sealPurdue News

August 8, 1997

Shotgun fungi stain house siding

WEST LAFAYETTE, Ind. -- Tiny black specks on house siding or white cars sometimes appear in late summer, and the culprit is an organism known as shotgun fungi, according to Peggy Sellers, director of the Purdue University Plant and Pest Diagnostic Center.

This fungus, which can live in wood mulch that surrounds houses, has an unusual method of dispersing its spores. (Spores are the fungi's equivalent of seeds in flowering plants.) These fungi belong to a group known as bird's nest fungi, because they have small "fruits" that resemble a bird's nest with tiny eggs (the spores) in it. "Eventually, the 'nest' opens and the spores are violently shot into the air with enough force to propel them as high as a two-story building", Sellers said.

The fungi are also sometimes known as artillery fungi, which is appropriate, because the organisms can also aim their spores to a certain extent. "The fungus will shoot the spores toward a light source, which will include reflected light that is coming off glass or light-colored buildings or vehicles," Sellers said.

The contents of the exploding cells are sticky, which enables the spores to adhere to plants or passing animals. "The sticky substance is designed to withstand the rigors of animal digestive systems, because some fungi species complete their life cycle by returning to dung," Sellers said. "Attempting to remove the spots from surfaces is generally futile."

To attempt to remove these spots from buildings, Sellers recommends a few methods. Soaking the area with soap and water, followed by gentle scraping, may loosen the spores. However, this method can damage the surface or the paint, so this must be done with care. Diluted bleach may help to remove these spots, but this can also damage the surface or paint, and it can also damage nearby plants if the solution falls on them. Before using bleach water, do a small test in an inconspicuous area first.

To prevent the fungus from splattering your siding or automobile again, Sellers recommends using gravel mulch, stone, pea gravel, black plastic, or some other non-organic mulch next to buildings instead of wood chips. "This will reduce the problem, although this solution may not fit in with the overall garden design," Sellers said. Another alternative would be to add fresh wood chips each year so that the old mulch is completely covered, Sellers said.
CONTACT: Peggy Sellers, (765) 494-7071

Compiled by Chris Sigurdson, (765) 494-8415; E-mail,
Purdue News Service: (765) 494-2096; e-mail,

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