Artillery Fungi “Pepper” Surrounding Vegetation and Structures
Gail Ruhl, Senior Plant Disease Diagnostician, Dept. of Botany & Plant Pathology, Purdue University
Artillery fungi are a type of white rotting, wood decay fungi that belong to the genus Sphaerobolus (Greek for “sphere thrower”). Artillery fungi live on moist, landscape mulch and are responsible for the little black spots (spore masses) found on nearby rocks, leaves and other structures. The spore-bearing fruiting structures are very small, 1/10 of an inch across, and are thus very hard to see in the mulch. These fungi have a unique propulsion mechanism for dispersing their 'spore packets”. The contents of the "exploding" cells are sticky, and enable the peridioles to adhere to surfaces such as plants, house siding, car windshields, etc. The fungus is sensitive to light, and will direct the peridioles towards a light source, including reflected light off of white buildings or vehicles.
The “bird’s nest fungus”, another mulch inhabitant, is often confused with the artillery fungus. The bird’s nest fungus does not actively “shoot” spores. The little egg-shaped spore packets of the birds’ nest fungus are splashed out of the ‘nest with drops of rain or irrigation water.
The use of cypress mulch and large pine bark nuggets or nonorganic mulch (gravel, stone, black plastic, etc.) can help. Attempting to remove the spots from surfaces is difficult and generally futile. You can try soaking the area with soap and water, followed by gentle scraping to loosen the peridioles, but care must be taken to avoid damage to the surface or the paint.
An excellent Q & A web page on Sphaerobolus: http://www.personal.psu.edu/faculty/d/d/ddd2/
A publication on fungi found growing in mulch:
click images to enlarge
Image by Gail Ruhl
All images other than the first by Mary Welch-Keesey, Purdue University Consumer Hort Specialist, White River Gardens