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.
SEEDLINGS: Leaves folded in bud. Sheaths, ligules,
and blades resemble those of mature plants.
MATURE PLANT: Loosely 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 magnification).
- 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.
- Herbicide: 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.
For More Information:
Detailed information about Longspine
Sandspur is available at
the Washington
State Noxious Weed Control Board Web Site. |
