By Island County Extension Agent, Donald B. Meehan

MOSS AND CRANEFLY PROBLEMS IN HOME LAWNS

This the time of the year a lot of people are noticing their lawns. Many are finding it is being overtaken by moss, or they are finding large areas almost devoid of grass. These problems are common to those of us living in the Pacific Northwest where moss grows well in the winter and where the European Cranefly has become established. First, let us look at the moss problem. It is a common ailment in our area because of the mild and wet winters. It is present in home lawns for a variety of reasons. Anytime a lawn is in poor condition, where soil is exposed, moss has an opportunity to grow and establish. Lawns which have not been encouraged to grow to a healthy state by fall will be susceptible. Fertilizer and water are two ingredients which must be provided each year to keep grass healthy. Soils which become overly compacted need to be aerated to provide adequate air to the roots of grass. Thatch buildups reduce or prevent the movement of water to the root zone and should be removed. If you have areas in your lawn which have been building up a large moss population, you might stop to evaluate why it got started in the first place. Did you fail to fertilize 3 - 5 times throughout the growing season? Do those areas seem overly compacted? Is there a large thatch buildup preventing your summer watering from doing its job? Have you been watering enough during our last two exceptionally dry summers? If you identified any of these problems, then you may be able to start getting your moss problem under control, and more importantly, your lawn in good condition. Keep in mind that moss prefers to grow in the winter season and peaks during the early spring. Grass, on the other hand, grows from spring to fall. If the grass is at its best in the fall, the moss will be less able to compete for space during the winter. Well, this is all fine and dandy, but how do you deal with the moss problem you have right now? The first action you need to take is to remove as much of the existing moss as is possible. This is an important step and thatching will do this well. Heavy raking will also work, but have a glass of lemonade close by to keep you cooled down. Next, treat the mossy areas with iron compounds. These come in several forms. Liquid ferric sulfate is the most effective. Fertilizers with iron compounds also work well if they are a near-dust formulation. Lime and copper sulfate have been shown through research to be almost useless in killing moss. Some moss killers contain zinc sulfate and will do a nice job of killing moss but can also be hard on the grass as well. Beware of buying products called moss killers unless the label specifically states you may use it for controlling moss in LAWNS. Many moss killers are on the market for killing moss on sidewalks, roofs and driveways. The chemicals in these may be harmful to plants. Be sure to read the label to know what you are buying. Once the lawn moss killer has been applied, you will want to work on providing adequate fertilizer several times throughout the growing season. Be sure to water properly, getting good soil penetration to a depth of 12 to 24 inches. Water longer periods but less frequently to encourage deeper root growth. If you have questions about lawn care, WSU-Cooperative Extension has written many publications about specific lawn problems faced by the Western Washington homeowner. Call our office for a listing. We will be glad to mail one to you. CRANEFLIES ARE A PROBLEM, TOO The other major lawn problem seen in lawns this time of the year is damage caused by European Cranefly larvae (Leatherjackets). This damage is characterized by loss of grass in large areas. Sometimes this loss will appear scattered throughout a large area. Cranefly larvae feed on the root crowns of grass and clover during the fall and spring. High populations of the larvae will create obvious damage. Low populations often do not cause enough damage to notice and warrant no action by the homeowner. When trying to determine why your lawn is loosing grass, you need to search the root zone of the grass. If Cranefly larvae are the culprit, they will not be visible on the surface. You must dig up a section of the lawn near the edge of the damaged area and tear the roots apart to find the larvae. Looking only in the soil beneath the roots may not reveal any larvae. At this time of the year larvae will be approximately 3/4 to 1 and 1/4-inch long. If damage is severe, there are no biological control measure which will be of value to prevent the lawn from continuing to be damaged. Chemical control is generally recommended to save the lawn. Two insecticides are recommended by WSU for controlling Cranefly larvae, Diazinon and Dursban. Both can be hazardous to children, pets and birds. Generally, one good application which is watered into the root zone will provide adequate control. The results will be obvious the day after, when all of the damaging pests have migrated to the surface. For more information contact our office for a two-page publication called EB 856, "The European Cranefly: A lawn Pest".



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