Plant Growth Regulators’ Effect on

Growth of Mixed Cool-Season

Grass Stands at Fort Drum

Antonio J. Palazzo, Paul Zang, Robert W. Duell,

Timothy J. Cary and Susan E. Hardy September 1996

SPECIAL REPORT 96-24
Abstract: Mowing is one of the more expensive operations in managing roadside and other low-maintenance turfgrass areas. The objective of this study was

to evaluate the performance of two plant growth regulators (PGRs)—mefluidide (Embark) and imidazolinone

(Event)—in reducing the development of seedheads

and inhibiting the vertical growth (plant height) of

mixed turf swards at multiple sites over a two-year

period. Mefluidide applied at the manufacturer’s recommended rate (2.3 L/ha or 2 pints/acre) provided the

best general control of plant height and seedhead

development compared to mefluidide at lower rates or

imidazolinone at both recommended and lower rates

or a combination of mefluidide and imidazolinone at

lower rates. Within the control areas (no PGR), plant

height did not correlate with plant weight. Therefore,

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the timing of treatments is critical since increases in

plant height and weight occur at different times during

the spring. At the early May application time, mefluidide

applied at the recommended rate inhibited both plant

height and weight. The effects of this treatment on

plant growth were similar in most of the eight sites

tested. However, PGR performance was affected by the

presence of earlier maturing grasses in the sward,

microclimatic factors, and broadleaf weeds. There was

no difference in the effectiveness of the treatments

when the materials were applied again during the

following season. Despite some variation in its effect,

the mefluidide treatment at the recommended rate was

consistent enough among all test locations, turf species, and microclimates to recommend using this technique in the demonstration stage of the trial.
Special Report 96-24

Plant Growth Regulators’ Effect on

Growth of Mixed Cool-Season

Grass Stands at Fort Drum

Antonio J. Palazzo, Paul Zang, Robert W. Duell,

Timothy J. Cary and Susan E. Hardy September 1996

Prepared for

ENVIRONMENTAL DIVISION, FORT DRUM

and

U.S. ARMY FORCES COMMAND

Approved for public release; distribution is unlimited.

US Army Corps


of Engineers

Cold Regions Research &


Engineering Laboratory
ii

PREFACE

This report was prepared by Antonio J. Palazzo, Research Agronomist, Geochemical Sciences Division, Research and Engineering Directorate, U.S. Army Cold Regions Research and Engineering Laboratory (CRREL), Hanover, New Hampshire;

Paul Zang, Forester, Fort Drum, New York; and by Robert W. Duell, Consultant,

Timothy Cary, Physical Science Technician, and Susan E. Hardy, Research Program Specialist, Geochemical Sciences Division, Research and Engineering Directorate, CRREL.

Funding for this work was provided by the Environmental Division, Public

Works, at Fort Drum and the U.S. Army Forces Command, Fort McPherson,

Georgia.

The authors thank Alan Schwark, Range Control, Ann Johnson and Michelle

Tuckley, Public Works Division, Fort Drum, for helping to conduct this study, and

Dr. Gurdarshan S. Brar, formerly of CRREL, and William Woodson, U.S. Army

Environmental Center, Aberdeen, Maryland, for technical review of this manuscript.

The contents of this report are not to be used for advertising or promotional

purposes. Citation of brand names does not constitute an official endorsement or

approval of the use of such commercial products.
INTRODUCTION

Turfgrasses that provide a suitable vegetative

cover for parade grounds, roadsides, and housing areas are widely used in cantonment areas at

military facilities. In the training areas, grasses

are a cost-effective means of controlling erosion

on the gunnery ranges. In all these areas, the

grasses must be mowed to maintain the required

visibility or appearance of a mowed turf. Fort

Drum is currently mowing approximately 2,025

ha (5,000 acres) of turf in the cantonment area and

several hundred acres at the gunnery ranges.

Grasses are usually mown to reduce leaf height

or to remove seedheads.

The cost of mowing these lands is expensive in

labor and equipment and may add up to several

hundred dollars per acre annually. Innovative

techniques are required to reduce mowing costs,

control erosion, and maintain the aesthetics of

turf areas, allowing the labor and money saved to

be used for special projects or other maintenance

functions. Plant growth regulators (PGRs) have

the potential to reduce mowing costs.

