Plant growth regulator effects on winter hardiness of annual bluegrass putting green turf

Abstract

Cold deacclimation sensitivity has been cited as an important factor associated with winterkill susceptibility of annual bluegrass (Poa annua L.). Increased potential for deacclimation for this species has been attributed to higher metabolic activities in response to warm winter temperatures. We hypothesized that using plant growth regulators to inhibit turfgrass growth and metabolism during winter months could potentially suppress premature deacclimation and increase survival of annual bluegrass. The specific objectives of this study were to examine the effects of varying rates of autumn-applied trinexapac-ethyl (TE) and prohexadione-Ca (PC) on winter hardiness and spring recovery of an annual bluegrass putting green. The study was conducted over the winters of 2015-2016 and 2016-2017. Treatments included an untreated control and four rates of TE (0.05, 0.10, 0.2, and 0.4 kg a.i. ha -1 ) and PC (0.06, 0.12, 0.25, and 0.50 kg a.i. ha -1 ). Freezing tolerance was assessed based on controlled freeze tests to estimate the lethal temperature resulting in 50% regrowth (LT 50 ). General turfgrass health was also assessed based on visual turf quality and normalized difference vegetation index (NDVI). Late-autumn PGR applications impacted the freezing tolerance of annual bluegrass during Year 1, but no treatment effects were detected in Year 2. Plant growth regulator treated turf, pooled over chemicals and rates, exhibited lower freezing tolerance (Year 1), turf quality, and NDVI (Years 1 and 2) compared to untreated turf particularly at the higher application rates. By the end of May in both years, all treatments recovered to the same levels. INTRODUCTIONAnnual bluegrass (Poa annua L.) in high maintenance turf is often considered a problematic weed (Huff, 2003). Annual bluegrass is sensitive to a range of abiotic and biotic stresses,

Current Outlook on Ice Encasement Stress and Management Strategies in Turfgrasses

“…Conversely, some PGRs may reduce turfgrass survival of winterrelated stresses such as ice encasement. PGRs that inhibit gibberellic acid (GA) biosynthesis showed some evidence of reducing annual bluegrass tolerance to ice encasement and promoted loss of freezing tolerance, but the results were not always consistent in each year (DaCosta et al, 2021;Laskowski et al, 2018). This is important because PGRs that inhibit GA biosynthesis are the most applied PGRs in the turfgrass industry to reduce mowing frequency and for other purposes.…”

Evaluation of Fall and Winter Trinexapac-ethyl Applications on Ultradwarf Bermudagrass Putting Green Color, Quality, and Green Cover

“…Plant growth regulators are frequently applied to UDB putting greens (Reasor et al 2018) and they can alter plant hormone production (McCullough et al 2004), suggesting they may affect UDB cold tolerance. Mixed results have been reported on the influence of plant growth regulators on cold tolerance and cold de-acclimation in cool-season grasses (DaCosta et al 2021;Laskowski and Merewitz 2020), but they could potentially increase cold tolerance in the warm-season UDB. Plant growth regulators that alter plant hormone levels, increase stress responses, and/or reduce carbohydrate expenditure could potentially improve UDB tolerance to cold stress like what has been shown by Steinke and Stier (2004) in supina bluegrass.…”