ESTABLISHMENT OF
BERMUDAGRASS AND ZOYSIAGRASS
BY SEED
A Thesis
Submitted to the Faculty
of
Purdue University
by
Aaron J. Patton
In Partial Fulfillment of the
Requirements for the Degree
of
Master of Science
August 2003
ii
To Ella, thanks for your love, support and example.
iii
ACKNOWLEDGEMENTS
I would like to express my gratitude and thanks to the many individuals who have
helped and supported me during my studies. First, I would like to thank Dr. Zac Reicher for
recruiting me to come to Purdue University and teaching me a great deal about research, teaching
and extension. I have learned a great deal through his example. I would also like to thank the
other individuals in the turf group, including Don Fassnacht, Glenn Hardebeck, and Dan
Weisenberger for showing me the ropes. Thanks to Beverly Bratton for giving me a hard time. I
would also like to thank J.D. Cash, Kristi Walker, Eric Kohler and Kim Hooper for their
friendship and support.
I would like to thank my parents for their support to Ella and me during our graduate
studies. I thank Ella for the long hours she has spent editing my writing and for being the best
possible wife a husband could ask for. I would also like to thank God for his plan for me and
thank him for placing good people in my life. “As iron sharpens iron, so one man sharpens
another.” Proverbs 27:17
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TABLE OF CONTENTS
Page
LIST OF TABLES........................................................................................................................... v LIST OF FIGURES ......................................................................................................................viii ABSTRACT.................................................................................................................................... ix CHAPTER ONE - LITERATURE REVIEW.................................................................................. 1
Introduction ............................................................................................................................... 1 Establishment ............................................................................................................................ 3
Seeding date .............................................................................................................................. 5 Seeding rate ............................................................................................................................... 6 Herbicides.................................................................................................................................. 7 Fairway Renovation .................................................................................................................. 8 References ............................................................................................................................... 11
CHAPTER TWO - ESTABLISHMENT OF SEEDED BERMUDAGRASS AND ZOYSIAGRASS ..................................................................................................................... 17 Abstract ................................................................................................................................... 17 Materials and Methods ............................................................................................................ 19 Results and Discussion............................................................................................................ 21 References ............................................................................................................................... 25
CHAPTER THREE - TURFGRASS RENOVATION WITH SEEDED ZOYSIAGRASS IN THE TRANSITION ZONE................................................................... 33 Abstract ................................................................................................................................... 33 Materials and Methods ............................................................................................................ 37 Results and Discussion............................................................................................................ 39 References ............................................................................................................................... 43
CHAPTER FOUR - SUMMARY AND CONCLUSIONS ........................................................... 50 APPENDIX.................................................................................................................................... 52
v
LIST OF TABLES Table Page 1. Effects of seeding date on coverage of Mirage bermudagrass and Zenith zoysiagrass and
post seeding accumulated growing degree days........................................................... 27
2. Effects of seeding rate on winterkill of Mirage bermudagrass. ................................................. 28
3. Site and management information on four locations for the seeding rate and herbicide strategy studies. ............................................................................................................ 45
4. Effect of seed rate and glyphosate applied prior to seeding on ‘Zenith’ zoysiagrass coverage in October following seeding. ....................................................................... 46
5. Effect of seed rate and herbicides applied after zoysiagrass seedling emergence on annual grassy weed coverage on 31 July...................................................................... 47
6. Effect of seed rate and herbicides applied after seedling emergence on ‘Zenith’ zoysiagrass coverage on 25 Oct (2 September for Richmond)..................................... 48
Appendix Table
1
7. Effects of seeding date and over-wintering on Mirage bermudagrass coverage when rated in October and May following seeding. .............................................................. 52
8. Effects of seeding date and over-wintering on Zenith zoysiagrass coverage when rated in October and May following seeding. ........................................................................... 53
9. Effects of seeding rate and over-wintering on percent coverage and tiller density of Zenith zoysiagrass rated and counted in October and May following seeding. ........... 54
