Artillery fungus on siding

How to Remove Black Spots on Vinyl Siding

Question: I have black spots all over my vinyl siding—thousands of them, about the size of a ballpoint pen tip. They are hard, and when you pick them off, they leave a small brown stain. They are even as high up as my gutters. It seems they are only on the siding above my mulch beds. I have heard that the mulch can spit its coloring out and also that it could be mold from the mulch. I have tried house and siding cleaner and a pressure washer, to no avail. I also tried Krud Kutter and a Scotch-Brite sponge, which works, but it would take five years to clean the siding that way. What are these spots and what can I use to remove them?

Answer: The black tar-like spots that are all over your vinyl siding are more than likely a fungus called Sphaerobolus stellatus, better known as artillery, or shotgun fungus. Although it’s most often found on the east coast, it can grow anywhere and especially thrives in areas that have cool, damp Springs, or rainy Fall weather conditions.

As for where it grows or how it found your siding, artillery fungus is a notorious wood-dwelling fungus that’s usually found growing in wood-based mulches, especially those that are a combination of bark and hardwood. This may be where it’s stemming from in your yard as you mention that the fungus seems to be limited to growing on the siding closest to your mulch beds. This fungus can grow on multiple surfaces including wood siding, fences, decks, and cars.

Artillery fungus is difficult to get rid of because of its sticky properties. That’s why, if it’s at all possible, it’s best to wash the fungus away when the spores have freshly landed, which is normally when the weather is cool and damp and the temperatures are between 50 and 68 degrees Fahrenheit.

How to Remove Artillery Fungus

There are a lot of “magical’ remedies you will discover online, including specialty soaps and anti-fungal treatments, that claim they’ll get rid of this type of fungus just by being sprayed onto the siding. According to the leading horticulturists that study artillery fungus every day, these kinds of statements are not true. What it really comes down to elbow grease. Anything safe for your siding can be used to help loosen it up a bit, but it truly comes down to scrubbing by hand to get it all off.

That being said, what we can do other than tell you to keep doing what you’re doing, is to offer you some suggestions that others say have worked for them in the past.

Most Common Recommendations for Removal

One thing almost every suggestion included was to keep the surface wet while you cleaned it. Use a scraper or putty knife to remove the fungus before trying to scrub it, and then once you’ve picked a cleaner, allow it soak into the surface from a few minutes, up to a few hours before you begin trying to scrub it away. No matter which you try, should you try any, just be sure that you test it first by trying it in a place on the siding that won’t matter should it be discolored, as it likely will with most of these recommendations.

Bleach – The most common trial and error method in removing artillery fungus is bleach, however, it doesn’t always work and seems to be a temporary solution. Also, it still requires a lot of scrubbing. Keep in mind that it might also bleach the paint on the siding. Do a test spot somewhere inconspicuous.

Peroxide – Hydrogen peroxide has also been said to work, especially at higher strengths. Apply it, allow it to bubble, and then brush it off with a wet scrub brush or sponge.

Mouthwash – Mouthwash is something many swear by for cleaning artillery fungus off of vinyl siding, especially mint-laced varieties. As with bleach, saturate the area with the mouthwash and allow it to penetrate before scrubbing it off. Others have tried a combination of bleach and mouthwash; just be careful mixing any chemicals together.

Melamine Foam – Better known as the Mr. Clean Magic Eraser, melamine foam pads work best after the area is sprayed with one of the cleaners above and allowed to soak into the siding for a few hours. Then, scrub with the pad to erase the remaining spores. This method may be expensive depending on the size of the space you’re working on, since Magic Erasers tend to fall apart rather quickly. Note that the bleach seems to get rid of the actual fungus, while the Magic Eraser removes the stain left behind by it.

How to Prevent Artillery Fungus

To prevent the regrowth of fungi on your siding once you remove what’s already there, you will need to use mulches that are non-wood based. If the mulch is being used purely for landscaping and visual appeal, some alternatives include stone products like pea gravel, lava rock, or crushed stone.

Using compost with no wood in it is also a good alternative. Studies have shown that the Artillery fungus spoors did not grow when only compost was used.

If you wish to keep the wood-based mulch, you can try to keep the fungus at bay by adding a layer of fungus-resistant mulch such as cypress or cedar nuggets to keep the fungus from spreading. Raking the mulch often during the moist months to expose the fungi to the dry air can keep the spores from spreading.

