Moss Algae Control in Lawns by cam67257


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                      Moss & Algae Control in Lawns
Mosses are nonparasitic, primitive green plants that           •   Planting a more shade-tolerant grass
have fine, branched, threadlike stems with tiny                    (keeping in mind that an area receiving less
leaves. They reproduce by means of wind-blown                      than four hours of full sunlight per day is too
spores. Mosses typically form a thick, green mat on                shady for grasses).
the soil surface. They produce their own food and              •   Mowing grasses in a shady area at the top of
do not kill grass plants but rather fill in the spaces in          their recommended mowing height range to
the lawn where grass is not growing.                               encourage deep rooting and provide
                                                                   maximum leaf surface area to intercept the
If mosses are present in your lawn, it indicates that              limited sunlight in order to manufacture
conditions are not favorable for the growth of a                   food. For more information on
healthy stand of grass but are favorable for the                   recommended mowing practices, you can
growth of mosses. The conditions that favor mosses                 request HGIC 1205, Mowing Lawns.
over grass include: excessive shade, acidic soil,              •   Planting a shade-tolerant groundcover rather
poor drainage, compacted soil, excessive irrigation,               than a grass.
low soil fertility or some combination of these                •   Covering the area with mulch (pine
conditions.                                                        straw,bark, etc.).
                                                               •   Pruning some limbs, especially lower ones,
While mosses can be removed mechanically or                        from shrubs and trees.
killed chemically, unless the underlying conditions            •   Removing some of the trees and shrubs.
are altered culturally to favor grass production, any
                                                               •   Enjoying the moss as a low-maintenance
solution that is attempted will be temporary. The
                                                                   groundcover that requires little, if any,
conditions that are commonly associated with moss
                                                                   watering, no fertilizer or mowing, and stays
growth and their cultural controls are described
                                                                   green all year so long as it does not receive
                                                                   much traffic.
Algae are unicellular or multicellular, threadlike
                                                            Acidic Soil: Mosses prefer acidic soil. With the
green plants that can form a dense coating or scum
                                                            exception of centipedegrass, most lawn grasses
over the soil surface. This scum can form a tough
                                                            prefer a pH of 5.8 to 6.5. Centipede prefers a pH
black crust on the soil when it becomes dry, and
                                                            between 5.5 and 6.0. If the pH of your soil is lower
will act as a barrier to water movement into the soil.
                                                            than that recommended for your grass, you can raise
Algal scum can be found on soils that are
                                                            the pH by adding agricultural or dolomitic lime.
waterlogged and compacted, especially during
                                                            The higher pH will not kill the mosses, but will
sunny, warm and humid conditions.
                                                            favor the growth of the grass.
Cultural Control                                            To determine the pH of the soil, take a soil sample
Dense Shade: In general, mosses can tolerate more           to your county Cooperative Extension office. For
shade than grasses can. If the mosses present in            more information on how to take soil samples, you
your yard are limited to shady areas, your options          can request HGIC 1652, Soil Testing.
Poor Drainage: While mosses will grow in well-           draining areas. As both of these areas are already
drained soil, they grow better in wet soil than do       prone to moss problems, excess moisture just adds
grasses. Excessively wet soil is one of the more         to the problem.
difficult conditions to alter. Possible solutions
include:                                                 It is best to water your lawn only when it is needed.
    • Altering the contour of or trenching the area      When you see signs of moisture stress such as grass
        to drain water.                                  with a dull, bluish-gray cast, footprinting (the
    • Altering the elevation of the area (if the wet     presence of footprints when you walk on the lawn
        area is small) by adding sand or soil.           late in the day), and wilting or folding grass leaves,
    • Installing French or tile drains (if the wet       you should irrigate with ⅔- to ¾-inch of water. This
        area is more extensive).                         amount will moisten the soil to a depth of 4 to 6
    • Digging a sump (a pit that receives                inches. The key to proper watering of the lawn is to
        drainage) in the low spots, backfilling with     water infrequently but deeply. For more information
        sand.                                            on watering your lawn, you can request HGIC 1207,
                                                         Watering Lawns.
Compacted Soil: Soil compaction prevents a lawn
from growing vigorously. It also often prevents          Low Soil Fertility: If required nutrients are limited
internal drainage, providing wet conditions              in your soil, lawn growth and quality may be
favorable to mosses. When the top 4 inches of soil       limited, also. Those nutrients that are essential for
are compacted, movement of air, water and                growth can be added to the soil through fertilizer
nutrients to the grass roots is adversely affected. In   applications. In addition to providing the pH of your
addition, it is difficult for grass roots to penetrate   soil, a typical soil sample analysis will determine
compacted soil. These factors place stress on the        the levels of phosphorus, potassium, calcium,
grass and decrease its ability to recuperate from        magnesium, zinc and manganese in your soil. The
damage.                                                  nitrogen requirements of the turfgrass cannot be
                                                         reliably evaluated by a soil test. As a result, the soil
To determine if your soil is compacted, use a soil       test will not contain a nitrogen recommendation.
probe to take a few plugs of soil. This can be done      For recommended nitrogen applications for your
with a piece of ½- to ¾-inch diameter metal pipe.        lawn, you can request HGIC 1201, Fertilizing
The probe should easily penetrate the top 4 to 6         Lawns.
inches of soil. Use a smaller diameter rod to push
the plug of soil out of the pipe. Examine the plugs      Lawn Renovation
for the fine white roots. Grasses growing in             Once you have altered as many of the underlying
compacted soil tend to be shallow-rooted. The roots      conditions as possible, you can remove the moss by
may not extend further than 1 inch into the soil         hand raking or by using a chemicals such as ferrous
when they should extend 6 or more inches.                sulfate monohydrate (Scotts Moss Control or Ortho
                                                         Moss-B-Gon) or potassium salts of fatty acids
A process known as core aeration or aerification         (Safer Brand Moss & Algae Killer or Garden Safe
will help alleviate soil compaction and improve          Moss & Algae Killer Concentrate) to kill it (read
growing conditions for the grass. This process           and follow label directions and precautions).
involves physically removing cores of soil from the      Another control option is the use of copper sulfate
lawn, and for some lawns should be repeated              or ferrous (iron) sulfate mixed at the rate of 5
annually. Aerification is not expensive and can be       ounces in 4 gallons of water sprayed over 1000
accomplished with a spading fork, a manual sod-          square feet. After the moss has been killed, apply 5
coring tool or a power-driven core aerator. For more     to 10 pounds of ground limestone to inactivate the
information about aerating lawns, you can request        copper sulfate prior to reseeding with grass, which
HGIC 1200, Aerating Lawns.                               may be toxic to grass seedlings. Other options
                                                         include ground limestone (75 to 100 pounds per
Excessive Irrigation: Automatic watering on a            1000 square feet) or hydrated lime (2 to 3 pounds
regular schedule tends to promote problems with          per 1000 square feet in 3 gallons of water), or
excessive moisture, especially in shady or poorly        diluted bleach (2 to 4 ounces per gallon of water),
or dishwashing detergent (2 to 4 ounces per gallon                                                                reseeding with grass, which may be toxic to grass
of water). Note: one ounce equals two tablespoons.                                                                seedlings. The dead algal crust may have to be
These materials kill the moss because they act as                                                                 removed by raking.
desiccants (drying agents), should be applied by
over the moss-infested areas during winter through                                                                If large bare areas remain after moss or algae
early spring (December through April) when moss                                                                   removal that require renovation, follow the
is actively growing and temperatures are cool.                                                                    recommendations provided in HGIC 1204, Lawn
Apply when the lawn soil is moist. To be effective,                                                               Renovation.
they need a 24-hour rain-free period after
application. As the moss starts to die, it will turn                                                              Prepared by Janet McLeod Scott, HGIC Information Specialist, and
                                                                                                                  Bert McCarty, Turf Specialist, Clemson University. Revised by Joey
orange-brown or golden brown. Once the moss is                                                                    Williamson, HGIC Information Specialist. (New 01/00. Revised
dead, remove it by raking.                                                                                        09/09.)

