Fact Sheets - Artillery Fungus
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Pest Management Fact Sheet #5103
Artillery Fungus
Bruce A. Watt, Extension Plant Pathologist
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The artillery or shotgun fungus (Sphaerobolus spp.) is responsible for causing unsightly spots on objects located in its immediate vicinity. These spots are often mistaken as tar, scale insects or insect frass, but are actually spore masses (glebae) that have been forcibly ejected from the fungus. The firing mechanism consists of a build up of osmotic pressure, which can send the glebae distances up to 20 feet. This ejection is accompanied by an audible retort generated by 1/10,000 hp. When the glebae hit a surface, a sticky coating causes them to adhere, producing small black spots about 1/10 inches in diameter. Once the glebae have adhered to a surface, they are nearly impossible to remove without damaging the surface.
Problems with Sphaerobolus damage tend to occur most frequently during the cool, wet days of the spring and fall because sporulation does not occur above 77oF. This is advantageous to the fungus because its spores are more likely to land on a moist surface, which favors germination and growth. It grows on moist organic matter such as dung and rotting wood and prefers sunny locations. The fruiting body discharges its gleba towards a strong light source such as the sun or a bright, reflective surface. Commonly, where problems exist, there are organic mulches being used in the area. Any rotting wood should be suspect as a potential source of the problem. Typically, the source is an organic mulch such as bark mulch but any rotting wood, such as old greenhouse benches, etc., could also be the problem area. Occasionally damage is also seen inside houses when mulches are used in houseplants.
Control of this fungus can be difficult. No fungicides have been registered for use against this fungus. Control consists mainly of altering the habitat so the fungus does not grow. Where mulch is suspected, 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. Inorganic mulches, which would not support growth of the fungus, would be a more permanent solution.
When Using Pesticides
ALWAYS FOLLOW LABEL DIRECTIONS!
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