Yellow foxtail [Setaria
pumila (Poiret) Roemer & Schultes][SETLU] Photographs
Green foxtail [Setaria
viridis (L.) Beauv.][SETVI] Photographs
[Setaria faberi R. Herrm.][SETFA][CDFA list: B] Photographs
Map of Distribution
Complete synonymy is complicated and
beyond the scope of this publication.
DESCRIPTION: Simple to loosely tufted summer annuals
with bristly spike-like panicles. These species are often
associated with agriculture and are widely distributed throughout
much of the world. The seeds are a valuable food source
for numerous bird species. Immature plants are palatable to livestock.
All utilize the C4 photosynthetic pathway.
SEEDLINGS: First leaves
are typically parallel to the ground. Except for blade lengths,
vegetative characteristics resemble those of mature plants. Yellow
foxtail seedlings can mature within 40 days.
Stems typically erect to bent and ascending, branched at the base.
Blades rolled in bud, flat, typically with pronounced
pale midveins below. Ligules consist of a fringe of short
hairs. Sheaths open. Auricles lacking.
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and UNDERGROUND STRUCTURES: Roots fibrous, shallow.
SPIKELETS/FLORETS: Panicles dense, spike-like,
with persistent awn-like bristles (sterile branchlets) below each spikelet
or spikelet cluster. Spikelets ellipsoid to ovoid, glabrous, lack awns, consist
of 2 short glumes, a sterile lemma (sterile floret), and a fertile floret.
Fertile lemmas +/- hard, transversely ridged, margins tightly
enfold paleas. Spikelets disperse as units without bristles. Refer
to the Comparison of foxtails
(Setaria spp.) table for important differences.
Wind- and self-pollinated.
CHARACTERISTICS: Old flower spikes may persist into winter and consist
of bristles and spikelet stalks with cup-shaped tips after spikelets
have fallen. Yellow foxtail spikes are typically yellowish,
while those other foxtails become brown.
sites, roadsides, ditch banks, fields, pastures, cropland, orchards,
vineyards, gardens. All tolerate a broad range of environmental
conditions and grow in moist or dry soils. Yellow foxtail also
grows in turf and is most frequent on moist soils. Giant foxtail
grows best on fertile sandy soils.
PROPAGATION/PHENOLOGY: Reproduce by seed. Seeds disperse with
agricultural and other human activities, water, soil movement,
animals, and as crop seed and hay contaminants. Seeds are hard-coated
and most float on water. Seed production and germination requirements
are variable, depending on biotype and environmental conditions.
Optimal temperatures for germination are typically between20-35º
C (68-95º F). Cool moist stratification enhances germination.
Yellow and green foxtail seeds are usually dormant
at maturity and require an afterripening period of ~ 2-4 months
before they can germinate. Giant foxtail seed dormancy
at maturity is variable, and seeds produced later in the season
are often less dormant than those produced earlier. Most seeds
survive only a few years under typical field conditions. Some
deeply buried seed of yellow and green foxtail may
survive for up to ~ 12 years or more. Seedlings emerge spring
through summer from soil depths to ~ 10 cm (~ 4 in), with optimal
emergence from 1-2 cm (~ 0.3-0.75 in).
FAVORING/DISCOURAGING SURVIVAL: Hand removal or cultivation as needed before seeds
are produced can control infestations.
Bristly foxtail [Setaria verticillata (L.) Beauv.][SETVE], knotroot
foxtail or marsh bristlegrass [Setaria gracilis Kunth; synonyms
S. geniculata (Lam.) Beauv., S. parviflora (Poir.) Kerguelen][SETGE],
and African bristlegrass [Setaria sphacelata (Schum.) Moss][Bayer
code: none] resemble the species described above. Refer to the Comparison
of foxtails (Setaria spp.) table for important distinguishing characteristics.
Bristly foxtail occurs in the South West region and San Joaquin Valley,
to 200 m (660 ft). Introduced from Europe. Knotroot foxtail is a native
perennial with short, knotty rhizomes. It is widespread throughout
much of the U.S, but relatively uncommon in California. Knotroot foxtail
is usually not considered a weed in natural habitats. It typically inhabits
open dry or wetland sites, grasslands, and chaparral. However, it is sometimes
weedy in agronomic crops, orchards, vineyards, and drainage areas. It spreads
primarily by seeds. Knotroot foxtail occurs in the Centralwestern region,
Central Valley, South Coast, Mojave Desert, and southwestern Great Basin (SNE),
to 400 m (1300 ft). African bristlegrass is an uncommon wetland perennial
with short rhizomes. It is scattered in the Central Valley (Butte, Solano,
Tulare, Stanislaus, Kern cos.) and Cascade Range foothills (Tehama Co.), to
300 m (1000 ft). Introduced from tropical Africa as an experimental forage grass.
Prevention: Giant foxtail is a competitive summer annual
grass that reduces yields in many crops. Giant foxtail is a large problem in
the Midwest but is still relatively uncommon in California. To avoid new infestations,
use only certified seed and always clean equipment after working in infested
Mechanical: Tillage is effective in controlling seedlings
and young plants. In row crops, cultivation integrated with herbicides has been
very effective in controlling giant foxtail.
Chemical: a number of herbicides are effective on giant
foxtail which, are beyond the scope of this publication. However, repeated use
has led to resistance to at least three modes of action including Photosystem
II inhibitors, ALS inhibitors, and ACCase inhibitors in the Midwest and North
Central states. To date, no giant foxtail herbicide resistance has been reported
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