10. Effects of seeding rate on Zenith zoysiagrass coverage in 2002. ............................................ 55
11. Effects of seeding rate on Zenith zoysiagrass digital analysis coverage in 2002. ................... 56
12. Effects of seeding rate on Zenith zoysiagrass tiller density in 2002........................................ 57
13. Effects of seeding rate on Mirage bermudagrass coverage in 2002......................................... 58
vi
Appendix Table Page
14. Effects of seeding rate on Mirage bermudagrass digital analysis coverage in 2002................ 59
15. Effects of seeding rate on Mirage bermudagrass tiller density in 2002. .................................. 60
16. Effect of herbicides and timing in the greenhouse on Zenith zoysiagrass seedling clipping dry weights. .................................................................................................... 61
17. Effect of seed rate and glyphosate applied prior to seeding on Mirage bermudagrass coverage 30 days after seeding..................................................................................... 62
18. Effect of seed rate and glyphosate applied prior to seeding on Mirage bermudagrass coverage 60 days after seeding..................................................................................... 63
19. Effect of seed rate and glyphosate applied prior to seeding on Mirage bermudagrass coverage 90 days after seeding..................................................................................... 64
20. Effect of seed rate and glyphosate applied prior to seeding on Mirage bermudagrass coverage in October following seeding. ....................................................................... 65
21. Effect of seed rate and glyphosate applied prior to seeding on Mirage bermudagrass grid count 30 days after seeding. .................................................................................. 66
22. Effect of seed rate and glyphosate applied prior to seeding on Mirage bermudagrass grid count 60 days after seeding. .................................................................................. 67
23. Effect of seed rate and glyphosate applied prior to seeding on Mirage bermudagrass grid count 90 days after seeding. .................................................................................. 68
24. Effect of seed rate and glyphosate applied prior to seeding on Mirage bermudagrass grid count in October following seeding. ..................................................................... 69
25. Effect of seed rate and glyphosate applied prior to seeding on Zenith zoysiagrass coverage 30 days after seeding..................................................................................... 70
26. Effect of seed rate and glyphosate applied prior to seeding on Zenith zoysiagrass coverage 60 days after seeding..................................................................................... 71
27. Effect of seed rate and glyphosate applied prior to seeding on Zenith zoysiagrass coverage 90 days after seeding..................................................................................... 72
28. Effect of seed rate and glyphosate applied prior to seeding on Zenith zoysiagrass grid count 30 days after seeding. ......................................................................................... 73
29. Effect of seed rate and glyphosate applied prior to seeding on Zenith zoysiagrass grid count 60 days after seeding. ......................................................................................... 74
30. Effect of seed rate and glyphosate applied prior to seeding on Zenith zoysiagrass grid count 90 days after seeding. ......................................................................................... 75
vii
Appendix Table Page
31. Effect of seed rate and glyphosate applied prior to seeding on Zenith zoysiagrass grid count in October following seeding.............................................................................. 76
32. Effect of seed rate and herbicides applied after seedling emergence on Zenith zoysiagrass coverage on 31 July................................................................................... 77
33. Effect of seed rate and herbicides applied after seedling emergence on Zenith zoysiagrass coverage on 2 September. ......................................................................... 78
34. Effect of seed rate and herbicides applied after seedling emergence on Zenith zoysiagrass grid coverage on 2 September................................................................... 79
35. Effect of seed rate and herbicides applied after seedling emergence on Zenith zoysiagrass grid coverage on 25 Oct (2 September for Richmond). ............................ 80
viii
LIST OF FIGURES
Figure Page 1. Location of the transition climatic zone for turfgrass species in the United States. ................. 16
2. Effects of seeding date on the coverage of Mirage bermudagrass averaged over 2000 and 2001. Backtransformed means are presented and vertical bars indicate LSI (P=0.05)........................................................................................................................ 29
3. Effects of seeding date on coverage of Zenith zoysiagrass averaged over 2000 and 2001. Backtransformed means are presented and vertical bars indicate LSI (P=0.05)........................................................................................................................ 30
4. Effects of seeding rate on Mirage bermudagrass tiller density and backtransformed coverage averaged over 2001 and 2002. Vertical bars indicate LSD for tiller density and LSI for coverage (P=0.05). ....................................................................... 31
5. Effects of seeding rate on Zenith zoysiagrass tiller density and backtransformed coverage averaged over 2001 and 2002. Vertical bars indicate LSD for tiller density and LSI for coverage (P=0.05). ....................................................................... 32
6. Geographic location of 4 seeding rate and herbicide strategy studies. ..................................... 49
ix
ABSTRACT Patton, Aaron J. M.S, Purdue University, August 2003. Establishment of Bermudagrass and Zoysiagrass by Seed. Major Professor: Zachary J. Reicher.