The PGR “Embark” contains mefluidide {N-

[2,4-dimethyl-5-[[(trifluoromethyl)-sulfonyl]

amino] phenyl] acetamide}, which was commercially introduced in 1978 as a seedhead and foliar

suppressant for use in rough turf areas (Elkins

1983, Johnston and Faulkner 1985). Watschke et

al. (1992) provided an excellent review on methods of application and the functions of mefluidide

within plants. Field and Witford (1982) reported

that applications of mefluidide should be limited

to green and actively growing grass. For leaf

growth regulation, mowing the sward 4 to 5 days

before or after the application will provide a

sustained mowed appearance. The timing of

mefluidide applications is more critical for optimal seedhead control; it should be applied at least

14 days before seedhead emergence. Turf injury

is a factor to be considered when using PGRs.

Some stand density losses have been observed

(Wakefield and Fales 1977) and visual injury is

more pronounced when the grass is environmentally stressed (Duell et al. 1977), but these factors

are less important in low-maintenance turf situations. The effectiveness of PGRs in reducing

turfgrass growth has been reported to be substantially reduced during years of low rainfall

(Reynolds et al. 1993).

Mefluidide retards plant growth through the

inhibition of cell division and meristematic activity in the responsive plant areas where the compound is absorbed. Mefluidide is absorbed by the

leaf and exhibits little translocation to other leaf

organs, roots, and lateral growth meristems (Field

and Witford 1982, WSSA 1983). Penetration of

leaf tissue occurs most readily at basal leaf sheaths

and leaf axils, where cell division and elongation

occur, causing reduced sheath extension and

canopy height. Uptake is complete in 4 to 6 hours

after application (Tautvydas 1983). Mefluidide also

causes uncontrolled cell division in reproductive

apices, distorting stem extension and impairing

seedhead development (Field and Witford 1982).

Because of limited movement within the plant,

uniform spray coverage and distribution is essential (Watschke et al. 1992).

The PGR “Event” contains imidazolinone [5-

ethyl-2- (4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl) nictotinic acid]. This compound has an

extremely high margin of safety (Watschke et al.

1992). It has post-emergence herbicide activity on

many annual and perennial grasses. Watschke et

al. (1992), in their review of PGRs, reported that

some studies with this PGR have shown the compound to suppress foliar growth and seedhead

Plant Growth Regulators’ Effect on Growth of

Mixed Cool-Season Grass Stands at Fort Drum

ANTONIO J. PALAZZO, PAUL ZANG, ROBERT W. DUELL,

TIMOTHY J. CARY AND SUSAN E. HARDY
production of cool-season species, while another

study with the similar species did not find any

significant control of cool-season grass growth.

The overall objective of this research is to provide statistically clear and scientifically sound data

on the effectiveness of two plant growth regulators (PGRs) to reduce the development of

seedheads and inhibit the vertical growth (plant

height) of mixed turf swards at multiple sites.

STUDY AREA

Four roadside turfgrass sites, a gunnery range

and an earth-covered magazine (ECM) site were

subjected to various combinations of applications of two plant growth regulators (PGRs) in

1994 and 1995. The four roadside sites were located along Hospital Lane, Memorial Drive and

5th Armored Division Drive (two sites). The Memorial Drive and 5th Armored Division Drive

sites were seeded about eight years ago, and are

mowed biweekly during the growing season.

The other sites (on Hospital Lane and on the gunnery range) are mowed less frequently (approximately monthly).

Prior to treatment, the treated sites had the

following characteristics and botanical compositions:

• Memorial Avenue: Level roadside area containing a mixed botanical composition dominated by tall fescue (Festuca arundinacea

Shreb.)

• 5th Armored Division Drive: Sloping roadside area containing a mixed botanical composition dominated by tall fescue and Kentucky bluegrass (Poa pratensis L.) and some

fine fescue (Festuca sp.) and infested with

vetch (Vicia sp.) and knapweed (Centaurea

maculosa L.).

• Hospital Lane: Level area consisting of fine

fescues and contaminated by knapweed.

