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

Abstract

Annual 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.

ROOT AND SHOOT PERFORMANCE OF THREE CREEPING BENTGRASS CULTIVARS AS AFFECTED BY NITROGEN FERTILITY*

“…Long wave ultra-violet (320± 400 nm) light (Model B-100AaR Blak-Ray Ultra-Violet Lamp, UVP, Inc., San Gabriel, CA) was used to facilitate viewing of actively growing viable roots (16,17,23). Root measurements commenced 12 April 1997 and terminated 25 September 1998, totaling 39 independent observations.…”

“…These inconsistencies, common to bentgrass root research, may in part result from the relationship of root length density (RLD) to shoot density at shallow soil depths. Improvements have been made by reporting bentgrass rootto-shoot ratios (RSR), speci®c root lengths (SRL) (15), and viable root length measurements (16,17,18).…”

Carbon Dioxide Exchange Rate and Chlorophyll Content of Turfgrasses Treated with Flurprimidol or Mefluidide

“…Cooper et al (1987) showed an increase in root elongation and rooting depth from applications of mefluidide to annual bluegrass (Poa annua var. reptans (Hausskn.)…”

Phytotoxic effects, regrowth, and 14C-sucrose translocation in Canada thistle treated with mefluidide, flurprimidol, and systemic herbicides

“…The highest rate of foliar-applied mefluidide inhibited height growth 2 weeks after application, but mefluidide also caused chlorosis and leaf malformation at the two higher rates. Hanson and Branham (1987) and Cooper et al (1987Cooper et al ( , 1988 obtained seedhead suppression in Poa when mefluidide was applied at 0.28 kg/ha or less, and short-term yellowing of foliage occurred. We found that mefluidide applications of 0.54 kg/ha delayed flowering in Canada thistle for at least 3 weeks with no foliar chlorosis (data not shown).…”

“…(Cooper et al 1987(Cooper et al , 1988. Similarly, Hanson and Branham (1987) demonstrated that movement of photosynthate to roots of 'Majestic' Kentucky bluegrass (Poa pratensis L.) could be enhanced following applications of mefluidide.…”