New cultivars of bermudagrass (Cynodon spp. Rich.) and zoysiagrass (Zoysia japonica
Steud.) established by seed are desirable for golf and athletic turfs due to minimum establishment
and maintenance costs. Little is known about establishing bermudagrass or zoysiagrass by seed
since they are relatively new. Our first objective was to determine optimum and acceptable
seeding dates and seeding rates with ‘Mirage’ bermudagrass and ‘Zenith’ zoysiagrass.
Bermudagrass coverage rated before dormancy was greatest when seeded as late as 1 Aug. 2000
and 15 July 2001 and zoysiagrass coverage was greatest when seeded from 1 to 15 June in both
years. Bermudagrass required >950 accumulated growing degree days (GDD, base 5 °C) for
maximum establishment, while zoysiagrass required >1750 accumulated GDD. There was no
clear relationship between winter survival and seeding date for zoysiagrass, and no seeded
bermudagrass survived either winter in Indiana. Seeding rates of 12 to 49 kg ha-1 and 49 to 98 kg
ha-1 were optimum for bermudagrass and zoysiagrass, respectively, in areas that were fumigated
prior to seeding.
Two additional studies were performed to determine methods that would hasten
renovation using seeded zoysiagrass. The effect of preemergence and postemergence herbicides
and seeding rates on the establishment of zoysiagrass were evaluated in Indiana and Kentucky on
golf courses areas that were not fumigated. In the first study, interseeding zoysiagrass into
x
existing perennial ryegrass (Lolium perenne L.) without the use of glyphosate prior to seeding
resulted in only 2% zoysiagrass coverage 120 days after seeding (DAS). However, zoysiagrass
coverage reached 100% by 120 DAS when using glyphosate prior to seeding. For weed control
after seeding, MSMA (monosodium methanearsonate) + dithiopyr (S,S-dimethyl 2-
(difluoromethyl)-4-(2-methylpropyl)-6-(triflurormethyl)-3,5-pyridinedicarbothioate) applied 14
days after emergence (DAE) or MSMA applied at 14+28+42 DAE resulted in best annual grassy
weed control and the greatest amount of zoysiagrass establishment. Applying MSMA + dithiopyr
14 DAE resulted in 7% less zoysiagrass coverage at one of the four locations by when compared
to MSMA applied at 14+28+42 DAE. Seeding rate effects were significant at three of the four
locations. Zoysiagrass coverage at the end of the growing season was 3 to 11% more when
increasing seeding rates from 49 kg ha-1 to 98 kg ha-1.
From my research, optimum bermudagrass establishment occurs when seeding 1 June to
1 August at 12 to 49 kg ha-1, and when >950 GDD can accumulate by first frost. Optimum
zoysiagrass establishment occurs when seeding from 1 to 15 June, seeding 49 to 98 kg ha-1, and
when >1750 GDD can accumulate by first frost. Successful zoysiagrass renovation in the
transition zone is most dependent on adequate glyphosate control prior to seeding and
applications of MSMA at 14+28+42 DAE, but establishment is only marginally dependent on
seeding rates greater than 49 kg ha-1.
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CHAPTER ONE - LITERATURE REVIEW
Introduction
The United States is divided into four major climatic zones, which include the cool-
humid, cool-arid, warm-humid and warm-arid zones (Christians and Engelke, 1994; Beard and
the USGA, 2002). There is also a fifth region known in the turf industry as the transition zone
(Fig. 1), which is located between the cool-humid and the warm-humid regions. Both cool-
season and warm-season turfgrasses are present in the transition zone, but few turfgrass species
are well-adapted to this region.
Even though both cool-season and warm-season grasses grow in the transition zone, golf
courses primarily have cool-season grasses such as annual bluegrass (Poa annua L.), Kentucky
bluegrass (Poa pratensis L.), creeping bentgrass (Agrostis palustris Huds.) or perennial ryegrass
(Lolium perenne L.) for fairways. Golf course superintendents struggle to maintain cool-season
grasses during the summer because of disease pressure, water requirements, excessive heat, and
golfer traffic (Beard, 1973). Cool-season grasses decline in summer causing poor golfing
conditions in spite of countless hours and dollars spent to maintain acceptable playing surfaces.
