These are typical, frequently asked questions (FAQ) that I normally
field during the spring and summer (very seldom in the winter) -- along
with a brief summary of typical answers. Answers are meant to be
(hopefully) informative, not very technical, and are not meant to offer
concrete solutions. The questions are generally in the order that they
are asked…
Q: We have these small, black spots that look like specks of
tar, all over our white, vinyl siding on our house. It’s on the
porch, my windows, but it is worse on the siding. It goes all the way
up to my second-story windows, and is even under my soffitt and on my
gutters. What do you think it is?
A: Sound like you have the infamous “artillery fungus”.
Click here to see what the spores
of the artillery fungus looks like on house siding.
Q: I think I've seen some spots on my car. Does the artillery
fungus also get on cars?
A: Yes, this is common on the sides of automobiles when cars are parked
near mulched areas that are infested with the artillery fungus. It is
especially noticeable on white sports cars – at least these are
the owners that complain the most.
In fact, we have had complaints where private companies
have artillery spores on 50-100 cars in their parking lots. The next
question asked is, “How do we remove the spots from the sides of
cars?” We don't know, but some suggestions have included: power
washing if the artillery fungus spots are very new and paint/wax on the
cars is also new and shiny; automotive-paint rubbing compounds; and
removal (if there are only a few spots) with the edge of a credit card.
However, you must be very careful not to damage the car's finish. See
some car owners' attempts at removing the spots from cars at the end of this
section. These are NOT recommendations!!!
Q: Does the artillery fungus hurt pets?
A: Not a problem.
Q: So, what exactly is the artillery fungus?
A: The artillery fungus is a white-rotting, wood-decay fungus that
likes to live on moist landscape mulch. It is in the genus
Sphaerobolus (Greek for “sphere thrower”) and is very
common across the USA, especially in the East, as well as many other
parts of the world. The most common species in Pennsylvania seems to be S. iowensis (contrary to previous reports – including our
own). The artillery fungus is technically a
“Basidiomycete” fungus (like the common mushroom
that we eat), and probably is most closely related to a group of fungi
called “earth
stars”. However, the artillery fungus is much smaller that the
earth star that you may see occasionally growing in your yard. There may be other fungi and fungi-like organisms
growing in your mulch.
Q: I can’t see it in the mulch – just how big is the
artillery fungus? Is it the same as those little cups called the
“bird’s nest fungus”?
A: The artillery fungus is quite small – the fruiting bodies are
about 1/10 of an inch across and are very hard to see in the mulch.
They are much smaller than the “bird’s
nest fungus” with which are oftenconfused. By the way, the
bird’s nest fungus does not actively shoot its spores – those
little “eggs” of the bird’s nest fungus are splashed
out when a drop of rain hits the cup.
Q: Why is it called the “artillery” fungus? Is it
also called the “shotgun fungus”?
A: The term artillery refers to the fact that the artillery
fungus actively (uses energy) shoots its spore masses, sort of like a
cannon or howitzer (an artillery piece). We will call these
“spores,” although they are actually spore masses, or gleba.
The spores are usually shot only a short
distance, several feet, but the wind can carry them for longer distances, even up to the second story of a house.
The term “shotgun fungus” usually refers to Pilobolus, a different kind of fungus that is common on
fresh horse dung.
Q: Why do light-colored houses and cars have more
problems than darker cars and houses?
A: In nature, the artillery fungus shoots its spores towards the light.
In the absence of direct sunlight, it shoots the spores at highly
reflective surfaces, such as white house siding. And, of course, the
black spots show up better on white surfaces, so they are noticed
more easily.
Q: The artillery fungus problem seems to be much more severe now, than in the good old days. I don’t remember this being a
problem 20 - 25 years ago. Why is it now a problem?
A: 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, 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 probably hold more moisture than the older coarsely ground
mulches – this favors fungi, because they need moisture to survive!
Q: Why is this problem more severe in some years than in
others?
A: 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.
Q: The number of spots seems to be worse on the north side of
my house. Is this just my imagination?
A: It is not your imagination, and you are a good observer. The
artillery fungus often grows better in the mulch on the cool, shady side of
the house (usually the north side of the house here in the Northeast)
where growing conditions are more suitable for the fungus.
Q: Are those spots alive? Will they hurt my house, like eat holes in
my siding?
A: Yes, they’re alive, but not in the sense that they can hurt
your siding. They are dormant, or sleeping, and pose no threat to the
siding other than staining it.
Q: So, how do I get the artillery fungus off my house siding?
Will any cleaning chemicals remove it? Power washing? How about just
plain scraping? Do the spores stick to all kinds of siding?
A: The spore masses of the artillery fungus stick like super-glue. We
have not found a way to get them off without leaving a stain or damaging
the siding, especially on old dry siding. Power washing may work
on brand new (only) vinyl siding that still has a shiny, oily,
sheen.
