Plant Pathology Infobytes

May 21, 1998
Time for Slime Mold Invasion of Landscape Beds

Hardwood mulch makes a great addition to landscape beds. This material adds a "finished" look to the landscape, helps conserve moisture, and reduces weed and grass growth. While hardwood mulch is popular with home landscapers, beds which have been recently dressed with this type mulch are favorite invasion areas for slime molds.

Just what is a slime mold? These harmless creatures are members of the plant kingdom and are closely related to fungi. When slime molds invade landscape beds, they typically form layers of spongy, slightly raised growth on the surface of the mulch. These creatures of the plant world often present a striking appearance, since they produce an amazing variety of colors ranging from light pink, brown, bright yellow, and other colors.

Slime molds never fail to attract the attention of home landscapers who aren't sure of the identity of these creatures. Slime molds seemingly show up overnight and often grow from a circular area of several inches in diameter to patches several feet across within a few days.

Although slime molds may present an alarming appearance, it should be noted they grow externally on the surfaces of leaves and stems without parasitizing plants. So don't become alarmed if slime molds appear in your landscape planting.

Slime molds normally live on or close to the soil surface where they feed on decaying organic matter, bacteria, and other microbes. They move about in a manner more closely akin to animal than plant life, creeping along by forming finger-like projections. These projections pull the body of the slime mold across the soil surface.

When the slime mold is ready to reproduce, it "crawls" up on raised areas of hardwood mulch, lower stems and foliage of landscape plants, or even garden hoses. From these locations, the slime mold releases millions of dusty-gray spores. Spores are tiny "seeds" which will insure future generations of slime molds. The only purpose for a slime mold seeking a higher spot is to insure distribution of spores over a further distance than it would be possible from the soil surface.

Since slime molds don't feed on living plants, control measures aren't necessary. However, if they become too numerous and unsightly, break up the spore masses by raking, brushing, or hosing down with water. Fungicide sprays as a means of slime mold control are not recommended.

If you need further information, please feel free to give us a call at the County Extension Office.


Written by the late Dr. Frank Killebrew

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