Keep in mind that fungus-resistant mulch is a bit of a misnomer because, although they’re labeled as such, these are not completely anti-fungal and will not prevent fungal growth entirely. Using wood mulch will always carry a high risk of having artillery fungus.

Getting rid of the fungus is possible, but it’s not going to be easy. Find a good cleaner that works for you and begin scrubbing. Or, better yet, hire someone to do the scrubbing for you.

Artillery Fungus Treatment – How To Get Rid Of Artillery Fungus

You may have seen artillery fungus (Sphaerobolus stellatus) and not even know it. The fungus resembles scaly dirt or mud spots and is found on light colored housing, cars and exterior surfaces. It is also found in manure and bark mulches. The name is derived from the Greek for “spear thrower” because of its ability to propel spores at quite some distance. Learn how to get rid of artillery fungus and what you can do to prevent the spotting on your property.

What is Artillery Fungus?

Those annoying black spots that creep up your siding or splash along the side of your car may not be mud spatters but artillery fungus. What is artillery fungus? It is Sphaerobolus, a common fungus that sticks firmly to light or white colored surfaces and resembles spots of tar. Its adhesion properties are legendary and the spots can be difficult or even impossible to remove without damaging the surface.

This common fungus is often found in bark mulch, especially hardwood mulch, too. There is some suggestion that artillery fungus in mulch

such as cedar and pine bark nuggets may occur less frequently than hardwood. It is most prevalent on the north side of a building and shoots spores towards bright light.

This fungus produces a cup-shaped peridiole which contains fruiting bodies. When the cup fills with water, it inverts and shoots out the fruiting bodies. These are most obvious when attached to a light colored surface, such as white housing siding. Once they attach, the fungus is very difficult to get off. Is artillery fungus harmful? It does no real damage to surfaces and is not a toxic mold. It is, however, unsightly and difficult to remove.

What Causes Artillery Fungus?

The best conditions for the formation of the spores are cool, moist and shady conditions. This is why the spores are more noticeable on the north side of a house. They are more prevalent on light colored structures because the peridiole shoots the fruiting bodies towards light and light reflects best off of these lighter surfaces.

It is recommended that old mulch is raked to expose the spores to light and dry out the material, or 3 inches of new mulch added over the old to suffocate the spores of artillery fungus in mulch.

How to Get Rid of Artillery Fungus

There is no recommended artillery fungus treatment. If the spores are fresh, sometimes soap and water with a scrub brush will remove a bit of the fungus. You can power wash them off of vinyl siding but such methods can be damaging to cars and wood siding.

There is no fungicide registered as an artillery fungus treatment. There is research to suggest that blending mushroom compost at a rate of 40% with landscape mulch can suppress the spores. Also, the use of gravel or plastic mulch will not cause the formation of the spores. To kill the spores in lighter areas, cover the zone with black plastic and allow the sun to cook the spores out of the bark.

Mystery solved: Blame mulch for brown fungi spots

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A scientist says she has cracked the mystery of the strange spotty brown substance Bergen County residents have been finding on their vehicles and reporting to the Bergen County Health Department.

The problem likely rests in the common mulch you use in your garden beds, said Dr. Ann Herriott, a retired horticulturist who worked at Cornell Cooperative Extension’s Diagnostic Lab 25 years ago. It’s “artillery” fungus, she said.

In Carlstadt on Aug. 14, mysterious small brown droplets appeared on cars parked on Washington, Union and Madison streets, and were also reported in Wood-Ridge. The county health department came and took samples. Those test results were inconclusive, according to county officials.

Carlstadt officials have blamed the hard-to-remove spots on everything from the nearby Teterboro airplane traffic to the honeybees that are being kept by a Carlstadt beekeeper.

Those two theories have been debunked. Federal Aviation Administration officials said aircraft equipped with an on-board lavatory can’t discharge wastewater in flight. As for the honey bees leaving behind a substance, it wouldn’t be so hard to remove the droplets and less in volume.

Which is when Dr. Herriott stepped in to give her scientific two-cents.

Artillery fungus develops in the wood mulch commonly used in flower beds. It rests, that is, until it bursts. It is named due to the way it shoots up into the air before attaching to a nearby surface. The fungus is also known as “Mother Nature’s super glue” because it is extremely difficult to remove, according to Herriott.

“We puzzled over the same brown spots and found they were caused by spores of the artillery fungus that grows in wood mulch especially during wet years,” said Herriott. “The cells fill up, invert and burst, propelling the spores as high as six meters. Spores are shot at nearby objects. It’s a nuisance to remove the spores.”

