Fungi Wars: The Phantom (Mulch) Menace

The old saw about the price of freedom being eternal vigilance was recently proved again, this time quite close to home. As mentioned in my last post, the presence of the late, unlamented Killer Viburnum had been effectively distracting my attention from the depredations of a tiny but powerful menace literally underfoot.

Remember back in May 2015 when I was embroiled in the Mulch Madness of my first full year at the Money Pit/Temporary Garden? Specifically the eight yards of triple-shredded bark mulch, a fair portion of which was installed in the front planting bed between the front walkway and adjacent house/porch/garage. The K.V. was located at the outer end of this bed, abutting the driveway and garage as well.

With the K.V. now gone, the white painted cedar shingles on the house are in full view with no distractions. As I stood there musing upon likely new-siding colors (I strongly favor whatever shade of brown most closely approximates dirt, by the way; visual weight be damned, what I want nowadays is low maintenance) I noticed what appeared to be tiny black polka-dots on the white shakes.

There certainly were an awful lot of them. At first I thought they were pinholes and immediately began thinking about wood destroying insects – but no, they looked more like perfectly round tiny drops of black paint. But that was impossible, as there was not, nor ever had been, any black paint in sight.

They were also adorning the adjacent white aluminum gutter downspout.

I then looked upward and saw a veritable galaxy of spots on the underside of the small roof above the garage door as well! (The larger circles are the soffit vents; the smaller ones are the mystery dots.)

Naturally the roof braces hadn’t been spared either.

Of course my garage door is white. Or had been, that is. Now it’s black-dots-on-white.  A horrible thought struck me: Owing to the garage configuration, my car must live 24/7 in the driveway. I normally park it at least five feet away from the door, but you don’t suppose……?

Apparantly five or six feet away isn’t enough. This is the lefthand section of my hood (bonnet, for my UK friends).

I grabbed my trusty bottle of Windex and a couple of paper towels, and sprayed part of the garage door. And the downspout. No effect. Didn’t work on the car either. Then I turned to the aptly named “Awesome Cleaner” which has been known to return even the slimiest algae-covered white vinyl fencing to blinding white brightness in only a couple of sprays.

The polkadots laughed at it.  What was this evil, spotifying invader that refused to be dislodged?

Turns out that they are the spores of the Sphaerobolus fungus, commonly called “artillery fungus” because they blast out and can travel as much as 20 feet (6 m) from their source in – you guessed it – wood mulch. Any kind of wood mulch. All kinds of wood mulch. Including, obviously, mine. It is a “wood decaying” fungus, and  I had actually introduced this phantom menace myself, by mulching near the house. 😦

I did wonder if the spores had come from the mysterious Alien Fungus From the Planet Zork (prior encounters related here and here) but no: The artillery fungus ‘cups’ are extremely small, only about 1/10 of an inch, or about 2.5 millimeters in diameter. But despite being so tiny, their effect is powerful.

Further googling revealed that phrases such as “its adhesion properties are legendary”, “difficult or impossible to remove”, and “no effective fungicide” occur with depressing regularity. One of the best sites is an excellent Q and A page by Dr. Donald Davis of Penn State University. This is truly the ultimate in “everything you could possibly need to know about artillery fungus but wish you’d never had to read” informational sources.  Among other things, Dr. Davis informs us that:

In nature, the artillery fungus shoots its spores towards sunlight to aid in dispersal. In the absence of direct sunlight, it shoots the spores at highly reflective surfaces, such as white house siding.

The spore masses of the artillery fungus stick like super-glue. We have not found an efficient way to get them off without leaving a stain on the siding, especially on old dry siding. Power washing may work on brand new (only) vinyl siding that still has a shiny, oily sheen. However, even power washing usually fails. Each [miniscule] 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.

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. Or spore masses may already be present at a site on old mulch, previously infested plant leaves, rabbit or deer droppings, decaying leaves, and grass. These existing spores may immediately infest new applications of mulch….Spores may also be brought to the site on infested nursery plants, by being stuck to the undersurface of leaves, if the nursery also had an artillery fungus problem. When the leaves fall off onto the mulch… here we go again! 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. Under moist conditions, they germinate and reinfest the mulch.

Question 23 asks whether homeowners insurance would pay for replacing siding that has been cosmetically ruined by artillery fungus spores. The answer: 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.

