Your Best Shot Against Artillery Fungus

Category: Landscape

“Why do we have these small, black spots all over our siding and windows?!”

If you’re noticing small spots on your home, car, patio furniture or anything else in close proximity of your mulch beds, you have some Artillery Fungus nearby.

Artillery fungus is a wood-decaying fungus that likes to live in landscape mulch. The fruiting bodies of this fungi are about 1/10 of an inch across and are very hard to see. They actually resemble the end of a cannon barrel and at the right moment shoot their spores up 6-10 ft. onto siding and other objects nearby. There have even been instances on windy days where they’ve made their way onto surfaces as high as a second story.

In its natural habitat, artillery fungi shoot spores towards sunlight. In the habitat of home landscaping, the absence of direct sunlight in some areas will cause the fungi to shoot spores at highly reflective surfaces, such as white house siding and cars. Obviously the dark spores are easily spotted on lighter color surfaces as well.

Artillery fungus has been more prevalent than it has in the past. Landscaping trends over the past several decades has included the use of wood mulch, versus purely bark mulch like in the past. Cool spring and fall periods will always yield more of the fungus as well. It’s common to notice more of this fungi growing in shady environments and on the east and north sides of homes that aren’t in full sun most of the day, but have been found in full-sun environments as well.

Spores are very sticky and don’t take long to fasten themselves to surfaces, making them almost impossible to remove with most cleaners. They don’t pose any damage risk to surfaces other than cosmetic.

“So how do I keep from having or getting more artillery fungus?”

Where there is decaying wood (all mulch) there is the possibility of fungi. There is no way for you, a mulch supplier, or a landscaper to know if their mulch has this fungi in it. It may already be present at the site, transported by wind from your neighbor’s house, stuck to leaves that blow into your lawn, or come on nursery plants that you plant in your flower beds. It’s not something that can be easily avoided. There is no conclusive research about mulches that won’t grow the fungi. However, it has been shown that artillery fungi doesn’t grow as prevalently in large pine bark nuggets because they don’t get as soft and wet as other mulches when moisture is present.

red tipple stone

“So is there anything that can help me?”

If you spot a small group of the fungus, cover it with plastic and then dig it out and remove it from the site. Covering it before dislodging it may keep the projectiles from launching while moving it. It has also been shown that adding mushroom compost to your mulch beds on a regular basis has been shown to reduce artillery fungus. Adding 40% by volume to a typical mulching will greatly suppress the spread of artillery fungus. Likewise, property owners that put down mulch annually generally have less artillery fungus problems than ones that do so every couple years. In extreme cases, you can actually physically remove all of the mulch from your site and start over with new mulch. But, again, there isn’t any guarantee that the new mulch won’t contain the fungus. Some property owners have elected to replace mulch with decorative gravel, particularly in foundation beds that border light-colored siding or surfaces. Replacing either of those materials with groundcover plants could also be a desired alternative.

If you’d like more help with making your decision consult with a landscape company that is knowledgeable about artillery fungus, mulch and gravel options, and has a heart to help you find what solution is best for you. To read more from Penn State about artillery fungus and some suggestions about removing it from cars, buildings, etc. click here. If you’d like help addressing your landscaping concerns relating to artillery fungus, we’d love to talk with you about your project.

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