Monthly Archives: October 2010

  • Fairy Rings

    Identification:

    • Do you see rings or arcs of dark green in your turf?
    • Do you see rings or arcs of mushrooms?
    • Have you observed the rings or arcs for several years?

    If you answer yes to any of the above questions, you could have fairy rings in your turf.

    General Description of Fairy Rings

    Fairy rings are a group of diseases in turfgrass that are caused by fungi. There are thousands of fungi that can cause fairy rings. The most common type of fairy ring can be recognised in turf, because it causes the turf to grow dark green, in a ring or arc. These measure about 75-200mm wide as an arc, and up to a metre in diameter as a ring. Fairy rings can be many years old, and will grow as long as there is turf in which to grow. There are other types of fairy rings that cause the grass to turn yellow, others that can cause a patch of stunted, reddish turf, and still others that can cause the grass to wilt and die. You may notice that fairy rings do not grow together when they meet in a lawn. This is how arcs or pieces of fairy rings are formed.

    How do fairy rings get started?

    Fairy rings begin when a fungus starts growing in your turf. What causes a fungus to start growing in turf is not clear to scientists, but often grass that has a thatch layer and is growing on natural soils that receive ample moisture, will develop fairy rings. Fairy rings will grow in finely manicured turfs, sports turfs, golf greens, and unmown swards. In general, they grow at a rate of about 75-150mm per year.

    Can you see the fairy ring fungi?

    Yes, sometimes if you take a pocket knife and cut across the fairy ring, you will see white threads growing in the thatch. The white threads are mycelium of the fairy ring fungi.

    What causes the turf in a fairy ring to grow faster and look dark green?

    Fairy ring fungi are beneficial fungi that attack and breakdown dead and decaying plant material. Thatch is a mat of dead plant material, and the fairy ring fungi can live and grow in it. As they do, they cause the dead plant material to decay. The decaying material is used by many different microorganisms that live in the soil. When this happens, nitrogen and other nutrients important for turf growth are made available to the plant. Hence, the plant is able to use these nutrients to grow taller and darker.

    Do fairy ring fungi attack turf?

    Generally not, and if they do, they do not kill the grass. However, after the fairy ring fungi have colonised the thatch layer, and it starts to dry out, a problem arises for the turf . Turf and thatch that have fairy ring fungi colonising them resist being watered, much like a sponge after it has dried out. Thus, when turf colonised by a fairy ring dries out, it resists being watered. Therefore, this grass often does not get enough water. As a result, this grass suffers from drought, even though the grass outside and inside of the fairy ring grows well. If the drought lasts too long, this grass will be stunted, wilt, and could then die.

    What can you do about fairy rings?

    There are several things that you can do to avoid or reduce the appearance of fairy rings:

    (Before you have a fairy ring)
    Purchase good quality turf.
    Prepare your soil properly before installing turf or planting grass seed.
    (When you have a fairy ring in your turf)
    Fertilise your grass to reduce the appearance of the fairy ring.
    Aerate your grass to allow water to reach the grass roots in the fairy ring.
    Once or twice a year, spread and rake 6mm of good soil into your turf. See Rolawn Blended Loam™.

    Can you use a fungicide to eliminate fairy rings?

    Yes, there are fungicides approved for use to control fairy rings, but their effectiveness may be inconsistent. If you are considering the use of fungicides to treat fairy rings, consult a turf expert.

    We also recommend that you obtain advice about chemical and non-chemical grass treatment products directly from the manufacturers.

    Can you eliminate fairy rings without fungicides or soil sterilisation?

    Yes, but it is difficult. You would need to dig out and replace, to a depth of about 300mm, all of the soil within the fairy ring and about 300mm outside of the ring. This is not recommended.

    Remember: Fairy rings are caused by fungi that live in most soils, and they decompose dead plant material. Generally, they do not attack living turf, and the best method to control them is through masking their appearance with fertiliser.

  • Thatch

    Identification:

    • When you walk on your turf, is it spongy, soft and feel like a plush carpet?
    • If you look at the sides of your turf, do you see a thick layer of brown, spongy material?

    General Description

    Thatch is a natural part of the living turf and generally desirable. Thatch is a layer of dead turf material. Contrary to popular belief, it is not formed from the grass leaves that fall into the turf after mowing. Thatch forms for several reasons, but the most important is improper fertilisation. When grass is growing properly, it forms new roots, stems, and leaves as the old ones die. As long as new grass is formed at about the same rate as the old dies, there will be no thatch accumulation, but when the grass grows faster than the old material can be destroyed, thatch accumulates.

    Thatch is destroyed by naturally occurring fungi. By applying too much fertiliser to your turf, you can cause it to grow too fast for the natural soil fungi to destroy it, and thus thatch accumulates. It is okay for turf to have no thatch if you like firm turf, but your turf will suffer if the thatch layer grows too thick.

    Do some grass varieties form thatch faster than others?

    Yes, some grasses, like bentgrass and smooth stalk meadow grass do form thatch much faster than ryegrass or fescue. However, even among the different bentgrass and smooth stalk varieties that are commercially available, you can find some that form thatch faster than others. These grass varieties are made available to meet different needs. For example, a sports pitch requires both rapidly growing turf to heal itself and thatch to cushion the athlete's feet and body. Lawns that receive little traffic or limited amounts of fertiliser should be made of less aggressively growing varieties.

    What cultural practices will help control thatch accumulation?

    The most important is to fertilise properly. Next, encourage the roots to grow deeply through proper watering,and prevent your soil from becoming compacted. Light top dressing (Rolawn Topdressing can be used for this) with natural soils or amended sands which will encourage a greater rate of thatch decomposition.

    Mechanical de-thatching or scarification is the least effective means to reduce a thatch problem. De-thatching removes, at best, 30% of the thatch, and does nothing to reverse the cause of thatch production. It is recommended that de-thatching only be done in the late spring or autumn, and only when combined with proper fertilisation and watering.

    Remember: Thatch is a natural product of healthy turf. A thin layer of thatch improves the performance of your turf. Too much thatch is bad for your turf and indicates poor turf management.

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