The same conclusion was reached when the phenomenon happened 20 years ago in Englewood. The strange brown substance began appearing on vehicles parked in the Grand Avenue lot at the Patriot Center office complex, said executive assistant Lois Rusch, who worked for 21st Century McDonalds.

“After much detective work and great expense to the company having to pay for the cars’ detailing, a horticulturist determined these were mold spores being thrown through the air from the mulch beds surrounding the parking lot,” Rusch said.

Once the beds were treated, the spore issue disappeared, Rusch said, adding that she has encountered the problem at home as well, on a white vinyl fence. “The only thing I ever found to work is Mr. Clean sponges, after scraping the worst off.”

A Google search reveals the problem of mulch spores is widespread, with advice on how to remove the stubborn spots that adhere not only to cars, but siding and fences as well.

Midland Park residents Elizabeth and Jim Hyatt have been struggling to remove the spots on their vehicle and home for years but found Blue Corral car wash helps loosen the spots.

Trying to solve the mystery for two years, Hasbrouck Heights resident Nick Di Iorio said the problem has been costly. “I have to wash my car at least once a week. The stains at times can be so deep that I would have to compound and polish the car,” he said.

According to Economy Exterminators there is no fungicide registered at this time to control artillery fungus.The best way to manage the problem is to remove the old mulch and replace with pine bark nugget mulch, or use some synthetic mulches, such as shredded rubber or artificial pine needles. When replacing old mulch, always place it in a biodegradable bag and take it to a landfill.

Email: [email protected]

Getting Rid of Artillery Fungus

Here is what the spores look like on the vinyl siding:

Here is a photo of what the actual fungus that produces the black spores:

The artillery fungus, or shotgun fungus, is a wood-decay fungus that likes to live on moist landscape mulch. The worst thing about this fungus is that it shoots spores up to 20 feet, which often land on siding, cars and anything else that surrounds the mulch. It seems to have become a serious problem this year for many homeowners here in Western Massachusetts. This year we’ve had a lot of customers come in with this problem and ask for mulch recommendations. Unfortunately no natural mulch can resist the artillery fungus – Penn State Plant Pathology department has tested 27 different kinds of mulch and found that with enough time all of the mulches were supporting the evil spore-shooting mushroom. The only way to ensure that artillery fungus never comes back is to take out the mulch completely and replace it with stone, artificial mulch or ground-cover plants. However, if you dislike stone and still want to replace the fungus infested mulch with organic mulch, the best way to keep the shotgun fungus away is to use a course ground of wood chips ( our playground chips would do ). The larger pieces of wood will stay mostly dry and the artillery fungus won’t like it as much as moist, finely ground mulch. Generally, the key to preventing the artillery spores from ever sprouting is refreshing your mulch regularly.

As far as getting rid of the spores on your siding – that’s not a fun job. The most important part is to get them quick, as they are covered in sticky substance that will stay on the siding for good if not taken care of in a timely fashion. New vinyl siding that still has an oily residue on it can be power-washed within the first week. In other cases power-washing will be fruitless. Scraping the spores off one-by-one with a scraper or steel wool is tedious but effective. After that there will still be a stain left, which can be taken care of with an ink eraser or possibly bleach. Bleach, Simple Green, toothpaste and alcohol-based mouthwash have been known to work with various rates of success, and can be tried first before attacking the spores with a scraper. For removing spores off of cars oil, vinegar, car wax and tree sap remover have all worked for people that tested them.

The bottom line is that no organic mulch is completely safe from the artillery fungus. If you know that shotgun fungus has been attacking your neighborhood switching to stone in the areas surrounding the house would be the safest choice. If you simply can’t stand stone, then refreshing the mulch every year would be the second best thing to do.

UPDATE (October 2013)

We have done more research and talked to people that have had this problem about most effective ways of getting rid of the stains on the siding. As far as we know the most effective way of cleaning the black stains is to first break through the outer shell – by either scraping through each individual one with something sharp or by using mouthwash to soften the resin surrounding the spore (yes, it does sound strange). Once the outer shell formed by the resin is opened up, Mr. Clean Magic Eraser is said to do a fantastic job of cleaning up the black stains. This is incredibly time consuming and tedious work, but we have not yet found an easy way to make this problem go away. Best of luck!

