Moss Control Research at Cornell University

Summary of 2002 Research

Frank S. Rossi, Ph.D.

Bryum argenteum, silvery thread moss, continues to be a significant pest problem on golf courses throughout the US. Superintendent surveys conducted by Cornell University researchers indicated that close mowing, low soil potassium levels and surface organic matter accumulation are highly correlated with increased moss invasion. Additionally, observations suggest that the lack of metal-based fungicides, particularly mercury (Hg), have lead to persistent moss invasion.

Postemergence control programs have been reported with variable success...

Postemergence control programs have been reported with variable success. Recently, anecdotal evidence indicates spot treating with Ultra Dawn dish detergent can reduce moss populations but it appears to require consistent follow-up. Here at Cornell University we built upon observations from Oregon State University to develop consistent postemergence moss control programs with copper hydroxide based materials such as Kocide and Junction.

Research conducted from 1999 to 2001 determined that four to seven applications of 5 ounces of Junction applied between October and December at two-week intervals in 2 gallons of water per 1000 square feet provides consistent moss control. Further research explored the prevention of moss establishment under controlled environment conditions with multiple low rate (1 ounce) applications of Junction. Questions remained regarding the influence of less than 2 gallons of spray volume, pH of the spray solution and field testing of the prevention program.

Field research from 2001-2002 provided additional evidence regarding the effectiveness of Junction and has enabled us to more clearly define application parameters. A spray volume study looked at spring vs. fall applications of 5 ounces of Junction in 0.5, 1.0, 2.0 or 4.0 gallons of water per 1000 square feet. Again it appears that spring applications are less effective than fall (Figure 1). Also 2 gallon spray volume is most effective, providing 40% control, however the 1 gallon spray volume provided almost 30% control.

Figure 1. Influence of spray volume and timing on moss control with 4 applications of Junction at 5 oz. per 1000 square feet.

A second study looked at similar application rates of Junction (5 ounces) at 2 gallons spray volume in spray solutions with pH of 4.0, 5.0, 6.0, 6.5, 7.0 and 8.0. Fall applications of spray solutions at or below 6.5 provided excellent moss control (Figure 2). Also, a 0.5 unit increase from 6.5 to 7.0 reduces moss control almost 50%.

Figure 2. Influence of spray solution pH and timing on moss control with 4 applications of Junction at 5 ounces per 1000 square feet and applied in 2 gallons of water.

Interestingly, as spray solution pH decreased bentgrass injury (yellowing) increased...

Interestingly, as spray solution pH decreased bentgrass injury (yellowing) increased. We were able to determine from tissue samples that iron uptake is reduced when compared to untreated tissue iron levels. A follow up application of iron sulfate seemed to reduce the yellowing and increase iron tissue levels, but more work is needed to determine the role of iron and injury.

The final 2001 study was designed to field test the prevention program identified in the growth chamber. Weekly applications of 0.25, 0.5, 1.0, 1.5 or 2.0 ounces of Junction at the 2 gallon spray volume were made to an area without moss. Similar to growth chamber findings the weekly 1 ounce application completely prevented moss establishment (Figure 3). Plots treated with rates above 1 ounce developed the yellowing observed in the spray pH experiment. Again these were alleviated with applications of iron.

Figure 3. Influence of weekly applications of Junction on moss establishment.

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A second series of experiments were conducted to evaluate Terracyte, a sodium perchloride and lime based product for moss control. Spring applications were slightly less effective than Fall treatments for moss control (Figure 4). This is consistent with observations of Junction efficacy on moss. Apparently moss begins an acclimation period in response to day-length and temperature. This acclimation either enhances susceptibility or reduces the recuperative ability of the moss.

Figure 4. Influence of 4 consecutive day applications of Terracyte on moss populations.

This has been an exceptionally productive line of research, building on intial observations. Follow up research more thoroughly refined application parameters and should result in excellent moss control programs. The financial support from Tri-State research Foundation and Metropolitan Golf Course Superintendent Association and supplemented by Griffen LLC and the Hudson Valley Superintendents helped make it all possible. We are grateful for this support and look forward to further interaction with these outstanding organizations.