• Gunnery Range: Sloping area of low maintenance turf consisting primarily of Kentucky

bluegrass.

• Earth-covered magazine: Dominated by

quackgrass (Agropyron repens L.).

MATERIALS AND METHODS

Each site was laid out to receive seven treatments, which included five treatments with the

PGR Embark, containing mefluidide, and Event,

containing imidazolinone. Each PGR was applied

individually at the manufacturer’s recommended

rate and at one-third the recommended rates, and

the two PGRs were applied in combination at

one-third the recommended rate. Each site included two check plots: one mowed biweekly and

one unmowed. The minimum research plot size

was 1 × 9 m (4 × 30 ft), which provided a clear

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 before the experimental treatments.

The recommended and low rates for Embark

(mefluidide) were 2.3 and 0.8 L/ha (2 and 0.67

pints/acre); for Event (imidazolinone) they were

438 and 146 mL/ha (6 and 2 oz/acre), respectively. Due to a miscalculation, the Hospital Lane

plots received 1.5 times the rates applied to the

other plots in 1994. Prior to spraying we added

0.25% (V/V) nonionic detergent to the spray-tank

mixture to assist PGR absorption. The spraying

volume of the detergent was 39.36 L/ha (4.2 gal./

acre).

The PGRs were applied with a CO2-powered

sprayer (set at 34 lb/in.2 or 235 kPa) with the

single wide-angle even-edge Tee Jet 8006E nozzle

calibrated to apply 200 L/ha (21.36 gal./acre) in a

1-m width from a 50-cm height. The contents of a

2-L soft-drink bottle evenly covered 1/100-ha area

between the burned-in strips.

The roadside test areas were sprayed in early

spring on 10 May 1994 and on 2 May 1995. In

1995, the same treatments were applied again over

the 1994 roadside plots as well as on adjacent

untreated areas.

In 1994, the test sites were measured for PGR

effect on plant growth. On 9 June, the percentage

control of grass seedheads and foliage height were

recorded. Seedhead production was determined

by counting over a 0.5-m2 (1.5-ft2) area. Mean

foliar height was determined by readings of multiple drops of a 0.3-m2 (1-ft2) slotted cardboard.

The cardboard was dropped down a meter stick

and allowed to settle on the grass foliage; the

foliar height was the measured distance between

the cardboard and the soil surface. In 17 June

1995, counts were made using these same techniques at all test sites for seedhead number and

plant height.

Also in 1995, the growth rate of grasses was

determined in a separate area where the dry

weight of the grass was recorded by biweekly

harvesting. Half the area at this site was sprayed

2
biweekly with mefluidide at the recommended

rate and the other half was untreated. The turf in

this area consisted of mixed stands of tall and fine

fescue. Dry weights of the grasses harvested biweekly from this area were recorded after oven

drying at 70°C for 48 hours.

Analyses of variance of the data were performed using CoStat (1990) version 4.20 (CoHort

Software). Least significant differences (LSD) were

calculated at 5%.

RESULTS

1994 Experiments

Data on the control of seedheads are shown in

Table 1. Tall fescue seedheads, which dominated

the unmowed plots of 5th Armored Division

Drive, were well controlled by PGR treatments

except for the low rate of imidazolinone (onethird of that recommended). Seedheads at Hospital Lane, dominated by the earlier-flowering fine

fescue, were well controlled only by the recommended rate of mefluidide and by mowing. At

the ECM, where quackgrass dominated the vegetative cover, mefluidide controlled seedheads

better than imidazolinone and its effect was similar to the mowed control. The combination of the

two PGRs also controlled seedhead development

at the ECM site. At the 5th Armored Division

sites, broadleaf weeds (knapweed) were unaffected by the PGR treatments.

Mefluidide at the recommended rate provided

the best control of foliar height (Table 2). The

differences were greater for the Memorial Drive

sites than for the fine-fescue dominated Hospital

Lane location.

The effect of PGR treatment on turf color was

highly variable (Table 3). Color did improve with

time over the two rating dates of 9 June and 11

August 1994.

