Yellow foxtail [Setaria pumila (Poiret) Roemer & Schultes][SETLU] Photographs

Green foxtail [Setaria viridis (L.) Beauv.][SETVI] Photographs

Giant foxtail [Setaria faberi R. Herrm.][SETFA][CDFA list: B] Photographs Map of Distribution


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[
SYNONYMS] [GENERAL DESCRIPTION] [SEEDLINGS] [MATURE PLANT] [ROOTS and UNDERGROUND STRUCTURES] [SPIKELETS/FLORETS] [POSTSENESCENCE CHARACTERISTICS] [HABITAT] [DISTRIBUTION] [PROPAGATION/PHENOLOGY] [MANAGEMENT FAVORING/DISCOURAGING SURVIVAL] [SIMILAR SPECIES] [CONTROL METHODS]


SYNONYMS: Complete synonymy is complicated and beyond the scope of this publication.

GENERAL 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.

MATURE PLANT: 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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ROOTS 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.

POSTSENESCENCE 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.

HABITAT: Disturbed 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.

DISTRIBUTION:

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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).

MANAGEMENT FAVORING/DISCOURAGING SURVIVAL: Hand removal or cultivation as needed before seeds are produced can control infestations.

SIMILAR SPECIES: 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.

CONTROL METHODS:

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 areas.

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 in California.

References

Carey, J. B., D. Penner, and J. J. Kells. 1997. Physiological basis for nicosulfuron and primisulfuron selectivity in five plant species. Weed Science. 45: 22-30.
Fausey, J. C. and K. A. Renner. 1997. Germination, emergence, and growth of giant foxtail (Setaria faberi) and fall panicum (Panicum dichotomiflorum). Weed Science 45 (3):423-425.
Kegode, G. O. and P. R. Brent. 1998. Influence of environment during maternal plant growth on dormancy of shattercane (Sorghum bicolor) and giant foxtail (Setaria faberi) seed. Weed Science 46 (3): 322-329.
Kegode, G. O., P. R. Brent and T. B. Bailey. 1998. Influence of fluctuating temperatures on emergence of shattercane (Sorghum bicolor) and giant foxtail (Setaria faberi). Weed Science 46 (3):330-335.
Krausz R. F., G. Kapusta, and J. L. Matthews. 1993. The effect of giant foxtail (Setaria faberi) plant height on control with six postemergence herbicides. Weed-Technology 7 (2):491-494.
Mulugeta,D. and C. M. Boerboom. 1999. Seasonal abundance and spatial pattern of Setaria faberi, Chenopodium album, and Abutilon theophrasti in reduced-tillage soybeans. Weed Science 47 (1) 95-106.
Ritter, R. L., L. M. Kaufman, T. J. Monaco, W. P. Novitzky, and D. E. Moreland. 1989. Characterization of triazine-resistant giant foxtail (Setaria faberi) and its control in no-tillage corn (Zea mays). Weed Science. 37: 591-595.
Shukla, A., G. E. Leach, and M. D. Devine. 1997. High-level resistance to sethoxydim conferred by an alteration in the target enzyme, acetyl-CoA carboxylase, in Setaria faberi and Setaria viridis. Plant Physiology and Biochemistry 35: 803-807.
Stoltenberg, D. E. and R. J. Wiederholt. 1995. Giant foxtail (Setaria faberi) resistance to aryloxyphenoxypropionate and cyclohexanedione herbicides. Weed Science. 43: 527-535.
Wang, R. L. and J. Dekker. 1995. Weedy adaptation in Setaria spp. III. Variation in herbicide resistance in Setaria spp. Pesticide Biochemistry and Physiology. 51: 99-116.
Wiederholt, R. J. and D. E. Stoltenberg. 1996. Absence of differential fitness between giant foxtail (Setaria faberi) accessions resistant and susceptible to acetyl-coenzyme A carboxylase inhibitors. Weed Science. 44: 18-24.

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