John M. Randall, The Nature Conservancy

Family: Fabaceae (Pea Family)

Synonym(s): Alhagi camelorum, Alhagi pseudalhagi

Duration: Perennial

Habit: Shrub

Listed by:
Invasive Plant Atlas of the US: 1
Federal Noxious Weed: 0
TDA Noxious Weed: 1
TPWD Prohibited Exotic Species: 0

Description: Camelthorn is a deep-rooted, rhizomatous, perennial shrub, with roots that can extend six to seven feet into the ground. The spiny, intricately-branched shrub reaches 1.5 to four feet in height. The plant, which is grayish green and hairless, has simple, entire leaves that are alternately arranged. The leaf shape is oval to lance-shaped. The small (3/8 inch), pea-like flowers are pinkish purple to maroon and are borne on short, spine-tipped branches that arise from the leaf axils. The reddish-brown to tan fruits are constricted between the seeds, with a short narrow beak at the end.

History: Camelthorn was introduced into California from Turkey as an alfalfa seed contaminant and in packing materials around date palm offshoots. The only known population in the Pacific Northwest occurs on Bureau of Reclamation Land, Columbia Basin Project, Grant County, Washington. This infestation was first reported in 1956 along the lower Crab Creek drainage area and has since spread eastward toward Othello, where it now encompasses 20-25 sections of land.

Biology & Spread: Reproduction mostly by vegetative clones from rhizomes, occasionally from seed. Seed dispersed primarily by livestock browsing on fruits, but also by water and high winds blowing clumps of branches with fruits. Passing through a herbivore digestive tract or acid scarification appears to stimulate germination. Optimal temperature and soil depth for germination is near 27 ? C and 1 cm respectively. Light appears to inhibit germination. Seeds can survive submersion in water for at least 8 months and can remain viable for several years in semi-arid soils. Viability decreases rapidly after 1 year in cool, moist soil conditions.

Moving livestock that has browsed on fruits can disperse seeds to new locations. Lack of soil moisture during the warm growing season discourages seedling survival. Mechanical removal can encourage clonal reproduction and spread.

Ecological Threat:

US Habitat: Camelthorn occurs principally in deep moist soil, but it also occurs in dry, rocky, or saline soils. The plant is especially abundant along riverbanks, canals, and irrigation ditches, but it sometimes spreads into cultivated fields.

Distribution

US Nativity: Introduced to U.S.

Native Origin: S. Russia to Himalaya (Alfred Rehder, Manual of Cultivated Trees and Shrubs: Hardy in North America, The MacMillan Co., New York (1967)); Temp. & trop. Asia, Europe (Germplasm Resources Information Network); NatureServe Explorer

US States: AZ, CA, CO, ID, NM, NV, TX, UT, WA

Resembles/Alternatives: Russian salttree [Halimodendron halodendron (L.) Voss][Bayer code: none][CDFA list: A] is a deciduous thorny leguminous shrub previously grown as an ornamental. Unlike camelthorn, Russian salttree has evenly pinnate compound leaves clustered on short spurs, typically with 4 leaflets (sometimes 2 or 6), thorn-tipped branchlets below the spurs, and short black inflated pods that open slowly and are not constricted between seeds. Plants colonize sites by producing new shoots from lateral roots. Known infestations eradicated in the Central Valley (UC Davis Arboretum, Kern County Park) and central South Coast (Los Angeles basin). To 200 m (656 ft).

Management: Prevention: Alhagi pseudalhagi seeds have a very hard seed coat which allows them to easily pass through bovine or equine digestive tracts. Digestive scarification may increase seed germination. Despite the thorny stems, A. pseudalhagi leaves and seed pods are highly palatable and readily eaten by livestock. Preventative measures such as the use of certified weed free hay and restricted grazing where A. pseudalhagi is present are recommended.