Each spore mass can be physically scraped, “steel-wooled”,
or sanded off. Then the stain might be removed with an ink eraser, but
this is a pain, literally.
Beware of any cleansers that have claims that sound “too good to
be true”, with regards to removing the artillery fungus. It is
likely that they are, in fact, too good to be true. At the end of this
section I have listed some attempts that readers have used to remove artillery fungus.
Q: How did the artillery fungus get in my mulch? My neighbors
don’t have it – only me! Why me!
A: This is extremely difficult to answer. The artillery fungus commonly
occurs on dead trees, dead branches, rotting wood, etc. throughout the
Northeast. I have seen it in the forest on standing dead trees and limbs on the
ground, as well on wood in mulch-producing yards. If infested material
is used for mulch, the artillery fungus may be already in the mulch when
the load of mulch arrives at a job site, and may then grow rapidly along
your foundation during cool moist conditions. However, this is likely a problem only when mulch is not composted.
Or spore masses may already be present at a site on old mulch,
previously infested plant leaves,
rabbit or deer dropppings, decaying leaves, and grass. These existing spores may immediately infest new applications of
mulch. In some cases, the spores also may be transported for very short
distances via wind from adjacent infested sources. Spores may also be brought to the site on infested nursery
plants, by clinging to the undersurface of leaves, if the nursery also
had an artillery fungus problem. When the leaves fall off onto the
mulch the attached spores inoculate the mulch… here we go again!
People can also spread the artillery fungus in various ways. Some
homeowners make the mistake of sanding, scraping, or otherwise removing
the spore masses from the sides of their houses, and letting them fall
onto their foundation mulch. Such spores are dormant, but very much
alive, germinate and infest the mulch.
Q: You mean that the artillery fungus can come in on plants and
shrubbery that I am planting along my foundation?
A: Yes, this is possible, but only if the nursery had an artillery fungus problem in its
pots or beds. But, this does not appear to be very common in my
experience.
Q: In your studies, have you found any wood/bark mulches that the
artillery fungus absolutely will NOT grow on?
A: No. All mulches that we studied eventually supported the artillery
fungus after being outside for several years. However, some mulch
performed better than others.
Q: So what mulch(es) appear to be best?
A: We tested 27 mulches in the field, and found that some supported more
artillery fungus than others. In one study, the most resistant
mulch was large pine bark nuggets. The large bark nuggets
stay hard and dry, conditions that the artillery fungus does not like. Cypress mulch also performed well, as it probably contains some anti-fungal, anti-decay
chemical(s). However, there may be some environmental reasons for not using cypress.
Click here for an article
from the Journal of Enviromental Horticulture entitled
“Artillery Fungus Sporulation on 27 Different Mulches- A Field
Study.”
Q: I have heard that used "mushroom compost" will suppress the
artillery fungus. Will it?
A: Used mushroom compost, also known as "mushroom soil," "spent
mushroom substrate (SMS)," and even "black gold" is a great product, if
you live in an area where you can get it! Mushroom compost has many
beneficial aspects for gardeners, one which is that it supoorts
micro-organisms that inhibit many unwanted pest fungi. Mushroom compost is pasteurized before it is used to grow mushrooms, and then the used compost is pasteurized again when it leaves the mushroom house, so it should not contain weed seeds. Our research at Penn
State has shown that blending used mushroom compost with a landscape
mulch at about 40 % will greatly suppress artillery fungus sporulation. Very "green" and environmentally friendly.
Click here for an article
from the Journal of Environmental Horitculture entitled
“Use of Mushroom Compost to Suppress Artillery Fungus.”
Q: How about artificially colored mulches?
A: We have tested mulches of various colors, as well as the chemicals
themselves that are used to color the mulches. The chemicals in our tests,
at the concentrations used, did not inhibit the artillery fungus.
Colored mulches appeared to very slightly, but only
temporarily, inhibit the artillery fungus. We attribute this to
the colored mulches being slightly more water repellent and therefore
remain drier than the non-colored mulches, at least at first. As the
colors faded due to rain and sunlight, the artillery fungus moved right
in.
Q: Should I put down new mulch each year?
A: Interestingly, homeowners that put down new mulch each year generally
have less of the artillery fungus problem. But, we have not confirmed
this practice. But it does seem to work, if you don't miss a year!
Q: How about composted mulch? Is it better or worse?
A: You really need to ask this question to a compost expert, but most good mulch today is composted to some degree. However,
I would insist on a thoroughly composted mulch.
Q: What if I just paint over the spores on my wood
siding?
A: That will probably seal them in. It may solve your problem, but will
give a pebbly appearance to your paint job. Each repainting will
seal in the artillery fungus even more.
Q: Are there any registered fungicides that will kill the
artillery fungus? How about a weak solution of household
bleach?
