Orobanche ramosa L., branched broomrape
Former Pest Rating: A
CURRENT Pest Rating: A | Proposed Seed Rating: P
This plant has been rated as “A” on the CDFA Plant Pest Rating list for some years.
History & Status:
Branched broomrapes are annual plants that grow from seed and require a plant host to survive. It is a parasitic plant that grows on the roots of Broad-leaf hosts and obtains all of its nutrients and water from these plants. Seeds germinate in response to chemicals released by host plant roots. The broomrape seedling root then attaches itself to the host plant root and remains underground until flowering. The plant has no chlorophyll and no noticeable leaves. Flowering stems emerge from the ground about 6 weeks after germination; flowering and seed set occur within 2–3 weeks. Seed capsules dry and shatter in summer. One plant can produce over 100,000 seeds and seeds may lay dormant in the soil for more than 40 years. Broomrape seed can be spread by livestock, machinery, vehicles, flooding, and contaminated fodder, seed and soil. Branched broomrape is among the world’s worst crop weeds and poses a serious threat to the vegetable industry in California. It has been reported to attack 25 different crops including lettuce, tobacco, and tomatoes. Once established, branched broomrape can reduce crop yields by up to 70% and it is extremely difficult to eradicate. For this reason, it is often regulated and trading partners that import fresh host material may limit or exclude trade in these commodities.
Official Control: Branched broomrape has been an “A” listed noxious weed in California for many years. There was a state control and eradication program in California for branched broomrape that lasted over 20 years; it was discontinued in the late 1970s. It is also a federally listed noxious weed and is listed as noxious in Alabama, Arizona, Florida, Massachusetts, Minnesota, North Carolina, Oregon, South Carolina, Texas, and Vermont.
California Distribution: Branched broomrape was known from about a dozen infestations of agricultural fields in Central and Southern California. Most of these sites have been developed over the years and therefore the plant is likely eradicated at these sites (there have been no detections in over 30 years). A known extant infestation is in northern San Benito County; this population reappeared after more than 30 years, when the field was planted to tomatoes. A second occurrence was found in 2014 in San Joaquin County, in an area near known infestations from the 1970s.
California Interceptions: Vouchered specimens are known from Sacramento, Alameda, San Benito, San Joaquin, Santa Clara, and Ventura Counties.
United States: Branched broomrape has been found in California, Illinois, Kentucky, North Carolina, New Jersey, and Texas.
International: Branched broomrape is native to the Mediterranean. It is reported as naturalized and as an environmental and agricultural weed in Europe and western Asia. It has also been detected in Australia where they are transitioning from attempted eradication efforts to ongoing management.
This risk Branched broomrape would pose to California is evaluated below.
Consequences of Introduction:
1) Climate/Host Interaction: The plant has attacked crops in many countries spanning many climates. It is highly variable and this variation seems to be tied to differential ecological preferences. Therefore, It scores as High (3) in this category.
Evaluate if the pest would have suitable hosts and climate to establish in California. Score:
– Low (1) Not likely to establish in California; or likely to establish in very limited areas.
– Medium (2) may be able to establish in a larger but limited part of California.
– High (3) likely to establish a widespread distribution in California.
2) Host Range: Risk is High (3) as branched broomrape attacks 25 crop species and probably has the potential to attack many native species as well.
Evaluate the host range of the pest. Score:
– Low (1) has a very limited host range.
– Medium (2) has a moderate host range.
– High (3) has a wide host range.
3) Pest Dispersal Potential: Branched broomrape produces numerous seeds are documented to last for decades and are able to spread via equipment and on animals (including humans). The seed bank is highly persistent. Branched broomrape receives a High (3) in this category.
Evaluate the natural and artificial dispersal potential of the pest. Score:
– Low (1) does not have high reproductive or dispersal potential.
– Medium (2) has either high reproductive or dispersal potential.
– High (3) has both high reproduction and dispersal potential.
4) Economic Impact: Evaluate the economic impact of the pest to California using the criteria below.
