(Alhagi camelorum Fisch., Alhagi maurarum Medik.)
Status: Camelthorn is recognized as a noxious weed on the Coconino, Kaibab and Prescott National Forests. And is a restricted noxious weed in Arizona.
Life History/Identification: Camelthorn is a member of the pea family, Fabaceae. It is a perennial shrub with deep roots and extensive rhizomes. The plant is from 1 ½ to 4 feet high and is covered with spines. The spines are yellow tipped. The leaves are small and wedge shaped. The undersides of the leaves are covered with small hairs. Camelthorn has small pea- like pink flowers. The seedpods are maroon to brown in color. The seedpod is constricted between each seed, forming a distinct outline around each seed. Reproduction can occur from seeds or from the extensive underground rhizomes. The extensive rhizomes can grow to over 6 feet deep and can spread over an area of 40 feet or more. New plants can be produced from deep within the ground. Each new plant can form its own rhizome system. The successful establishment rate from seeds is very low. Reproduction is mostly from rhizomes but can also be spread by seeds dispersed by animals, wind or water. Seeds do not sprout in direct sunlight but will sprout when buried in shallow soil. Seeds in or under animal manure have a higher success rate of germination and survival. Camelthorn is a native of the Mediterranean area and Asia and was accidentally introduced into the United States around 1915. It is now found in 35 states.
Known Locations: This species had been found on the Coconino National Forest on Leupp Highway and on Forest Road 545. It has also been found on Highway 64 on the Tusayan Ranger District, east of Grand Canyon National Park. It is reported to occur in the Wupatki National Monument along some of the access roads. Many locations of this plant have been found on the Navajo Reservation and are reported in the SWEMP Database.
Impacts: Camelthorn has the ability to spread over large areas due to its clonal nature. It has been reported to penetrate asphalt and building foundations. This has been observed in the Winslow and Holbrook areas. Livestock browse on camelthorn and may contribute to its spread. No data was found on the nutritional value of camelthorn to grazing animals. As with all invasive exotic plants, camelthorn impacts native ecosystems by competing with native species for their habitat.
Education can be a valuable way to combat any weed infestation. Currently most people are probably unable to identify camelthorn and recognize it as a noxious weed. Education in the identification of the plant may help reduce its spread.
Many infestations of camelthorn appear to be occurring along roadways throughout Northern Arizona. Distribution of the plant may be occurring by transportation on vehicles. Vehicle travel through noxious weed populations should always be discouraged. Seeds and plants fragments may be traveling into the National Forests by vehicles traveling from infestations in other areas such as the Navajo Reservation. Cooperation among agencies could be a valuable asset in controlling infestations.
Grazing animals are known to spread camelthorn seeds through their feces. Seeds that pass through the digestive systems of the herbivores are scarified, therefore increasing the chance of reproduction. Currently, no known infestations occur on grazing lands on the Coconino, Kaibab or Prescott National Forests. However, if this should occur grazing in infested areas should be discouraged or movement of animals should be restricted for a period of time to ensure that the seeds are not spread from one place to another. Movement of wild herbivores is difficult to control. In areas of infestations, periodic surveys could help to monitor the occurrence of new populations.
Other measures such as the use of weed free hay and certified seed will help reduce the possibility of new introductions of this species.
2. Mechanical Control: Pulling or chopping is not an effective method of control. These techniques remove only the above ground portion of the plant and can encourage clonal reproduction by fragmenting underground rhizomes. Mechanical removal of this species may be a futile effort.
No information was found on the effects of fire on camelthorn. Since camelthorn originated in a desert environment where fire is not usually a major ecological factor, there may some potential for controlling this species through the use of fire. However, a more comprehensive review of the literature and consultation of experts should be done before anyone uses this technique to control the species.
3.Chemical Control:Noted here are chemical control techniques in use in other areas. Always check with weed specialists or chemical suppliers to ensure correct dosage and application. Mention of these products does not imply endorsement by the Northern Arizona Weed Council, San Francisco Peaks Weed Management Area, the USDA Forest Service, nor the Nature Conservancy. Currently the use of herbicides is not allowed on lands administered by the Coconino, Kaibab and Prescott National Forests. Always check with your local land manager before using herbicides on public lands. Grazon DS (active ingredients: picloram and triclopyr) can be used on camelthorn when it is actively growing in the spring and summer months. Two liters per plant of 1:80 Grazon mix injected up to 1 meter into the soil at the base of the plant has proven to be effective.
Tordon 75D (active ingredients: picloram and 2,4-D) is also a good herbicide to use in the spring and summer months. For more information on the use of herbicides on camelthorn, the Weed Management Library can be reached at 1-800-554-WEED
4. Biological Control: There are currently no biological control agents approved for use on camelthorn.
5. Integrated Control techniques available for the use on camelthorn are apparently limited. Traditional non-chemical treatments such as chopping and mowing do little to effectively treat this species. There are no biological control agents and the effectiveness of the use of fire is unknown. Therefore, the most effective non-chemical control of this species on land administered by the Coconino, Kaibab and Prescott National Forest is prevention.
References: Agriculture Western Australia – Declared Plant Control Handbook. Weed Name: Camelthorn (Alhagi camelorum). Recommended herbicides (3/23/2001)[online] Available: http://www.agric.wa.gov.au/progserv/plants/weeds/weed_control/weeds/trees/camelthorn.htm Non-Cropland Weed Group, University of California Cooperative Extension Service, Weed Science Program, Department of Vegetable Crops, University of California, Davis, Ca 95616. “Encyloweedia” [online]. Available: http://pi.cdfa.ca.gov/weedinfo/ Parker, Kittie F. An Illustrated Guide to Arizona Weeds. The University of Arizona Press. (3/23/2001) [online] Available: http://www.uapress.arizona.edu/online.bks/weeds/general.htm Phillips, B.G, Daevid Lutz and Debra Crisp. 1997. Noxious Weed List for Coconino, Kaibab and Prescott National Forests. On file at Forest Supervisors Office, Coconino National Forest.
USDA Animal and Plant Health Inspection Service, Plant Protection and Quarantine. Insect, Mites and Nematodes Introduced for Bio Control. 1999. http://www.aphis.usda.gov/ppq/bats/weedagen.htm Whitson, Tom D., Larry C. Burrill, Steven A. Dewey, David W. Cudney, B.E. Nelson, Richard D. Lee and Robert Parker. 1996. Weeds of the West. 630 pp., University of Wyoming Press.
Zimmerman, Julie A.C. 1996. Ecology and Distribution of Alhagi maurorum Medikus, Fabaceae. U.S.G.S. Southwest Exotic Plant Mapping Program. 8 pages. (3/23/2001) [online]. Available: http://www.usgs.nau.edu/swemp/Info_pages/plants/Alhagi/alhagititle.html