Slime Mold

After the recent rains we have received you may notice oily or sooty spots appearing in your lawn. These spots are often circular in shape and can be several inches to several feet wide. The culprit is most likely slime mold. Some slime molds appear as thin, white, yellow, or gray layers of slimy paste-like material that cover the leaf blades. These masses later dry to form bluish-gray, black or white powdery growths on the leaves. Although they may look alarming, slime molds pose no real harm to your lawn because they grow on dead organic matter and do not feed on green plants. If heavy infestations are causing a problem, they can be removed by mowing, raking, or using a forceful spray from a garden hose. Only use the water method during dry weather to keep from spreading the fungus further. In most cases the slime mold will turn black and disintegrate within a few days on its own.

Slime molds are favored by long periods of wet, humid weather. Poor drainage and heavy thatch can also increase the odds of occurrence. Fortunately, slime molds are simply using the leaf blade for structural support and they do not compete with the grass for nutrients. The visible discoloration is actually due to extensive sporulation by the fungus. Small, pinhead sized spore capsules can generally be seen on the leaf blades. Grass may begin to yellow when spore production is extremely heavy because the spore masses cause shading resulting in reduced photosynthesis.

Slime molds do not typically require chemical management because they will disappear when dry weather returns. For areas with light to moderate slime mold infestations, it is best just to let nature take its course.

More information on this and other home gardening topics can be found at the Alabama Cooperative Extension System Home and Garden website www.aces.edu/homegarden . For all your home gardening questions please call the Alabama Master Gardener Helpline toll-free at 1-877-252-GROW (Mon.-Fri. 9:00-4:00).