Evaluation of Combinations of Bispyribac-Sodium or Amicarbazone with Trinexapac-Ethyl or Paclobutrazol for Annual Bluegrass Control On Creeping Bentgrass Greens.

Acceptable annual bluegrass (Poa annua L.) seedhead reduction in golf greens can occur with repeated application of plant growth regulators, but complete control of annual bluegrass is difficult to achieve.  Bispyribac-sodium is labeled to control annual bluegrass in creeping bentgrass (Agrostis stolonifera L.) fairways but is not labeled for use on golf course greens.  Amicarbazone is a triazolinone herbicide which is currently being evaluated for use in turfgrass management. The objective of this research was to determine the annual bluegrass control and phytotoxicity to creeping bentgrass from application of low rates of bispyribac-sodium or amicarbazone with and without trinexapac-ethyl or paclobutrazol.  Field research plots (1.5 x 1.5 m) were treated during spring 2009 over a 56 d period with bispyribac-sodium (9.9 to 14.8 g ai/ha every 7 d) alone, amicarbazone (50 and 100 g ai/ha every 28 d) alone, and with either trinexapac-ethyl (57 g ai/ha every 28 d) or paclobutrazol (224 g ai/ha every 28 d) with an untreated control. All plots were fertilized weekly with soluble fertilizer (5 kg N/ha and 1 kg FeSO4/ha).  Plots were rated weekly for annual bluegrass control, turf quality, and herbicide phytotoxicity.  Annual bluegrass control at 28 d after initial treatment was 0% for all plots regardless of treatment.  Turf quality was significantly lower and herbicide phytotoxicity was significantly higher in bispyribac-sodium and amicarbazone treated plots compared to control, but both were acceptable for turfgrass management.