Infestations of algae and moss in lawns are usually associated with unfavorable conditions for growing healthy turf. Algae are green, threadlike unicellular or multicellular plants that can form a dense scum over the soil surface. When dry this scum forms a tough black crust that impedes water and nutrients into the soil.
Algae are competitive in compacted, waterlogged soils under warm, sunny, humid conditions and where turf is particularly sparse.
Mosses are green plants forming thick mats at the soil surface from tiny leaves arising from a central axis. Conditions favoring mosses include low fertility, poorly drained soils, soil compaction, low soil pH, wet soils and thin or weak turf. Mosses are very competitive in cool shady locations.
Physical or chemical removal of these pests will only be temporary unless the above mentioned conditions are improved. Therefore, if your lawn has these pests, it would be wise to have the soil analyzed to determine proper lime and fertilizer needs. Aerify compacted soils, improve drainage issues, avoid excessive watering and increase air movement and light penetration.
Algae and mosses can be temporarily controlled with sprays of copper or ferrous sulfate. Quicksilver (carfentrazone) is a relatively new herbicide that has activity on moss.
Published March 31, 2008
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@example.com