  • Summer Gardening: Weed War 101 (thrivefarm.wordpress.com)

George WeigelUnsightly artillery fungus spores show up clearly on light-colored siding and cars.

Mulch lends a tailored, streamlined finish to a landscape, but spreading wood mulch too close to your dwelling or driveway might not be such a good idea, especially if your home or car has a pale exterior.

You could find yourself dealing with artillery fungus. The fungus, also known as “shotgun” fungus, thrives on moist, rotting wood mulch, and forcibly ejects tiny black spores that look like specks of tar toward light-colored surfaces, including siding and automobiles. Hence the nickname.

According to experts, removing the unsightly, sticky, stubborn spots, which don’t cause any structural damage, is extremely difficult and, in many cases, impossible.

“We run into it quite frequently,” says Scott Como of Como’s Ohio Pressure Wash Inc. in Willoughby (ohiopressurewash.net). “Last year we washed over 550 houses, and at least half had the fungus on them.”

What’s more, Como says, “There’s no way to tell if your mulch is affected until it starts spotting your house.”

Jim Grenwis, owner of Perfect Touch Painting & Powerwashing in Cleveland Heights, says he has been hired only once to clean artillery fungus from a home, but it was a tough job.

“I hadn’t even heard of it until then,” Grenwis says. “The spots had reached up to the second floor on some areas of the house.”

It’s not a given that wood mulch abutting your house will lead to a splattered exterior. There has to be a certain level of moisture before the fungus develops, says Jacqueline Kowalski, extension educator at Ohio State University’s Cuyahoga County Extension.

“It occurs mostly when we have a really wet spring and or winter,” Kowalski says. “This year it’s not so conducive to its growing.”

Kowalski suggests switching to an all-bark mulch before the problem develops.

Jim Weber owns Ohio Mulch (ohiomulch.com), which has several locations, including Wickliffe. He also says homeowners can play it safe by opting for an all-bark product, such as pine bark nuggets, which are breathable.

Donald D. Davis, a professor and plant pathologist at Penn State, has an extensive Q&A about artillery fungus at the website http://tinyurl.com/yd6mn2t. Among other tidbits, Davis assures that artillery fungus doesn’t hurt pets. He explains that light-colored houses and cars are more susceptible to the fungus because the spores shoot toward sunlight, and light-colored objects such as houses and cars are the next best thing.

Davis doesn’t believe artillery fungus is new, but there is a wider recognition and awareness because more homeowners are beautifying their gardens with wood mulch than in the past.

To remove old, infested mulch, Davis advises putting it in a biodegradable bag and taking it to a landfill.

“Make sure you don’t put the infested mulch somewhere where you could be held responsible for someone else’s artillery fungus problem,” he advises.

As for removal, power washing may work on new vinyl siding that still has a shiny, oil sheen. Each spore mass can be physically scraped, “steel-wooled” or sanded off, then the stain removed with an ink eraser, “but this is a pain,” he says.

Davis’ article lists more than 30 DIY removal suggestions offered by readers. One writes, “Each spring I take a plastic scraper and remove all the spots I can find, then wash the siding with Clorox Clean-up. It’s time consuming and a painstaking process, but I manage to remove 98 to 99 percent of the spots, with a thin outer circle usually remaining.”

In other words, good luck.

Another site worth checking out is tinyurl.com/cotxwkp by gardening blogger George Weigel. He says two brands that are often mentioned for artillery fungus removal are Jomax House Cleaner and Mildew Killer, and Simple Green.

How Can I Get Rid of the Black Spots on My Siding Near Mulch?

It sounds as though your mulch has developed “artillery” or “shotgun” fungus (Sphaerobolus stellatus). The black specks are spore masses of the fungus. Artillery fungus has the ability to “shoot” its spores at objects such as light-colored house siding, fences, or cars. The spores stick to most surfaces and are almost impossible to remove. This fungus develops in wood-based mulches under cool, moist conditions. Cypress, cedar, redwood, and pine bark mulch seem to be resistant to the fungus.

Penn State University has looked at cleaning products to remove the artillery fungus spores from siding. Complete removal requires substantial effort and possible damage to siding, so try these cleaners in an inconspicuous spot first. Westley’s Bleech-Wite tire cleaner and Castrol Super Clean were the most effective cleaners for vinyl siding; Turtle Wax Foaming Wheel Cleaner and Botanic Gold multiuse botanical soap were best on aluminum siding. You should be able to find these cleaners at automotive stores.

