bodies of artillery fungi look like small, cream-colored or
orange-brown cups that are about 1/10 of an inch in diameter. There
is a single black “egg” in the cup, which is actually a sticky mass
of spores. These fruiting bodies appear on the surface of the mulch,
but are barely noticeable unless you are looking for them closely.
Areas of mulch with artillery fungi may appear matted and lighter in
color than mulch that has not been colonized. Bird’s nest fungus is
also commonly found in mulch, but is much larger and more
noticeable. It does not shoot a sticky spore mass as artillery
Tar-like spores of artillery fungus
orients itself toward bright objects, such as light-colored siding,
windows or shiny automobiles parked nearby. The fungi eject the
sticky spore mass, which can be blown by the wind as high as the
second story of a house. As you have discovered, the spore mass is
difficult to remove without damaging the surface. It is likely to
stain, even if you remove it successfully.
is being done on this problem, there are no known controls for
artillery fungus. There is nothing you can spray on mulch beds to
prevent the growth of artillery fungus, nor can researchers state
unequivocally that certain species of wood are absolutely resistant.
Dr. Donald Davis of Penn State University has observed that wood
based mulches are more likely to be colonized by artillery fungi
than bark based mulches, possibly because of bark’s higher lignin
Research done at
Penn State found that large pine bark nuggets were the most
resistant to colonization by artillery fungus. It also found that
artillery fungus was unable to produce spores on cocoa, cypress and
licorice root mulch under the conditions used to conduct the
experiments. It was also unable to colonize or produce spores on one
hundred percent sewage or yard waste compost, or spent mushroom
compost. Although dyed wood resisted colonization initially, the
artillery fungus did successfully colonize it once it had begun to
weather and break down.
Actual size of an artillery fungus spore
At this point, the
only surefire solution is to replace wood mulch with river rock or
other stone-based mulches in areas that abut houses and parking
areas. However, stone-based mulches do not provide the same benefits
to plants that wood mulches offer, such as adding organic matter to
the soil as they break down, and increasing soil microbial activity.
There is evidence that mixing wood mulch with 40 percent spent
mushroom substrate (also known as mushroom mulch or mushroom
compost) helps suppress artillery fungus spore production.
Research at Penn
State also looked at cleaning products to help remove the spores
from aluminum and vinyl siding. While some were more helpful than
others, one hundred percent removal required substantial effort and
possible damage to siding. Bleech-White, Castrol Super Clean and
Purple Muscle proved most effective on vinyl siding in her
experiments. Foaming Wheel Cleaner and Planet Solutions were most
effective on aluminum siding.
ON ARTILLERY FUNGUS
While there are no
simple answers at present, research on this problem is continuing.
Americans use millions of tons of mulch around landscape plantings
annually. Despite the problem with artillery fungus, the benefit to
the plants of properly applied organic mulches outweighs the
negative. One of the reasons that artillery fungus is so frustrating
is that it is part of the natural decomposition process that makes
organic mulches so beneficial to plant health in the first place. Of
course, no one minds when artillery fungus shoots its spores in the
woods as it breaks a fallen tree down into nutrients that nurture
germinating wildflower seeds and young saplings. It is just doing