Thou shalt not scalp seashore paspalum - GCSAA

The USGA and The GCSAA Foundation provided funding for this research.
Thou shalt not scalp
seashore paspalum
Scalping is especially hard on seashore paspalum.
R.R. Duncan, Ph.D., and R.N. Carrow, Ph.D.
Some turfgrasses are more susceptible
to scalping than others, and turfgrasses
differ in their recovery ability.
Ad ju s ting managem ent practi ce s
according to the turfgrass can limit the
potential for scalping.
Un l i ke other warm - s e a s on gra s s e s
su ch as bermu d a grasses (Cyn od o n s pp. )
or zoys i a grasses (Zoys i a s pp. ), s e a s h ore
p a s p a lum (Pa s palum va gi n a tu m) does not
to l era te scalping well , and 4- to 6-wee k
recovery peri ods are not uncom m on .
The recovery period is long because,
once scalping has occurred, the grass
is norm a lly pred i s po s ed to re ad i ly
ava i l a ble pathogen s . Diseases then
attack the grass,causing thinning of the
canopy density.
Scalping also forces the grass into a
defensive mode. In paspalum, going on
the defensive means that shoot maintenance
and recovery take a back seat to
root mainten a n ce and re - e s t a bl i s h-
ment, and rhizome development. (The
oppo s i te con d i ti on usu a lly exists in
bermudagrasses, which drop some of
the root system after injury while maintaining
the shoot system.) Once the
p a s p a lum rh i zomes and other roo t s
have been reinforced, recovery of the
shoot system is very rapid.
A softer nature
The physical nature of the paspalum
leaves and canopy also differs from that
of other warm-season grasses. Seashore
p a s p a lum ach i eves traffic to l era n ce
l evels — similar to those of hybri d
bermudagrass — because it has multiple
leaf levels from the top to the bottom
of the canopy. Its cells and stems
provide a cushion to traffic (wear and
com p acti on) because they have less
lignin and are more resilient. Paspalum
Seashore paspalum provides an ideal turf when it receives sufficient topdressing, proper fertility
treatments and adequate irrigation, and is mowed by trained mower operators.
More Info: www.gcsaa.org
■ Seashore paspalum does
not tolerate scalping well
and requires a long recovery
period.
■ Fertility, sand topdressing,
irrigation management,
mower type and cultivar
all contribute to the
effects of scalping
on turfgrass.
■ Fertility is the most important
factor in preventing
scalping of paspalum, and
spoon-feeding nitrogen
and potassium is critical.
■ Limited data are available
concerning the use
of growth regulators
on paspalum.
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GCM April 2002
canopies therefore have a soft, silky feel
com p a red to the sti f fer canopies of
bermudagrass and zoysiagrass.
The softer nature of the paspalum
canopy means that the actual mowing
height in the field is very close to the
bench setting because the canopy does
not slow down the mower as much.Any
management factor that further softens
the canopy (excess nitrogen, excess irrigation,
poor drainage,low potassium or
insufficient topdressing) can increase
the potential for scalping.
Scalping: causes and prevention
Practices that minimize the potential
for scalping in paspalum are the same
as those for other grasses, but adjusted
to paspalum’s specific requirements.
1. Fertility
Fertility, especially excess nitrogen
(which causes rapid shoot growth and
excess su cc u l en ce) and inadequ a te
potassium,is the most important factor
in reducing paspalu m’s su s cepti bi l i ty
to scalping.
Excess nitrogen should not be
applied to this grass at any time. SeaIsle
1 paspalum (www.seaisle1.com) maintains
good color even at low nitrogen
Tim Hiers, CGCS, mows a paspalum green at The Old Collier GC in Naples, Fla. Mower type,
surface smoothness and firmness, and individual mower operator skills can all play a part in
whether a green is scalped.
levels, so nitrogen is seldom necessary
for color retention. Nitrogen should be
primarily applied to control or regulate
shoot growth rates.
Adequ a te ava i l a ble po t a s s ium is cri t-
ical for high leaf tu r gor pre s su re mainten
a n ce and root sys tem devel opm en t ,
m a i n ten a n ce and functi on a l i ty. It is also
the first line of defense against many leaf
s pot diseases. Se a s h ore paspalum has a
h i gh requ i rem ent for po t a s s ium and is
h i gh ly ef f i c i ent in using it. Th erefore ,
adopting a spoon - feeding ferti l i ty program
(light ra tes app l i ed frequ en t ly or
use of h i gh - percen t a ge slow - rel e a s e
n i trogen produ cts) for both nitrogen
and po t a s s ium is essen ti a l .
