[Prosopis velutina Wooton][PRCJV]
Creeping mesquite [Prosopis
strombulifera (Lam.) Benth][Bayer code: none][CDFA list: A][Federal Noxious
Weed] Photographs Map of Distribution
DESCRIPTION:Winter deciduous shrubs or small trees, with thorns or spines. Mesquites are members
of the Mimosoideae subfamily of Fabaceae. Pods are sweet, fairly
nutritious, and relished by livestock, but heavy consumption can
cause digestive problems. Plants are often considered rangeland
weeds because they are prolific and highly competitive for moisture
with herbaceous grassland species.
oval, somewhat fleshy. Fast growing.
often slightly zig-zagging. Leaves alternate (sometimes appearing
fascicled on short shoots), twice-pinnately compound with
even numbers of pinnae (primary divisions of leaves) and leaflets.
Leaflets opposite, oblong.
back to top
and UNDERGROUND STRUCTURES:Plants develop spreading lateral roots that
can extend several meters outwards in all directions in the upper
soil layers and deep taproots to depths of 4 m or more.
Roots associate with nitrogen-fixing bacteria.
axillary. Flowers small, numerous, radially symmetrical,
with bell-shaped calyces. Petals 5. Stamens 10, extended
beyond petals. Insect pollinated. Species hybridize freely.
and SEEDS:Prolific, especially in dry years. Pods (loments)
flattened, leathery, slightly constricted between seeds, and not
opening at maturity. Seeds numerous, separated by spongy pulp
on sandy, rocky, medium to fine-textured soils in semi-arid and
by seed. Creeping mesquite also
reproduces vegetatively from creeping lateral roots. Fruits
are consumed and dispersed by animals. Rodents often plant seed.
A proportion of seed remains viable after ingestion by livestock.
These seeds typically have higher germination rates. Seed can
germinate under considerable moisture stress. Most seed germinates
between 20-40º C, and light is not required. Seed retained
within intact pods can remain viable for up to 40 years, but exposed
seeds dry out or decay more rapidly. Seedlings typically emerge
from soil depths of 1-2 cm. Seedling root growth can be up to
10 times more rapid than shoot growth. Plants mature after 3 years.
FAVORING/DISCOURAGING SURVIVAL:Livestock browsing on fruits can disperse seeds
to new sites. Quarantining livestock for ~ 6 days before moving
can help prevent introducing seed into new areas.
SIMILAR SPECIES:Honey mesquite [P. glandulosa
Torrey var. torreyana (L.Benson) M.Johnston] and screw bean [P.
pubescens Benth.] are native shrubs or small trees that are important components
of desert communities. Honey mesquite differs from velvet mesquite
by having glabrous to sparsely hairy leaflets mostly greater than 15 mm
long. Unlike creeping mesquite, screw bean has spike-like flower heads
and leaflets densely covered with hairs. Acacia species are easily
distinguished from the mesquites by having more than 10 stamens per flower.
Prevention: While this species is thought to have been
eradicated in Southeastern California, the hard seed may remain dormant for
many years and new plants may appear in previously infested areas. Cattle favor
mesquite pods and a large percentage of the seed remain viable thought the animal's
digestive tract. Cattle should be prevented from grazing creeping mesquite infested
areas when pods are present on the trees. Throughout the Southwestern United
States, many species of mesquite respond positively to overgrazing and grasslands
are subsequently converted to mesquite brushlands. Conversion back is very difficult
and temporary without reduced grazing pressure.
Mechanical: Creeping mesquite roots have not been well
described. However the species likely exhibits strong vegetative reproduction
from root buds. Removal of the creeping root system is necessary to prevent
regrowth. This is generally not feasible in dense infestations. Chaining or
plowing has been used in the past. However, this results in complete disturbance
of the plant community and may favor many invasive annuals.
Chemical: Similar species of mesquite have been effectively
controlled with the following methods. These methods are most cost effective
for sparse infestations. Foliar herbicide applications work well on bushy, many
stemmed plants less than eight feet tall. Applications should be made when in
early summer when the leaves become dark green and can continue until fruiting.
The foliage should be sprayed to a glistening but not to the point of runoff.
The optimal herbicides are a tank mix of clopyralid and triclopyr, each applied
at 0.5% v/v. For adequate coverage, a surfactant should be included at 0.25%
v/v). Diesel oil has been used to improve coverage at 5% v/v. If diesel is used,
then an emulsifier (1 oz/gal diesel oil) should also be added to mix the oil
and water. However, diesel is nor currently labeled for herbicide applications
Stem applications are effective on younger trees with few
stems and smooth bark. Triclopyr applied at 15% to 25% with diesel as a carrier
is an effective. However diesel is not labeled for herbicide applications in
California. Other oils including seed oils may be an effective replacement.
The stems should be covered from the ground to a height of 12 inches on all
sides for best effect. However, do not overspray the stems to the point of runoff.
Older, rough barked trees may be very difficult to control with this method.
An alternative is to remove old growth by cutting and then use basal bark treatments
on the regrowth.
Hexazinone can also be used as a soil applied treatment.
Hexazinone can be applied directly or in a 50%v/v solution at a rate of 3 ml
of hexazinone for every 3 feet of mesquite canopy diameter. This treatment may
take 2-3 years for complete kill of mesquite and the plants may go through several
periods of defoliation and regrowth during that time.
Juvenile mesquite has been reported to be susceptible to fire with increasing
resistance when plants reach two to three years of age. Winter burning has been
used to minimize damage to forage grasses and control young trees. However,
winter burns generally will not control larger trees. Summer burns have been
shown to be more effective on older trees, but may be risky due to the increased
potential for wildfire escapes. A combination of herbicide treatments followed
by prescribed fire may be effective for both controlling mesquite and removing
dead woody material.
back to top of page