1995 Experiments

The plant height data collected for each location and PGR treatment are shown in Appendix

A. Since the differences between treatments were

similar at most sites, we used the means of the

individual treatments for each harvest date at

each site (Table 4). No differences

were noted after the first rating date

(17 May 1995), which was about 15 days

after the treatments were applied. This

is probably related to the early effectiveness of all PGR treatments. Differences between treatments became apparent from the next rating date (30

May 1995) to the end of the rating period (25 July 1995). The results show

that mefluidide at the recommended

rate was statistically similar to the

mowed control in reducing plant

height. The next best treatments were

mefluidide at the low rate and the

mefluidide/imidazolinone combination. The imidazolinone treatment at

both rates studied did not control plant

height as well as those treatments that

included mefluidide.

Significant differences for plant

heights were also found between locations regardless of PGR treatment

(Table 5). The differences in locations

are probably due to the type of grasses

growing at each location. The Hospital

Lane site has the shorter growing fine

fescues and the other sites contain tall

fescue and Kentucky bluegrasses along

with the fine fescues.

Table 1. Percentage seedhead control on 9 June 1994 at the

5th Armored Division Drive I, Hospital Lane and earthcovered magazine sites.

5th Armored

Treatments Div. Drive I Hospital Lane ECM

1. Mefluidide, 2.3 L/ha 96.0 97.7 94.3

2. Mefluidide, 0.67 L/ha 95.3 6.0 95.0

3. Imidazolinone, 438 mL/ha 93.3 56.7 83.3

4. Imidazolinone, 136 mL/ha 38.3 21.7 7.0

5. Treatment 2 + 4 98.7 53.3 93.3

6. Mowed check 99.7 100.0 99.0

7. Unmowed check 1.0 21.7 0.3

Least significant

difference at 0.05 level

of probability 27.4 27.8 20.8

Table 2. Foliar height on 10 June 1994 at three sites.

5th Armored Memorial Hospital

Treatments Div. Drive II Drive Lane

1. Mefluidide, 2.3 L/ha 14.7 10.6 10.0

2. Mefluidide, 0.67 L/ha 21.0 14.0 12.0

3. Imidazolinone, 438 mL/ha 17.7 16.7 12.7

4. Imidazolinone, 136 mL/ha 26.0 20.7 15.7

5. Treatment 2 + 4 16.0 14.0 14.3

6. Mowed check 5.0 5.0 5.0

7. Unmowed check 33.0 22.3 18.3

Least significant

difference at 0.05 level

of probability 5.7 3.7 3.4

3
No differences in plant heights were observed

between the initial and the reapplication treatments at the two 5th Armored Division Drive

locations (Table 5). This indicates that the reapplication of the PGR was consistently as beneficial

the second year.

Seedhead control is important since seedheads

give the appearance that the turf requires mowing. Significant (probability less than 5%) differences in seedhead counts were noted for the type

of PGR used and the location of the test, but no

differences were found between the three rating

dates. Table 6 shows the number of seedheads

on 27 June in plots where the PGR was initially

applied in 1994 and then reapplied in 1995.

Mefluidide at the recommended rate provided

the best control of seedhead development, with

none of the treatments producing more than 2

Table 3. Visual estimates of green color (%) on 9 June and 11 August 1994 at three

locations.

5th Armored 5th Armored

Treatments Div. Drive I Div. Drive II Memorial Drive

9 June 11 June 9 June 11 June 9 June 11 June

1. Mefluidide, 2.3 L/ha 75.0 98.3 91.7 96.0 — 100.0

2. Mefluidide, 0.67 L/ha 99.3 96.3 99.3 92.0 — 92.0

3. Imidazolinone, 438 mL/ha 71.7 96.7 81.7 88.7 — 92.0

4. Imidazolinone, 136 mL/ha 93.0 93.3 99.3 87.3 — 88.0

5. Treatment 2 + 4 78.3 95.7 91.7 96.3 — 91.7

6. Mowed check 75.0 95.0 81.7 97.3 — 95.3

7. Unmowed check 99.3 86.7 58.3 85.0 — 88.3

Least significant

difference at 0.05 level

of probability 12.0 4.1 18.8 4.6 — 22.8

Table 4. Plant heights (cm) as influenced by various treatments in 1995.