Like other grasses,paspalum is most
prone to scalping during the transition
from grow-in fertility and topdressing
programs to mature turf stand mainten
a n ce progra m s . Se a s h ore paspalu m
responds readily to available nitrogen
(because of its high nitrogen uptake
and use efficiency). Therefore, it is necessary
to wean the grass off the aggressive
nitrogen fertility program necessary
for grow-in. Otherwise, the turf
will be very prone to scalping during
the tra n s i ti on peri od as the cut ti n g
height is lowered.
Dec rease the mowing hei ght gradu a lly
for paspalu m , n orm a lly by 0.02–0.03-
i n ch increm ents over 2–3-day peri od s
once the nitrogen levels have been
redu ced and shoot growth ra te is slowed .
One indicator that the nitrogen fertility
program is lean enough is when
dollar spot (Sclerotinia) starts showing
up on the paspalum. Then adequate
nitrogen can be maintained by spoonfeeding
without causing excess shoot
growth. Nitrogen applications should
be avoided until stolons start growing
from the remaining shoots and the disease
problem is under control. This
grass responds rapidly to soluble nitrogen
source s , wh i ch are ei t h er used
immediately or stored for later use.
Ch oi ce of ferti l i zer type (gra nu l a r,
l i qu i d ), m et h od of a pp l i c a ti on (ferti gati
on , foliar spray, gra nular) and solu bi l-
i ty (percen t a ge slow rel e a s e , h i gh ly solu-

le) all must be determ i n ed in con cert
with bu d get con s i dera ti on s . With pasp
a lu m , adopti on of a lean-and-mean
a pp l i c a ti on stra tegy in com p l i a n ce wi t h
envi ron m ental stew a rdship issues is po s-
s i bl e .Mac ronutri ents like nitrogen , po t a s-
s ium and magn e s ium and spoon - fed
m i c ronutri ents (espec i a lly manga n e s e )
a re important to maintain adequ a te , but
not too ra p i d , s h oot growth ra te s .
2. Sand topdressing
On paspalum (and bermu d a gra s s )
go l f green s , sand top d ressing du ri n g
grow-in must be applied at frequencies
and ra tes that maintain a thin mat
(thatch with high levels of sand so that
the sand provi des a firm su rf ace ) .
In adequ a te top d ressing produ ces a
s om ewhat puffy thatch layer, wh i ch
results in a much less firm surface that is
susceptible to scalping. The higher mowing
heights and rapid turf growth rates
required for grow-in make it easy to
apply insufficient sand topdressing for
true mat development.
In the best-case scen a ri o, a firm su r-
f ace is ach i eved du ring grow - i n .
Devel oping this ideal su rf ace du ring the
tra n s i ti on peri od is also accept a bl e ,
a l t h o u gh it is more difficult and requ i re s
f requ ent light verti c ut ti n g. If a firm su r-
f ace is not ach i eved by the time grow - i n
has been com p l eted , it may take som e
time to lower mowing hei ghts to playa bl e
l evels in an ef fort to avoid scalping.
Light verticutting aids in preventing
scalping du ring the tra n s i ti on from
grow-in to mature turf by allowing more
topdressing sand to integrate into the
turf surface. Heavy verticutting should
be avoided, however.
Good topdressing sand integrates easily
into seashore paspalum surfaces even
at close mowing heights and without
verticutting when applied at light rates
of 0.5 to 4.0 cubic feet of topdressing per
1,000 square feet.
3. Irrigation management
Pa s p a lum is very re s pon s ive to irri gati
on du ra ti on and frequ en c y. E m p l oyi n g
f requ ent irri ga ti on events of s h ort du ra-
ti on re sults in a shall ow root sys tem and
grass that wi ll not ex h i bit its full po tential
for dro u ght re s i s t a n ce and tends to
grow ra p i dly, e s pec i a lly if ferti l i ty is
h i gh . (“ Frequ ent irri ga ti on events of
s h ort du ra ti on” means irri ga ting every
1-3 days at ra tes that on ly rewet the su r-
f ace 4 inches of the root zone ra t h er
than rech a r ging the whole roo t - zon e
depth.) Un der these con d i ti on s , t h e
grass also tends to be more su cc u l en t
and ex h i bits too mu ch shoot growt h .
In f requ ent irri ga ti on app l i c a ti ons of
l on ger du ra ti on (irri ga ting every 4-7 days
with su f f i c i ent water to rech a r ge the roo t
zon e ,of ten abo ut 0.5 to 1.0 inch of w a ter
on a sand green) wi ll train the root system
deeper into the soil prof i l e ,while the
s h a ll ower roots take adva n t a ge of ra i n f a l
and irri ga ti on even t s .Hi gh eva po tra n s p i-
ra ti on ra tes and dro u ght stre s s
ep i s odes have little ef fect on
grass with a deep root sys tem
and a high rh i zome nu m ber.
Periods of drought stress
h a rden the grass to envi ronm
ental stre s s e s .
