Application Timing of Paint and Glyphosate Combinations in Dormant Zoysiagrass on Annual Bluegrass and Tall Fescue Control.

Turfgrass managers commonly apply glyphosate on dormant zoysiagrass (Zoysia spp.) to control cool-season grassy weeds.  More recently, turfgrass managers are using paints and pigments to color dormant zoysiagrass throughout the winter months.   Applications of glyphosate on dormant zoysigrass are well documented, but information concerning the interaction of glyphosate and paint applications is lacking.  Experiments were initiated in 2013 and 2014 at Colbert Hills Golf Course (CH) and Stagg Hill Golf Course (SH) in Manhattan, KS to evaluate the effects of glyphosate and glyphosate + Endurant (Turfgrass Colorant) application timing for annual bluegrass (Poa annua L.) or tall fescue (Schedonorus arundinaceus Schreb.) control and zoysiagrass spring green-up. Research at both locations was performed on a ‘Meyer’ zoysiagrass (Z. japonica Steud.) fairway. Research area at CH and SH was maintained at 1.3 cm and 1.9 cm mowing height, respectively.  CH contained approximately 50% tall fescue cover and SH contained 35% annual bluegrass cover at trial initiation.  At trial initiation (November 2013 and 2014) oxadiazon (3 kg ha^-1) was applied to all plots to prevent further annual bluegrass emergence. Treatments were arranged in a two by four factorial, randomized complete block design with four replications.  Factors were two herbicide combinations and four application timings.  Herbicide applications included glyphosate (1.1 kg ha^-1) and glyphosate (1.1 kg ha^-1) + Endurant (16.6% v/v). A non-treated check was included for comparison.  Application timings were mid November, December, January and February.  Treatments were applied using a CO₂ pressurized backpack sprayer calibrated to deliver 375 L ha^-1 at 221 kPa. Data was collected bi-weekly until 196 days after initial application (DAI). Data included visual percent annual bluegrass or tall fescue cover and visual percent green zoysiagrass. Analysis of variance was performed in SAS and means were separated according to Fisher’s Protected LSD at 0.05 significance level.  All treatments and application timings at SH, excluding the non-treated control, resulted in <5% annual bluegrass cover at 170 DIA.  Glyphosate and glyphosate + Endurant applications at any timing did not delay spring zoysiagrass green-up at SH and CH. In 2013, Glyphosate + Endurant applications in November, December resulted in 0% tall fescue cover, 170 DAI at CH while November and December applications of glyphosate alone resulted in 23% and 15% tall fescue cover.  In 2014, regardless of the addition of Endurant, November and December applications of glyphosate resulted in <5% tall fescue cover.  Results demonstrate that the addition of Endurant to glyphosate at early applications (November and December) may increase tall fescue control.