New vs older varieties of perennial ryegrass for overseeding

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I still drive a 38 year old EH Holden Standard Sedan because cars haven’t improved.
There are three things which hold true…
‘’Just because its old doesn’t mean it doesn’t work anymore’’
‘Technology is constantly improving’’
‘’Just because I have always done things one way doesn’t mean it cannot be improved. We are always
learning’’
All of these statements can be applied to the turf industry and in particular the use of perennial ryegrass
to oversow warm season grasses in the cooler months. Whilst new fungicide chemistry is constantly
being introduced and offers new modes of action and reduced usage rates, perennial ryegrass seems to
some extent to ‘’slip through the cracks’’.
Many turf managers make selections based on an historical familiarity with a particular variety and/or
the relationship that they might have with a particular company. Independent trial or research data is
seldom used in making a purchase decision.
In both Europe and the USA regular trials are carried out categorizing cultivars by performance. These
are produced to help the end user make informed decisions so that the end user can choose the best
cultivar for any particular situation.
For example The Sports Turf research Institute in 1981 produced The Turfgrass Seed Guide. The first
(Table 1) shows a complete list of perennial ryegrass cultivars according to chromosome number,
agricultural persistence and heading date.
Very Early Early Intermediate Late Very Late
i) Turf
type
diploid
cultivars
Derby
Game
Pennfine
Regal
Royal
Venlona
Arno
Barry
Caravelle
Causeway
Ensporta
Gazon
Majestic
Manhattan
Hornet
Hunter
Loretta
Player
Pleno
Score
Bellatrix
Saione
Sprinter

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The next table (Table 2) shows a direct comparison between perennial ryegrass cultivars with these
being ranked (A) good (B) medium and (C) poor.
Cultivar Tolerance
of artificial
wear
Persistence
without
wear mown
at 20mm
Compactness Freedom
from red
thread
Cleanness
of cut
Short
growth
Winter
hardiness
Loretta A A A C A A A
Majestic A A A C A A A
Sprinter A A A C B A A
Arno A A B B A A
Manhattan A A B C A A A
Score A A A B B B B
Barry A A B B A B
Pennfine B A A B A A B
Hunter B A A B B A B
Bellatrix A A B B B B
Derby A B B B A B
Ensporta A A A C C B C
Player B A A B A B
Wendy B A B B B A B
Caravelle B A B B C A B
Pelo B A B B A B B
Grandstand B A B B A B B
Melle B A B B A B B
Romney B A B C C A B
Lamora B B B B A B A
Perma B B B B A B B
Donata B B B A B B
Karin B B B B A B B
Angela B B B B A B B
Interestingly the only cultivar still commercially available in Australia some 36 years after this was first
produced is Caravelle but when you look at this data, even then it doesn’t really perform very well in a
number of key selection criteria.
In 1984 the following table (Table 3) was produced in the USA by G. Pepin, The Director of Research at
Pickseed West ranking 34 perennial ryegrass cultivars

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Cultivar Colour Tiller
Density
Leaf
Texture
Winter
hardiness
Mower
quality
Brown
patch
resistance
Endophyte
Level
Allstar 7 7 7 7 6 7 6
Barry 8 7 7 7 7 7 1
Belle 7 7 6 8 6 7 1
Birdie 7 6 6 7 6 7 1
Birdie II 7 7 7 5 7 7 8
Blazer 7 7 7 8 6 7 2
Caravelle 9 4 6 3 3 4 1
Citation 8 6 7 7 6 7 1
Citation II 8 6 7 6 7 7 9
Cowboy 7 6 7 5 5 6 6
Dasher 7 6 6 8 6 7 3
Del ray 6 7 6 8 7 7 3
Derby 7 6 6 6 6 7 3
Diplomat 7 8 7 8 5 7 1
Elka 5 6 9 8 8 5 1
Fiesta 8 6 7 8 7 7 2
Game 5 3 3 4 3 2 1
Gator 8 8 7 7 8 7 1
Linn 5 2 3 3 1 2 3
Loretta 5 7 8 7 8 5 1
Manhattan 6 5 6 8 5 5 1
Manhattan
II
8 8 8 6 8 7 2
NK 200 7 5 6 9 4 5 1
Omega 7 6 6 8 5 7 1
Omega II 7 7 7 7 7 7 5
Palmer 7 8 7 6 6 8 3
Pennant 7 6 6 8 5 7 8
Penn Fine 6 5 6 6 5 7 3
Prelude 8 8 6 6 6 7 5
Premier 7 7 7 6 6 7 5
Regal 8 6 6 8 7 7 8
Repel 7 7 7 7 7 7 9
Tara 8 7 7 6 7 7 1
Yorktown II 7 7 8 7 7 7 1
9 Darkest color, most density, finest texture, most winter hardiness, best disease resistance, and
highest endophyte level
Once again Caravelle is listed and once again apart from colour and endophyte levels it doesn’t really
perform very well.

