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Moss Control in Putting Greens

Tom Cook, OSU Horticulture Dept., Corvallis, OR


Over the last twenty years putting green maintenance has changed significantly. Mowing heights have moved steadily down to as low as 0.095" and it is common to see greens maintained at less than 0.125" for daily play. Fertility has also dropped to levels as low as 3 lbs. N/1000 sq. ft./year. To increase smoothness many people have turned to light frequent sand topdressing and increased vertical mowing. Many golf courses now have either sand based greens or soil greens with 6 to 8 " of sand built up on the surface. Sand greens are a challenge to irrigate and often require regular and precise applications of water to avoid localized dry spots. The results of these changes are fast smooth greens that impress the pros and low handicappers and make life miserable for the average golfers.

An unwanted side effect of contemporary putting green maintenance strategies has been an increase in moss in greens. Moss in putting greens is now common at most golf courses. It is often, though not always worse on bentgrass greens growing on sand base profiles. As it turns out most superintendents have reported poor results with traditional methods for moss control such as periodic iron applications. Starting in the spring of 1998 as part of the cooperative OSU/WSU research program funded by the T.U.R.F. program, we initiated phase one of research investigating moss control options.

Research Strategy
The moss that is invading putting greens appears to be Bryum argenteum or a related species. We are currently trying to get a positive ID on the most common types. Unlike common lawn mosses, which are active primarily in winter, this particular moss grows most vigorously in summer and survives in irrigated turf as a perennial. It does very well in full sun, and is not as reactive to iron fertilizers as the lawn mosses.

In our current trial we chose to look at nitrogen fertility levels and the effects of several different metallic compounds. All treatments were applied as liquids approximately monthly from 2/18/98 to 5/14/98. Specific treatments included the following:

  1. Iron from Ferrous Sulfate (heptahydrate) 0.2-lb Fe/1000 sq ft/application
  2. Iron from Ferrous Sulfate (heptahydrate) 0.4-lb Fe/1000 sq ft/application
  3. Iron from Ferrous Sulfate (heptahydrate) 0.6-lb Fe/1000 sq ft/application
  4. Copper from Copper Sulfate                     0.2-lb Cu/1000 sq ft/application
  5. Copper from Copper Sulfate                     0.4-lb Cu/1000 sq ft/application
  6. Copper from Copper Sulfate                     0.6-lb Cu/1000 sq ft/application
  7. Zinc from Zinc Sulfate                                0.2-lb Zn/1000 sq ft/application
  8. Zinc from Zinc Sulfate                                0.4-lb Zn/1000 sq ft/application
  9. Zinc from Zinc Sulfate                                0.6-lb Zn/1000 sq ft/application
  10. Copper from Copper hydroxide                 0.2-lb Cu/1000 sq ft/application
  11. Copper from Copper hydroxide                 0.4-lb Cu/1000 sq ft/application
  12. Copper from Copper hydroxide                 0.6-lb Cu/1000 sq ft/application
  13. Nitrogen from Ammonium Sulfate           0.25-lb N/1000 sq ft/application
  14. Nitrogen from Ammonium Sulfate          0.5-lb N/1000 sq ft/application
  15. Nitrogen from Ammonium Sulfate          0.5-lb N/1000 sq ft/application
  16. Iron from Ferrous Sulfate (heptahydrate)         0.2-lb Fe/1000 sq ft/application
  17. Nitrogen from Ammonium Sulfate          0.5-lb N/1000 sq ft/application
  18. Zinc from Zinc Sulfate                              0.2-lb Zn/1000 sq ft/application
  19. Nitrogen from Ammonium Sulfate          0.5-lb N/1000 sq ft/application
  20. Copper from Copper Sulfate                         0.2-lb Cu/1000 sq ft/application
  21. Nitrogen from Ammonium Sulfate          0.5-lb N/1000 sq ft/application
  22. Copper from Copper Hydroxide                 0.2-lb Cu/1000 sq ft/application
  23. Untreated Check Plot

Preliminary Results
Initial applications demonstrated color responses from Iron Sulfate, Copper Hydroxide, Ammonium Sulfate, and combinations of Iron Sulfate or Copper Hydroxide with Ammonium Sulfate. Slight yellowing occurred on plots treated with Zinc Sulfate and Copper Sulfate. Yellowing was worse at higher rates of these two compounds. This trend was repeated after each of the 5 sequential treatments. After 5 repeats plot density increased in plots receiving nitrogen from Ammonium Sulfate. Plot density decreased in plots receiving Zinc Sulfate and Copper Sulfate. Iron Sulfate and Copper Hydroxide had no apparent effect on plot density.

Moss responded differently to each treatment. Iron turned moss blackish brown eventually killing it apparently completely. Zinc and Copper compounds caused moss to turn reddish brown and by the end of the trial period appeared to cause complete kill. Ammonium Sulfate did not appear to injure moss but it did stimulate grass to grow and increase in density. By the end of the treatment period, no moss could be detected in any plots receiving Ammonium Sulfate, Iron, Copper, or Zinc alone or in combinations.

The best turf quality and moss control occurred where Ammonium Sulfate, Iron Sulfate, and Copper Sulfate were applied alone and where Ammonium Sulfate was applied in combination with either Iron Sulfate or Copper Hydroxide. Zinc Sulfate and Copper Sulfate were unacceptable due to turf injury resulting from repeated applications.

Future Plans

Starting with an established stand of moss we achieved successful moss control with repeated applications of several products when treatments started in late winter. The next step is to see whether the moss comes back during summer and also to attempt to control existing moss during the summer months. We were fortunate in spring of 1998 because the unusually mild wet weather allowed us to reapply several treatments frequently without causing phytotoxicity to turf. Our summer trials will determine if we can use rates that are high enough to kill moss without injuring the grass. In the fall we will repeat the spring treatments to see how turf and moss react at that time. Also in the plans is a trial looking at various soaps and detergents as selective herbicides for moss control.


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Last updated on May 05, 2013