued UV exposure from the sun, they will harden and adhere even more tightly to surfaces. Given the apparent texture of your siding, removal of these structures might be challenging. Nevertheless, see the following for information on these and related points:

https://www.thespruce.com/artillery-fungus-identification-prevention-5185963

https://extension.umaine.edu/ipm/ipddl/publications/5103e/

https://yardandgarden.extension.iastate.edu/how-to/managing-strange-looking-fungi-landscape-mulch - artillery

https://www.canr.msu.edu/resources/artillery-fungus-sphaerobolus-stellatus - :~:text=The black spots are masses,diameter and produces spores internally.

https://extension.psu.edu/solutions-to-artillery-fungus

https://elitepropainting.com/artillery-fungus-possible-removal/

Perhaps just a few passes with a power washer might improve the appearance?

Good luck. Please get back to us if you have additional, related questions. Thanks for consulting our forum.

Thanks for your latest response. We have been experiencing significant computer problems on our end. Responses such as yours have been delayed in getting to us Master Gardeners. We greatly apologize for the incurred delays. I am now only seeing your last comments.

You have asked a question that is difficult to answer. The black spots contain fungal spores that could exist for several years. It is theoretically possible that at some future point, these spores will germinate and become active. When you read the sites I previously sent you, you probably saw how difficult it is to remove these spots. If you remove nearby mulch, you will minimize the chances of fungal spread but will not eliminate its possibility.

The bottom line is that you are facing the lesser of two evils.

If you leave these spots on your siding and remove nearby mulch, it lessens the likelihood of future outbreaks of artillery fungi. It does NOT guarantee complete fungal elimination.

If you want a more complete guarantee, you will need to expend the time and expense of removing these fungal spots.

Good luck. Thanks for consulting us.