Influence of Plant Growth Regulators on Winter Hardiness of Annual Bluegrass Putting Green Turf.

Low temperature injury and winterkill are major limitations in the management of annual bluegrass on putting greens and fairways in New England. The objectives of this research were to (i) conduct a field experiment to examine the responses of different fall application rates of trinexapac-ethyl (TE) and prohexadione-calcium (PC) on freezing tolerance of annual bluegrass through winter and early spring months; and (ii) conduct a controlled environment experiment to examine the effects of TE, PC, and abscisic acid (ABA) on freezing tolerance of annual bluegrass. In the controlled environment experiment, plants were subjected to cold acclimation at -2°C for 2 weeks, and then placed at 8°C to induce deacclimation. After 1 d at 8°C, chemical treatments were applied and plants were evaluated for their freezing tolerance (lethal temperature resulting in 50% mortality, LT50) at 3 d deacclimation. Overall, untreated or plants sprayed with TE exhibited the highest freezing tolerance compared to other treatments. For field experiments, monthly freezing tolerance assessments of annual bluegrass from December through March will be reported.