PACE Turf - Turfgrass Information Center

Management of Poa annua on Overseeded Fairways

Summary: Product labels for several preemergent herbicides currently contain warnings that applications made less than 4 months before overseeding may result in damage to turf. In other words, applications must be made no later than June—too early to obtain season long control in Southern California. Data from the southeastern U.S. suggests that both Ronstar and Barricade can be applied as late as 6 - 8 weeks before overseeding without damaging emerging ryegrass. This replicated trial was set up to confirm these results under southwestern weather and turf management conditions and to investigate the following questions:

  1. Which herbicides can be applied closest to the overseeding date, without damaging turf?
  2. Which herbicides provide the best control of Poa annua? 

Key results include the following:

  • If the correct rates of pre-emergence herbicides are used (50-100 lbs/A Ronstar G, less than 2 lb/A Barricade 65 G), these products can be applied much closer to overseeding (4 - 8 weeks before overseeding) than their labels currently indicate. This strategy will result in little or no turf damage, and good weed control through April or May, or as much as 9 months post-application.
  • Of the thirty-six different treatments that were evaluated, the best poa control was observed with both pre-emergence herbicides (Ronstar and Barricade) and the post-emergent herbicide Prograss.
  • Turf quality (damage to ryegrass) was significantly influenced by the rate of Ronstar G used, with a significant negative correlation between rate and turf quality. Interestingly, the timing of application of Ronstar G had little negative impact on turfgrass quality, even when applications were made 10, 8, 6, 4 and 2 weeks before overseeding.
  • Higher rates of pre-emergence herbicides (Ronstar G at >100 lb/A and Barricade 65 G at 2 lb/A) caused severe damage to ryegrass when applied 2 - 10 weeks before overseeding.
  • Split applications of Ronstar (50 lb/A, 4-8 weeks before overseeding and 100 lb/A 6-12 weeks after overseeding) provided excellent poa control, with consistent lack of phytotoxicity. This strategy appears to be the most likely to ensure good weed control, without any concomitant damage to turf.

Printable version of full report

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

Cooperator:  Bill Kostes, Desert Dunes Golf Club

Sponsors: AgrEvo, Hi-Lo GCSA, Novartis, Rhone-Poulenc

 

Chemical and Cultural Controls for Moss, Bryum argenteum on Putting Greens

Summary: In two trials conducted at Friendly Hills Country Club, Whittier, CA, a variety of herbicides, fungicides, surfactants, algaecides and fertilizers were tested for their ability to decrease infestations of Bryum argenteum (silver thread moss) on a heavily moss infested poa/bent putting green. Key findings include:

  • Moss was positively identified as Bryum argenteum on the basis of leaf cell architecture (upper leaves with rhomboid-hexagonal cells) and the silvery-white color of the plants. A blue-green algae was consistently found in association with the moss.
  • The most effective treatments contained chlorothalonil (Daconil 2787 and Daconil Ultrex) or quaternary ammonia (RD-20), with up to 80% moss control achieved by the end of the 3 month trial. No phytotoxicity was observed with these treatments. The efficacy of these products may be related to their algaecidal activity.
  • Treatments which injured turfgrass (Lesco Iron Plus fertilizer, Ronstar 2G and Dimension) resulted in an overall increase in moss by the end of the study. Although these treatments initially injured the moss plants, lack of competition of from injured turf appeared to allow the moss to expand its invasion into areas of thinning and/or damaged turf.
  • Some treatments which were reported to control moss at other locations (Ferrous sulfate, Ultra Dawn, Subdue 2E mixtures) had no effect on moss populations in this trial. This may be due to the fact that all treatments were made using broadcast applications (2 - 4 gallons spray solution/1000 sq ft), rather than spot treatments. In a follow up trial investigating the use of Ultra Dawn applied as a spot treatment, drench-type applications (4 oz/gallon UltraDawn, applied in 80 gallons spray solution/1000 sq ft) were found to be extremely effective for control of moss.
  • If moss infestations are heavy, gradual removal of moss, as was observed using chlorothalonil or quaternary ammonia, is the most desirable strategy, since it avoids the appearance of large areas of dead or dying moss. However, if moss infestations are light, spot treatments with products that rapidly kill the moss may be the most effective strategy.

Printable version of full report

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

Cooperator: David Michael, Friendly Hills Country Club

Sponsor: Rohm and Haas, Zeneca, PACE Consulting

 

Pre-emergent Herbicides for Control of Smooth Crabgrass

Summary: In a replicated field trial conducted on a hybrid Bermudagrass tee at La Jolla County Club, La Jolla, CA, residual activity, various formulations, rates and application timings for the herbicides Dimension, Barricade, Ronstar and Pendulum were evaluated for pre-emergent control of smooth crabgrass, Digitaria ischaemum. Key results included:

  • In warm winter climates such as California, it is possible that applications of pre-emerge herbicides for control of crabgrass can be made later than the manufacturers currently recommend (current recommendations are to treat when soil temperatures reach 50 - 55° F), thus extending the activity of these products into the summer months. This is based on our observation that soil temperatures at La Jolla CC reached 50 - 55° F on 3/3/97, but crabgrass seedlings didn't emerge until 5/5/97--a full two months later.
  • The best performance (100% control for 4 1/2 months) came from Dimension 1EC at either 1.5 oz/1000 (applied once on 3/3/97) or 0.75 oz/1000 (applied twice on 3/3/97 and 5/5/97), Pendulum 60 DG, at 1.8 oz/1000 (applied once on 3/3/97), a single application of Barricade 65 WG, applied at 0.55 oz/1000, and split applications of Barricade 65 WG (applied 3/3/97 and 5/5/97) at either 0.28 oz/1000 followed by 0.28 oz/1000, or 0.37 oz, followed by 0.18 oz/1000.
  • Lower rates of Barricade did not perform as well as either the high rate of Barricade or the split applications of Barricade, and the granular formulation of Dimension did not perform as well as the Dimension 1EC formulation.
  • For reasons that are not clear, the performance of Ronstar 2G was equivalent to that of the non-treated control throughout the trial.
  • The most effective products had a residual activity of 140 days (4 1/2 months).

Full print version of report

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

Cooperator: Bruce Duenow, La Jolla Country Club

Sponsors: Dennis Shepard, Novartis; Randy Smith, Rohm and Haas

Page 3 of 4 pages  < 1 2 3 4 > 

Visit PACE Turf on Facebook! Visit PACE Turf on YouTube! Follow PACE Turf on Twitter!