Fight spring, summer turfgrass diseases now

Fall is a great time to guard against spring and summer diseases on warm-season grasses.
Spring dead spot, or SDS, is one of the most common and important diseases on bermudagrass in Georgia. It is difficult to manage without an integrated approach. The disease is most common on intensively maintained turf like golf courses or lawns.

SDS causes dead patches

The characteristic dead patches appear in the spring when the grass is breaking dormancy, and the problem can persist well into summer. The fungus that causes the disease attacks the roots and stolons in the fall and winter. This makes the grass more vulnerable to winter freeze damage, which leads to the dead patches of grass.

Late September through October is the best time to apply preventative fungicide applications if SDS has been a problem this past season. But this won’t provide complete control. Most infections can be eventually eliminated over a period of years by combining fall fungicide applications with sound cultural practices.

But maintaining a disease free lawn in the coming years can only be accomplished by eliminating the stress that allowed the disease organisms to attack the lawn in the first place. Lawns are stressed by poor soil conditions combined with an imbalance of nutrients. Compaction, poor drainage and thatch thicker than one inch are linked to SDS outbreaks.

Follow these tips

Applying nitrogen late in the season or excess nitrogen, especially with a potassium deficiency, can encourage the development of disease. An integrated management program to improve the lawn’s health includes the following steps:
• When planting new lawns, use cold tolerant cultivars.
• Aerate and remove thatch regularly.
• Irrigate deeply and less frequently. (Once per week in the absence of adequate rain.)
• Mow at the recommended height. Low-mowing height stresses lawns.
• Monitor pH and nutrient levels on a regular basis with soil tests. Keep potassium and phosphorus in balance with nitrogen.
• Maintain a pH between 5.5 and 6.0 if disease has been a problem. The pH can be lowered by using ammonium sulfate as a nitrogen source.
• Apply moderate levels of potassium in September and October to increase cold hardiness. If a deficiency of potassium is indicated on a soil test, two applications of potassium sulfate or potassium chloride can be applied at a 3 to 4 week interval for a total of 1 lb. of K2O per 1,000 sq. ft. Excess potassium should be avoided as it can also encourage disease.
• Do not apply nitrogen after August. Nitrogen should be added in recommended amounts in late spring and early summer. Use moderate amounts of nitrogen during the summer so that excess nitrogen is not carried over into the fall.
• Apply fungicides in late September or October if SDS was a problem the previous spring.

Other warm-season grasses, such as zoysia, centipede and St. Augustine, will also benefit from these general recommendations to prevent diseases like take-all and Rhizoctonia large patch. Follow recommendations for fertilizer applications for the particular grass species. A pH of approximately 6.5 is generally optimum for warm-season grasses.

See these sites for more help

For more information on maintaining turfgrass in Georgia, see the website www.Georgiaturf.com. For fungicide recommendations, contact your local University of Georgia Cooperative Extension agent or consult the Georgia Pest Management Handbook for Homeowners at www.ent.uga.edu/pmh/.

By Elizabeth L. Little 


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UGA acquires zoysiagrass collection

University of Georgia has received the zoysiagrass collection developed by Jack Murray, a turf breeder with the United States Department of Agriculture/Agricultural Research Service in Beltsville, Md. An agreement between Bladerunner Turf, Inc., which acquired the collection in 2000, and the University of Georgia Research Foundation, Inc., was signed to allow the UGA turf breeding program in Tifton to develop new turfgrass cultivars from the valuable zoysiagrass collection.

David Douget, owner of Bladerunner Farms, said the collection has already produced several commercially available varieties of zoysiagrass, and he has high hopes that UGA breeders will use the collection to further improve and refine cultivars for release.

Brian Schwartz, the University of Georgia researcher who heads the turf breeding program at UGA’s Tifton campus, said his team will use the plant collection to develop superior zoysiagrass cultivars adapted to the southeastern U.S. and similar environments around the world. “This collection will fill a need in Georgia and the southeast for new, improved zoysiagrass varieties,” said Schwartz.

The new collection adds to a turfgrass program that now includes four of the world’s top five warm-season turfgrass types — Bermuda, centipede, seashore paspalum and zoysia. Schwartz said zoysiagrass is a high-quality, slow-growing turf that requires less fertilizer than faster-growing Bermudagrass.

“This zoysiagrass collection gives us an opportunity to mix excellent plant material with a turfgrass breeding program that’s been active and hugely successful for more than 50 years,” said Schwartz, “and we intend to make the most of it.”


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Water-logged lawns

As flood waters across the state recede after record rainfall, homeowners are left with a messy aftermath to deal with. This includes water-logged lawns that could suffer from the effect of too much of a good thing.