Bermudagrass (Cynodon spp. Rich.) and zoysiagrass (Zoysia japonica Steud.) may be
potential solutions to the high cost of maintaining cool-season grasses. Bermudagrass is
commonly referred to as common bermudagrass, couchgrass, wiregrass or devilgrass, and is an
introduced grass species to the United States (Hanson et al., 1969). Originating from Africa,
bermudagrass is a warm-season turfgrass species that is well-suited for golf course fairways, tees
and athletic fields. There are many species of bermudagrass, but Cynodon dactylon var. dactylon
2
[L.] Pers. is the only turf-type bermudagrass specie that produces viable seed (Beard, 1973;
Taliaferro, 1995). Bermudagrass is well-suited for golf course fairways, tees and athletic fields.
When established, bermudagrass creates a vigorous, aggressive turf with high shoot densities
(Beard, 1973).
Zoysiagrass is commonly referred to as Japanese lawngrass or Korean lawngrass and is
an introduced grass species to the United States. The species was named after Austrian botanist
Karl von Zois and was introduced into the United States in the early 1900’s (McDonald and
Copeland, 1997). Originating from East Asia coastal areas, zoysiagrass is a warm-season
turfgrass species that is well-suited for golf course fairways, tees, and bunker faces. When
established, zoysiagrass creates a uniform, dense, low-growing, high-quality turf (Beard, 1973).
Bermudagrass and zoysiagrass are adapted to the transition, warm-arid, and warm-humid
zones. In the transition zone, bermudagrass and zoysiagrass grow vigorously during summer
months, but are dormant during cool periods of the year. Zoysiagrass produces a dense, more
playable fairway surface during winter compared to bermudagrass. Winter hardiness of
bermudagrass is less than that of zoysiagrass (Turgeon, 2002; Rogers et al., 1977). Low
temperature death will seriously thin bermudagrass established in northern areas of the transition
zone every four to five years (Anonymous, 1960), often during the first winter after establishment
(Philley and Krans, 1998).
Bermudagrass (Cynodon spp. Rich.) and zoysiagrass (Zoysia japonica Steud.) both have
excellent disease, heat, drought and wear tolerance (Beard, 1973). Currently, the only major
disease that affects bermudagrass in the transition zone is spring dead spot (Leptosphaeria korrae
Walker and Smith; Ophiosphaerella spp. Walker and Smith) (Martin et al., 2001; Couch, 1995),
while zoysiagrass only suffers from Rhizoctonia large patch disease (Rhizoctonia solani Kühn)
(Green et al., 1993). Conversely, numerous diseases affect cool-season grasses in the transition
zone including anthracnose (Colletotrichum graminicola (Ces.) Wils.), dollar spot (Sclerotinia
3
homoeocarpa F.T. Bennett), grey leaf spot (Pyricularia grisea (Cke.) Sacc.; telemorph
Magnaporthe grisea (Hebert) Barr), pythium (Pythium spp.), brown patch (Rhizoctonia solani
Kühn), pink snow mold (Microdochium nivale (Fr.) Samuels and Hallett), and summer patch
(Magnaporthe poae Landschoot & Jackson) (Couch, 1995). Disease susceptibility of cool-season
grasses increases maintenance costs and increases pesticide inputs into the environment.
Bermudagrass and zoysiagrass have excellent heat and drought tolerance compared to cool-
season grasses (Christians, 1998), resulting in reduced irrigation requirements and lower
maintenance costs (Biran et al., 1981). Bermudagrass and zoysiagrass also have high wear
tolerance during the summer (Youngner, 1961), and they have high growth rates when
temperatures are warm and golfer activity is highest (Unruh et al., 1996). In contrast, cool-season
grasses suffer from high temperature stress and physiological decline in the summer months when
golfer activity is highest (Beard, 1973).
Bermudagrass requires slightly higher maintenance than zoysiagrass (Beard, 1973).
Mowing heights of 1.3 cm to 2.5 cm are common for both species (Beard, 1973). Bermudagrass
requires more nitrogen per growing month compared to other warm-season species including
zoysiagrass, but both bermudagrass and zoysiagrass require less N yr-1 than cool-season grasses
in the transition zone (Beard, 1973).
