|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.
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:
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.
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.