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Compatibility, Safety and Efficacy of Ethephon Mixed with Snow Mold Fungicides in Winter
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Compatibility, Safety and Efficacy of Ethephon Mixed with Snow Mold Fungicides in Winter

Adam Van Dyke, M.S., CPAg, Professional Turfgrass Solutions LLC
Author email: adam@proturfgrasssolutions.com

Objectives

  1. Can ethephon be mixed with common snow mold fungicides in winter?
  2. Are these mixtures safe on putting green turf?
  3. Is the efficacy of either pesticide affected?
  4. Does including an early application of ethephon in winter improve annual bluegrass seedhead suppression in spring?

Disclaimers (from product labels used in this research): Always follow label directions.

  • Test all product tank mixes on a small area before using widely.
  • Do not combine fungicides in the spray tank with other pesticides, unless your prior use has shown the combination physically compatible, effective and noninjurious under your conditions of use.
  • It is impossible to test all combinations on every species and variety of plants under all conditions.
  • When tank mixing, observe all directions, precautions, and limitations on labeling all of product used.
  • Contact company representatives prior to using a spray mixture.

Materials and Methods

This RMEGI supported research was conducted from November 2016 until May 2017 on a putting green at Murphy Creek Golf Course in Aurora, Colorado. The turf was a mixture of 70%-80% annual bluegrass (Poa annua) and 20%-30% creeping bentgrass (Agrostis palustris) mowed at 0.125 inch and grown on a sand rootzone. Ethephon (Proxy; Bayer) was mixed with common snow mold fungicides, Interface Stressgard and Mirage Stressgard (Bayer) or Instrata and Banner Maxx II (Syngenta), and applied at two winter timings of presnow cover and post-snow melt. This was done to evaluate the compatibility and safety of these mixtures on greens because preceding spring seedhead programs with winter ethephon applications has improved annual bluegrass seedhead suppression – and the timing coincides with fungicide applications for snow mold protection.

Pre-snow treatments were applied on November 30, 2016 and included: Proxy at 5 fluid ounces/1000ft2 + Interface at 6 fluid ounces/1000ft2 + Mirage at 2 fluid ounces/1000ft2; Interface + Mirage alone; Proxy at 5 fluid ounces/1000ft2 + Instrata at 9 fluid ounces/1000ft2 + PAR (pigment; Harrell’s) at 0.36 fluid ounces/1000ft2; and Instrata+PAR alone. Post-snow treatments were applied on February 20, 2017 and included: Proxy at 5 fluid ounces/1000ft2 + Mirage at 2 fluid ounces/1000ft2; Mirage alone; Proxy at 5 fluid ounces/1000ft2 + Banner Maxx at 2 fluid ounces/1000ft2; and Banner Maxx alone. Combination treatments of Proxy mixtures and fungicides alone applied at both winter timings (pre- and post-snow) were also included (Table 1). Winter treatments were applied with a backpack sprayer operating at 40 psi, through a boom with four TeeJet AI-11002VS nozzles in 2 gallons/1000 ft2 (87 gallons/acre) to 4-foot x 6-foot plots arranged in a randomized complete block design replicated four times. Winter treatments were followed by the standard spring seedhead program used at the golf course.

The first spring application occurred March 10, 2017 (made by the maintenance staff) and included Proxy at 5 fluid ounces/1000ft2 + Primo Maxx (Syngenta) at 0.125 fluid ounce in 1.5 gallons/1000 ft2 (65 gallons/acre) with a Toro 5500 sprayer operating at 30 psi. Follow-up applications of Proxy + Primo were made on April 5 and April 20, 2017. Plots receiving just fungicides Instrata at the pre-snow timing followed by Banner Maxx at the post-snow timing, were covered with boards in spring for an untreated seedhead control. All other plots received the spring program applications. Plots receiving just fungicides Interface + Mirage at the pre-snow timing followed by Mirage at the post-snow timing, were the spring program check – to compare the efficacy of

 

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including ethephon at the winter timings to just the spring program. The full treatment list including products, rates, and application timings is listed in Table 1.

Granular fertilizers supplied 0.5 lbs. nitrogen (N)/1000ft2 on April 3 and another 0.5 lbs. N/1000ft2 on May 3, 2017 to the entire trial. A liquid fertilizer supplied 0.2 lbs. N/1000ft2 to all plots except the untreated that were covered by boards on April 20, 2017. No aerification was done in spring and no other pesticides were applied during the study.

