Artillery fungus seems to be more severe now. I don't remember this being a problem 20 - 25 years ago. Why?
This is a tough question. Wider recognition and awareness of the artillery fungus by the public certainly has led to a perceived increase in the problem. However, I think the problem is also realistically more severe than in past years, partly due to increased use of landscape mulch. There is more mulch being used these days, and therefore, more favorable material for the artillery fungus in our urban and suburban areas.
The artillery fungus may be just as common out in mulched flower beds far away from your house, but it is not noticed at that location. But, put the same mulch (and artillery fungus) next to your house foundation, add a white or reflective siding, and you may have a severe problem!
In addition, it is my experience that the artillery fungus seems to prefer wood as opposed to bark. Much of the mulch that we use today is recycled wood - in the past, most mulch was bark. In addition, the finely-shredded mulches used today hold more moisture than the older coarsely ground mulches - this favors fungi, because they need moisture to survive!
Why is this problem more severe in some years than in others?
The artillery fungus grows better and produces more spores during wet years, such as 2003 and 2004 (here in the Northeast). It is most common during the cool spring and fall, and is much less of a problem in the hot dry periods of mid-summer. And, not at all a problem during the winter here in Pennsylvania.