Bermudagrass and zoysiagrass provide excellent playing surfaces for golfing and other
sports at a lower annual maintenance cost than cool-season grasses. Due to low maintenance
costs and reduced need for pesticides, many golf course managers are considering establishing
warm-season fairways in the transition zone.
Establishment
Bermudagrass and zoysiagrass are commonly established vegetatively by sprigs or sod.
Sprigging and solid-sodding are expensive relative to seeding. For example, the cost of sprigging
4
bermudagrass is estimated at approximately $2,500 ha-1 and solid sodding zoysiagrass may cost
$37,000 ha-1 or more. Although bermudagrass is commonly established by sprigging,
bermudagrass seed has been available for a number of years. The first available bermudagrass
that could be established by seed was discovered in Arizona and is commonly referred to as
“Arizona Common” (Taliaferro, 1995). However, this selection is coarse and not widely used as
a fine quality turf. Numerous seed established cultivars with improved cold tolerance, texture and
density are now commercially available (NTEP, 2002). Many of these new seeded cultivars are
as well-suited for fine quality turf as traditional vegetative cultivars.
Zoysiagrass seed has also been around for a number of years, but was not commonly used
because of low seed production and poor germination rates (Portz et al. 1981; Yeam et al., 1981;
Samudio, 1996). Recently, cultivars with increased seed production have been developed as well
as treatments to improve germination rates. Like bermudagrass, many of the new seeded
zoysiagrass cultivars produce high-quality turf (NTEP, 2001).
As a result of these improvements, warm-season grass establishment by seed is now
being considered on golf courses and athletic fields. Bermudagrass and zoysiagrass
establishment by seed is less labor intensive than vegetative establishment and more cost
effective at less than $2,200 ha-1. In addition, establishment from seed is faster than either
sprigging bermudagrass (Munshaw et al., 1998) or strip-sodding zoysiagrass (Portz et al., 1981).
Seeded bermudagrass and zoysiagrass may allow more use on golf course fairways and tees, and
athletic fields. Since seeded bermudagrass and zoysiagrass cultivars are relatively new, there are
several factors that should be investigated. These factors include seeding rates, seeding dates,
post-seeding herbicide selection and timings, and renovation of existing cool-season stands.
5
Seeding date
Cool-season grasses are best established in later summer or early spring. Late summer is
preferred since competition from summer-annual weed is reduced and air and soil temperatures
are more appropriate for growth (Watschke and Schmidt, 1992). Seeding after the optimum date
with a slow germinating species such as Kentucky bluegrass or a winter injury prone species such
as tall fescue (Festuca arundinacea Schreb.) or perennial ryegrass is often unsuccessful. Unlike
cool-season grasses, seeding a warm-season grass in late summer is seldom successful because
there is not sufficient time for adequate establishment before frost (Musser and Perkins, 1969).
Johnson and Thompson (1961) reported that late spring to early summer plantings are
preferred for warm-season grasses. This allows the longest period with warm soil temperatures
necessary for adequate establishment of warm-season grasses (Beard, 1973). Ahring et al. (1975)
reported that Arizona Common bermudagrass seeded after 9 May in Oklahoma resulted in greater
freeze injury than when seeded earlier. Further research confirmed that bermudagrass should be
established by seed early in summer to increase winter survival (Munshaw et al., 1998; Hensler et
al., 1999). However, Ahring et al. (1975) reported an experimental strain of bermudagrass was
not affected by freeze treatment when seeded as late as 21 July in Oklahoma, indicating potential
improvements in cold hardiness through plant breeding. Zoysiagrass was established when
seeded 1 July in Southern Illinois (Portz et al., 1981). Zoysiagrass cultivars established by seed
are tolerant of winters in the transition zone (NTEP, 2001), but no information is available on the
effects of seeding date on winterkill. It is important to define the optimum as well as acceptable
seeding dates for bermudagrass and zoysiagrass establishment and winter survival.
Since temperature affects the growth of these grasses (Unruh, 1996), it would be
beneficial to apply a growing degree day (GDD) model to their establishment. Frank et al. (1998)
used accumulated post-planting GDD to determine the requirements for establishment and
6
survival of buffalograss by seed. A similar model would be useful for bermudagrass and
zoysiagrass and could also be used to make recommendations for areas outside of Indiana.
