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Plant Diagnostic Clinic
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Take-all patch, caused by Gaeumannomyces graminis var. avenae, has been identified on several courses in the Mississippi Valley. All confirmed cases to date have occurred on new courses or on greens sodded from a nursery treated with methyl bromide. Greens at risk for take-all patch are:
The take-all fungus is a poor competitor when confronted with a diversity of other soil microorganisms. Take-all decline is a natural biological control phenomenon in which the severity of disease decreases over time as the population of competitive microorganisms increases. Take-all decline has been intensively studied in the wheat/take-all system. The soils suppressive to take-all in wheat have been a rich source of microorganisms such as the fluorescent pseudomonad bacteria that are antagonistic to the take-all fungus. In areas where no grass has grown for years or in cases where the root zone was treated with methyl bromide, the populations of the organisms suppressive to the take-all fungus require time to build up.
Figure 1
Symptoms of take-all patch on a bentgrass putting green
The take-all fungus is a darkly pigmented root-infecting organism. Although symptoms typically don’t occur until heat and moisture stress periods, infection actually occurs under cool, wet conditions in the spring and fall. Symptoms of take-all in our region occur in mid-summer as dinner plate sized patches of off color, wilted looking turf (Fig. 1).
The roots of take-all infected plants are deteriorated, with a black discoloration of the vascular cylinder (Fig. 2). Because of poor root function, symptom expression often follows a period during which the greens were allowed to dry out. Patches are easy to spot early in the morning, because dew tends to leave the patches first.
Figure
2
Discoloration of bentgrass roots infected by the take-all fungus
Take-all is more severe under high soil pH. Use of nitrate fertilizers, which results in a high pH at the rhizosphere should be avoided when take-all patch is a problem. Ammonium forms of nitrogen such as ammonium sulfate actually reduce the pH of the rhizosphere and have been shown to reduce the severity of take-all.
Fungicide application after symptoms appear will have little effect on the disease. Infection and deterioration of the roots have already occurred and the symptoms are simply a moisture stress response.
The following management practices should be used on greens with a history of take-all or greens at risk:
Take-all patch is expected to decline over time. However, because the pH of the irrigation water in much of the Mississippi Valley is very high, symptoms may linger, requiring the use of acid injection.
Updated 4/1/05
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