Zoysiagrass – Diseases
Zoysiagrass lawns can withstand diseases if they are properly cared for. This includes fertilizing properly, mowing at the right height and watering when needed. It is better to control diseases by proper maintenance than by using fungicides.
There are three common diseases of zoysiagrass lawns:
BROWN PATCH is most prevalent on zoysiagrass which has been heavily fertilized when night temperatures are above 68 degrees and day temperatures are above 80 degrees. Dead patches of grass may start small but can grow and join together to make patches more than 3 feet apart. Sometimes, there will be a ring of brown, dead grass surrounding a patch of green grass. To control brown patch, fertilize zoysia moderately in summer and if you irrigate, do it in very early morning. There are lawn fungicides available to control brown patch. Read the label carefully and use the rate and timing that is indicated.
DOLLAR SPOT occurs when nights are cool and days are warm in the spring and again in the fall. The spots of dead grass are about the size of your hand. They are very noticeable on closely mowed lawns. Look for a lesion on the grass blade, particularly on the edge of the grass blade. Sometimes these areas go all the way across the blade, causing the tip to die and to take on a straw color. The pattern and color of lesion development on the foliage is a good means of distinguishing dollar spot from brown patch.
Dollar spot is associated with a lack of fertilizer and drought conditions. To control it, apply a moderate amount of fertilizer and irrigate deeply only one time per week. There are lawn fungicides available to control dollar spot patch. Read the label carefully and use the rate and timing that is indicated.
RUST is usually noticed when a cloud of orange powder shoots out from a lawnmower. The disease depends on the cool, moist conditions of late fall. It is likely to be more severe in shady areas. Try to control it first by applying a moderate amount of fertilizer. Use a low nitrogen fertilizer in fall. Five pounds of 5-10-15 per 1000 square feet of lawn is recommended. Mow every 4-5 days and try to catch the clippings if possible. There are lawn fungicides available to control rust. Read the label carefully and use the rate and timing that is indicated.
You have brown patches of dead grass in your lawn. Is it the common lawn disease ‘brown patch’ or is it something else? The answer is important: if it is brown patch you probably need to spray with a fungicide. If is not, you’ll waste your money buying expensive fungicides.
DISEASE vs ENVIRONMENT While brown patch does cause patches of dead grass, other things can cause the same symptoms. If the area is poorly drained and water stands on a spot for more than 24 hours, the grass roots will rot, causing a dead patch. If you have a sodded lawn less than one year old, it is possible the soil underneath the sod was never plowed to relieve compaction. Where the sod has rooted poorly, brown patches will develop as dry weather sets in. If one part of the lawn was once used as a baseball home plate or a soccer goalie area, the earth beneath is almost as hard as concrete. It’s easy to see why green grass would turn brown there.
BROWN PATCH SYMPTOMS If you eliminate environmental causes of the brown patch, what are the true symptoms of the disease? True brown patch spots are small to begin with but in warm weather they can enlarge rapidly. Seen from above, the patch will look like a doughnut – a ring of tan grass having a patch of green grass in the center. Individual grass blades will be brown down to the crown – where the blade emerges from the ground – but the crown will be green. Early in the morning during hot, damp weather you might see a white fungal web at the edge of the dead grass patch.
KEEP GRASS HEALTHY Remember that the fungus that causes brown patch is constantly present. It can not be eliminated. Your grass gets sick because it is weak and becomes susceptible to the disease. You can help keep the grass strong by fertilizing only when the grass needs it: during the cool months for fescue and during the warm months for Bermuda grass.
WATERING Never water in the early evening. The best time to water is in early morning. Turfgrass is much more susceptible when it has lush, green growth plus warm nighttime temperatures. Warmth at night can not be avoided but lush growth can be moderated. The second step is to water at the right time. Since brown patch needs 14-16 hours of wet leaf surface to reproduce itself, water only after the dew has dried in the morning. An alternative is to water after nightfall. Since the grass is wet with dew anyway, watering in the dark does not unnecessarily extend the wet period.
FUNGICIDES If you are absolutely sure you have brown patch, the disease can be controlled with fungicides. Look online for products labeled for brown patch control. Although they are effective, their cost may cause you to reconsider their use. To cure brown patch in a lawn requires an application of fungicide every 14 days. A lawn fungicide costs approximately $20 per 1000 square feet per application. For a typical 5,000 square foot lawn, that comes to $100 every two weeks. Let your pocketbook be your guide!
POSITIVE IDENTIFICATION Obviously, it would be nice to have a positive identification of a disease before you decide on the best course of action. You can get that positive ID from your local Extension office (contact your county Extension office). Bring them a sample of your sick grass; it will be sent, free of charge, to the state disease lab in Athens for identification and treatment recommendations.
Q: I had brown patch disease throughout my lawn this summer. Can I put anything in the soil to eliminate the disease?
A: A one word answer: “No”. The fungus spores of brown patch are in the soil all of the time. They can not be eliminated. You only have a problem with brown patch when the grass becomes susceptible to it – because of drought stress or over-fertilizing or over-watering. All three of those conditions are under your control. If you water deeply once each week during dry weather and avoid fertilizing after May, brown patch won’t be nearly the problem it has been.
Remember that control and management of the disease are key. Don’t wait until you need a fungicide. Use fertilization, watering and mowing properly to avoid brown patch.
LAWN DISEASE ID
If you suspect that you may have a turf grass disease, your sampling procedure is critical in order to get an accurate diagnosis. Go to the suspected disease area. Find where the live grass meets some dead grass. This is called the disease margin area. You need to cut a 4 X 4 inch square that has half dead grass and half live grass in it. Include the roots. Do not allow the sample to heat, do not allow the sample to dry out. Place in a paper bag or plastic bag which is not sealed. If you cannot bring the sample in the same day you cut it, it is best to refrigerate it. Take it to your local county Extension office. They would prefer to get the sample on Monday or Tuesday so that they can mail it to the plant disease lab without any delay in the mail. Results will be mailed to you in about 10 days.
Q: We have a large spot in our yard where the grass won’t grow. We have Emerald zoysia sod in the rest of the lawn but in this same spot, year after year, the zoysia dies in the winter. What should we do to the soil to make the zoysia grow there?
A: When grass won’t grow in a sunny area, I look for two things: compacted soil and/or soggy soil. Earth that is too hard simply will not let grass roots penetrate deeply enough to keep the plant happy. If the roots can’t explore several inches of soil, they can’t get the moisture or nutrients needed in times of stress. If the soil stays too wet for extended periods, the roots similarly fail to thrive.
In both cases, lack of oxygen limits how deeply the roots can go. So my first suggestion is that you dig up the soil in the dead spot to a depth of six inches, perhaps adding some bagged manure to the earth, rake it smooth and lay more sod. Second, observe the spot after a rainfall or after you irrigate. Does water accumulate there? Can you redesign the water flow so it passes quicky over your yard? If you correct the rooting zone under the sod, I think your problem will be solved.