How to Clean Spots on Vinyl Siding

Vinyl siding is one of the most popular exterior coverings for homes. While this is partially because of its affordability, many homeowners opt for vinyl siding instead of brick or wood because it is relatively easily to maintain. Generally speaking, if you have a power washer or hose and a few household cleaning products, you can easily make your vinyl siding look as good as new year after year. Nevertheless, dirt, grime, and spots will inevitably appear on your siding from time to time. Here are a few useful top spot-cleaning tips we’ve discovered to help keep your vinyl siding looking its very best.

Table of Contents

  • General cleaning tips
  • Mold/mildew spots
  • Mulch/dirt spots
  • Safety precautions

General cleaning tips

Thankfully, regular maintenance of your vinyl siding is fairly straightforward and simple. A garden hose or pressure washer and a soft bristled brush will clear away cobwebs, dirt, and debris on most areas of your siding.

If you opt for a pressure washer, most professionals recommend using it on the lowest setting in order to prevent damage to the siding materials. It’s also a good idea to check with your siding manufacturer, since some experts advise against pressure washing siding. Finally, angle your pressure washer directly at the side of the house rather than in an upwards direction—angling can potentially push dirt and debris up behind the siding slats rather than down and off the wall.

Homeowners who like visual instructions for cleaning jobs will appreciate this vinyl siding cleaning video. In addition to demonstrating good practice for cleaning, it offers great tips such as switching your exterior power off, covering exterior outlets and lights, closing windows and doors, and laying down plastic sheets for protecting brickwork and plants or landscaping.

Mold/mildew spots

Over time and through repeated changes in weather, vinyl siding will attract and develop mold or mildew spots—especially in north-facing and other shaded areas. The Vinyl Siding Institute (yes, there really is such an organization) offers some helpful and specific tips for dealing with stubborn moldy spots on your siding.

Store bought cleaners such as Windex will usually do the job for these kinds of spots, but if you want to make your own chemical-free solution, you can use a natural mixture of vinegar and water. If neither of these options works, try making your own concoction from other commonly found household cleaners. This is what the professionals from the Vinyl Siding Institute and Bob Vila recommend:

1/3 cup powdered laundry detergent

2/3 cup powdered household cleaner

1 quart liquid laundry bleach

1 gallon of water

For best results, use a cloth or soft bristled brush and start from the bottom so your cleaning solution doesn’t leave streaks or just drip off the side of the house.

Mulch/dirt spots

If you notice lots of tiny black or dark brown spots developing on your siding above a landscaped area of your yard (as seen below), it is most likely artillery—otherwise known as shotgun—fungus. Artillery fungus is a wood-dwelling fungus commonly found in mulch.

Getting rid of artillery fungus is slightly more complicated than the basic cleaning regimen for vinyl siding and will require significantly more effort than a regular scrub down. Most experts recommend using a mixture of cleaning products (as above) and good old fashioned elbow grease. Check out this post ffor in-depth cleaning instructions and product recommendations.

If you want to prevent further artillery fungus growth, it’s best to choose non wood-based mulches, compost, or stone for your beds instead of standard wood chip.

Safety precautions

As with any household cleaning job, it is essential that you take proper safety precautions to protect yourself and your home before getting started.

If you choose to use store-bought products to clean your vinyl siding, make sure to read all instructions thoroughly and do a spot check on an unseen area of siding in case the product reacts with the surface.

After applying any cleaning product to your siding, it’s important that you rinse it away afterward. This will help prevent streaking and any residual product damaging your exterior or landscaping.

Do not use abrasives such as steel wool or Brillo pads or corrosive products like furniture polish, nail polish remover, or undiluted bleach to clean your siding, as they could potentially damage the plastic and the area around your siding.

Finally, remember that your own personal safety is important. Make sure that anyone who is around during your cleaning job is wearing goggles, gloves, and masks if the products you are using contain fumes. If you need to use a ladder for hard-to-reach areas, get a friend or family member to help you with your ladder if at all possible. Finally, keep children and pets well out of the way when you’re cleaning your siding.

