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CDFA Plant Health

Noxious Weed Photographic Gallery

Camelthorn [Alhagi pseudalhagi (M. Bieb.) Desv.][ALHPS][CalEPPC: red alert][CDFA: A] Photographs Map of Distribution


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[SYNONYMS] [GENERAL DESCRIPTION] [SEEDLINGS] [MATURE PLANT] [ROOTS and UNDERGROUND STRUCTURES] [FLOWERS] [FRUITS and SEEDS] [POSTSENESCENCE CHARACTERISTICS] [HABITAT] [DISTRIBUTION] [PROPAGATION/PHENOLOGY] [MANAGEMENT FAVORING/DISCOURAGING SURVIVAL] [SIMILAR SPECIES] [CONTROL METHODS]


SYNONYMS: Caspian manna; Persian manna; A. camelorum Fischer; A. maurorum Medicus

GENERAL DESCRIPTION: Noxious green shrub to 1 (2) m tall, with simple leaves, many thorny branches, and an extensive root system. Plants spread rapidly by clonal vegetative reproduction from vigorous rhizomes. A desert plant introduced from the Mediterranean region and western Asia. Intense eradication programs have eliminated most populations in the state.

SEEDLINGS: Lack thorns. Cotyledons ovate, thick, leathery, ~ 5-10 mm long. Often found growing in cattle manure from seed passed through digestive tract. Seedling shoots grow slowly compared to its roots and to shoots of alfalfa and some clovers.

MATURE PLANT: Stems +/- glabrous, greenish, longitudinally ridged, and highly branched, with the leaf axil of nearly every node supporting an ascending leafless branchlet, 2-5 cm long, tipped with a thorn about 5 mm long. Leaves alternate, sparse, simple, thick, leathery, elliptic or obovate, and 7-20 mm long, with petioles 1-2 mm long and stipules about 1 mm long. Upper leaf surfaces glabrous (sometimes sparsely hairy) and covered with minute red dots. Lower leaf surfaces are sparsely (to moderately) covered with hairs. Deciduous in cool climates. Morphology is variable depending on environmental conditions. Thorns are smaller and fewer, and leaves larger and more numerous in moister habitats.

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ROOTS and UNDERGROUND STRUCTURES: Extensive rhizomes present. Woody root system can grow more than 2 m deep and to a distance of 8(12) m or more in all directions. Rhizomes at depths to 1.5 m produce new shoots and deep vertical roots at about 1-1.5 m intervals. In turn, each new clone sends out rhizomes in all directions. Infestations can spread at a rate of about 10 m per year.

FLOWERS: June-July. Two-6 short-stalked flowers are produced alternately along each thorn branchlet axis. Flowers pea-like, with magenta to pink petals 8-9 mm long. Sepals persistent, fused and cup-like, with small unequal teeth. Stamens 10, with bases of 9 filaments fused into a tube around the style and 1 separate. Self-fertile. Flower production is high under hot, dry conditions (700- 4000/plant) and low (sometimes to 0) under moist, shady conditions. Only a low percentage (~20%) of flowers set seed.

FRUITS and SEEDS: July-August. Pods (loments) reddish-brown at maturity, slender, often curved, 1-3 cm long, constricted between seeds, and often tipped with a small spine. Pods do not split open to release seeds but can break apart between seeds. Seeds 5-8, oval, yellowish or greenish-brown with dark mottling or solid dark brown, smooth-textured, about 3 mm long, and 2.5 mm wide. Soft- and hard-coated seeds are produced. Fruits are eaten by herbivores, especially cattle and horses.

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POSTSENESCENCE CHARACTERISTICS: Woody tissues persistent after plant death.

HABITAT: Arid agricultural areas and riverbanks where roots can access water tables or other water sources during the growing season. Often grows in heavy soils. Tolerates some salinity. Above ground parts killed by hard frosts.

DISTRIBUTION: Uncommon. Southeast of Sierra Nevada (sw Inyo Co.), Mojave and Sonoran Deserts (cw San Bernardino Co., e Riverside Co.); sporadic populations to west Texas; to 500 m (1650 ft). Previous infestations in the Central Valley have been eradicated.

PROPAGATION/PHENOLOGY: 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 º 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.

MANAGEMENT FAVORING/DISCOURAGING SURVIVAL: 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.

SIMILAR SPECIES: 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).

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CONTROL METHODS:

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.

References

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.

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3/18/15