Treatments 17 May 30 May 14 June 27 June 11 July 25 July

1. Mefluidide, 2.3 L/ha 8.8 7.8 14.0 13.9 13.1 14.0

2. Mefluidide, 0.67 L/ha 9.5 10.2 17.6 18.9 21.5 25.1

3. Imidazolinone, 438 mL/ha 9.4 9.9 19.3 25.7 29.7 28.8

4. Imidazolinone, 136 mL/ha 8.7 10.4 21.0 27.1 29.7 34.1

5. Treatment 2 + 4 9.0 9.4 17.7 17.1 16.8 19.5

6. Mowed check 11.3 9.1 12.7 12.2 12.1 14.9

7. Unmowed check 11.5 13.1 25.4 27.7 32.6 32.4

Least significant

difference at 0.05 level

of probability 1.2 1.4 1.4 6.1 7.2 2.7

Table 5. Plant heights (cm) as influenced by various experimental locations in 1995.

Location 17 May 30 May 14 June 27 June 11 July 25 July

5th Armored Div. Drive I Single* 10.1 8.9 19.2 23.5 30.0 31.7

5th Armored Div. Drive I Reapply† 9.5 8.2 16.5 20.1 24.4 27.0

5th Armored Div. Drive II Single 11.0 11.7 21.4 22.2 23.4 26.8

5th Armored Div. Drive II Reapply 11.8 12.5 23.2 26.3 26.1 28.4

Hospital Lane Single 8.3 8.3 13.6 13.8 12.8 12.3

Hospital Lane reapply 7.9 10.4 15.6 16.3 16.4 18.5

LSD at 5% 1.2 1.2 1.9 3.8 5.5 6.4

* Single = PGR applied in 1995 only

† Reapply = PGR applied in 1994 and 1995

4
seedheads/m2 at any of the locations. The number of seedheads produced by the unmowed check

varied widely and was probably dependent on

soil conditions at that location and the type of turf

growing at the site. Mefluidide applied in combination with imidazolinone and at the lower rate

provided the next best control of seedhead develTable 6. Seedhead counts taken at each location on 27 June 1995.

5th Armored Div. 5th Armored Div.

Hospital Lane‡ Drive I Drive II Memorial Drive

Treatments Single* Reapply† Single Reapply Single Reapply Single Single

1. Mefluidide, 2.3 L/ha 2.9 0.8 1.4 1.3 0.9 2.2 1.6 1.6

2. Mefluidide, 0.67 L/ha 23.2 6.8 4.7 7.4 8.6 10.9 11.8 10.5

3. Imidazolinone, 438 mL/ha 29.2 18.3 9.0 8.4 14.3 12.2 13.1 14.9

4. Imidazolinone, 136 mL/ha 39.6 21.8 10.4 7.0 16.7 11.1 14.4 17.3

5. Treatment 2 + 4 18.6 8.3 4.6 5.4 5.4 5.8 14.7 9.0

6. Mowed check 0.1 0.0 0.0 0.0 0.0 0.0 0.0 0.0

7. Unmowed check 48.2 18.8 12.7 8.7 22.0 10.1 19.4 20.0

LSD at 5% 13.2 4.8 4.9 2.7 4.1 6.3 10.9

* Single = PGR applied in 1995 only

† Reapply = PGR applied in 1994 and 1995

‡ Hospital Lane received 1.5 times the recommended rate in 1994

35

30

25

20

15

10

5

Plant Height (cm)

20 30 10 20 30 10 20

May Jun Jul

Unmowed Check

Desired Mowing Height

Mowed Check

Mefluidide

Application Date: 2 May 1995

LSD = 2.29

Figure 1. Effect of a plant growth regulator (PGR)

on roadside vegetation maintenance (mefluidide applied at 2.3 L/ha).

opment; these treatments provided about 50%

decrease in seedhead development over the

unmowed check. Imidazolinone provided only

an average of 13 and 25% control of seedhead

development for the low and recommended rates

of application.

Plant height data recorded biweekly from PGRtreated and untreated plots at the six roadside

locations are shown in Figure 1. The unmowed

control produced consistently taller plants than

the mowed control. The greatest differences between dates occurred between 30 May and 14

June 1995, where there was about a 100% increase

in height. The PGR treatment was mefluidide at

the recommended rate and the mean height of

treated plants was never greater than 15 cm (6

in.). Increases in plant height did not correlate to

those recorded for plant weight.