Artillery Fungus Spots

Have you seen tiny black spots on house siding, cars or plants?
Small, shiny black spots that look like specks of tar are a moderately common occurrence in Iowa and the rest of the eastern U.S. Sometimes the spots are as high as 18 feet off the ground and attached to everything, though they show up best on light-colored house siding.
One cause of the shiny black spots is a fungus called Sphaerobolus spp. with the common name of artillery fungus. Artillery fungus is a wood-decay fungus common in moist wood-chip mulch. The fungus forms fungal bodies very similar to cup fungi such as the birds nest fungi (http://www.mushroomexpert.com/birdsnests.html ).
What makes this fungus fascinating and what gives it the common name artillery fungus, is its ability to “shoot” packs of spores as a dispersal mechanism. Black packs of spores that appear as discs (1 to 2 mm in diameter) are forcibly discharged into the air from the fungus on the wood chips.
The spore packets are ejected because of the buildup of liquid that causes the cupped cells to burst and propel the spores up to 18 feet into the air. The spore packs are projected toward the light and a sticky substance ensures attachment where they land.
Black spots on the leaves of plants may look like a disease, insects or their products (frass) but inspection of the mulch surface will show the real source. The spots can be a nuisance, but the good news is that these fungi won’t cause any structural damage to the landing surface. However because of the sticky material the spore packs have, it is tough to scrub the spots from the surface of house siding or cars.
We are not aware of any fungicide treatments to prevent the unsightly look caused by the artillery fungus. To prevent further spots, one consideration would be to replace wood chip mulch with other mulch alternatives such gravel or stone. If you like all the benefits of wood mulch, adding 3-4 cm of new mulch may help bury the fungal bodies and reduce the problem, but keep in mind the fungi may find the way up in the mulch after some time.


Artillery fungus spots on hosta leaf. Photo by Becky Oelkers, Cerro Gordo County Extension & Outreach Office, Iowa State University.


Artillery fungus spots on plastic vase. Photo by Becky Oelkers, Cerro Gordo County Extension & Outreach Office, Iowa State University.

George Weigel This spout and siding have been shot with the tarry black gleba of mulch-borne artillery fungus.

Q:

My sister and her husband have artillery fungus all over their new house. They are freaking out and are talking about removing all of the mulch they put down this spring. That sounds like a ton of work. I know you wrote about mixing 40 percent mushroom soil with 60 percent mulch to eliminate the fungus. I am wondering if they could add the mushroom soil to the flower bed that is already producing the fungus and just mix it in? If so, would you estimate about 2 inches of mushroom soil on top of 3 inches of existing mulch? Would mixing in mushroom soil stop the fungus or is it too late once it’s already producing the fungus? I also remember you recommending a product that removes the tarry spots from surfaces. Could you tell us the name of that product?

A: This is a common problem without a good solution (yet). Dr. Don Davis at Penn State – one of the nation’s leading artillery-fungus researchers – says the only sure-fire way to stop these pesky fungi from firing their tarry dots all over houses is to remove the mulch. Take away the food and you take away the problem.

I wouldn’t be too crazy about facing that job either, though. So option two is managing the problem and attempting to limit future trouble. The new research on 40 percent mushroom compost mixed with 60 percent wood mulch seems to be the most promising idea. Ideally, that would be mixed first and applied as one layer.
Absent research on this, I would guess if your sister added 2 inches of mushroom compost and mixed it into the existing mulch, she’d get pretty good control. That should suppress new firings, much like an original, up-front mix would have. My main concern, though, is that she’d then have 5 inches of total covering, which is too much.

Since the worst tarring is over for this year, I’d focus on cleaning off this year’s sticky dots then switch over to pine-bark nuggets next spring. An inch topping of those right over the existing mulch should at least cut down on next year’s firing – if not all but eliminate it. The existing mulch should break down by an inch or so by then so you won’t go over the maximum 3-inch layer. (Penn State testing found that pine-bark nuggets as well as cypress and cedar mulches are some of the least likely mulches to harbor artillery fungus.)

There’s some evidence that topping even hardwood mulch every year with fresh hardwood mulch suppresses artillery fungus, which seems to prefer semi-decayed wood. That might well work, but it makes me a little nervous. If you fall behind or miss a year, you might then get a big outbreak.

Some people have switched to weed fabric topped with stone, but that’s not as healthy for plant growth as an organic bark or wood mulch. Leaves and grass are great mulches, but they break down too fast.

Personally, I like the long-term idea of using low-growing plant groundcovers as underplantings for foundation shrubs. These eliminate the need for mulch altogether. These include liriope, pachysandra, sweet woodruff and hardy ginger in the shade and creeping sedum, leadwort, vinca and liriope in sunnier spots.