Economic Impact: A, B, C, D
A. The pest could lower crop yield.
B. The pest could lower crop value (includes increasing crop production costs).
C. The pest could trigger the loss of markets (includes quarantines).
D. The pest could negatively change normal cultural practices.
E. The pest can vector, or is vectored, by another pestiferous organism.
F. The organism is injurious or poisonous to agriculturally important animals.
G. The organism can interfere with the delivery or supply of water for agricultural uses.
Economic Impact Score: Branched broomrape receives a High (3) in this category. Branched broomrape can lower crop productivity in susceptible row crops by up to 70%. This can affect land value and result in quarantine.
– Low (1) causes 0 or 1 of these impacts.
– Medium (2) causes 2 of these impacts.
– High (3) causes 3 or more of these impacts.
5) Environmental Impact: Evaluate the environmental impact of the pest on California using the criteria below.
Environmental Impact: A, B, D
A. The pest could have a significant environmental impact such as lowering biodiversity, disrupting natural communities, or changing ecosystem processes.
B. The pest could directly affect threatened or endangered species.
C. The pest could impact threatened or endangered species by disrupting critical habitats.
D. The pest could trigger additional official or private treatment programs.
E. The pest could significantly impact cultural practices, home/urban gardening or ornamental plantings.
Score the pest for Environmental Impact.
Environmental Impact Score: Branched broomrape receives a High (3) in this category. Branched broomrape is likely to trigger new treatments by land managers. The plant has not yet spread to the wild in California. However, certain native plants such as clovers (Trifolium) are likely susceptible to branched broomrape. These include such rare or endangered species as showy Indian clover (T. amoenum), Buck’s clover (T. buckwestiorum), and Monterey clover (Trifolium trichocalyx).
– Low (1) causes none of the above to occur.
– Medium (2) causes one of the above to occur.
– High (3) causes two or more of the above to occur.
Consequences of Introduction to California for Branched broomrape: High (15)
Add up the total score and include it here.
–Low = 5-8 points
–Medium = 9-12 points
–High = 13-15 points
6) Post Entry Distribution and Survey Information: Branched broomrape has been recently found in three counties in California, but may be eradicated. It receives a Medium (-2) in this category.
Evaluate the known distribution in California. Only official records identified by a taxonomic expert and supported by voucher specimens deposited in natural history collections should be considered. Pest incursions that have been eradicated, are under eradication, or have been delimited with no further detections should not be included.
-Not established (0) Pest never detected in California, or known only from incursions.
–Low (-1) Pest has a localized distribution in California, or is established in one suitable climate/host area (region).
–Medium (-2) Pest is widespread in California but not fully established in the endangered area, or pest established in two contiguous suitable climate/host areas.
–High (-3) Pest has fully established in the endangered area, or pest is reported in more than two contiguous or non-contiguous suitable climate/host areas.
The final score is the consequences of introduction score minus the post entry distribution and survey information score: High (13)
The experience in the mid 20th century of California and in Australia show the potential of this species to disrupt crop systems. Its effects on the environment are more speculative and necessarily more uncertain.
Conclusion and Rating Justification:
A terrible agricultural weed because of its ability to produce large numbers of long-lived seeds and its ease of spread. It deserves an A rating as it is likely to have a high impact if it spreads again in California. Development has removed most known sites, but it is otherwise difficult to treat.
Baldwin, B. G., D. H. Goldman, D. J. Keil, R. Patterson, T. J. Rosatti, and D. H. Wilken, editors. 2012. The Jepson manual: vascular plants of California, second edition. University of California Press, Berkeley.
Consortium of California Herbaria: ucjeps.berkeley.edu/consortium/
Cooke, D. 2002. Control of branched broomrape; a literature review. Animal and Plant Control Commission of South Australia.
Flora of North America Editorial Committee, eds. 1993+. Flora of North America North of Mexico. 16+ vols. New York and Oxford.
NSW Department of Primary Industries. Weed alert; branched broomrape: http://www.dpi.nsw.gov.au/agriculture/pests-weeds/weeds/profiles/broomrapes
USDA Plants Database, Orobanche ramosa: http://plants.usda.gov/core/profile?symbol=orra
Dean G. Kelch, Primary Botanist; California Department of Food and Agriculture; 1220 N Street, Sacramento, CA 95814; Tel. (916) 403-6650; plant.health[@]cdfa.ca.gov
Comment Period: CLOSED
45-day comment period: 7/18/17 – 9/1/17
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