A: There are no fungicides labelled for use against the artillery
fungus in landscape mulch. Bleach, if it worked, would be very temporary, since it leaches
out with each rain. We have tested many different fungicides in the
laboratory, but have to take the experiment to the field. Click here for an article from the
Journal of Environmental Horitculture entitled “In vitro screening of fungicides to control artillery fungi.”
Q: I can’t get those black spores off my siding, without
leaving a lot of small brown stains. My siding is ruined. Will my homeowner’s insurance pay for residing my house?
A: Some insurance companies will and others won’t. It depends on
your insurance company, your agent, the exemptions in your policy, and
especially your lawyer.
Q: I just checked my policy. My homeowner’s policy states
that it does not cover (that is, there is an exemption)
“molds”. Is the artillery fungus a mold?
A: This is another difficult question, and one that lawyers like to
argue. Mold is generally thought of as being a superficial, fuzzy fungus
growing on damp or decaying organic matter. Like that fuzzy stuff on old
“moldy” bread or on an old orange. The artillery fungus
does exhibit such growth during part of its life cycle, when living in
damp mulch, and therefore is (at least at times) a “mold” during part of its
life cycle.
Q: What is a biological definition of a mold?
A: Biologically, the term "mold" has been used to generally describe a
lot of different organisms such as slime molds, sooty mold, pink mold,
blue mold on cheese, water molds, etc. These terms may be found in most
modern, scientific textbooks or dictionaries dealing with
“Mycology” (the study of fungi). This general biological
usage makes the term mold very inclusive; under such a general
usage, therefore, molds include many types of organisms, such
as the artillery fungus, at least during part of its life cycle.
Q: But the actual spores stuck to the side of my house are not
molds, are they? If not, then does my insurance policy include
them?
A: The spores on the side of your house are the reproductive structures
of the fungus (although not biologically correct, think
“seeds”). A good analogy is that they are shot like bullets
from a gun. Just as the “bullets” are not the same as the
“gun”, the “spore masses” on your house are not
the same as a “mold”. Lawyers can put whatever spin they
want on such terminology. And they do.
Q: Can you recommend a good lawyer who can solve my artillery fungus
problem?
A: No.
Q: But, this is America! Who can I sue? Who is responsible? Is the
contractor that applied the mulch responsible? Is the person who made
the mulch responsible? Is the store that sold me the mulch
responsible?
A: Since the artillery fungus can enter the chain of events at various
places, I don’t see how anyone can be held responsible, unless
they willingly supplied mulch with known artillery fungus in it. Which,
of course, no good businessman would do! In my opinion, it is nearly impossible to prove where the artillery fungus entered the chain of events. This again is a subject for
the lawyers.
Q: So, what is the final, ultimate solution to my problem???
A: Take out all of the infested mulch (usually just around the
foundation - not out in the yard), bag it in a biodegradble bag, and take it to a landfill.
Then put down a layer of black plastic, and overlay it with stone or artificial (non-organic) mulch.
Q: But, I don’t like stone - it’s so cold! I want to
stay organic, and, like, use, like some sort of wood/bark mulch. Yet I
can’t stand the artillery fungus. It’s driving me bonkers.
What should I do?? I’m at my wit’s end.
A: Well, then, you have to learn to live with the problem. That is, you
cannot beat the artillery fungus (at this time), so manage it. Use
mulches that the artillery fungus doesn’t like, such as
large pine bark nuggets. Then, put down a fresh layer of
mulch each year – we have no evidence for this, but yearly
applications of layers of mulch seem to inhibit the artillery fungus.
Another possiblity, but one we haven not investigated, is to use ground
cover such as ivy, periwinkle, or pachysandra in place of the
mulch around your foundation. It seems likely that the artillery
fungus would not grow well under the canopy (on the fallen dead leaves)
of such ground-cover plants. Or, establish lawn right up to your
foundation. An artifical mulch made of plastic, old tires, etc. should
work, but we have not tested it.
Q: OK, I am going to remove my old, infested mulch. But, what do I
do with it?
A: The best thing to do is probably bag it in a biodegradable bag and take it to a
landfill. At least the mulch is organic and will rot away. Make sure you
don’t put the infested mulch somewhere where you could be held
responsible for someone else’s artillery fungus problem. This is
out of my field, but it has been suggested that the infested mulch could
be put in a yard waste-composting facility. But you really need to ask
this question to a “compost expert.”
Q: Do you ever get suggestions regarding removal of the spores from
surfaces like cars or houses, and have you ever tried any of them?
A: Yes, I have received many suggestions regarding removal of spores from cars or houses. I have not tried any of them. No, I have listed a few suggestions from readers below, but I emphasize that these have not been tested are not my recommendations.
Note that most
involve abrasives, and a lot of "elbow grease", especially if the spots
have been on the surface for some time! So, one is really just scraping
off the spots, which may land back in the mulch.... Having said that,
please let me know if any of these actually do work! Again, these are not my recommendations.
Reader's Suggestions For Removal From Cars
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