Plant Pathology Infobytes

August 27, 1999
Take-all Root Rot - Tough on Turf Grass

There was a point in mid-summer when homeowners felt they were fighting a losing battle trying to keep their lawns in tip-top shape. Extended hot, dry weather created stressful growing conditions statewide. The task of maintaining healthy turf for some homeowners was made more difficult by a disease which appears to be on the increase in lawns across the state. St. Augustinegrass and centipedegrass lawns suffering from extreme drought stress were hardest hit by this fungal incited disease.

This disease, referred to as "take-all" is caused by the fungus Gaeumannomyces graminis var. graminis , was identified in several Mississippi counties during the late summer and fall of 1998 by the Plant Pathology Turf Disease Research Group at Mississippi State University.

According to researchers Dr. Larry Trevathan and Ms. Maria Petersen, disease symptoms in affected areas of turf are circular to irregular in shape and may resemble symptoms of brown patch, another fungal incited disease which has been common in the state for many years. Also, the problem may be mistaken for chinch bug damage, or drought symptoms, which have been widespread as a result of extended dry weather.

What should you look for if you suspect a take-all disease problem in your turf? Patches of diseased St. Augustinegrass or centipedegrass at first appear yellowish green. These symptoms are followed within a short time by death of affected grass. Turf in badly diseased lawns dies out completely; eventually, most of the turf in a lawn may become diseased as the causal fungus spreads outward to unaffected areas. As diseased stolons die, severe thinning of the turf occurs in areas of several feet to over fifteen feet. Damaged turf is gradually invaded by grassy and broadleaf weeds.

It is important to remember that take-all is a root disease, and symptoms observed above ground are the result of fungal invasion of this area of the plant. By the time leaf symptoms are observed, the root system has already been severely damaged. Damage to the root system in the form of root rot prevents transport of water and nutrients throughout the plant. Eventually, this leads to death of the grass. Examination of diseased stolons of St. Augustinegrass or centipedegrass reveals dark brown rotted roots. A key symptom of take-all root rot is the ease of removal of patches of infected turf from the soil, whereas healthy turf is difficult to remove, since the roots are unaffected by rot and remain attached to the soil.

Dr. Trevathan emphasizes that take-all root rot is a stress disease. Weather events of late summer in 1998 allowed take-all to extensively invade roots. This, along with a relatively mild winter, allowed the buildup of additional levels of take-all inoculum. For this reason, more problems from take-all root rot occurred this season than in 1998, Trevathan notes.

If you suspect your turf is a take-all victim, you may want to have your lawn checked for the presence of the take-all causal fungus. While it may be possible to make an on-the-spot diagnosis, it's likely that a sample will have to be taken and sent to the Plant Pathology Laboratory at Mississippi State University for disease verification. Check with us at the County Extension Office for details on the correct procedure for collecting a sample for analysis.

While take-all may be responsible for your turf problems, it should be reemphasized that other factors can lead to poor growth of turf grass. In addition to disease, a variety of environmental stresses are often responsible for poor turf growth. These include improper fertilization, chemical injury, mower problems, insect injury, localized dry spots, soil compaction, poor soil drainage, excessive thatch, and competition from other plants.

If laboratory analysis reveals that your lawn is affected by take-all root rot, what steps should be taken? This disease can be minimized by following proper cultural practices.

  • Eliminate excessive irrigation.
  • Avoid applying high rates of lime and maintain a soil pH of 5.5 to 6.0.
  • Mow turf at recommended height and intervals so that no more than one-third of the leaf tissue is removed each time the grass is mowed. This practice will reduce stress and vulnerability of the turf to disease attack. Check with the County Extension Office for a free copy of Extension publication 13222, "Establish and Maintain Your Home Lawn," where this information is provided. This publication is a good source of tips for other cultural practices as well.
  • Fertilizers may influence take-all severity. Acidifying fertilizers such as ammonium sulfate or slow-release urea may be helpful in disease control; avoid applications of ammonium nitrate fertilizer on lawns where take-all has been identified.
  • Maintain a recommended level of potassium; turf which is low in this essential growth element appears to be more vulnerable to attack by the take-all fungus.
  • Few available fungicides provide control of this disease. Immunox (generally available at most garden supply stores) may reduce the degree of disease severity; however, application of this fungicide should be started when the first symptoms of take-all are observed and used in conjunction with other recommended control procedures to be effective.
  • In lawn areas where most of the turf has been killed by the disease, it probably will be necessary to re-establish turf. Follow recommended establishment guidelines to avoid stress and chances for disease recurrence.

Since take-all root rot represents a new disease for the state, researchers and Extension plant pathologists at Mississippi State University continue their efforts to develop management procedures for take-all root rot disease control.



Written by the late Dr. Frank Killebrew

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