Extended rainy days causes mushrooms and slime molds 07-16-07

The recent daily showers have provided many of our previously drought stricken lawns with some extended soil and turf wetness. And that has stimulated the appearance of fairy ring and slime mold fungi. I have received several calls from somewhat panicky homeowners alarmed about a devastating looking fungus or slime attacking their lawns. The attack is not near the detriment that it appears.

Slime molds, which appropriately describe these fungi, will cover the turf leaves with a dusty-gray, black, or even dirty yellow mass. When you look closely, you see tiny, round balls scattered over the plant. If you rub these balls between your fingers, a minute sooty-like powder will cover them. This sooty-like powder is the reproductive spores of the fungi.

Slime molds normally live on the soil where they feed on decaying organic matter. They do not feed on living plants, but only use them for support during reproduction. The damage to turf and other plants would be only from shading them from sunlight, which may cause the leaf blades to temporarily turn yellow.

They most often occur in wet weather during spring, summer, and fall. They disappear rapidly as soon as it becomes dry. Control is usually not necessary. You can break up the masses by sweeping with a broom or by spraying with a strong stream of water. In prolonged damp weather, you can apply any good garden or turf fungicide to affected areas.

Mushrooms also have been popping up everywhere in water soaked lawns. These can be more problematic as many of these fleshy fungi are toxic to mammals and can also be associated with fairy rings in the lawn. Avoiding high levels of organic matter in the soil from decaying tree roots, heavy thatch layers, etc. will help reduce the potential for fairy rings and mushrooms.

Published July 16, 2007

Dr. Wayne Wells is an Extension Professor and Turfgrass Specialist. His mailing address is Department of Plant and Soil Sciences, Mail Stop 9555, Mississippi State, MS 39762. [email protected]