Velvet mesquite [Prosopis velutina Wooton][PRCJV]

Creeping mesquite [Prosopis strombulifera (Lam.) Benth][Bayer code: none][CDFA list: A][Federal Noxious Weed] Photographs Map of Distribution

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GENERAL 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.

SEEDLINGS:Cotyledons oval, somewhat fleshy. Fast growing.

MATURE PLANT:Branches 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.

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ROOTS 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.

FLOWERS:Flower heads axillary. Flowers small, numerous, radially symmetrical, with bell-shaped calyces. Petals 5. Stamens 10, extended beyond petals. Insect pollinated. Species hybridize freely.

FRUITS 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

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HABITAT:Typically grows on sandy, rocky, medium to fine-textured soils in semi-arid and arid regions.


PROPAGATION/PHENOLOGY:Reproduces 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.

MANAGEMENT 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 in California.

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.

Prescribed Fire
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.

References (mainly for P. glandulosa)
Bainbridge, David A.; Virginia, Ross A. 1990. Restoration in the Sonoran Desert of California. Restoration and Management Notes. 8(1): 3-14.
Beasom, Samuel L.; Inglis, Jack M.; Scifres, Charles J. 1982. Vegetation and white-tailed deer responses to herbicide treatment of a mesquite drainage habitat type. Journal of Range Management. 35(6): 790-794.
Bovey, R. W.; Meyer, R. E. 1981. The response of honey mesquite to herbicides. B-1363. College Station, TX: The Texas A&M University, The Texas Agricultural Experiment Station. 12 p.
Fisher, C. E.; Meadors, C. H.; Behrens, R.; [and others]. 1959. Control of mesquite on grazing lands. Bull. 935. College Station, TX: Texas A&M University, Texas Agricultural Experiment Station. 24 p. In cooperation with: U.S. Department of Agriculture.
Goen, J. P.; Dahl, B. E. 1982. Factors affecting budbreak in honey mesquite in west Texas. Journal of Range Management. 35(4): 533-534.
Jacoby, P. W.; Ansley, R. J.; Meadors, C. H.; Cuomo, C. J. 1990. Control of honey mesquite with herbicides: influence of stem number. Journal of Range Management. 43(1): 36-38.
Jacoby, P. W.; Meadors, C. H.; Ansley, R. J. 1990. Control of honey mesquite with herbicides: influence of plant height. Journal of Range Management. 43(1): 33-35.
Jacoby, P. W.; Meadors, C. H.; Foster, M. A.; Hartmann, F. S. 1982. Honey mesquite control and forage response in Crane County, Texas. Journal of Range Management. 35: 424-426.
McDaniel, Kirk C.; Brock, John H.; Haas, Robert H. 1982. Changes in vegetation and grazing capacity following honey mesquite control. Journal of Range Management. 35(5): 551-556.
McPherson, Guy R.; Wright, Henry A.; Wester, David B. 1988. Patterns of shrub invasion in semiarid Texas grasslands. The American Midland Naturalist. 120(2): 391-397.
Parker, Kenneth W.; Martin, S. Clark. 1952. The mesquite problem on southern Arizona ranges. Circular No. 908. Washington, DC: U.S. Department of Agriculture. 70 p.
Reynolds, H. G.; Bohning, J. W. 1956. Effects of burning on a desert grass-shrub range in southern Arizona. Ecology. 37(4): 769-777.
Roundy, Bruce A.; Jordan, Gilbert L. 1988. Vegetation changes in relation to livestock exclusion and rootplowing in southeastern Arizona. The Southwestern Naturalist. 33(4): 425-436.
Scifres, C. J.; Brock, J. H.; Hahn, R. R. 1971. Influence of secondary succession on honey mesquite invasion in north Texas. Journal of Range Management. 24: 206-210.
Wright, Henry A.; Bunting, Stephen C.; Neuenschwander, Leon F. 1976. Effect of fire on honey mesquite. Journal of Range Management. 29(6): 467-471.

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