Moss and algae control in lawns (09-11-2006)

Is your lawn plagued with mosses or algae?

Mosses are nonparasitic, primitive green plants with very tiny leaves on branched threadlike stems. Mosses reproduce from wind blown spores and can form thick, green mats on the soil surface. They produce their own food and do not kill the lawn grasses, but rather fill in any bare spaces where turf is not growing. Generally if mosses are present in your lawn, there are conditions more favorable for moss growth than for turf growth. Excessive shade, poor drainage, compacted soil, acidic soil, low fertility, excessive irrigation or a combination of several of these conditions favor moss over turf.

Algae are single cell or multicellular, threadlike green plants that can form a dense coating or scum over the soil surface and when dry will create a tough black crust on the soil acting as a barrier to water movement into the soil. Algae are most often found on soils that are waterlogged and compacted.

Cultural practices that improve the conditions more favorable for turf growth are the only alternatives to permanently alleviate the problems with mosses and algae. Altering the slope or elevation of the lawn or installing drain tiles may be necessary to improve the drainage. Core aerification can alleviate soil compaction and adding lime and fertilizer will improve soil acidity and fertility. Planting turf species that are more adapted to shade for shady areas, or more acid loving species such as centipede where the soil pH is low may be better options for some areas of the lawn.

Once the underlying conditions have been corrected you can remove moss by raking or by using chemicals such as ferrous sulfate monohydrate or potassium salts of fatty acids. Other options include ground limestone, diluted bleach, or dishwashing detergent. These materials kill the moss by acting as drying agents or desiccants. Potassium salts of fatty acids or copper sulfate can be used to control algae. Ground limestone may need to be applied to deactivate the copper sulfate prior to planting new grass seed.

Published September 11, 2006

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