In the separate area adjacent to 5th Armored

Division Drive, plant biomass production and

plant heights were recorded biweekly from the

mefluidide-treated and untreated mixed turfgrass

stands. Significant differences in plant biomass

were found for harvest date, PGR treatment, and

their interactions. Biweekly increases in plant biomass were between 40 and 61% for the untreated

grasses and only 9 and 22% for the treated plots.

The yields on the final harvest (2 June 1995) was

100% greater in the control as compared to the

treated grasses (Fig. 2).

DISCUSSION AND CONCLUSIONS

Plant heights and appearance of seedheads are

usually the most identifiable indicators for determining when mowing should occur. The need for

5
70

60

50

40

30

20

10

20 30 10 20 30

May Jun

Dry Biomass (g/m2)

Treated

Untreated

10

Figure 2. Plant yields recorded biweekly from PGR

treated and untreated mixed turfgrass stands.

mowing is a very subjective decision. For the purposes of this study, we have assumed that when

the turf reaches a height of 12.5 cm (5 in.), it should

be mowed.

Mefluidide applied at the recommended rate

of 2.3 L/ha provided the best control of plant

height and seedhead development in 1995 (Fig.

1). Mefluidide applied at the low rate of 0.8 L/ha

provided some control, but not as much as the

2.3-L/ha rate. Most sites seemed to have the same

general trends of differences in growth control

between treatments. Reapplication of the same

PGR treatments the following season produced

similar results in growth and seedhead retardation. Rapid increases in plant height were not

correlated with that for plant weight within the

control treatments or under normal growing conditions. Therefore, the timing of PGR applications

is critical to sufficiently inhibit the various growth

spurts. The effect of PGR application on turf color

was highly variable, but the color did improve

after about two months.

The 1994 results showed that certain factors,

such as early maturing quackgrass, the presence

of broadleaf weeds, and the effects of a cool microclimate in a fine-fescue-dominated area, will

have an effect on PGR performance, and the

growth inhibiting effect of applying a PGR will

not be consistent over all turf areas. This inconsistency may necessitate additional mowing during

the spring season. Although PGRs did not work

uniformly over all areas, the mefluidide treatment

at the recommended rate was consistent enough

between test locations covering many turf species

and microclimates to move it from the experimental to the demonstration stage of trial.

Control of broadleaf weeds will be necessary

since the PGR is not effective in reducing their

growth rate. Future applications of mefluidide

should include a broadleaf weed herbicide. Recommendations for future trials or practices should

also include mowing the site 4 to 5 days before

and after application of the PGR to obtain a uniform turf stand in terms of height. The PGR should

be applied in early May and the chemical should

be effective for a period of 4 to 6 weeks.

LITERATURE CITED

CoStat (1988) Users Manual. Berkeley, California:

CoHort Software.

Duell, R.W., R.M. Schmitt and S.W. Cosky (1977)

Growth retardant effects on grasses for roadsides.

In Proceedings of the 3rd International Turfgrass Research Conference (J.B. Feard, Ed.), Munich, Germany.

11–13 July. Madison, Wisconsin: International

Turfgrass Society, ASA-CSSA-SSSA, p. 311–323.

Elkins, D.M. (1983) Growth regulating chemicals

for turf and other grasses. In Plant Growth Regulating Chemicals (L.G. Nickel, Ed.), Vol. II. Boca

Raton, Florida: CRC Press.

Field, R.S. and A.R. Witford (1982) Effect of simulated mowing on the translocation of mefluidide

in perennial ryegrass (Lolium perenne L.) Weed Research, 22: 177–181.

Johnston, D.T. and J.S. Faulkner (1985) The effects of growth retardants on swards of normal

and dwarf cultivars of red fescue. Journal of Sports

Turf Research Institute, 61: 59–64.

Reynolds, J.H., W.A. Krueger and C.L. Waller

(1993) Plant growth regulator effects on growth

and forage quality of tall fescue. Agronomy Journal, 85: 545–548.

