Hopefully no one out there is currently plagued with this pest - if you are, you're in for some additional spring cleaning duties. It's a messy one!
Also called shotgun fungus, these members of the genus Sphaerobolus are usually spotted (yes, I'm making bad puns again) covering the sidings of houses or the exteriors of vehicles. Artillery fungus colonizes wood, so if you're laying down wood mulch, you may be encouraging its growth. The peridioles (spore packets) of Sphaerobolus are interesting: they rest above cup-shaped cells that gradually fill with water. Eventually, the cells invert, which causes the peridioles to burst, exploding outward in a distance up to 20 feet! The spores immediately adhere to any surface situated in the blast zone...which most often happens to be cars and houses.
Just to make things more delightful, artillery fungus is really, REALLY difficult to remove. Part of the problem is that you don't want to use harsh chemicals or scrapers on the surfaces that the fungus sticks to. This website has a few potentially workable suggestions, the most notable of which is employing a combination of Mr. Clean Magic Erasers and a bit of mouthwash. Bleach and hot water and plenty of elbow grease apparently works as well. Definitely test a small area of before you start your cleaning project, as you don't want to ruin any painted surfaces.
As for prevention of further attacks, it should be noted that there isn't really an effective fungicide on the market to deal with artillery fungus. (I'm not fond of chemicals, so I probably wouldn't recommend one even if such a thing was available). The best option is to consider whether or not you really need wood mulch, especially near the foundation of the house or alongside the driveway. Replacing the wood mulch with gravel or another desireable product may be a simple solution to a labour-intensive problem. As well, bear in mind that the wood chunks found in potting soil might also be a haven for the fungus.
So far, I've been lucky and haven't had any artillery fungus attacks in my garden! How about you?
Here is a video that gives you an idea of how artillery fungus grows and disperses, and the mess it can make: