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Saturday, November 6, 1999

Check grass for symptoms of turf disease
Take-all patch rot can be cured with right fungicide

Autumn in South Texas brings with it increased rain, cooler temperatures and high humidity. These are perfect conditions for fungal development in plants, especially in turf. In the past several weeks we have had many inquiries about St. Augustine lawns with dead spots that are spreading. Most of the problems have been identified as take-all patch.
   Take-all patch is a serious root rot disease caused by the soil-borne fungus Gaeumannonyces gramminis var. graminis, which results in the development of brown, dead areas of turfgrass. It was first discovered on St. Augustine grass in 1991, but it also has been found in bermudagrass, zoysiagrass and centipede grass.
   Early symptoms appear as yellowish (chlorotic), thinning turf in either circular or irregular patches. The roots are often short, blackened and rotten. The grass stems, or stolons, can often be lifted from the soil because of the poor root system. The yellowing grass blades eventually die and become brown, followed by stolon death.
   This disease often is misdiagnosed as Rhizoctonia brown patch. Plant pathologists and turf specialists found that most of the dying turf problems in our area have been identified as take-all root rot; in fact, very few cases of brown patch have been seen in the Coastal Bend. The early symptoms are the same. The blades become yellow and can be easily removed from the stolon with a gentle tug. The base of the blade infected with brown patch is usually slimy and rotten. The key difference is that the stolons remain green with brown patch but often die with take-all patch. Also, brown patch does not cause extensive root rotting. Control of take-all root rot consists of both cultural and chemical practices. Good surface and subsurface drainage is important. The heavy rains of October left many areas under water and poorly drained clay soils super-saturated for extended periods of time resulting in an abundance of take-all patch. It is difficult to improve your drainage without ripping up your lawn and starting from scratch. However, improving your irrigation practices can partially compensate for poor drainage.
   Avoid overwatering. A common mistake is to water shallow and frequently. If is better to water infrequently but deeply (6-8 inches) as the turfgrass needs it. Watch your turf. It will tell you when it needs water by becoming dull green in color and the blades fold up to reduce water loss. Less frequent watering not only reduces fungal development but it also produces a stronger, deeper root system.
   Also, water early in the morning, allowing the grass to dry before noon. Evening watering increases the humidity and moisture level for an extended period of time and encourages fungal root rots.
   Proper fertilization will keep your grass strong and healthy, making it less susceptible to disease. A fall fertilization with a slow-release nitrogen fertilizer is encouraged. If you have not already done so, fertilize with a winterizer (60-70 percent slow release nitrogen) before the end of the month. After fertilizing, remember to water in the fertilizer.
   Fungicide applications should be considered where take-all root rot is present. Fall and spring applications have proven to be the most effective because of the activity of the fungus during these cool, humid seasons. Fungicides that are either labeled for control of these diseases or have been shown to be promising in research tests include: Banner, Bayleton (triadimefon), Eagle, Rubigan, Sentinel, and thiophanate-methyl (Fungo 50, Cleary's 3336, Proturf Systemic Fungicide, Topsin-M). If you have questions, ask your local nursery worker to help you find the product for use on take-all patch.
   It is suggested that the fungicides be applied in a high volume of water or that irrigation be applied immediately after application, before the fungicide dries on the leaves, so it can move down into the root zone. Also remember that fungicides are most effective as a preventative treatment and much less effective as a cure. However, success has been found when applying the fungicide after the infected stolons (runners) are raked out and the soil is gently loosened. Two or three applications at 3-4 week intervals may also help. Remember that you must read the label and follow directions. Also note that these products should not be applied during high temperatures to prevent phytotoxicity problems.
   References to fungicides is made for educational purposes and is not intended as an endorsement. Follow manufacturer's recommendations and precautions on all product labels. These recommendations are based on the TAEX publication L-5170, Take-all Root Rot of Turfgrass. The above-mentioned products were labeled for use as of the date of publication of the aforementioned information sheet. Labels change unexpectedly, thus it is important to always read the label.


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