Algae can be controlled by using potassium salts of                                                               This information is supplied with the understanding that no
                                                                                                                  discrimination is intended and no endorsement by the Clemson
fatty acids (Safer Brand Moss & Algae Killer or                                                                   University Cooperative Extension Service is implied. All
Garden Safe Moss & Algae killer Concentrate) to                                                                   recommendations are for South Carolina conditions and may not
kill it (read and follow label directions and                                                                     apply to other areas. Use pesticides only according to the directions
                                                                                                                  on the label. All recommendations for pesticide use are for South
precautions) or copper sulfate mixed at the rate of 2                                                             Carolina only and were legal at the time of publication, but the status
to 3 ounces (about one teaspoon) in 8 gallons of                                                                  of registration and use patterns are subject to change by action of
water sprayed over 1000 square feet. After the algae                                                              state and federal regulatory agencies. Follow all directions,
                                                                                                                  precautions and restrictions that are listed.
has been killed, apply 5 to 10 pounds of ground
limestone to inactivate the copper sulfate prior to

                                                                                   The Clemson University Cooperative Extension Service
    offers its programs to people of all ages, regardless of race, color, sex, religion, national origin, disability, political beliefs, sexual orientation, marital or family status and is an equal opportunity employer.
 Clemson University Cooperating with U.S. Department of Agriculture, South Carolina Counties, Extension Service, Clemson, South Carolina. Issued in Furtherance of Cooperative Extension Work in
                                                                          Agriculture and Home Economics, Acts of May 8 and June 30, 1914
                                                                                                   Public Service Activities

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