PACE Turf - Turfgrass Information Center

Phytotoxicity of rye removal herbicides to seashore paspalum

Summary: A small plot replicated trial was conducted to evaluate the phytotoxicity of rye removal herbicides to seashore paspalum. Of the treatments tested, Kerb and Revolver produced no significant damage to paspalum, with or without the addition of a chelated iron supplement (Sprint 330). Monument produced significant damage to paspalum that lasted approximately 4 weeks at both rates tested. The addition of Sprint 330 did not alleviate this effect.

Full print version of report (336 KB)

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

Cooperator: Brian Darrock, Fairbanks Ranch Country Club

Sponsor: Chris Olsen, Bayer; Dean Mosdell, Syngenta

Role of phosphorus in suppression of Poa annua on bentgrass greens

Summary: The lack of Poa annua on the five-year-old A4 greens at Talega suggest that low soil phosphorus might play a role in limiting invasion by poa. This report summarizes the findings of a study conducted by George Kenny at Talega that reveals the approximate minimum level of phosphorus that is needed to maintain healthy bentgrass with the target of suppressing poa invasion.

  • In order to continue the poa control strategy of low phosphorus management, do not apply excessive phosphorus. The target is between 20 and 30 ppm Mehlich III P to maintain adequate bentgrass growth at the lowest phosphorus levels possible. For increased accuracy in phosphorus testing, use the Olsen test for phosphorus and target a minimum of 5 ppm in the soil for adequate growth of bentgrass. Olsen P values above 5 ppm may be needed if iron levels are increased or the turf begins to display the purple symptoms of phosphorus deficiency.
  • Do not apply more than ½ lb P2O5/1000 sq ft in a single application. MAP is a good source but monopotassium phosphate 0-52-34 will also do a good job while applying potassium at the same time without the added nitrogen.
  • Apply 2 lbs 0-0-50/1000 sq ft monthly throughout the year to provide needed potassium. Irrigate following application.

Full print version of report (471Kb)

Investigators: Larry Stowell (PACE Turfgrass Research Institute), George Kenny (Talega Golf Club)

Poa annua invasion of bentgrass greens: the role of bentgrass quality

Summary: Common sense and experience tell us that the higher the turfgrass quality, the harder it will be for Poa to invade. But until recently, there was very little scientific data available to back up this intuition. Fortunately, we have been able to review data collected from four, multi-year bentgrass variety trials and have confirmed what we expected -- that the speed of Poa invasion is directly related to the quality, or performance of the bentgrass. In other words, generally, the best looking turf had the slowest Poa invasion rates, and the worst looking turf had the fastest Poa invasion rates.

When researchers make turfgrass quality ratings, they are taking a visual measurement that takes into account the color, fineness of the leaf blades, uniformity, and density of the turf. Usually, turf is rated on a scale of 1 to 9, with a 9 representing the best turfgrass quality possible. Although this rating system may appear flawed because it is subjective, it has turned out to be an effective method for selecting improved turfgrass cultivars and also for a range of other applications (Skogley and Sawyer, 1992).

Full print version of report (104Kb)

Investigators: Larry Stowell (PACE Turfgrass Research Institute), Reed Yenny (Mesa Verde Country Club), Ali Harivandi (University of California)

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