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Summer Disease Management on Poa annua/Bentgrass Greens with New Fungicide Products

Summary: In replicated field trials conducted on a poa/bentgrass putting green, fungicides were tested for efficacy and phytotoxicity against a variety of summer diseases. Key results include:

  • An unseasonably cool summer produced unusual disease patterns, with Rhizoctonia causing the most significant damage to turf, and anthracnose causing only limited damage. Summer patch was observed, but caused insignificant damage to turf.
  • Symptoms caused by Rhizoctonia spp. were well controlled by several of the products tested, including BAS 500, BAS 505, Heritage and Eagle. A rotation of Banner (2.0 oz/1000 sq ft) followed by monthly applications of Compass at the high rate (0.4 oz/1000 sq ft) also provided excellent control.
  • It is possible that the high application volumes used in the study (3.5 gallons/1000 square feet), in combination with the fact that irrigation immediately followed fungicide applications may have interfered with the activity of Compass, whose mode of action is mesostemic, rather than systemic.
  • A rotation of Banner (3 bi-weekly applications in May/June) followed by high rates of Compass (2 monthly applications) performed significantly better against Rhizoctonia than season-long monthly applications of Compass at the same rate. It is likely that early season treatments with Banner helped to decrease the disease inoculum levels, allowing the Compass to perform better later in the season.
  • Good control of Rhizoctonia lasted up to 6.5 weeks for BAS 500, BAS 505, Heritage and Eagle.
  • Anthracnose, caused by Colletotrichum graminicola was well controlled by almost all of the treatments tested, with the exception of the low rate of BAS 505 (0.15 oz/1000 sq ft).
  • No phytotoxicity was observed for the majority of products. However, BAS 505 produced moderate levels of phytotoxicity on most rating dates, with the higher rate (0.25 oz/1000 square feet) producing higher levels of damage than the lower rate (0.15 oz/1000 square feet). The observed damage was primarily to Poa annua. As a result, a gradual increase in bentgrass was observed in plots sprayed with BAS 505, particularly in the plots treated with the high rate. This type of gradual suppression of Poa annua may have commercial value to superintendents attempting to maintain pure bentgrass stands.

Printable version of full report

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

Cooperator: John Martinez, SCGA Member’s Club

Sponsors: BASF, Novartis, Rohm and Haas, Zeneca


Evaluation of Fungicides for Control of Summer Patch

Summary: In a replicated field trial at Hacienda Golf Club, La Habra Heights, CA, fungicides were tested at various rates, in various combinations and sequences for control of summer patch on a Poa annua putting green. Key results include:

  • Heavy disease pressure was observed, with summer patch (Magnaporthe poae) causing the most severe damage. Anthracnose (Colletotrichum graminicola) and Rhizoctonia spp. were also present in test plots, and were responsible for turf damage as well.
  • The best summer patch control was observed in fungicide rotation programs that used azoxystrobin (Heritage) or azoxystrobin and thiophanate-methyl (Cleary’s 3336) in the latter part of the season, and a sterol inhibitor (tebuconazole or propiconazole) in the early part of the season. In addition to providing very good control of summer patch, anthracnose and Rhizoctonia, these programs have the additional merit of rotating among different classes of fungicides, and thus helping to avoid development of fungicide resistance.
  • Rotations of Bayleton with Heritage, as well as the experimental product Compass (trifloxystrobin) provided some control of summer patch, but the overall control achieved was not acceptable, with these treatments performing significantly better than the check on only zero to two out of seven rating dates. The combination of Compass plus Banner did not perform any better than Compass alone. This may be due to the fact that the mixture was applied monthly, while the unaccompanied Compass (0.20 oz/1000) was applied bi-weekly.
  • Tebuconazole (Lynx) not only provided very good control of summer patch and anthracnose in this and other trials, but also was effective in selectively removing Poa annua from bentgrass, without damaging the bentgrass.  This feature makes Lynx an interesting option for superintendents who are trying to maintain Poa-free bentgrass greens.
  • All products provided excellent control of anthracnose, and most products (with the exception of trifloxystrobin) provided excellent control of Rhizoctonia spp.

Printable version of full report

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

Cooperator:  Rafael Barajas, Hacienda Golf Club

Sponsor:  Bayer, W.A. Cleary’s, Novartis


Evaluation of Preventative Fungicides for Control of Summer Patch of Poa Caused by Magnaporthe poae

Summary: In a replicated field trial at Arrowhead Country Club, San Bernardino, CA, monthly preventative treatments of Heritage at 0.2 and 0.4 oz/1000 sq ft and Lynx at 1.5 oz/1000 sq ft provided good to excellent control of summer patch compared to monthly applications of Bayleton at 4.0 oz/1000 sq ft or the non-treated control plots. Heritage and Lynx also provided significantly improved turfgrass quality compared to the Bayleton and non-treated plots, although Lynx applications did result in significant, but reversible damage to turf. Bayleton turfgrass quality and control ratings were not significantly higher than the non-treated control plots on many of the rating dates. Based upon these results, Heritage or Lynx would be good replacements for the commercial standard Bayleton.  Due to their solid performance, as well as their high residual activity, the use of Heritage or Lynx should also result in fewer pesticide applications per season for control of summer patch.

Printable version of full report

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

Cooperator:  John Harkness, Arrowhead Country Club

Sponsors:  Gary Braness, Bayer and David Ross, Zeneca


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