Plant Pathology Infobytes

April 6, 1999
Take-all Root Rot: New Disease for Home Lawns in Mississippi

"Next year I am going to have a better looking lawn!" From your lawn's point of view, next year is already here. It's time to get started with a health care program that will help improve the appearance of your turf.

That job could be a lot tougher if your St. Augustinegrass or centipedegrass was a victim of a fungus disease which made its appearance in Mississippi in the late summer and fall of 1998. This disease, referred to as "take-all root rot," was identified by the Plant Pathology Turf Disease Group at Mississippi State University from samples sent to the laboratory from various parts of the state.

Take-all has been diagnosed on turfgrass samples ranging in location from the Hinds County area as far north as Lee County. This suggests the fungal pathogen (Gaeumannomyces graminis var. graminis responsible for the disease could be widely distributed in the state.

According to Research Plant Pathologist, Dr. Larry Trevathan, disease symptoms in affected areas are circular to irregular in shape and may resemble symptoms of brown patch, another fungus incited disease which has been common in the state for many years. However, take-all root rot and brown patch should not be confused, since management strategies for the two diseases differ.

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 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.

Dr. Trevathan notes that take-all root rot is a stress disease. Weather events of late summer in 1998 allowed take-all to extensively invade roots and eventually kill large areas of grass.

If your turf was "wiped-out" last season, it would be a good idea to have your lawn checked for the presence of take-all root rot. Check with the County Extension Office for details on procedures for collecting a sample for analysis at Mississippi State University.

Bear in mind that other factors can lead to poor growth of turf grass. In addition to disease, a variety of environmental stresses can cause turf to thin out or otherwise look unhealthy. Such stresses can 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.
  • Currently available fungicides provide little control of this disease.
  • 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 are currently investigating management procedures for take-all root rot disease control.



Written by the late Dr. Frank Killebrew

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