Compatibility of mixing Proxy with the snow mold fungicides described above was determined by following label mixing directions. Two-liter plastic soda bottles (67.7 fluid ounces) were filled with water and the proportionate amounts of the products to the one-liter (33.8 fluid ounces) level. After thoroughly mixing, the solution was set aside to stand for 15 minutes. Incompatibility is indicated by signs of separation, globules, sludge, flakes, or other precipitates. Physical compatibility is indicated if the combination remains mixed, or can be remixed readily. The products were sprayed within 20 minutes of mixing. Phytotoxicity was monitored after each treatment application on a 0%-100% injury scale, where 20= the highest acceptable discoloration to the turf.

Seedheads of annual bluegrass were first observed in early-May, and visually assessed on a 0%-100% cover scale on May 12 and May 23, 2017. Statistical calculations of both dates were done to determine seedhead pressure over time. Suppression (or control) was determined by calculations of seedhead means relative to pressure in untreated turf. Turf quality was rated at each winter application timing, and in May when seedheads peaked on a 1-9 scale, where 6= the lowest acceptable quality. A CM-1000 chlorophyll meter (Spectrum Technologies, Aurora, IL) was also used to quantify turf color on a 0-999 index scale. Three measurements were taken in each plot and averaged for the plot mean, with higher numbers equaling darker green turf. All data was analyzed for differences using ARM ver. 2017.4 (Gylling Data Management, Brookings, SD) with means compared using Fishers’ protected LSD at a 95% confidence interval. Data that was skewed or not homogeneous were subjected to transformations to normalize the data. 

 

Mixing Compatibility and Turf Safety

At the pre-snow timing, there were no signs of incompatibility when Proxy was mixed with Interface+Mirage or with Instrata (Figure 1). Also, there were no clogging issues when these mixtures were sprayed through the boom described above with TeeJet 50 mesh stainless steel screens. Proxy mixtures with Mirage or Banner Maxx at the post-snow timing also appeared compatible with no spraying issues (Figure 2). No phytotoxicity occurred from any treatment at any time in this experiment, so these mixtures appear safe for putting greens – but always follow label directions and contact company representatives before using a spray mixture.

 

Seedhead Suppression

The treatments had significant effects on the suppression of annual bluegrass seedheads in spring (Table 2). Specific effects include:

  • Seedheads peaked in late-May and covered 74% of untreated turf on May 23, 2017 (Table 2).
  • The spring program suppressed 50% of seedheads (Figure 3). Suppression was improved when the spring program was preceded by a winter application of ethephon (Figure 4).
    • Including a pre-snow application of Proxy suppressed 75% (mixed with Interface+Mirage) and 82% (mixed with Instrata) of seedheads. The fungicides did not influence efficacy.
    • Including a post-snow application of Proxy suppressed 74% (mixed with Mirage) and 81% (mixed with Banner Maxx) of seedheads, with fungicides again not influencing efficacy. 
    • Including Proxy at both winter timings suppressed 80% (mixed with Bayer fungicides) and 91% (mixed with Syngenta fungicides) of seedheads.
      • Making both winter applications of Proxy with Bayer fungicides did not improve suppression over and single-timing treatment, but making both winter applications of Proxy with Syngenta fungicides improved suppression over both single-timing treatments of Proxy with Bayer fungicides.
  • *NOTE* The influence of Proxy on fungicide efficacy could not be determined because snow mold damage did not occur in this experiment.

 

Turf Quality and Color

The treatments had significant effects on turf quality on 1 of 2 dates, but not on turf color on either date (Table 3). Specific effects include:

  • Proxy mixed with Bayer or Syngenta fungicides at the pre-snow timing (in Nov.) or post-snow timing (in Feb.) did not influence turf quality (Table 3). No visible discoloration, crown rising, or other injury that would negatively impact quality, was observed from applying Proxy with these fungicides at common times for snow mold protection (Figure 5).
  • Turf quality was most influenced in May from treatments that included Proxy at winter timings because seedhead control was improved.
    • Quality was best when Proxy was applied at both winter timings (Table 3), but making a single winter application of Proxy also improved quality over the spring program in May. The fungicides used at these winter timings with Proxy did not influence turf quality in May. 
  • Turf color, as measured by chlorophyll indices, was not different in February from pre-snow treatments, or in May after post-snow treatments (and spring program applications) (Table 3). Although not statistically different, turf receiving both winter applications of Proxy had higher numerical indices, supporting the seedhead and quality differences in the canopy observed in this trial.

 

Summary

Proxy mixtures with common fungicides used in winter for snow mold protection, were compatible, spayed well, and did not cause injury to the putting green. Plus, annual bluegrass seedhead suppression was improved in spring from applying Proxy in winter. The standard spring program of Proxy+Primo suppressed 50% of seedheads. Preceding the spring program with a single winter application of Proxy (either pre-snow cover, or post-snow melt) boosted suppression between 75% and 82%. For Proxy mixed with Bayer fungicides, making both winter applications did not improve suppression over either single application – and the same was true for Proxy mixed with Syngenta fungicides. However, seedhead suppression was better from both winter applications of Proxy mixed with Syngenta fungicides compared to either single winter application of Proxy mixed with Bayer fungicides (91% to 75%, respectively). There may or may not be a fungicide effect on seedhead suppression, and should be investigated further. The fungicides mixed with Proxy during winter did not influence turf quality going into, or coming out of winter, but quality was improved in May due to greater seedhead suppression. Spring quality was better when both winter applications of Proxy were made.

