Mosses are primitive plants that can invade all turfgrass species. Fossil records show mosses have been around for approximately 350 millions years. The presence of moss today indicates it is an ancient survivor that is highly adaptable. There are over 9,000 species of moss but only a few invade turf. In highly maintained turfgrasses, like golf course putting greens, silvery-thread moss (Bryum argentum) is the most common species. A few other species can infest lawns.
Mosses are nonvascular plants meaning they lack xylem and phloem that characterize vascular plants. This is significant because nutrients and water are not translocated in moss. Nutrients and water are absorbed directly into plants usually through structures called rhizoids. The fact that mosses do not have vasucluar systems represents one of the main challenges in managing moss: systemic herbicides (glyphosate, 2,4-D, etc) will not work because there is no vascular system to translocate the herbicides.
Infestations of moss in turf are usually associated with unfavorable conditions for growing healthy, dense turf. Mosses are branched, threadlike green plants with leaves arising from all sides of a central axis. Mosses may grow erect or prostrate. They typically form a thick green mat at the soil surface. Conditions favoring the growth of mosses include low fertility, poorly drained soils, high soil acidity, excessively wet soils, soil compaction, 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. They are an invasive weed in closely mown golf course putting greens.
Physical or chemical removal of moss will only be temporary unless growing conditions are improved. In landscape areas you may choose to use a mulch cover (pine straw, bark, etc.) or plant a shade-tolerant ground cover instead of turfgrass. The following practices can help you prevent or control moss.
- Plant shade-tolerant grasses. (See Extension publication AG-69, Carolina Lawns.)
- Make sure nitrogen fertility is adequate. Moss is often associated with low nitrogen fertility, particularly on golf course putting greens.
- Conduct a soil test to determine proper fertilizer needs. Proper fertilization will aid in preventing weed encroachment.
- Avoid excessive watering and improve irrigation scheduling if necessary.
- Aerify (core) compacted soils.
- Increase air movement and light penetration in shaded areas by removing unnecessary undergrowth and pruning tree limbs.
- Improve drainage.
- In lawn-height turf or bare-ground treatments, moss may be controlled with copper or ferrous sulfate sprayed at 3–5 ounces per 1,000 square feet in 4 gallons of water. Applying concentrated amounts (10 ounces per 1,000 square feet) of ferrous ammonium sulfate to the moss spots when the moss is damp offers another means of control. Ferrous ammonium sulfate should not be watered in. An application of 5 to 10 pounds of ground limestone per 1,000 square feet prior to reseeding will help to inactivate the copper sulfate that may be toxic to grass seedlings. Physical removal of the moss by raking may be needed to allow for recovery in these areas. Prepare a new seedbed and replant if large bare areas exist. Follow good establishment practices as discussed in Carolina Lawns, AG-69.
- Repeat applications of the fungicide chlorothalonil has shown activity for controlling moss but may not be used in residential turf. Repeat applications of chlorothalonil are effective when air temperatures are above about 80F. Applications at lower temperatures are ineffective.
- In low-mow golf course turfgrass, the best control success has often involves using a herbicide that has activity for controlling moss. Carfentrazone (Quicksilver) has been the most effective selective herbicide used to treat slivery thread moss in turfgrass. It will require repeat applications (6.7 fluid ounces of product per acre) usually at 10–14 day intervals for control. However controlling moss will be temporary unless turfgrass growing conditions are improved. A management program including both core aerification and carfentrazone applications, along with careful water management, is often the most successful long-term strategy.
- Whatever chemical approach is used, successful management of moss will also require a simultaneous management strategy that stimulates turfgrass growth. Most often, this means an application of nitrogen fertilizer.
Publication date: Sept. 1, 1995
Revised: Sept. 12, 2022
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