Seeding rate
Proper seeding rates are necessary for good establishment. A low seeding rate can result
in a sparse stand with low density and high weed competition (Madison, 1966; Parr, 1982). To
offset problems caused by low seeding rates, turf managers often use high seeding rates to insure
rapid turf coverage. However, a high seeding rate can slow maturity, and seedlings cannot
develop until the population is thinned and competition is reduced (Madison, 1966). Although
high seeding rates produce higher seedling densities shortly after emergence, densities are often
similar among seeding rates after one year (Madison, 1966; Lush, 1990). Establishment cost,
physical injury, and disease susceptibility will increase, and plant size, maturity, root growth and
winter hardiness will decrease with higher seeding rates (Madison, 1966; Beard, 1973; Landry
and Choi, 1995; Rossi and Millett, 1996; Munshaw et al., 2001).
Recommended seeding rates for bermudagrass vary. Seeding rates between 12 and 24 kg
ha-1 increased stolon fitness and could increase winter hardiness of ‘Mirage’ bermudagrass
compared to higher seeding rates (Munshaw, 2001). Conversely, Brede (1994) found that
greatest winter hardiness resulted when seeding ‘Cheyenne’ bermudagrass at the rate of 150 kg
ha-1 possibly due to an increase in the overall biomass of the stand. It is important to determine
proper seeding rates to maximize winter hardiness since bermudagrass is often killed in the first
winter after seeding (Philley and Krans, 1998). Recommended seeding rates also vary for
zoysiagrass. Portz et al. (1981) recommended seeding at 38 to 98 kg ha-1 whereas Landry and
Choi (1995) found 98 kg ha-1 produced the highest shoot and root growth in the greenhouse. It is
necessary to determine the optimum range of seeding rates, the potential benefits of higher
7
seeding rates for hastening bermudagrass and zoysiagrass establishment, and the effect of seeding
rates on winter survival.
Herbicides
Annual grassy weeds such as crabgrass (Digitaria spp.) and goosegrass (Elusine indica
L.) germinate in late spring to early summer at the same time seeded bermudagrass and
zoysiagrass are germinating. Weed control is essential for acceptable establishment of
bermudagrass or zoysiagrass since competition with annual grasses will significantly reduce
establishment rates of vegetatively established cultivars (Carroll et al., 1996; Johnson, 1973).
Due to the rapid establishment and growth rate of bermudagrass, weed competition is greatly
reduced and does not impair establishment as greatly as with zoysiagrass. However, control of
these grassy weeds is important for good establishment. McCalla et al. (2002) are currently
investigating the safety of preemergence and postemergence herbicides on bermudagrass
seedlings.
Current herbicide label recommendations only allow application to established
zoysiagrass because there are little data on the use of herbicides on zoysiagrass seedlings.
Fenoxaprop-ethyl [(±)-2-[4-[(6-chloro-2-benzoxazolyl) oxy] phenoxy] propionic acid], MSMA
(monosodium methanearsenate), siduron [1-(2-methylcyclohexyl)-3-phenylurea], and dithiopyr
[S,S-dimethyl 2-(difluoromethyl)-4-(2-methylpropyl)-6-(triflurormethyl)-3,5-
pyridinedicarbothioate] are labeled to control crabgrass and goosegrass and are safe when applied
to established zoysiagrass (Dernoeden, 1987; Boyd and Rodgers, 1999), but siduron is the only
herbicide previously researched for its effects on seedlings. Portz et al. (1981) found that the
preemergence herbicide siduron applied at seeding did not reduce coverage of ‘Korean common’
zoysiagrass during establishment. However, siduron provides poor long-term control of annual
grasses (Dernoeden, 1984).
