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Number 4, 1998
Wet Spring Encourages Yellow Nutsedge Invasion
Large populations of yellow nutsedge (Cyperus esculentus)
have developed in areas having wet weather this past spring and
early summer. Also known as yellow nutgrass, yellow nutsedge is
a warm season perennial member of the Cyperaceae (Sedge Family)
that reproduces by seeds and also from tubers (nutlets). While
its natural range includes most of the United States (including
all of Illinois), this North American native is most troublesome
in the southeast, including the southern portion of the Land of
Lincoln.
Life Cycle and Appearance:
Individual yellow nutsedge plants have upright,
grasslike leaves that emerge from a fibrous root system and scaly,
white or light-colored rhizomes.
Tubers - The tubers develop rapidly six to eight weeks after the
plants emerge, usually during late July and August and can persist
for many years in the soil. Forming at the ends of rhizomes (not
in chains as occurs in other sedges such as purple nutsedge),
the nutlets can reach up to 4/5 inch in length. New plants emerge
from tubers from late May to mid-July.
Leaves - Leaves emerge from the Yellow Nutsedge plant's base,
are 3-ranked, grasslike, and light yellow-green. They are 1/8
to 1/2 inch wide, up to 3 feet long, and have parallel veins with
a prominent midvein. The upper surface is shiny or waxy and the
lower surface is dull. The growth rate of the leaves is rapid
during summer; they often grow above the canopy of cool season
turf.
Flowers - Nutsedge inflorescences are flat-topped and multiple-branched
with long leaf-like bracts beneath. They appear burr-like and
occur at the end of stout, triangular (in cross section), yellow-green
stem. Each branch of the inflorescence is composed of multiple
yellow-to-golden brown spikelets, each up to 1-1/4 inches long.
The inflorescences appear July to September during 12-to-14-hour
days.
Ecology:
Yellow nutsedge is often an indicator of poor drainage.
It grows on all soil types, especially wet or moist sites or sites
receiving heavy irrigation. It normally appears on soils with
a pH of 5.0 to 7.0. Yellow nutsedge does not tolerate shade and
will tolerate dry sites once it is established.
Control:
Due to the tubers' reproductive capacity, controlling
yellow nutsedge is very difficult after the tubers have formed.
To control without chemicals, maintain turf density and health
through proper culture; mechanically remove or pull nutsedge plants
soon after germination, and increase drainage in moist or wet
areas. Mow low (less than 1" on turf species tolerant of
that practice) and frequently to reduce growth from plant base.
Purchase nutsedge-free sod and soil. Fertilize turf in autumn
after nutsedge growth has slowed. Chemical controls for yellow
nutsedge include fumigation and herbicides. Fumigate (methyl bromide)
high-value sites contaminated with yellow nutsedge prior to planting.
Several postemergence herbicides can be applied in an attempt
to control yellow nutsedge, but be aware that total control is
often difficult, and each of these products may require multiple
applications. Basagran T/O (bentazon) is a contact herbicide and
Manage (halosulfuron) is a systemic product. A third option are
products containing MSMA including Daconate 6, 912 Herbicide,
MSMA 6.6, MSMA Turf, and Quadmec Trimec Plus (2,4-D + MCPP + dicamba
+ MSMA). For each of these products, the herbicide label provides
information about adjuvants and additional recommendations for
controlling this pesky plant. Turf managers have reported that
applications of Roundup (glyphosate) have resulted in poor yellow
nutsedge control. Be sure to read, understand and follow all label
directions for the safest, most effective weed control.
(Tom Voigt and Bruce Branham)
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