June 2, 2004 | By: Ellen Brightwell
LEXINGTON, Ky.

The only bad things about slime molds are their name and appearance. They are unsightly, but not harmful.

Some slime molds look like a dog has gotten sick at the stomach. It is alarming to see these slimy patches in yard mulches and grasses. There have been reports of people taking dogs to the veterinarian, or accusing neighboring dogs of coming into their yard. Other slime molds are smaller and less conspicuous.

They do not cause diseases, are not parasitic, and won’t harm people and pets.

“Slime molds are primitive, unusual creatures,” said Paul Vincelli, Extension plant pathologist with the University of Kentucky College of Agriculture. “Fungi slither around below ground for weeks or months feeding on microbes in organic matter. Abundant wet weather in late spring and early summer stimulates them to emerge into the light to reproduce by creating millions of microscopic spores. The fungi sacrifice their entire bodies to produce these spores.

“The fungi were once considered animals because of their slithering, creeping behavior.”

The molds quickly appear as four- to six-inch patches of white, cream, gray or purple with a crusty surface. Some become a foot or more in size. They use grass leaf surfaces, mulches and ground-touching shrub or tree branches as support structures from which spores are dislodged by the wind, water, mowers, other equipment or movement by people or animals. Temporarily shading grass leaves may weaken the plants but does not cause severe or permanent damage.

Slime molds tend to appear in the same vicinity year after year. They like cool, shady, moist locations filled with moisture-laden organic matter. Poorly drained areas and those with heavy thatch may increase the likelihood of slime molds. More than 700 species are reported to exist.

“You can reduce potential development by aerating mulch with a gardening tool, pruning overgrown plants and trees to decrease moisture and reducing thatch in the lawn,” Vincelli said. “Chemical preventive treatments are not recommended or required. Historically, they have not been effective. Treatment really isn’t necessary because slime molds will disappear as soon as drier weather appears.”

People with heavy infestations, or those who simply cannot stand the unaesthetic site, can remove slime molds by mowing, raking, poling, or using a forceful water stream from a garden hose. Be sure to wait for warmer weather before using the hose to keep from spreading the fungus or creating conditions for future development.

Contact: 

Writer: Ellen Brightwell 859-257-4736 ext. 257
Source: Paul Vincelli 859-257-3000, ext. 330