RMD-13-04: Consolidated Pest Risk Management Document for pest plants regulated by Canada
Appendix 15A: Pest Risk Assessment Summary for Zygophyllum fabago (Syrian bean-caper)

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Identity of Organism

Name: Zygophyllum fabago

Synonyms: None found

English common names: Syrian bean-caper, Syrian beancaper

French common names: Fabagelle

Description: Zygophyllum fabago is a much-branched herbaceous plant with a deep, well-developed tap root. The plants grow almost 1 m tall and wide and are bushy. The succulent leaves are opposite and compound with a single pair of leaflets each 1 to 3 cm in length. The whitish to yellow flowers are borne in the leaf axils. The fruit is a five-valved capsule with a single seed in each valve. The capsules are oblong, and cylindrical and five sided (Davison and Wargo 2001; Robbins et al. 1951).

Zygophyllum fabago has the ability to dominate a site and eliminate the native vegetation. It grows on disturbed sites such as roadsides, corrals, and gravel pits. It can form large dense colonies that exclude native plants and animals. The thick, waxy leaves allow the plants to survive long periods of drought and the extensive root system provides a competitive advantage over native species. It is considered unpalatable to livestock (Davison and Wargo 2001).

The species reproduces by seed and spreading roots. Root fragments can produce new plants. The stems die back to the ground each winter. In very cold areas it can function as an annual, with new plants growing from seed each year (Davison and Wargo 2001).

Organism Status

Zygophyllum fabago is not reported to occur in Canada, and no evidence was found that it is cultivated in Canada (CFIA 2008; CNLA 2009). Based on this information, it is considered absent from the PRA area.

Current Regulatory Status

Zygophyllum fabago is not currently regulated in Canada. It is not regulated as a federal noxious weed in the U.S., but is regulated in the following states: California, Idaho, Nevada, Oregon and Washington (USDA-ARS 2009; USDA-NRCS 2009).

Probability of Entry

Zygophyllum fabago is thought to have been imported to the United States in contaminated alfalfa seed. There is a possibility that it may have escaped from gardens as the flower buds are used as a caper substitute in its native range (Davison and Wargo 2001).

Table 1 : Summary of Pathways for Zygophyllum fabago (Syrian bean-caper)
Type of pathway Specific pathways
Natural dispersalZygophyllum fabago spreads primarily by seeds (Davison and Wargo, 2001). No information could be found to document how seeds spread in natural situations. This pathway is unlikely given that there are no known documented occurrences in counties adjacent to the Canadian border. The species is reported as possible in Okanogan County, Washington, however there are no supporting collections (Wooten 2010).
Intentional introduction

Some websites list seeds of this species for sale as a medicinal herb. It is thought that it might have escaped from gardens as the flower buds are used as a caper substitute in the native range (Davison and Wargo 2001).

Intentional introduction for planting is the most likely pathway for entry into Canada. It is available for sale on-line, but it is difficult to know how much interest there is.

Unintentional introduction

The species is "thought to have been imported to the United States at the turn of the century in contaminated alfalfa seed" (Davison and Wargo 2001).

This pathway is unlikely, unless seed is imported from the native range. The species is not a common weed of agricultural fields.

Root fragments can sprout to form new plants (Davison and Wargo 2001). It is possible that they could be transported on equipment.

This is certainly a possibility, but it could be reduced as a pathway by keeping soil from entering the country.

Probability of Establishment

Zygophyllum fabago is native to Afghanistan, Iran, Iraq, Israel, Jordan, Lebanon, Syria, Turkey, Armenia, Azerbaijan, Georgia, Ciscaucasia, Turkmenistan, Pakistan, Russian Federation, Ukraine and Romania (USDA-ARS 2009). It is introduced in southern Europe (France, Spain, Sardinia) (Pankhurst 1998), North America (western U.S.) (USDA-NRCS 2009), Puerto Rico and Australia (Western Australia and New South Wales) (Randall 2007).

