production of cool-season species, while another
containing imidazolinone. Each PGR was applied
study with the similar species did not find any
individually at the manufacturer's recommended
significant control of cool-season grass growth.
rate and at one-third the recommended rates, and
The overall objective of this research is to pro-
the two PGRs were applied in combination at
vide statistically clear and scientifically sound data
one-third the recommended rate. Each site in-
on the effectiveness of two plant growth regula-
cluded two check plots: one mowed biweekly and
tors (PGRs) to reduce the development of
one unmowed. The minimum research plot size
was 1 9 m (4 30 ft), which provided a clear
seedheads and inhibit the vertical growth (plant
height) of mixed turf swards at multiple sites.
visual assessment on the effectiveness of each
treatment. The plots were initially outlined in
April by applying Roundup herbicide to "brown"
10-cm (4-in.) lines approximately one week be-
STUDY AREA
fore the experimental treatments.
Four roadside turfgrass sites, a gunnery range
The recommended and low rates for Embark
and an earth-covered magazine (ECM) site were
(mefluidide) were 2.3 and 0.8 L/ha (2 and 0.67
subjected to various combinations of applica-
pints/acre); for Event (imidazolinone) they were
tions of two plant growth regulators (PGRs) in
438 and 146 mL/ha (6 and 2 oz/acre), respec-
1994 and 1995. The four roadside sites were lo-
tively. Due to a miscalculation, the Hospital Lane
cated along Hospital Lane, Memorial Drive and
plots received 1.5 times the rates applied to the
5th Armored Division Drive (two sites). The Me-
other plots in 1994. Prior to spraying we added
morial Drive and 5th Armored Division Drive
0.25% (V/V) nonionic detergent to the spray-tank
sites were seeded about eight years ago, and are
mixture to assist PGR absorption. The spraying
mowed biweekly during the growing season.
volume of the detergent was 39.36 L/ha (4.2 gal./
The other sites (on Hospital Lane and on the gun-
acre).
nery range) are mowed less frequently (approxi-
The PGRs were applied with a CO2-powered
sprayer (set at 34 lb/in.2 or 235 kPa) with the
mately monthly).
Prior to treatment, the treated sites had the
single wide-angle even-edge Tee Jet 8006E nozzle
following characteristics and botanical composi-
calibrated to apply 200 L/ha (21.36 gal./acre) in a
tions:
1-m width from a 50-cm height. The contents of a
Memorial Avenue: Level roadside area con-
2-L soft-drink bottle evenly covered 1/100-ha area
taining a mixed botanical composition domi-
between the burned-in strips.
nated by tall fescue (Festuca arundinacea
The roadside test areas were sprayed in early
spring on 10 May 1994 and on 2 May 1995. In
Shreb.)
1995, the same treatments were applied again over
5th Armored Division Drive: Sloping road-
the 1994 roadside plots as well as on adjacent
side area containing a mixed botanical com-
untreated areas.
position dominated by tall fescue and Ken-
In 1994, the test sites were measured for PGR
tucky bluegrass (Poa pratensis L.) and some
effect on plant growth. On 9 June, the percentage
fine fescue (Festuca sp.) and infested with
control of grass seedheads and foliage height were
vetch (Vicia sp.) and knapweed (Centaurea
recorded. Seedhead production was determined
maculosa L.).
by counting over a 0.5-m2 (1.5-ft2) area. Mean
Hospital Lane: Level area consisting of fine
foliar height was determined by readings of mul-
fescues and contaminated by knapweed.
tiple drops of a 0.3-m2 (1-ft2) slotted cardboard.
Gunnery Range: Sloping area of low main-
The cardboard was dropped down a meter stick
tenance turf consisting primarily of Kentucky
and allowed to settle on the grass foliage; the
bluegrass.
foliar height was the measured distance between
Earth-covered magazine: Dominated by
the cardboard and the soil surface. In 17 June
quackgrass (Agropyron repens L.).
1995, counts were made using these same tech-
niques at all test sites for seedhead number and
plant height.
MATERIALS AND METHODS
Also in 1995, the growth rate of grasses was
determined in a separate area where the dry
Each site was laid out to receive seven treat-
weight of the grass was recorded by biweekly
ments, which included five treatments with the
harvesting. Half the area at this site was sprayed
PGR Embark, containing mefluidide, and Event,
2
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