Evaluation of Primo Rates and Application Timing Strategies for Improved Transition and Turf Quality

March 14, 2005

Summary: A study was conducted on overseeded common bermudagrass fairways to determine the optimal rate, application timing and frequency of application of Primo to achieve improved Fall transition from common bermudagrass to ryegrass. A similar trial conducted in 1996/97 by the PACE Turfgrass Research Institute indicated that the highest quality overseeded turfgrass resulted when Primo applications (0.5 oz/1000 sq ft) were made at the time of the first ryegrass mowing. To confirm these results, a streamlined version of the study was repeated in 1997/98. Key results include:

• Overall, a single application of the 0.5 oz or 0.75 oz/1000 sq ft rate of Primo L provided the most consistent positive results when the product was applied to ryegrass, 1 - 9 days after the 1st mow. In contrast, applications made according to Primo L label instructions (1-5 days before overseeding) had no positive effects on turfgrass quality. Based on two years of data supporting this conclusion, a change in label application timing recommendations should be considered for the Low Desert, where the unique renovation and overseeding strategies that are practiced may dictate modifications in product use patterns.
• The turf quality improvements were observed 7-8 weeks after Primo applications were made, suggesting that the growth regulator effect of Primo on ryegrass, which typically lasts 4 weeks, only partly contributed to the results. Based on the data, it is likely that Primo applications made at the time of the first mowing caused significant and selective reductions in bermudagrass growth without a similar impact on ryegrass, allowing denser and more vigorous establishment of overseeded ryegrass in the treated plots.
• Primo L treatments (0.5 - 2.0 oz/1000 sq ft) made to bermudagrass, 1 - 14 days before overseeding, had no positive effects on turfgrass quality. Again this was similar to results observed in 1996/97. However, applications made to bermudagrass may be advisable as a green waste management tool.
• Double applications of Primo (an initial treatment of Primo prior to overseeding, followed by a second application after overseeding) did not appear to enhance the chances of improved ryegrass quality under the weather and overseeding conditions experienced in the Low Desert.
• None of the treatments tested caused any negative effect on the Spring transition from ryegrass to bermudagrass.  This is in contrast to results seen in the previous year’s study.

Printable version of full report

Principal Investigators:  Wendy Gelernter, Ph.D. and Larry J. Stowell, Ph.D., CPAg

Cooperator:  Mike Kocour, The Springs Club

Sponsors: Hi-Lo Desert Golf Course Superintendents Association and Novartis