Southern sandbur [Cenchrus
echinatus L.][CCHEC][CDFA list: C] Photographs
Field sandbur or Coast
sandbur [Cenchrus incertus M. Curtis][CCHIN][CDFA list: C]
Longspine sandbur or
Mat sandbur [Cenchrus longispinus (Hackel) Fern.][CCHPA][CDFA
list: C] Photographs
DESCRIPTION:Introduced summer annuals, to 0.6 m tall,
with loose spikes (racemes) of spiny burs at maturity.
Field sandbur is annual in CA, but can be biennial or perennial
elsewhere. Plants provide good forage for livestock before burs
develop. However, bur spines are stiff and can injure the mouths
of animals and the hands and feet of people working in infested
crops, orchards, or vineyards. Field and longspine sandburs
are similar and difficult to distinguish.
in bud. Sheaths, ligules, and blades
resemble those of mature plants.
tufted. Culms branched and often abruptly bent near the base (geniculate).
Ligules consist of a fringe of hairs, 0.5-1.5 mm
long. Often there is a tuft of hairs ~ 2-3 mm long at the position
of the auricles. Sheaths open, flattened, +/- glabrous, margins
narrowly membranous, sometimes lined with a few long hairs. Collar
narrow, lighter in color. Blades flat, sometimes folded, appear
+/- glabrous, but are rough with very short hairs (visible with
back to top of
and UNDERGROUND STRUCTURES:Roots fibrous, shallow. Sometimes roots at the nodes.
SPIKELETS/FLORETS:Spikelets (1-8) enclosed by fused, spiny bracts
that form a bur. Racemes of burs loosely spike-like, terminal.
Main flowering axis (rachis) wavy. Burs disperse
as units. Upper leaves sometimes partially enclose the lower burs.
Spikelets consist of 2 florets. Only the upper floret is fertile.
CHARACTERISTICS:southern sandbur: Late
in the season, lower foliage becomes straw-colored and stems turn
reddish or maroon. After a frost, entire plants become straw-colored.
Stems with burs can persist through winter. Dispersed burs can
remain on or near the soil surface through the following summer.
colonizes open, disturbed sites in fields, orchards, vineyards,
alfalfa, cultivated crops, ditch banks. Often infests sandy, well-drained
by seed. Burs disperse by clinging
to skin and fur of animals, shoes and clothing of humans, tires,
farm machinery, and by floating on water. Seedlings emerge in
spring or early summer, and growth is rapid under moist conditions.
FAVORING/DISCOURAGING SURVIVAL:Sandburs compete poorly with dense vegetation and
rarely become established in well-managed pastures. Disturbances
that bury burs and remove existing vegetation stimulate germination
and enhance seedling establishment. However, repeated cultivation
before burs develop reduces the seed bank and can eventually eliminate
an infestation. Under mowing regimes, plants grow low to the ground
and can still produce burs.
the sandburs, bufflegrass [Cenchrus ciliaris L.][PESCI]
has stiff-bristly bracts separate to near the base and straight
main flowering axes. Bufflegrass is a perennial with rhizomes
and sometimes stolons. It infests disturbed sites and fields in the South
Coast region (Los Angeles Co.) to 100 m (330 ft) and is increasing in distribution
in many areas in the Southwestern U.S. Bufflegrass is especially troublesome
in southwestern deserts that receive summer rain. Introduced from Africa and
Biology and prevention: Three
weedy Cenchrus species occur in California. They are found in irrigated crops
and along roadsides and disturbed areas. The spiny burs are a nuisance to
farm workers and may cause injury and seriously interfere with crop harvests,
resulting in increased costs and decreased productivity. Burs are troublesome
to animals; they are easily caught in hair, fur, and wool, and reduce wool
quality and cause injury to livestock, wildlife and pets.
Seed dispersal occurs by animals, farm equipment, tires, and in contaminated
hay and other forage crops. Water is also important for dispersal, as burs
float and may be carried for miles in irrigation ditches and other waterways.
All three species are normally annuals with the exception of C. incertus,
which may overwinter as a short-lived perennial. Nevertheless, all are subsequently
dependent upon seed production for survival. Individual plants can produce
more than 5,000 burs, with 1-3 seeds per bur. Plants produce (primary) seed
with low dormancy and (secondary) seed with higher levels of dormancy. Light
may inhibit germination and cause induced dormancy in secondary seed. Seed
viability is believed to be short, but may be up to three years. Seedlings
generally emerge in the spring, but additional seedling flushes can occur
with irrigation or late season rainfall.
Mechanical: Tillage is effective when plants are small. However, large
plants of all three species may root at the nodes, resulting in large tussocks
that are difficult to sever. Tillage may also increase seed germination by
burying seed on the soil surface where light inhibits germination. Intensive
cultivation throughout the season following each flush of seedlings has been
used for eradication, but may take up to three years. Deep plowing is effective;
however, seed may germinate from depths of 11 cm.
Repeated mowing or heavy grazing prior to flowering will reduce, but not eliminate
seed production. Animals will avoid grazing mature plants, which can result
in serious mechanical injury if no other forage is available. Mowing is most
effective when plants are at the boot stage of development.
Biological: There are no
biological control agents for sandbur. Sandbur does not compete well in shaded
conditions and maintaining a dense cover in pastures can prevent invasion.
Most competitive forage crops may reduce but not eliminate seed production
by established plants.
Fire: There is little information
on utilizing controlled burns for sandbur management. However, flaming is
an effective control technique when conducted prior to seed set.
Chemical: There are several herbicides registered for sandbur control
in California. However, their utilization is dependent upon the cropping situation.
Nonselective treatments include glyphosate (0.75-1.5 lb ae/A) and diuron (2.7-7.5
lbs ai/A); bromacil (5-6.2 lb ai/A) in citrus; benefin (3.3-4.1 lb ai/A) in
lettuce and alfalfa; fluazifop (0.25-0.375 lb ai/A) in several fruit, nut,
and vegetable crops; trifluralin (0.36-1.0 lb ai/A) in certain crops; and
MSMA (1.8 lb ai/ 40 gallons water, spray to runoff) in non-crop areas. There
are currently no known cases of herbicide resistance in any species of Cenchrus.
However, repeated applications of the same herbicide or same mode of action
may select for resistant plants.
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