As a county extension agent, the questions I get are all over the map. One minute I may be talking about pond management or shrimp-like creatures in a ditch and the next minute providing information on how to solve a particular insect problem or turf disease. I have always enjoyed solving mysteries and puzzles. But every once in a while there are those cases that ends with a head scratch and my favorite quote, “I don’t know, but I will find out and get back with you.”
For the past several years, a number of homeowners have been fighting a losing battle with their turfgrass. Most have been in a vicious cycle of spring planting, fertilizing, watering and watching as the re-established area reverts back to bare ground. There are several plant diseases that cause turfgrasses to die out, but take-all root rot is occurring in several areas of the county without regard to the location, including farm lawns or multiple lawns spreading throughout subdivisions.
Take-all root rot, caused by the fungus Gaeumannomyces graminis var. graminis, emerged a few years ago as a disease that can turn a healthy, lush lawn into bare ground infested with unsightly weeds. It can be easily confused with another fungus, brown patch, or even drought stress. Brown patch is easier to treat than take-all, and the turf usually will recover. Take-all, however, can lead to the complete destruction of the turf. It is important to remember that this is a root disease, and by the time leaf symptoms are noticeable, the root systems already have been severely damaged. The first symptoms of take-all appear in the spring and summer. Leaves will gradually turn yellow, which leads to an overall yellow appearance of the lawn. Later, severe thinning of the turf will occur that can lead to large areas of dead grass and bare ground. Grass roots become rotted and detach from the grass.
There are no textbook answers for solving this plant disease. Chemicals have no guaranteed results, and at best are preventative in nature instead of solving the problem. Following specific cultural methods helps, but they are limited in fixing the problem. What can you do to help stop take-all before it takes over your lawn? The following tips can help minimize the damage of this disease and other fungal problems:
• Limit the amount of nitrogen fertilizer. Have a soil test performed every three years and carefully follow the recommendations for fertilizer application rates and times. The lower the first number (nitrogen) is on the fertilizer bag, the better. Avoid high-nitrogen fertilizers and use one with higher potassium analyses.
• Irrigate at 2 inches of water per week. Place a shallow container under the sprinkler system and see how long it takes for the can to fill up with water — that’s 1 inch. It is usually best to water about three times a week rather than every day.
• Irrigate during periods when the grass is naturally wet or early enough during the day so the grass can dry before nightfall. But remember if you irrigate during the day a good amount of the water evaporates away and will not be available to the plant.
• Do not “scalp” your lawn. The damaged root system needs more grass to support it. Make sure you are following the recommended cutting height for your particular type of grass. Keep mower blades sharpened so clean cuts will be made.
The above management practices offer the best defense against take-all. If chemicals are to used, remember there are no silver bullets, a fungicide application in the fall (before dormancy) and early spring will prove to be most effective. Immunox Lawn Disease Control (active ingredient: Myclobutanil) or Triadimefon (Bayleton), such as Bayer Advanced Fungus Control for Lawns are registered fungicides available to homeowners at local retail garden centers for control of this disease. Other fungicides that may be purchased online or at smaller garden centers such as Rubigan (fenarimol), Heritage (azoxystrobin), Banner Max (propiconazole), Cleary’s 3336 (thiophanate methyl), and Insignia (pyraclostrobin), may help control take-all root rot. Apply these fungicides with 2.5-3 gallons of water per thousand square feet to reach the root system or lightly water in the fungicide.
Remember, if applying fungicides, always read and follow label directions carefully.
For more information contact your local county extension office.