8
Dithiopyr, a preemergence herbicide with early postemergence activity, has longer
residual activity than siduron and provides better weed control for cool-season turf renovations
(Reicher et al., 1999). Dithiopyr applied shortly after emergence of cool-season turfgrass species
causes little injury. Dithiopyr at 0.56 kg ha-1 can be applied 10 days after emergence (DAE) to
Kentucky bluegrass, 14 DAE to perennial ryegrass, 17 DAE to creeping bentgrass and 21 DAE to
tall fescue (Festuca arundinacea Schreb.) (Reicher et al, 1999; Reicher et al, 2000; Ralston,
2002). Preliminary field work shows that dithiopyr is safe on zoysiagrass seedlings 14 DAE or
later (Reicher and Hardebeck, 2002b). However, dithiopyr can reduce coverage when applied too
soon after seeding (Reicher et al, 1999; Reicher and Hardebeck, 2002b). Monosodium
methanearsenate does not cause injury to other warm-season grasses such as seedling
buffalograss, but fenoxaprop-ethyl caused injury and reduced seedling coverage (Fry and Upham,
1994). However, on cool-season grasses fenoxaprop-ethyl is less phytotoxic than MSMA, and
fenoxaprop-ethyl is safe to use on some cool-season seedlings (Dernoeden, 1987). Established
‘Meyer’ zoysiagrass is tolerant to MSMA and fenoxaprop-ethyl (Dernoeden, 1987; Boyd and
Rodgers, 1999), but no information is available on their effects on seedling zoysiagrass.
Therefore, fenoxaprop-ethyl and MSMA should be evaluated for safely controlling annual grassy
weeds in zoysiagrass seedling turf.
Fairway Renovation
The objective of fairway renovation is to convert from one species to another as quickly
as possible. If renovation disturbs golfers or closes fairways for long periods, golf courses lose
revenue. Gradual conversion by plugging with bermudagrass and zoysiagrass has been attempted
in the past as a way to convert the existing cool-season turfs into warm-season turfs. Walden and
Chambers (1995) planted twenty-five cultivars of zoysiagrass as plugs into existing stands of tall
9
fescue in an attempt to convert to zoysiagrass. However, no zoysiagrass had established in tall
fescue after two summers of growth due to interspecific competition.
Interseeding a new species directly into existing turf does not disrupt golfers, but may not
be successful because of competition from existing grasses (Eggens, 1979). Interseeding
creeping bentgrass or Kentucky bluegrass into highly competitive annual bluegrass is only
marginally successful (Eggens, 1979; Guassion and Branham, 1989; Reicher and Hardebeck,
2002a). Interseeding a species or cultivar into another similar species or cultivar is unsuccessful
because the new seedlings have little or no competitive edge over the existing established grass
(Kendrick and Danneberger, 2002). However, seeding a warm-season grass into a cool-season
grass may be successful because of their distinctly different seasonal growth cycles. Little
information exists on interseeding a warm-season grass into a cool-season stand. Zoysiagrass
interseeded into perennial ryegrass produced only 5% coverage after one growing season in
Kansas (Zuk and Fry, 2002). However, one seeding rate (49 kg ha-1) was used in their study in
spite of suggested seeding rates of 38 to 98 kg ha-1 (Portz et al., 1981; Landry and Choi, 1995).
Furthermore, Madison (1966) reported higher seeding rates of cool-season grasses increase
seedling number shortly after emergence. Therefore, higher seeding rates may give zoysiagrass
seedlings a competitive advantage when interseeding existing cool-season turf.
The objectives of my research were to
1. Identify the range of acceptable seeding dates for bermudagrass and zoysiagrass
and determine if a relationship exists between winter survival and seeding date,
while also identifying the length of time and GDD required to reach 95%
coverage;
2. Identify the range of acceptable seeding rates of bermudagrass and zoysiagrass
and determine if a relationship exists between winter survival and seeding rate;
3. Evaluate common crabgrass control products for safety on seedling zoysiagrass;
10
4. Determine the effect of seeding rate and non-selective herbicides on zoysiagrass
establishment when interseeding into perennial ryegrass; and
5. Determine the effect of seeding rate and post-seeding herbicides on zoysiagrass
conversion on 4 golf courses in the transition zone.
11
References
Ahring, R.M., W.W. Huffine, C.M. Talifero, and R.D. Morrison. 1975. Stand establishment of
bermudagrass from seed. Agron. J. 67:229-232.
Anonymous. 1960. Winter kill problems with bermudagrass. Mid-Continent Turfletter, USGA
Green Section No. 3. p.1-2.
Beard, J.B. 1973. Turfgrass science and culture. Prentice Hall, Inc., Englewood Cliffs, NJ.
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Fig. 1. Location of the transition climatic zone for turfgrass species in the United States.