Root Growth, Seedhead Production, and Quality of Annual Bluegrass as Affected by Mefluidide and a Wetting Agent1

Abstract

AbstractAnnual bluegrass [Poa annua ssp. reptans (Hauskins) Timm.] often comprises a large portion of golf course greens, yet its shallow root system and extensive seedhead production limit its turf quality. The purpose of this investigation was to determine if annual bluegrass seedheads could be suppressed and rooting enhanced by the plant growth regulator mefluidide [N ‐(2,4‐dimethyl‐5‐{[(trifluoromethyl) sulfonyl]amino} phenyl)acetamide] and the wetting agent Aqua‐Gro (polyoxyethylene esters and ether of cyclic acid and alkylated phenols, silicone anti‐foam emulsion). Chemicals were applied prior to seedhead emergence during 1983 and 1984 to annual bluegrass grown in a rhizotron in fine quartz sand. Root elongation of mefluidide‐treated annual bluegrass was superior to the control for 2 to 4 weeks following Spring 1983 application. Maximum rooting depth of mefluidide‐treated turf was significantly greater than that of Aqua‐Gro‐treated or untreated turf during May 1983. Aqua‐Gro applied at either 4.2 or 8.4 L ha−1 generally did not affect rooting. In 1983, mefluidide (0.07 or 0.14 kg ha−1) prevented seedhead emergence throughout the entire seedhead production period (approximately 8 weeks) when applied under environmental conditions favoring uptake. Leaf tip yellowing occurred for 3 to 4 weeks following mefluidide application. Mefluidide‐treated turf, however, exhibited quality superior to untreated turf for approximately 6 weeks following discoloration. Aqua‐Gro provided little seedhead suppression and reduced quality for about 10 days following application. In 1984, environmental conditions were not conducive to chemical uptake so 1983 results were not corroborated. Mefluidide appears promising as an annual bluegrass management tool; however, more information is needed to determine the influence of environmental conditions on mefluidide uptake and its ability to suppress seedheads and enhance rooting at low rates.