Artillery Fungus
We have a sister company, Easy Button Power Wash LLC, and artillery fungus is something we notice on occasion. This is a pretty good article supporting regularly top dressing of mulch, or completely changing to another substrate. If top dressing, fall is likely the best time to do so as growing conditions for the fungus fall between 50-70 degrees. Putting the top dressing down in late fall each year provides the least opportunity for growth on the new layer of mulch.
Watering 2 times per week instead of daily in the spring may also help prevent large infestations of artillery fungus.
Once the spores have set, you're pretty much stuck with them unless you are willing to invest lots of personal time scraping at the spores. It takes about two weeks for the spores to set so if you notice them on your siding, move fast!