Excess irri ga ti on causes
ad d i ti onal su cc u l en ce in the
tu rf l e aves and a sof ter su r-
f ace zon e ,wh i ch can also lead
to scalping. The grass can
t a ke excess water and prol
on ged wet soi l - profile con d i-
ti on s , but scalping po ten ti a l
i n c reases accord i n gly, u su a lly
because the tu rf su rf ace is less
f i rm and is more prone to tra f f i c - rel a ted
go u ging of the su rf ace . Poor dra i n a ge
can also produ ce the same re sults in wet
eco s ys tem s .
The grower must balance the management
of salts with supplying judicious
quantities of water for the turf
while complying with water conservation
requirements. Use of highly saline
water may alter the decision to verticut
lightly, because the cut ends of the turf
could be more prone to salt desiccation
and injury.
4. Mower type
Especially on greens, the type of
Scalping predisposes seashore paspalum to diseases
such as Helminthosporium, indicated by the
reddish-brown color of the grass.
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mower used can cause or prevent scalping.
Some new mowers cause minimal
scalping problems regardless of grass
type. Mowers with dual rollers are less
likely to scalp the grass than are mowers
with only a single roller. Of course, surface
smoothness and firmness and individual
mower operator skills affect the
operation of any greens mower. Blade
sharpness and the use of brushes vs.
groomers also can influence scalping.
5. Cultivar
Some paspalum cultiva rs , su ch as
deriva tives of the old Ad a l ayd or
Exc a l i bur sources that ori gi n a ted from
Au s tra l i a ,a re more sen s i tive to scalping.
Cu l tiva rs with lower levels of s a l i n i ty
to l era n ce seem to be more prone to
s c a l p i n g, but all cultiva rs can be scalped .
Growth regulators
Growth reg u l a tors are com m on ly
applied to bermudagrasses to minimize
scalping, especially in mid- to late summer.
Growth regulator use could help
on seashore paspalum, but limited data
are available. Given what is currently
known about plant growth regulator
re s pon s e , Primo (tri n ex a p ac - et hyl )
should be used cauti o u s ly with this
grass, and small areas should be tested
before applying the chemical to large
areas. Identical rates applied at different
locations (Hawaii,Florida and Georgia)
have given different results — some
positive and some negative.
Primo is somewhat effective in suppressing
seed h e ads in paspalu m .
App l i c a ti ons of Cutless (flu pri m i do l )
will suppress growth significantly above
85 F and below 75 F. Trimmit (paclobutrazol)
and Proxy (ethephon) have been
applied at varying rates and timing with
mimimal side effects,and both are effective
at seedhead suppression, although
envi ron m ental interacti ons have
occurred (as noted above for Primo).
E m b a rk (mef lu i d i de) and malei c
hydrazide responses on paspalum are
unknown. Use of irrigation water with
high salt levels will also have a growth
regulator effect.
After scalping
O n ce scalping has occ u rred and a disease
or diseases have attacked the gra s s ,
determine wh i ch pathogen(s) are causing
the probl em . A topical fungi c i de wi ll
s top the pathogen from spre ad i n g.
Aera ti on fo ll owed by top d ressing and
a pp l i c a ti on of a po t a s s ium + cyto k i n i n
produ ct wi ll help rei n force the root system
and lead to a horm onal shift tow a rd
n ew shoot produ cti on at a faster recovery
ra te . Using cytokinin is essen tial on
s a l t - a f fected sites because salt acts as a
growth reg u l a tor.
An o t h er opti on is app lying gra nu l a r
and foliar manganese to co u n ter take - a ll
( Ga eu m a n n o myces gra m i n i s) disease,wh i ch
is favored wh en scalping occ u rs and environ
m ental con d i ti ons are favora bl e. ■
References
1. Carrow, R.N., and R.R. Duncan. 1998. Saltaffected
turfgrass sites: assessment and management.
Ann Arbor Press. Chelsea, Mich.
2. Carrow, R.N., D.V. Waddington and P.E. Rieke.
2 0 0 1 . Tu rfgrass soil ferti l i ty and ch em i c a l
problems: assessment and management. Ann
Arbor Press. Chelsea, Mich.
3. Duncan,R.R.2001. All seashore paspalums are
not created equal. Golf Course Management
69(6):54-60.
4. Du n c a n , R . R . , and R.N. Ca rrow. 2 0 0 0 .
Seashore paspalum — the environmental turfgrass.
Ann Arbor Press, Chelsea, Mich.
Inadequate sand topdressing during grow-in can produce a puffy thatch layer, which results in
a softer surface that is susceptible to scalping.
R . R . Du n c a n , Ph . D. (e-mail: rdu n c a n @ ga e s .
griffin.peachnet.edu), and R.N. Carrow, Ph.D., are
researchers at the University of Georgia — Griffin.
GCM April 2002