Preliminary Report

Objective

The primary objective of this trial is to determine whether repeated applications (2, 3, or 4) of Proxy (ethephon) or Proxy + Primo (trinexpac-ethyl) causes phytotoxicity to Providence creeping bentgrass maintained at putting green height. A secondary objective is to evaluate turf quality of putting green turf treated with Proxy, Proxy + Primo, or Trimmit (paclobutrazol) growth regulators. The Trimmit was applied at two rates alone and with additional fertilizer.

Materials and Methods

The trial was initiated on March 21, 2008 at the Lewis-Brown Horticulture Farm in Corvallis, Oregon. The site was a Providence creeping bentgrass putting green which was built in the mid 1990’s on a 12 inch sand/compost mix and has been cored spring and fall using 5/8 inch tines. Annual bluegrass encroachment has been limited by removing plants with a knife every spring. The pH of the green has hovered around 6.0.

The green was fertilized every two weeks from April through the first week of May applying 0.25 lbs of nitrogen. The green was mowed at 0.145 inches at the start of the trial and lowered slowly to 0.115 inches by the end of May. On June 5, the mowing height was then raised to 0.125 inches for the rest of the trial and 0.25 lbs of nitrogen from ammonium sulfate was applied. These changes lessened the turf injury. The putting green was cored on June 24th with 5/8 inch tines.

The treatments were applied with a CO2-powered plot sprayer with a 5 foot boom using TeeJet 80015 nozzles sprayed at 30 psi. The Proxy and Proxy + Primo treatments were applied at 1 gallon of total spray solution per 1,000 square feet. The Trimmit treatments were applied at 2 gallons of total spray solution per 1,000 square feet. 0.125 inches of irrigation was applied to the plots treated with Trimmit after application using a watering can.

The trial was designed to evaluate 2, 3, and 4 applications. However, because of the severe injury to the plots treated with Proxy, the fourth application was not made.

Visual turf color or quality ratings were made on April 18th, May 2nd, May 17th, May 30th, and June 13th. Visual turf injury ratings were made on May 2nd, May 17th, May 30th, and June 13th. Data from each rating date were subjected to analysis of variance using a randomized complete block design with 3 replications. Differences between means were determined by LSD at the 5% level.

The Treatments applied were as follows:   Rate Trt #Treatments"Oz/1000"Apps1Proxy (ethephon)522Proxy533Proxy53*4Proxy + Primo (trinexpac-ethyl)5.0 + .12525Proxy + Primo5.0 + .12536Proxy + Primo5.0 + .1253*7Trimmit + Irrigation*** (paclobutrazol)0.1253*8Trimmit + Irrigation***0.253*9Trimmit + Irrigation*** + 0.25 lbs N**0.1253*10Trimmit + Irrigation*** + 0.25 lbs N**0.253*11Untreated Checknana * The 4th application was not made because of severe injury to plots treated with proxy.
** Anderson’s 25-5-18 + micros soluble fertilizer (24% urea 4% nitrate) was used as fertilizer source.
*** Irrigation was applied at 0.125 inches of water.

The applications were made on the following dates:

  • 3/21 - All treatments
  • 4/11 – Primo only on treatments 4, 5, & 6
  • 4/25 - Second application of all treatments (5 weeks after first application)
  • 5/02 - Primo only on treatments 4, 5, & 6
  • 5/23 – Third application of all treatments (4 weeks after second application)

Results

  • Proxy caused significant phytotoxicity to the bentgrass putting green after two applications. The injury was first noticeable 7 days after the second application and became obvious 2 weeks after second application. Proxy lightened the turf color after one application. April, May, and June were unseasonably cool which may have made the turf injury worse and delayed recovery since the bentgrass was not growing vigorously.
  • The turf injury seemed to be exacerbated by lower mowing heights. This observation coincides with other research indicating that Proxy can cause stem elongation which results in scalping.
  • Adding Primo to Proxy lessened the turf injury.
  • Trimmit darkened the turf and caused the leaf blades to become coarser over time (coarseness became prominent after 3 applications). This effect appeared to be more prominent on the plots treated at the high rate of Trimmit plus added nitrogen. It is unknown whether the leaf coarseness would influence ball roll distance.

Table 1: Turf Color & Turf Quality (1 – 9; 9 = best) (Dates of application – 3/21, 4/25, & 5/23)

  Rate Trt #Treatments"Oz/1000"Apps1Proxy (ethephon)522Proxy533Proxy53*4Proxy + Primo (trinexpac-ethyl)5.0 + .12525Proxy + Primo5.0 + .12536Proxy + Primo5.0 + .1253*7Trimmit + Irrigation*** (paclobutrazol)0.1253*8Trimmit + Irrigation***0.253*9Trimmit + Irrigation*** + 0.25 lbs N**0.1253*10Trimmit + Irrigation*** + 0.25 lbs N**0.253*11Untreated Checknana 

* Note, the green was fertilized (0.25 lbs of N) and the mowing height was raised from 0.115 to 0.125 inches on June 5th.

Table 2: Turf Injury (1 – 9; 9 = most injury) (Dates of application – 3/21, 4/25, & 5/23)   Rate Trt #Treatments"Oz/1000"Apps1Proxy (ethephon)522Proxy533Proxy53*4Proxy + Primo (trinexpac-ethyl)5.0 + .12525Proxy + Primo5.0 + .12536Proxy + Primo5.0 + .1253*7Trimmit + Irrigation*** (paclobutrazol)0.1253*8Trimmit + Irrigation***0.253*9Trimmit + Irrigation*** + 0.25 lbs N**0.1253*10Trimmit + Irrigation*** + 0.25 lbs N**0.253*11Untreated Checknana