Algae and moss infestations in turf (3-1-10)

Algae and moss infestations in turf are associated with unfavorable conditions for growing healthy, dense turf. Algae are tiny threadlike single cellular or multi-cellular plants that form a thin dense green scum over the soil surface. When dry this scum will form a hard black crust serving as a barrier impeding the entrance of water and nutrients into the soil. Compacted, waterlogged soils, thinned turf canopy, and warm, sunny, humid conditions are conducive for algae growth

Mosses are green plants with very small leaves arising from a central axis that form a thick green mat at the soil surface. Soils that are excessively wet have low fertility, poor drainage, and high soil acidity favors the growth of mosses. Thatch and soil compaction are problems that weaken and thin turf and also enhance moss presence. Mosses are very competitive in cool, moist, shaded locations, such as the north side of buildings and wooded areas.

Physical or chemical removal of algae or moss will only be temporary unless growing conditions are improved. Cultural practices that will help prevent or control these pest include:

1) Aerify to reduce compaction.

2) Conduct a soil analysis to determine proper fertilization and soil pH adjustments.

3) Improve drainage and avoid excessive watering.

4) Increase air movement and light penetration which will also improve turf density and health.

5) Plant shade tolerant grasses, ground covers or use mulch in areas where heavy shade is unavoidable.

Copper sulfate, ferrous sulfate, and ammonium sulfate and other chemicals may be helpful for temporary control of mosses and copper sulfate is active on algae. Excessive use of chemicals, however, may become toxic to the turf. Punching holes in the algae crust or physical removal of the algae crust or moss will help allow for turf recovery. For large bare areas preparing a new seedbed and replanting may be necessary.

Published March 1, 2010

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. wwells@ext.msstate.edu