So far as getting spots off walls, they’ll wipe off with cloth and most any spray cleaner if you get to them when still wet. Once they dry, they’re very difficult to get off. Elbow grease is the first ingredient no matter what else you use. Some people have had success with a bleach solution and Brillo pad (be careful you don’t scratch siding), and others use RV cleaning solutions (mainly sold to scrub tar off RV wheels). Two brands of cleaners that are often mentioned for artillery-fungus removal are Simple Green and Jomax.

Cooperative Extension: Insect Pests, Ticks and Plant Diseases

Artillery Fungus

Pest Management Fact Sheet #5103

Authors: Dr. Alicyn Smart, Dr. Bruce Watt, and Abigayl Novak

For information about UMaine Extension programs and resources, visit extension.umaine.edu.
Find more of our publications and books at extensionpubs.umext.maine.edu.

Other Name: Shotgun fungus
Pathogen: Sphaerobolus stellatus

Introduction

Figure 1. Ejected peridioles stuck to Rhododendron Leaves. Photo by UMaine Cooperative Extension.

The artillery fungus (Sphaerobolus spp.) is a wood-decaying fungus responsible for causing unsightly spots on objects located in its immediate vicinity. These spots are often mistaken for tar spots, scale insects, or insect frass. The spots are actually glebal masses (peridioles) that have been forcibly ejected from the tiny cup-like structures of the fungus (see Figure 1.). The firing mechanism, estimated to 1/10,000 hp and powered by a build-up of osmotic pressure, can shoot the glebal mass a distance of up to 20 feet. The ejection is said to be accompanied by an audible sound. When the mass hits a surface, a sticky coating causes it to adhere, producing a small black spot about 1/10 inches in diameter. Once the mass has adhered to a surface, it is nearly impossible to remove without damaging the surface itself.

Host

  • Wood mulch

Symptoms and Signs

Artillery fungus produces black spots and are actually masses of mature cup shaped spores and can be misdiagnose as bird’s nest fungus. Damage of Sphaerobolus tends to occur most frequently during the cool, wet days of spring and autumn due to fruiting bodies not being produced at temperatures above 77°F. High temperatures are advantageous to the fungus because the glebal mass is less likely to land on a moist surface, which will favor fungal growth. Sphaerobolus grows in moist organic matter, such as dung and rotting wood, and prefers sunny locations. The fruiting body tends to discharge toward a strong light source such as the sun or a bright, reflective surface. Commonly, when Sphaerobolus damage occurs, organic mulches have been used in the area, but any rotting wood should be suspected as a potential source for the fungus to grow. Occasionally damage is seen inside of houses when mulches have been used in houseplants.

Management

Control strategies consist mainly of altering the habitat so the fungus does not grow. Where mulch is suspected as the fungus source, it should be removed and new mulch put down in its place. Alternatively, a new layer of mulch may be placed on top of the old mulch to act as a barrier. Large-nugget bark mulches of pine, Atlantic white cedar, or cypress are more suppressive to Sphaerobolus than most other organic mulches, but inorganic mulches would not support any growth of the fungus and would be a more permanent solution. Some examples include rubber mulch and stone mulch. No fungicides have been registered for use against this fungus.

Alasoadura, S. O. “Fruiting in Sphaerobolus with special reference to light.” ANN BOT, 1963. 123-145. Volume 27 Issue: 105.

Brantley, Elizabeth A., Donald D. Davis and Larry J. Kuhns. “Biological control of the artillery fungus, Sphaerobolus stellatus, with Trichoderma harzianum and Bacillus subtilis .” Journal of Environmental Horticulture, 2001. 21-23. Volume: 22 Issue 1.

Davis, Donald D., et al. “Artillery fungus sporulation on 27 different mulches – A field study.” Journal of Environmental Horticulture, 2001. 117-123.

Geml, Jozef, Donald D. Davis and David M. Geiser. “Influence of selected fungicides on in vitro growth of artillery fungi (Sphaerobolus spp.).” Journal of Environmental Horticulture, 2005. 63-66. Volume: 23 Issue: 2.

Hazelrigg, Ann. Artillery Fungus. n.d. <https://pestid.msu.edu/plant-diseases/artillery-fungus/>

WHEN USING PESTICIDES, ALWAYS FOLLOW LABEL DIRECTIONS!

Alicyn Smart, DPM
Plant Pathologist and Director of the Plant Disease Diagnostic Laboratory
University of Maine Cooperative Extension

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