Tautvydas, K.G. (1983) Synergistic growth retardation of grasses with mefluidide/PGR combinations. p. 51–56. In Proceedings of the 10th Annual

PGRSA Meeting.

Watschke, T.L., Prinster, and J.M. Breuninger

6
(1992) Plant growth regulators and turfgrass management. In Turfgrass (D.V. Waddington, Ed.).

Madison, Wisconsin: ASA-CSSA-SSSA.

Wakefield, R.C. and S.L. Fales (1977) Effects of

growth retardants on the shoot and root growth

of roadside turfgrasses. In Proceedings of the 3rd

International Turfgrass Research Conference (J.B.

Feard, Ed.), Munich, Germany. 11–13 July. Madison, Wisconsin: International Turfgrass Society,

ASA-CSSA-SSSA, p. 303–309.

WSSA (1983) Herbicide Handbook. Champaign, Illinois: Weed Science Society of America.

7
APPENDIX A: PLANT HEIGHT DATA (CM) RECORDED FROM INDIVIDUAL TREATMENTS

AT VARIOUS SITES IN 1995

5th Armored Division 5th Armored Division

Hospital Lane* Drive I Drive II

Treatments Single† Reapply** Single Reapply Single Reapply

17 May 1995

1. Mefluidide, 2.3 L/ha 7.0 8.3 9.2 8.2 9.7 10.2

2. Mefluidide, 0.67 L/ha 8.1 7.7 8.8 10.2 11.3 11.2

3. Imidazolinone, 438 mL/ha 8.3 8.8 8.7 8.9 11.1 10.6

4. Imidazolinone, 136 mL/ha 7.0 7.6 8.2 9.8 11.0 9.7

5. Treatment 2 + 4 7.5 8.8 8.4 9.0 11.1 10.5

6. Mowed check 7.8 8.5 12.5 13.7 13.3 12.3

7. Unmowed check 9.3 8.2 10.7 13.0 15.2 12.6

LSD at 5% = 3.13

30 May 1995

1. Mefluidide, 2.3 L/ha 8.4 6.7 7.6 7.9 7.7 8.7

2. Mefluidide, 0.67 L/ha 11.3 8.1 8.5 9.9 12.7 10.6

3. Imidazolinone, 438 mL/ha 10.1 9.7 6.8 9.9 12.2 10.7

4. Imidazolinone, 136 mL/ha 10.2 8.2 9.6 9.1 14.3 11.2

5. Treatment 2 + 4 9.5 7.6 8.8 8.4 11.2 10.7

6. Mowed check 10.1 8.8 6.3 7.7 10.1 11.6

7. Unmowed check 12.9 9.3 9.4 9.2 19.6 18.1

LSD at 5% = 3.17

14 June 1995

1. Mefluidide, 2.3 L/ha 10.8 10.8 13.0 15.3 18.7 15.2

2. Mefluidide, 0.67 L/ha 15.3 12.7 14.8 15.7 28.2 18.8

3. Imidazolinone, 438 mL/ha 16.2 14.5 18.8 19.0 24.2 23.0

4. Imidazolinone, 136 mL/ha 17.5 16.3 17.0 21.0 26.8 27.5

5. Treatment 2 + 4 16.3 14.3 17.2 18.3 21.7 18.3

6. Mowed check 11.7 11.0 11.8 14.3 14.0 13.5

7. Unmowed check 21.2 15.3 22.7 30.8 28.8 33.7

LSD at 5% = 5.04

27 June 1995

1. Mefluidide, 2.3 L/ha 9.1 9.2 17.2 14.8 18.5 14.7

2. Mefluidide, 0.67 L/ha 17.9 13.5 13.8 19.7 29.0 18.5

3. Imidazolinone, 438 mL/ha 17.7 15.3 37.2 25.3 29.0 29.8

4. Imidazolinone, 136 mL/ha 19.3 19.8 18.8 29.8 42.0 32.5

5. Treatment 2 + 4 17.3 12.5 14.8 19.8 19.2 19.0

6. Mowed check 9.3 9.4 18.7 12.3 12.0 11.7

7. Unmowed check 23.2 16.8 19.9 42.7 34.5 29.3

LSD at 5% = 14.152

11 July 1995

1. Mefluidide, 2.3 L/ha 7.0 7.5 19.6 13.0 17.0 14.3

2. Mefluidide, 0.67 L/ha 20.4 12.3 19.5 23.1 29.0 24.7

3. Imidazolinone, 438 mL/ha 20.7 14.2 48.8 36.0 24.7 33.5

4. Imidazolinone, 136 mL/ha 17.1 17.8 24.2 43.7 45.2 30.0

5. Treatment 2 + 4 17.2 11.5 14.7 23.5 17.2 16.8

6. Mowed check 7.4 7.5 27.7 9.7 10.0 10.2

7. Unmowed check 25.2 18.8 16.2 61.2 39.7 34.5

LSD at 5% = 14.511

8
5th Armored Division 5th Armored Division

Hospital Lane* Drive I Drive II

Treatments Single† Reapply** Single Reapply Single Reapply

25 July 1995

1. Mefluidide, 2.3 L/ha 9.6 8.3 17.5 12.2 16.8 19.5

