Proxy 2SL (ethephon) is a plant growth regulator that has been shown to limit the vertical growth of various turfgrass species. This study was conducted to determine the effects that Proxy applications would have on the visual quality, e.g., the color, density, and uniformity of creeping bentgrass maintained at fairway height. An area of ‘1019’ creeping bentgrass located at the Iowa State University Horticulture Research Station was treated with Proxy 2SL and evaluated as follows.

The study was organized as a completely randomized block design, which was replicated three times. Each replication consisted of five treatments - four Proxy treatments and one untreated control - that were randomly assigned to an individual 5 X 5 ft plot within the block. Proxy 2SL treatments consisted of the following application rates: 0,1.5, 3.0, 5.0 and 10.0 fl oz of Proxy/1000 ft².

All treatments were applied before the onset of warm summer temperatures; however, the application frequency and date of application differed among the treatments. The 3.0, 5.0 and 10.0 fl oz of Proxy/1000 ft² treatments were applied just once. The aforementioned treatments were applied on June 24. The 1.5 fl oz of Proxy/1000 ft² treatment was applied multiple times at an interval of 14 days. The first of the multiple application treatments was made on May 26, 1999 — eight applications of the 1.5 fl oz of Proxy/1000 ft² treatment were made over the duration of the study.

Treatment applications were made using a C0₂ powered backpack sprayer calibrated to apply 3.0 gallons of material/1000 ft². The turfgrass utilized in this study was established on a growth medium consisting of 1/3 Nicollet soil, 1/3 peat, and 1/3 sand. The growth medium had a pH of 8.05, an organic matter composition of 3.04%, 3 ppm of nitrogen, 2 ppm of phosphorus and 41 ppm of potassium.

Turf evaluations of color, density, uniformity, and phytotoxicity were made on a weekly basis following chemical treatment. Phytotoxicity was noted as either absent or present while color, density, and uniformity were ranked on a scale of 1 to 9; with 9=best, 5=lowest acceptable and 1=worst.

The weekly evaluations for color are located in Table 1. Statistically significant differences in color occurred on June 30, July 7, August 11, August 25, September 1, September 9, and September 15. Beginning approximately two weeks after chemical application, the Proxy-treated plots began to appear a lighter shade of green, a yellow-green color. Four weeks after the chemical application, however, the Proxy-treated plots began to turn a brilliant green color. A notable exception was the 1.5 fl oz/1000 ft² treatments. The repeated applications of Proxy resulted in a continuous, but acceptable, reduction in color quality when compared to the controls and other Proxy treatments. No observable color differences existed on July 21, July 28, and August 18, however. This color discrepancy became even more pronounced during August when the other treated plots were darkening in color. As an additional note, the only observed phytotoxicity occurred with the 10.0 fl oz/1000 ft² treatment the week following the chemical application, June 30. No browning of the leaf tissue occurred — only a minimal yellowing of the treated area.

The Proxy treatments improved the density of the creeping bentgrass at all rates (Note Table 2). Beginning July 7 with the 10.0 fl oz/1000 ft² treatments and July 14 with the remaining treatments, numerous finer textured leaf blades began to appear within the individual plots. Density was not significantly affected until July 21, however. The Proxy treated plots were much shorter, tighter, and denser than the turf found in the untreated controls. It was quite difficult to discern density differences between treated plots during the early stages of the study, but during mid-August, the 1.5 fl oz of Proxy/1000 ft² treatments eclipsed the other treatments — clearly due to the continuing application of product.

The uniformity of the grass plots was also influenced by the Proxy treatments. Significant differences occurred on July 21, July 28, August 11, August 25, September 1, September 9, and September 15 (Note Table 3). The treated plots produced a grass stand that was far less "grainy" with a more consistent color and density than the untreated controls. As mentioned earlier, the chemical treated plots appeared to be much shorter, tighter and denser — more uniform.

Table 1. Visual assessment¹ regarding the color of ‘1019’ creeping bentgrass treated with the following rates of Proxy 2SL plant growth regulator².

²The initial application of the 1.5 fl oz of Proxy/1000 ft² treatment was made on May 26.

³An application of the 1.5 fl oz of Proxy/1000 ft² treatment was made on this date.

⁴The single application treatments of 3.0, 5.0 and 10.0 fl oz of Proxy/1000 ft² and the multiple application treatment of 1.5 fl oz of Proxy/1000 ft² were applied on this date.

NA —The LSD test is not applicable, the differences between means are not significantly different when a =0.05

Table 2. Visual assessment¹ regarding the density of ‘1019’ creeping bentgrass treated with the following rates of Proxy 2SL plant growth regulator².

²The initial application of the 1.5 fl oz of Proxy/1000 ft² treatment was made on May 26.

³An application of the 1.5 fl oz of Proxy/1000 ft² treatment was made on this date.

⁴The single application treatments of 3.0, 5.0 and 10.0 fl oz of Proxy/1000 ft² and the multiple

application treatment of 1.5 fl oz of Proxy/1000 ft² were applied on this date.

NA —The LSD test is not applicable, the differences between means are not significantly different when a =0.05.

Table 3. Visual assessment¹ regarding the uniformity of ‘1019’ creeping bentgrass treated with the following rates of Proxy 2SL plant growth regulator².

²The initial application of the 1.5 fl oz of Proxy/1000 ft² treatment was made on May 26.

³An application of the 1.5 fl oz of Proxy/1000 ft² treatment was made on this date.

⁴The single application treatments of 3.0, 5.0 and 10.0 fl oz of Proxy/1000 ft² and the multiple application

treatment of 1.5 fl oz of Proxy/1000 ft² were applied on this date.

NA —The LSD test is not applicable, the differences between means are not significantly different when a =0.05.