Information on Lawn and Turf -- Moss, An Online Guide to Plant Disease Control, Oregon State University

Pacific Northwest 1998 An Online Guide to Plant Disease Control

Lawn and Turf -- Moss

Cause: Moss is a primitive plant that can be a weed in turf situations. Moss is enhanced by human activities, especially by close mowing in late fall, which chops up the plants and distributes the fragments over the lawn. Brachythecium species are the common in home lawns but rare in putting greens; Bryum spp. are also important in greens. Many other species also can occur and become weedy, and although moss is often associated with moist, shady sites, there are species adapted to many different environments including dry, open sites. Mosses need contact with moisture to grow but can survive in a desiccated state for long periods. If a healthy turf stand cannot be maintained at a site, the moss will continue to be a problem. No amount of moss-killer will change this.

Symptoms: When moss first colonies an area it produces a black, slimy mat across the area before the green vegetative structures form. The green structures are composed of branch like filaments called protonema and are easily confused with algae. These then bud out and give rise to more familiar green strictures. Mosses can take many shapes and forms. Stems and leaves are complex with conducting strands, midribs and a great diversity of cell forms. Leaves may be grouped in pairs, threes and even sets of five. Bryum argenium is found on open sites and has a silvery appearance. B. lisae colonies are green to yellow-green tufts or clumps.

Most of the green in this picture is due to moss and not grass.

Cultural control: The most successful long term strategy for moss control is to grow grass that out-competes the moss. Excessive moisture must be eliminated, the proper species of grass must be planted in the problem areas, and the grass must be maintained by proper watering and fertilization to promote growth that will exclude the moss.

Ensure good drainage through aeration, installation of drainage, and/or sand topdressing.
Control thatch to promote good rooting of turf plants and to enhance drainage.
Maintain soil pH between 5.8-6.6 and provide adequate nutrition by a balanced fertilizer program. Golf greens should be fertilized with 0.5 lb N/1000 sq ft. per month. Increase K to 0.6 lb/1000 sq ft per month, and apply 0.1-0.2 lb iron/1000 sq ft per month.
Provide good air circulation and adequate sunlight by pruning nearby trees and shrubs.
Do not overwater turf. Be sure to irrigate sufficiently during the dry season to promote growth.
Mow turf at the correct cutting height for the species of grass grown.
Try to remove moss by hand or power-raking. Reseed with a grass species more suited to the site. For shady sites try Poa trivialis, colonial bentgrass, or annual bluegrass. Fine and tall fescues have marginal shade tolerance, and Kentucky bluegrass and perennial ryegrasses have poor shade tolerance.
Consider alternatives to turf if good conditions for turf growth cannot be met.

Chemical control: These must be used in conjunction with the cultural controls above for successful control. Dethatch first and then apply these products so you get good uniform coverage.

Treat with ferrous sulfate applied to dampened plant surface when moss is growing most actively. For best results, remove as much moss as possible by hand or by power-raking before treatment. Turfgrass temporarily darkens for 1 week after treatment. Sidewalks and driveways are permanently stained by these materials.
1. Lilly Miller Moss Out Lawn Granules or Fortify Moss Control Granules at 0.4 lb/100 sq ft.
2. Fred Meyer Lawn Moss Control at 0.8 lb/100 sq ft.
Security Moss and Mildew Killer (28% Zn plus 2.5% Cu) at 1 lb/1,000 sq ft.

Content edited by: Leslie MacDonald, Melodie Putnam & Jay W. Pscheidt on January 1, 2009

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