the Fate of Field Paspalum Control - The Paginator

TURF TALK
By Peter H. Dernoeden, Ph.D., and Christopher P. Ryan, Dept. of Plant Science and Landscape Architecture, University of Maryland
ield or smooth paspalum
(Paspalum laeve Michx.) is an
increasing weed problem in
turfgrass sites in Maryland. Field
paspalum is a warm-season perennial
that has a bunch-type growth habit,
but plants may develop one or two
short (1.5 to 2.0 cm) rhizomes. Vernation
is folded, and foliage is typically
grayish green or yellow green. Leaves
and sheaths are hairy and have a short
(1.0 to 2.0 mm) membranous ligule.
Paspalum rapidly spreads by
seed. Seedheads appear in late summer
(usually September), and spikelets are
formed opposite on the inflorescence.
Seeds are distinctly disk shaped (i.e.,
round, with flat sides).
This species often is confused with
dallisgrass (P. dilatatum Poir.), which
is not as commonly found as field
paspalum as far north as Maryland.
The distribution of dallisgrass in
Maryland has not been assessed in
recent years, but it is believed to
be now more commonplace than
previously reported.
The new control problem
Since the 1960s, monosodium and
disodium methanearsonates (MSMA
and DSMA) have been used on turf to
control field paspalum, dallisgrass
and crabgrass (Digitaria spp.). MSMA
and DSMA are organic forms of
arsenic that are relatively non-toxic
and are considered less toxic than
aspirin. (Inorganic forms of arsenic,
like calcium arsenate, are highly toxic
and were banned from use on turf
several decades ago.)
DSMA was withdrawn from the
market several years ago. On December
31, 2010, the EPA cancelled registration
of MSMA use for residential,
commercial and sports turf maintenance.
Existing stocks of MSMA,
however, may be used legally on residential,
commercial and sports fields
until December 31, 2013. Sale of all
products containing MSMA for use
on golf courses, sod farms and highway
right-of-ways will end on December
31, 2012, and use of existing
8 MTC TURF NEWS