Several stages of artillery fungus development. The brown, shiny sphere, center, is a peridiole, which possibly was launched from another fungus some distance away. A peridiole loaded on the membrane is seen in the right center of the photo.

Hours of mulching results in a tidy, weed-free landscaped area surrounding your home.

One day you notice dark, reddish brown spots, the size of small BB's, peppering your home's windows, frames and siding to a height of about four meters.

That means the mulch you spread may have carried artillery fungus.

Artillery fungus (Sphaerobolus stellatus) is named appropriately (Sphaer, sphere; bol, thrower; stell, star). Star refers to the shape of the peeled-back peridium (spore-bearing structure) from which the peridiole (brown spore sphere) is launched, leaving a four to nine petal ground “star” behind.

Spore pods are launched by inflation of a membrane located under the spore pod, similar to inflation of an automobile air bag. Inflation of the membrane results from gasses created by reaction of chemicals within the fungus. Expansion of the membrane can propel the spore pod up to four meters in height and six meters in distance, an amazing feat for a tiny fungus only a few millimeters wide by two centimeters long.

The fungi's bright yellow color enhances their visibility. While the spores are not harmful to humans or pets, they can stain your home, deck or car if not cleaned promptly and thoroughly.

As with other fungi, artillery fungus is present in the natural environment. When conditions are favorable, the fungus grows. Moist areas with shade and woody material present are the environment in which this fungus thrives. For the homeowner, the north side of the home is the most likely location for artillery fungus to strike, where moist wood mulch is spread in a shady area.Prevent the introduction of artillery fungus into your landscape by carefully selecting your mulch.For example, stone, pine needles, red cedar and recycled plastic mulches do not encourage artillery fungus growth.Penn State Extension has suggestions for types of mulch that thwart artillery fungus spread. Visit www.bit.ly/fungusprevent.Changing or covering wood mulch with fresh mulch annually helps mitigate the propagation of artillery fungus. Carefully examine woody mulch you intend to purchase. Avoid old, last year's bargain-priced mulch containing partially decomposed chipped trees, shredded waste lumber, particle board, sawdust and similar fine-particle-wood debris.

Wood mulch creates shade and holds moisture, the perfect habitat for artillery fungus. The longer this mulch is exposed to the natural environment, the higher the chance that artillery fungus is present.Purchase freshly prepared mulch to reduce the period during which any fungus has had time to become established.When removing the fungus from home and other structures, time is of the essence. If you see the peridioles on your siding, deck and other surfaces, prompt remedial action is necessary.Remove the conditions which create a favorable environment for artillery fungus to spread. Covering active fungus with a disposable paint tarp or applying fresh mulch suppresses peridiole spread and prevents further damage.Removal and destruction of old wood mulch removes the existing fungus and the favorable host environment. Infected mulch should be removed to an area well away from structures, vehicles and other host materials.Use of removed mulch as the “brown” component for a compost pile can result in decomposition of the woody material. Use of this compost is only recommended in sunny areas. Prompt cleaning of affected surfaces following removal or isolation of the fungus is prudent.There are a number of methods to remove the artillery fungus peridioles (spots) from decks and vinyl siding. All require manual labor while wearing cuffed rubber gloves, full length clothing and safety glasses.<i>Michael Pavelek II is a Penn State Master Gardener of Butler County.</i>

Artillery fungus on windows and siding.