2. Mefluidide, 0.67 L/ha 24.0 11.2 34.3 16.8 31.7 32.5

3. Imidazolinone, 438 mL/ha 23.3 12.2 38.7 38.2 33.5 26.7

4. Imidazolinone, 136 mL/ha 18.9 16.2 38.2 54.5 42.8 34.3

5. Treatment 2 + 4 16.4 12.8 22.7 33.8 14.7 16.5

6. Mowed check 7.3 7.9 20.3 8.7 21.5 23.7

7. Unmowed check 30.0 17.0 17.6 57.8 37.8 34.3

LSD at 5% = 17.00

* Hospital Lane received 1.5 times the recommended rate in 1994

† Single = PGR applied in 1995 only

** Reapply = PGR applied in 1994 and 1995

9
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September 1996

Plant Growth Regulators’ Effect on Growth of Mixed Cool-Season

Grass Stands at Fort Drum

Antonio J. Palazzo, Paul Zang, Robert W. Duell,

Timothy J. Cary and Susan E. Hardy

U.S. Army Cold Regions Research and Engineering Laboratory

72 Lyme Road Special Report 96-24

Hanover, New Hampshire 03755-1290

Environmental Division Headquarters

85 First Street West U.S. Army Forces Command

Fort Drum, New York 13062-5097 Fort McPherson, Georgia 30330-6000

Approved for public release; distribution is unlimited.

Available from NTIS, Springfield, Virginia 22161

17

Cold regions Plant growth regulators Turfgrasses

UNCLASSIFIED UNCLASSIFIED UNCLASSIFIED UL

Mowing is one of the more expensive operations in managing roadside and other low-maintenance turfgrass

areas. The objective of this study was to evaluate the performance of two plant growth regulators (PGRs)—

mefluidide (Embark) and imidazolinone (Event)—in reducing the development of seedheads and inhibiting the

vertical growth (plant height) of mixed turf swards at multiple sites over a two-year period. Mefluidide applied

at the manufacturer’s recommended rate (2.3 L/ha or 2 pints/acre) provided the best general control of plant

height and seedhead development compared to mefluidide at lower rates or imidazolinone at both recommended and lower rates or a combination of mefluidide and imidazolinone at lower rates. Within the control

areas (no PGR), plant height did not correlate with plant weight. Therefore, the timing of treatments is critical

since increases in plant height and weight occur at different times during the spring. At the early May application

time, mefluidide applied at the recommended rate inhibited both plant height and weight. The effects of this

treatment on plant growth were similar in most of the eight sites tested. However, PGR performance was

affected by the presence of earlier maturing grasses in the sward, microclimatic factors, and broadleaf weeds.

There was no difference in the effectiveness of the treatments when the materials were applied again during the

following season. Despite some variation in its effect, the mefluidide treatment at the recommended rate was

consistent enough among all test locations, turf species, and microclimates to recommend using this technique in

the demonstration stage of the trial.

For conversion of SI units to non-SI units of measurement consult ASTM Standard E380-93, Standard Practice for Use of the

International System of Units, published by the American Society for Testing and Materials, 1916 Race St., Philadelphia, Pa.

19103.