So if fungicides don’t work, and cleaners etc don’t work (at least not without ruining the surfaces) what’s the answer? Dr. Davis to the rescue again:

Take out all of the infested mulch (usually just around the foundation – not out in the yard), bag it in a biodegradable bag, and take it to a landfill. Then put down a layer of landscape cloth or black plastic, and overlay it with stone or an artificial (non-organic) mulch.

Which is what will become one of my first garden projects in the spring. Once it’s all gone (and my lower back, no doubt, permanently broken because the only “safe” way will be to scoop every bit of mulch up with disposable-gloved hands and deposit it directly into black plastic trash bags) I will put down landscape fabric and Timberlite (volcanic rock) mulch. At least that will match the brick walkway, more or less.

I can’t afford to replace the now-spotty white garage door, so will have to experiment with trying to carefully scrape all the spores off. I figure it should take about two years… optimistically! At least the mini-roof, its underside, and the attendant downspout are now gone, having been removed as part of the roof replacement last week. And the wood siding will be replaced in late spring or early summer.  Obviously all of the mulch needs to be gone, and the Timberlite installed, before then!

As for my car, it is already 15 years old and I was planning to replace it in the late summer or fall of this coming year (2018) anyhow. I was originally planning to get the same color (pale gold) but now I am seriously considering something much darker,  in case the Phantom Mulch Menace ever returns. Needless to say, this has been the first and LAST time that I will ever put any kind of wood mulch anywhere near my house. A tough lesson but one now taken completely to heart!

MARCH 2018 UPDATE: I’ve been asked whether artillery fungus occurs in coir mulch; that’s a very good question! Coir is coconut fiber, not wood, and so theoretically it should not harbor a wood fungus but it is still cellulose which is a property that both wood and coir share and which any fungus can feed upon as it decomposes. Coir has a low/slow decomposition rate but it still does decompose, which is what the artillery fungus establishes itself in. Only mulches that do not decompose at all (gravel, stone, volcanic rock, even – ugh – recycled rubber) are fungus-safe.

(Dr. Davis’ page concludes with a list of 72 spore-removal attempts that have been reported to him as successful, with the caveat that Penn State did not replicate the methods and thus he is merely reporting, rather than recommending. I can personally vouch for the fact that the Windex method touted by one writer did not work at all, on my surfaces at least.)

  6 comments for “Fungi Wars: The Phantom (Mulch) Menace

  1. December 28, 2017 at 11:41 pm

    My goodness. How bizarre. Sorry to hear about its impact.

  2. December 29, 2017 at 3:52 am

    Wow, you really are in a sci-fi film.

  3. Adine
    December 29, 2017 at 5:41 pm

    I live in northern California (San Joaquin County……one of the most productive agricultural counties in USA). One of the main ground covers around houses, buildings and public landscapes is bark mulch. Lots of it. It is considered not only decorative but used for water conservation.

    We have an extremely well known and respected agricultural university: University of California in Davis, CA. It is “justly famous for its outstanding programs in the biological and agricultural sciences.” I would contact them through their website, if possible. They could either help you or give you a suggestion where to go for help.

    Good luck.

    • December 30, 2017 at 10:44 am

      UC Davis is indeed a very fine institution. 🙂 Though I have to say that Penn State and Cornell University are just as good when it comes to “bio/aggie” studies, and they all agree on the fact that removing artillery fungus spores is basically impossible without damaging whatever they’ve landed on. And that there’s no way to kill it in wood mulch, or to avoid it other than not using a wood mulch at all. One of Mother Nature’s cruel jokes, clearly. 😉

      I should have included a link to an excellent PDF that is on the state of Connecticut’s Cooperative Extension Service website, that has photos of the artillery fungus in all its stages of development. A new info-bit in this PDF is that the spores can remain viable for as much as 10 or 12 years! So if they are scraped off a surface (even glass) and happen to fall into a moist location, even a 10-year-old “dot” can re-animate and create a brand new fruiting body that will in turn produce live spores. Sounds like fodder for a sci-fi/horror movie, doesn’t it?!

      Click to access sphaerobolus_spp_-_the_artillery_fungus_05-03-10r.pdf

  4. December 30, 2017 at 5:36 am


  5. January 4, 2018 at 9:52 am

    Oh dear! Sounds like a tricky adversary. Sometimes it seems that you just can’t win.

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