 

Acknowledgements

A huge thanks to Superintendent, and current RMGCSA Vice President, J. Eric Strasheim, for his unwavering support and technical assistance with this project. It couldn’t have happened without you! And to the RMEGI Board for providing funds to explore this exciting new area of research.

   

Table 1. Winter ethephon treatments applied with fungicides on a mixed annual bluegrass/creeping bentgrass green and evaluated for turf safety and annual bluegrass seedhead suppression in spring compared to standard fungicide and spring seedhead programs at Murphy Creek Golf Course, Aurora, CO, 2016-17. 

Treatment  Description Product/Rate (fl.oz/1000) Application Date
 1

Pre-snow fungicide only Post-snow fungicide only

Instrata/9

Banner Maxx/2

Nov. 30, 2016
Feb. 20, 2017

 2 Pre-snow fungicide only

Post-snow fungicide only

+Spring 1st app

+Spring 2nd app

+Spring 3rd app 
Interface/6+Mirage/2

Mirage/2

Proxy/5+Primo/0.125

Proxy/5+Primo/0.125

Proxy/5+Primo/0.125 
Nov. 30, 2016

Feb. 20, 2017

Mar. 10, 2017

Apr. 5, 2017

Apr. 20, 2017 
 3 Pre-snow fungicide+ethephon#1

+Spring 1st app

+Spring 2nd app

+Spring 3rd app 
Instrata/9+Proxy/5

Proxy/5+Primo/0.125

Proxy/5+Primo/0.125

Proxy/5+Primo/0.125 
Nov. 30, 2016

Mar. 10, 2017

Apr. 5, 2017

Apr. 20, 2017 
 4 Pre-snow fungicide+ethephon#2

+Spring 1st app

+Spring 2nd app

+Spring 3rd app
Interface/6+Mirage/2+Proxy/5

Proxy/5+Primo/0.125

Proxy/5+Primo/0.125

Proxy/5+Primo/0.125 
Nov. 30, 2016

Mar. 10, 2017

Apr. 5, 2017

Apr. 20, 2017 
 5 Pre-snow fungicide only

Post-snow fungicide+ethephon#1

+Spring 1st app

+Spring 2nd app

+Spring 3rd app 
Instrata/9

Banner Maxx/2+Proxy/5

Proxy/5+Primo/0.125

Proxy/5+Primo/0.125

Proxy/5+Primo/0.125 
Nov. 30, 2016

Feb. 20, 2017

Mar. 10, 2017

Apr. 5, 2017

Apr. 20, 2017 
 6 Pre-snow fungicide only

Post-snow fungicide+ethephon#2

+Spring 1st app

+Spring 2nd app

+Spring 3rd app 
Interface/6+Mirage/2

Mirage/2+Proxy/5

Proxy/5+Primo/0.125

Proxy/5+Primo/0.125

Proxy/5+Primo/0.125 
Nov. 30, 2016

Feb. 20, 2017

Mar. 10, 2017

Apr. 5, 2017

Apr. 20, 2017 
 7 Pre-snow fungicide+ethephon#1

Post-snow fungicide+ethephon#1

+Spring 1st app

+Spring 2nd app

+Spring 3rd app 

Instrata/9+Proxy/5

Banner Maxx/2+Proxy/5

Proxy/5+Primo/0.125

Proxy/5+Primo/0.125

Proxy/5+Primo/0.125 
Nov. 30, 2016

Feb. 20, 2017

Mar. 10, 2017

Apr. 5, 2017

Apr. 20, 2017 
 8 Pre-snow fungicide+ethephon#2

Post-snow fungicide+ethephon#2

+Spring 1st app

+Spring 2nd app

+Spring 3rd app 
Interface/6+Mirage/2+Proxy/5

Mirage/2+Proxy/5

Proxy/5+Primo/0.125

Proxy/5+Primo/0.125

Proxy/5+Primo/0.125 
Nov. 30, 2016

Feb. 20, 2017

Mar. 10, 2017

Apr. 5, 2017

Apr. 20, 2017 

 

 

 

 

Click here for downloadable version of report 

Contact Gary Leeper at RMGCSA
Voice: 303-255-9611 Fax: 303-458-0002
12011 Tejon St., Ste. 700., Westminster, CO 80234 EMAIL: info@rmgcsa.org