“Excessive rainfall creates an unfavorable soil environment for root growth,” said Alfredo Martinez, a University of Georgia Cooperative Extension plant pathologist. “The oxygen is displaced in the soil pores by water.”

Roots need oxygen

Without oxygen, root growth is restricted. In extreme cases, toxic gases such as hydrogen sulfides and metallic sulfides can accumulate, he said.

The result is weak or dead plants. Water-logged soil stays warmer longer and can increase turfgrass damage.

“Turfgrass injury due to flooding appears as dead brown areas,” Martinez said.

Symptoms will appear a few days after the flood water recedes, and the injured areas will follow the outline of low flooded areas. The first sign of trouble is raw sewage-like odor, which indicates a lack of oxygen in the soil.

After long periods of flooding, turfgrass can partially rot, he said.

“As with diagnosis of many turfgrass problems, history of the area is critical to correctly identify the problem,” Martinez said.

Watch for signs of damage

Additional problems associated with excess water are the diseases that thrive in extremely moist conditions and take advantage of the stressed plants.

The extent of damage depends on the length of flooding, said UGA Extension turfgrass specialist Clint Waltz.

Bermuda grass and bahia grass are most tolerant of flooding. Centipede is least tolerant. Zoysia and St. Augustine are intermediate.

To assess damage, look for white roots, green leaves or green or white runners above and below the soil surface. Green and white indicate a healthy plant while soft, milky white or brown stems and roots suggest the plant is dead.

Lend a helping hand

Lightly rake brown turf areas to determine if some grass has survived.

To help your lawn recovery from the flood:

* Improve surface and subsurface drainage. Keep drains clean. Dig temporary surface drains or put in subsurface drains.

* Remove any sediment like soil and organic debris on the surface by raking or shoveling to help surviving turf recover. Mow off dead leaves.

* Apply one-half pound of nitrogen per 1,000 square feet to encourage grass recovery. Follow normal maintenance practices the rest of the year.

If 40 percent to 50 percent of the area has healthy grass, there’s probably enough left to ‘grow in’ the rest, Waltz said.

Replacement an option

If more than 60 percent is lost, consider using sod, seed, plugs or planting a cover to restore the lawn. Sod produces an instant lawn with less long-term mess.
You can seed tall fescue now until early-November. Plugs should be installed later in the growing season.

You can establish a temporary cover with ryegrass or tall fescue. This should be done from mid-September through early-November. Turf-type tall fescue seeded at five pounds to six pounds per 1,000 square feet may survive if seeded in September. Higher seedling rates will lead to disease and other stress problems and should be avoided.

If tall fescue is used and bermuda, centipede or zoysia is wanted, the tall fescue will survive until next summer when centipede can be seeded or sodded into the tall fescue providing a gradual transition.

“In conditions like these, keeping things simple and being patient are the best strategies,” Waltz said.

For more information on caring for your turfgrass and landscape, contact your local UGA Extension agent at 1-800-ASK-UGA1. Or, visit the Web site www.GeorgiaTurf.com.

By Sharon Dowdy
University of Georgia

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UGA licenses new Bermuda grass that thrives in sun

An internationally recognized turfgrass researcher from the University of Georgia has developed a new Bermuda grass that thrives in sun and produces healthy turf in areas with less than half the light normally required for other Bermuda grass.

The new grass, licensed by the University of Georgia Research Foundation, Inc., to New Concept Turf, will soon be available to homeowners for planting lawns; to developers for recreational facilities, sports complexes and golf courses; and to urban area landscapers.

TifGrand was developed by Wayne Hanna, professor of plant breeding and genetics in the Department of Crop and Soil Sciences at University of Georgia’s College of Agricultural and Environmental Sciences.

“Although TifGrand produces a beautiful turf in full sun, its major contribution will be the production of nice turf in areas with reduced light -- up to 60 percent less light than is normally required for healthy Bermuda grass growth,” Hanna said.

Hanna is a world-renowned plant breeder. During his 37-year career, Hanna has developed winter-hardy, pest-resistant Bermuda grasses able to handle high traffic. These grasses now grow on golf courses around the world and in major sports stadiums.

Hanna has spearheaded the screening of Bermuda grass for hybrids that naturally deter mole crickets, the No. 1 lawn and turf pest in the Southeast. He and his research team have been awarded seven patents.

New Concept Turf, a Georgia-based company specializing in marketing new turfgrasses, has contracted The Turfgrass Group of Ft. Valley, Ga., to exclusively handle licensing of TifGrand for sod production. TifGrand will be licensed to a selected number of growers beginning in summer 2009. It is expected to be available in the general market in 2010.

For more information on TifGrand and licensing opportunities, contact Bill Carraway, vice president of marketing for The Turfgrass Group, 770/207-1500, or visit www.theturfgrassgroup.com.

By Terry Hastings
University of Georgia

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