Managing moss and algae in turf (10-05-09)

Mosses are green plants with tiny leaves arising from all sides of a central axis. Mosses may grow prostrate or erect. They typically form a thick green mat at the soil surface. Conditions favoring the growth of mosses include poorly drained soils, low fertility soils and/or with strong soil acidity, soil compaction, excessively wet soils, and excessive thatch or a combination of these factors that add up to thin or weak turf. Mosses are very competitive in cool, moist, shaded locations, such as the north side of buildings and wooded areas.

Algae are unicellular or multicellular threadlike green plants that form a dense thin green scum over the soil surface. This scum may form a tough black crust when dry which acts as a barrier impeding the entrance of nutrients and water into the soil. Algae are competitive in compacted, waterlogged soils mostly under warm, sunny, humid conditions.

Infestations of moss and algae in the turf are associated with unfavorable conditions for growing dense, healthy turf.

The following practices can help you prevent or control moss and algae:

a) Plant shade-tolerant grasses.

b) Conduct a soil test to determine proper lime and fertilizer needs. Liming will reduce soil acidity. Proper fertilization will aid turf density and prevent weed, moss, and algae encroachment.

c) Avoid excessive watering and improve irrigation scheduling if necessary. d) Aerify compacted soils.

e) Increase air movement and light penetration in shaded areas by removing unnecessary undergrowth and pruning tree limbs.

f) Improve drainage. Copper sulfate, ferrous sulfate and selective fungicides can be applied to help chemically reduce moss and algae, however, physical or chemical removal of these pests will only be temporary unless growing conditions are improved

Published October 5, 2009

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