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Kopec et al (1988) looked at 36 varieties for winter performance when oversowing a couch fairway
including Caravelle. In fact Caravelle did exactly what it would be expected after a slow establishment.
Gave a dark green colour over the winter months and then keeled over once temperatures increased.
Interestingly neither the 2005-2007 New Zealand ryegrass trials and the 2007-2008 Australian ANTEP
Trials included Caravelle.
All the above leads nicely onto the issue of endophytes and transitional ryegrass. The key questions
when oversowing for example couch are:
1) Do endophytes from the perennial ryegrass cause an issue with the underlying couch or is it
shade from the oversown grass?
2) With the introduction of the sulfonylurea herbicides surely better higher quality and better
performing varieties can be used as the means of chemically removing them actually exists
now? In the 1980’s these were not available.
3) As a general rule if the couch has 100 days without competition from an oversown grass it will
recover (weather conditions being favourable).
Endophytes, shade and Ryegrass
Research by McCarty et al (2010) concluded that results obtained when soil was amended with shoot
debris demonstrated perennial ryegrass can inhibit couchgrass germination and growth in controlled
environments. They concluded that unequivocally proving allelopathy would require identifying and
extracting allelochemicals from perennial ryegrass, applying them to couchgrass, and observing growth
suppression which was beyond the scope of this experiment.
However, being a generous guy lets agree that allelopathy does occur and high levels of endophyte
within ryegrass can impact on couchgrass growth. Does this really matter if the underlying couch is fully
established and possesses a strong root network coupled with the fact that the ryegrass is annually
transitioned out once temperatures increase and the couch is actively growing?
Shaded couchgrass develops thin, etiolated leaves, increases internode length, and a poorly developed
root system. Over time, shade results in a thin canopy intolerant to traffic. Under traffic stress, the stand
will rapidly thin to the point of stand failure, weed intrusion, and finally, poor surface performance.
Couldn’t these same indicators be incorrectly attributed to allelopathy in many instances?
Transition
The majority of Turf Managers now use chemical aids to achieve a successful transition. However, using
these correctly can prove tricky as water pH and temperature can have a major impact on the success or
failure of any works carried out.
An interesting article by Dr. T Vassey in 2010 discussed the issues of growing couchgrass on California
Coast due to the existing temperatures coupled with cloud and fog limiting the plants ability to
photosynthesize. He recommends chemically removing the ryegrass in order to give the underlying
couch as much time as possible to grow. He recommends applying the registered products when the
couchgrass has reached approximately 50% green-up of any un-overseeded areas.

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Work carried out by Gelernter and Stowell (2003) looked at the Efficacy of sulfonylurea herbicides for
improved transition on couchgrass fairways. Overall, the best combination of results (increased
couchgrass stand with the smallest duration and least severe yellowing of turf) was produced when
applications were timed at couchgrass cover greater than 50%, when average air temperatures were
18°C or higher, and/or when average soil temperatures (6” depth) were 21°C or higher.
water pH
Increasing pH can increase the solubility of sulfonylurea herbicides, and theoretically increase their
activity (this has yet to be thoroughly proven).
So why use old ryegrass technology which in some case is over 35 years old, when far
superior varieties are available at a lower cost and that can now be transitioned out
extremely effectively using herbicides now available on the market? All of the newer varieties
are less disease prone (saving on potential fungicide applications) and exhibit higher wear
tolerance.