Mechanical: As observed with other deep rooted perennials, infrequent tillage is ineffective in controlling A. pseudalhagi, and may increase shoot density. Severed rootstocks may also be spread to new areas by tillage equipment. The use of heavy equipment is discouraged in infested areas. Where land manipulation is necessary, equipment should be cleaned on site.

Biological: There are no currently registered biocontrols for A. pseudalhagi in the United States. Carmin (1950) documented a Eurytomous wasp capable of forming galls in the vascular tissue of A. maurorum, and Gurha (1983) reported dry rot caused by Rhizoctonia bataticola in the same. No mention is made of the potential of either as a biocontrol agent for Camelthorn.

Chemical: There have been relatively few published studies on the chemical control of A. pseudalhagi. Koehler (1956) reported a 95 % reduction following three years of 2,4-D applied at 4 lb/A twice each year. Kerr et al (1965) suggested first year applications of 2,4-D at 3 lb/A be applied during budding, when root carbohydrate levels are low, and subsequent applications when foliage is mature. Nir (1982) found that 1.5 lb/A 2,4-D and 1.5 lb/A dicamba both gave 70% control when applied separately and 95% control when applied together. No mention was made of the treatment evaluation interval in this study. Alon (1988) found fluoroxypyr (1.1 lb/A) provided good control of camelthorn without injuring dates. However, fluoroxypyr is nor registered for use in California. Nir (1973) also found tank mixes of bromacil and picloram to be effective in controlling roadside infestations of A. maurorum. The phenoxy type herbicides listed above (2,4-D, dicamba, and fluoroxypyr) will affect a wide range of broadleaf plants and therefore may be unsuitable for use in riparian areas. Picloram, one of the more effective treatments, is not labeled for use in California. Bromacil will also affect a wide range of grass and broadleaved plants. While not reported, glyphosate applied with a rope-wick style applicator may provide some control with repeat applications. Clopyralid (Transline) is a newly registered herbicide in California and has good activity on legumes, but has not been tested on camelthorn. Careful consideration should be made in regard to applying herbicides near streams or rivers, or areas with a shallow water table where camelthorn is present.

USE PESTICIDES WISELY: ALWAYS READ THE ENTIRE PESTICIDE LABEL CAREFULLY, FOLLOW ALL MIXING AND APPLICATION INSTRUCTIONS AND WEAR ALL RECOMMENDED PERSONAL PROTECTIVE GEAR AND CLOTHING. CONTACT YOUR STATE DEPARTMENT OF AGRICULTURE FOR ANY ADDITIONAL PESTICIDE USE REQUIREMENTS, RESTRICTIONS OR RECOMMENDATIONS. MENTION OF PESTICIDE PRODUCTS ON THIS WEB SITE DOES NOT CONSTITUTE ENDORSEMENT OF ANY MATERIAL.

Listing Source

Texas Department ofAgriculture Noxious Plant List
Texas Parks and Wildlife Department Prohibited Exotic Species
Invaders Program
Federal Noxious Weed
Union of Concerned Scientists
United States Forest Service Southern Research Station

Text References

State of California Detection Manual. 1982. Camelthorn. Parker, K. F. An Illustrated Guide to Arizona Weeds. University of Arizona Press. Tucson, AZ. Weeds of California.

Ball, W.S. and W.W. Robbins. 1933. Camelthorn, Alhagi camelorum (Fisch.). Monthly Bulletin of the California State Department of Agriculture 22:258-260.

Bottel, A.E. 1933. Introduction and control o camelthorn, Alhagi camelorum (Fisch.). Monthly Bulletin of the California State Department of Agriculture 22:261-263.

Hickman, J.C., ed. 1993. The Jepson Manual: Higher Plants of California. UC Press, Berkeley, CA.

Kerr, H.D., W.C. Robocker and T.J.Muzik. 1965. Characteristics and control of camelthorn. Weeds 13(2):156-163.

Data Source

Encycloweedia, California Department of Food and Agriculture

Last Updated: 2005-10-22 by DEW