Pest Management Fact Sheet #5103
Bruce A. Watt, Extension Plant Pathologist
The artillery fungus (Sphaerobolus spp.) is 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, but are actually glebal masses (peridioles) that have been forcibly ejected from the tiny cup-like structures of the fungus. The firing mechanism, estimated to generate 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.
Problems with Sphaerobolus damage tend to occur most frequently during the cool, wet days of the spring and autumn because the fruiting body is not produced above 77°F. This is advantageous to the fungus because the glebal mass is more 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 of the problem. Occasionally damage is seen inside of houses when mulches have been used in houseplants.
Control of Sphaerobolus can be difficult. No fungicides have been registered for use against this fungus although some may be marginally effective. Some biocontrol agents, such as the fungus Trichoderma, may also limit the growth of Sphaerobolus but have not been registered for this use. 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 to act as a barrier. Large-nugget bark mulches of pine, Atlantic white cedar, or cypress are more suppressive to Sphaerobolus than most organic mulches, but inorganic mulches would not support any growth of the fungus and would be a more permanent solution.
ALASOADURA, S. O. 1963. Fruiting in Sphaerobolus with special reference to light. ANN BOT Volume: 27 Issue: (105) Pages: 123-145
Brantley, Elizabeth A.; Davis, Donald D.; Kuhns, Larry J. 2001. Biological control of the artillery fungus, Sphaerobolus stellatus, with Trichoderma harzianum and Bacillus subtilis. Journal of Environmental Horticulture Volume: 19 Issue: 1 Pages: 21-23
Davis, Donald D.; Kuhns, Larry J.; Akina, Kristen; et al. 2004. Artillery fungus sporulation on 27 different mulches – A field study. Journal of Environmental Horticulture Volume: 22 Issue: 3 Pages: 117-123
DYKSTRA, M. J.1982. A CYTOLOGICAL EXAMINATION OF SPHAEROBOLUS-STELLATUS FRUITING-BODIES. Mycologia Volume: 74 Issue: 1 Pages: 44-53
Geml, Jozsef; Davis, Donald D.; Geiser, David M.2005. Influence of selected fungicides on in vitro growth of artillery fungi (Sphaerobolus spp.). Journal of Environmental Horticulture Volume: 23 Issue: 2 Pages: 63-66
When Using Pesticides
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Pest Management Unit
Cooperative Extension Diagnostic and Research Laboratory
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