Within the western U.S., there are populations in 6 counties in Washington and 5 counties in Idaho. It has not yet been reported from Oregon and all infestations in California are thought to have been eradicated (Karl et al. 1996). There are reports from a number of other states (see figure 1). However, the record for Pennsylvania is based on an old collection at ballast dumps at Philadelphia harbour which has never been repeated (Ruiz and Carlton 2003). As the species is not included in any of the major northeastern flora, it is very likely that the New York record is also based on ephemeral populations at a port location (Fernald 1950; Gleason 1968; Gleason and Cronquist 1963).

Figure 1: Range of Zygophyllum fabago (Syrian bean-caper) in North America

Figure 1. Description follows.
Description for Figure 1:

This map shows the range of Zygophyllum fabago (Syrian bean-caper) in North America indicating its presence through the use of the colour green. The states covered in green are: New York, Pennsylvania, Texas, Kansas, Colorado, New Mexico, Montana, Idaho, Washington, Nevada and California

Source: USDA-NRCS 2009

The current range in the U.S. suggests that the species would be hardy to NAPPFAST zone 5. However, persistent Zygophyllum fabago populations are restricted to dry regions, including deserts (Davison and Wargo 2001), so the potential range as an invasive weed species is limited to southern B.C. in Canada (see figure 2). It should be noted that the coastal parts of the range on the map are probably too wet to be suitable for this species.

Figure 2: Potential range of Zygophyllum fabago (Syrian bean-caper) in Canada

Figure 2. Description follows.
Description for Figure 2:

This image shows the potential range of Zygophyllum fabago (Syrian bean-caper) in Canada, more specifically in British Columbia. Red is used to indicate the regions in which Zygophyllum fabago at risk according to the Canadian Plant Hardiness Zones map, in this case NAPPFAST Hardiness Zones 5-9. In Canada, the potential range of Zygophyllum fabago is limited to southern British Columbia where it has a scattered presence. This image is narrowed to include parts of the U.S. more specifically Washington, Oregon, and Idaho where the red has more of a prevalent presence and is heavily condensed downwards beyond the image.

NAPPFAST zones 5-9.

Probability of Spread

On a local scale, plants can spread by root fragments, but the usual means of dispersal is by seeds (Davison and Wargo 2001). The seeds of Zygophyllum speciesare mucilaginous (Beier et al. 2003), which might allow them to attach to animals or people for distribution, but this does not seem to be documented.

Potential Economic Consequences

The biggest economic threat from Zygophyllum fabago is to ranchers. The plants can form dense masses that displace beneficial species on rangelands. Control with herbicides is difficult because of the waxy leaf surfaces and because of the extensive root system. The plants are not palatable to livestock (Anonymous 2007), so infestations reduce the amount of useful forage available to browsers. Herbicides have shown some promise in controlling this weed, but repeated applications are necessary because of the thick, waxy leaves (Davison and Wargo 2001). In the dry rangelands invaded by this species, it is unlikely that control with herbicides would be economically feasible.

Potential Environmental and Social Consequences

Zygophyllum fabago has the ability to dominate native vegetation in suitable dry habitats, being described as "almost as invasive as" Peganum harmala (African-rue) and Tribulus terrestris (puncture vine), which are related weed species (Davison and Wargo 2001).

Uncertainty

There is not a great deal of information available on the biology and impacts of this species. So far, its distribution and impacts have been limited. In particular, there is almost no information about seed dispersal.

Conclusion

Based on the outcome of this pest risk assessment, Zygophyllum fabago is likely to establish and become invasive in parts of Canada, including southern B.C., if it is introduced to these areas. This plant should be considered for regulation under the Plant Protection Act and Seeds Act.

Technical Issues for Consideration

There should be no difficulties in detection and identification of seeds or plants of this species. Root pieces might be more difficult to identify.

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