When considering the relationship between fertility and disease, nitrogen fertility typically comes to mind. For example, maintaining adequate nitrogen fertility is a way to avoid the onset of dollar spot and red thread. But in the case of take-all patch, manganese is what you need to keep this disease in check.
Take-all patch disease is caused by the fungus Gaeumannomyces graminis var. avenae. This fungal pathogen attacks roots and stems of bentgrass (Agrostis spp.) during cool, wet weather. Although root and crown rot can occur throughout the growing season, you'll most commonly see symptoms of the disease during the months of April to June and September through November. Symptoms appear as reddish-brown to orange-bronze colored circular patches that are at first only 2 to 3 inches in diameter. Patches, however, are perennial and may range up to 36 inches in diameter on sites chronically affected by the disease The centers of affected patches are often colonized by weeds or resistant grasses such as fescue or Poa species. Sometimes take-all patch declines in severity on its own, but the decline may take seven or eight years to occur and, in the meantime, new infections can appear at other locations on your golf course without notice.
The disease is most commonly found on newly constructed golf courses or on older courses that have undergone renovation. Poorly drained soils or soils with high pH levels favor the development take-all patch, as do light textured (sandy) soils, low organic matter, low fertility and recently fumigated sites. Heavy applications of lime or alkaline irrigation water may also stimulate severe outbreaks of the disease. Moreover, soils with low levels of plant-available manganese are especially vulnerable to the infection.
Some notable characteristics of the pathogen provide clues about how to manage bentgrass turf to minimize take-all patch development. The optimum soil pH for growth of the G. graminis variety avenae is approximately 7.0. The pathogen has the ability to rapidly convert plant-available manganese or applied-fertilizer manganese to forms that are unavailable for plant uptake. Applications of the nitrate form of nitrogen fertilizers also encourage the disease.
Researchers recently conducted experiments over a three-year period on a golf course in central New Jersey in an effort to determine fertilizer management practices that could suppress this devastating disease. They evaluated manganese fertilizer, applied to fairway turf as a foliar spray, at several different frequencies of application and rates.
Research clearly showed that manganese fertilization can effectively suppress take-all patch. Researchers found that manganese fertilization reduced disease severity by about 70 percent.
When researchers compared different times for manganese fertilizer application, they found that one spring or fall application of manganese was equally effective in suppressing disease symptoms. In general, the application of 2 pounds of manganese per acre was as effective as the 8 pounds rate in the study. It is possible, however, that higher application rates (6 to 8 pounds per acre) may be more effective when you're treating soils that have very low soil test levels of manganese.
Surprisingly, the long-term effectiveness of manganese applications was very limited in this study. Although manganese applied within the current year was generally more effective than older manganese fertilizer applications, the beneficial effect of manganese in suppressing take-all patch generally did not persist for more than 12 to 18 months.
TAKE THE TEST
Manganese availability typically decreases as microorganisms convert manganese in soil to unavailable forms. Also, removing the clippings from playing surfaces can also remove significant amounts of manganese from the soil. Clipping removal on golf course fairways is estimated to remove from 0.2 to 1.7 pounds of manganese per acre each year. For these reasons, it is necessary for you to reapply manganese fertilizer. One annual application of 2 or more pounds of manganese per acre is, therefore, recommended for the most effective suppression of take-all patch. More frequent applications did not enhance control in this study.
Soil testing can help you identify sites that are likely to be manganese deficient and that are, therefore, more vulnerable to take-all patch disease. Interpretation of a soil test for manganese should evaluate both the level of manganese and the soil pH. More research, however, is needed to develop guidelines about how to best interpret soil test levels of manganese in relation to the potential occurrence of take-all patch disease.
You should view manganese fertilization as only one part of an overall soil fertility program designed to minimize the incidence and severity of take-all patch. Soil pH management and a sound nitrogen fertility program are also important factors.
For best results, you should maintain soil pH levels to between 6.0 and 6.2. Soil pH levels above 6.2 will encourage take-all patch development, while pH levels below 6.0 can result in nutrient deficiencies and other cultural problems such as increased localized dry spot. In order to monitor pH changes that may occur following the application of any soil amendment, you should measure soil pH annually. Also, be careful to avoid excessive applications of lime, and check the calibration of your spreader to reduce the possibility of over application.
Because alkalinizing nitrogen sources (e.g. calcium nitrate or potassium nitrate) can greatly enhance the severity of this disease, avoid the use of nitrogen fertilizers that contain large quantities of nitrate nitrogen. Ammonium sources of nitrogen, such as ammonium sulfate or sulfur-coated urea, acidify the soil and this helps to control the disease. Due to the potential for foliar burn during hot, humid weather, you should irrigate after you apply ammonium fertilizer. The acidity produced by the use of ammonium nitrogen also helps to improve the availability of manganese in soil.
Fungicides have proven to be effective to reduce the incidence of take-all patch when you use them in combination with good cultural management practices. To achieve optimum control, use preventive applications in the fall and early spring before symptoms appear. Of the various products currently labeled for turf, the sterol-inhibiting (e.g., Banner MAXX, Eagle, Rubigan, Bayleton), the strobilurin or QoI (e.g., Heritage or Compass), or the benzimidazole (e.g., Cleary 3336 or Fungo 50) fungicides have proved most effective for the control of this disease.
J. R. Heckman is extension specialist in soil fertility, B.B. Clarke is extension specialist in plant pathology and J. A. Murphy is extension specialist in turfgrass management, all at Rutgers University (New Brunswick, N.J.).
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