Portuguese broom | Pest Rating Proposals and Final Ratings

California Pest Rating for

Cytisus striatus: Portuguese broom

Family: Fabaceae

Pest Rating: B | Proposed Seed Rating: P

PEST RATING PROFILE

Initiating Event:

Cytisus striatus has no rating in the past and it is growing widely in coastal areas especially in San Francisco, San Diego and Mendocino counties. It’s a B category noxious weed listed in Oregon. Due to this, a risk assessment of this known weed is critical to designate an official rating.

History & Status:

Background: Cytisus striatus is perennial, leguminous shrub known by the common names Portuguese broom, striated broom and hairy-fruited broom. It is six to nine feet tall with many slender stems that are silky-hairy when young and become more or less smooth when mature. Stems are covered sparsely by small leaves consisting of one to three leaflets. Pale yellow, pea-like flowers arise from the leaf axils singly or in pairs. Mature fruit pods are densely white-hairy, and each contains several seeds. Portuguese broom strongly resembles Scotch broom (Cytisus scoparius) which is invasive noxious weed in California. The main features that distinguish this species from Scotch broom are the paler yellow flower color, 8-10 versus 5-8 angles on the stem, and the densely white-hairy fruit pods of Portuguese broom³.

Cytisus striatus is the least common of the broom species in North America, occurring in California and Oregon. It currently occupies sixty-five acres in the Marin Headlands, Marin County, where it forms dense cover with one mature shrub per two square meters. It is found occasionally in other parts of the Bay area, and has been reported in Mendocino and San Diego counties¹. Its similarity to Cytisus scoparius may explain it lack of detection in central and south coastal counties¹.

Worldwide Distribution: Cytisus striatus is native to Morocco, Portugal and Spain. It is reported in a number of northwestern European countries including England, Scotland, Wales and France. It has also been introduced into California and Oregon in the USA and Argentina^3.

Official Control: Cytisus striatus is classified as a Category B noxious weed in Oregon⁶.

California Distribution: It was introduced to California in the 1960s as an erosion-control plant⁵. It is spreading in San Francisco Bay Area especially in Marin Headlands. It is also reported in Mendocino and San Diego counties, as well as in Yosemite National Park¹.

California Interceptions: Cytisus striatus has not been intercepted in California through regulatory pathways (Pest and Damage Report Database, CA Department of Food and Agriculture)¹⁰. It has been documented by State personnel.

The risk Cytisus striatus (Portuguese broom) would pose to California is evaluated below.

Consequences of Introduction:

1) Climate/Host Interaction: Cytisus striatus is established in the San Francisco Bay Area and is still spreading in other areas of California. Therefore, Cytisus striatus receives a High (3) in this category.

Evaluate if the pest would have suitable hosts and climate to establish in California:

– 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) Known Pest Host Range Cytisus striatus do not require any one host, but grow wherever ecological conditions are favorable. It receives a High (3) in this category.

Evaluate the host range of the pest.

– 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: Cytisus striatus reproduces 15,000 seeds per year⁴. Seeds are released ballistically from the pod, then further dispersed by ants, other animals and water runoff along the ground. Portuguese broom can resprout from its root crown when cut, particularly during the growing season³. It receives a High (3) in this category

Evaluate the natural and artificial dispersal potential of the pest.

– 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: Cytisus striatus can invade cropland by growing in dense stands. It displaces both native plants and cultivated plants; this could negatively change normal cultural practices. It receives a Medium (2) in this category.

Evaluate the economic impact of the pest to California using the criteria below.

Economic Impact: A, 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: 2

– 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: Cytisus striatus is capable of invading and establishing dense populations in coastal prairie, coastal scrub, oak savannah, and open-canopy woodlands⁷. Cytisus striatusis likely to trigger new chemical treatments by ranchers and land managers. Rare taxa that might be affected include grassland species such as showy Santa Cruz clover (Trifolium buckwestiorum), CA filaree (California macrophylla), Santa Cruz tarplant (Holocarpha macradenia) and Alameda whipsnake (Masticophis lateralis euryxanthus). The plant can disrupt natural communities. Cytisus striatus receives a High (3) in this category.

Evaluate the environmental impact of the pest on California using the criteria below.

Environmental Impact: A B, C, 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 significantly impacts cultural practices, home/urban gardening or ornamental plantings.

Environmental Impact: Score: 3

– 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 Cytisus striatus (Portuguese broom): High (14)

–Low = 5-8 points

–Medium = 9-12 points

–High = 13-15 points

6) Post Entry Distribution and Survey Information: Cytisus striatus has been reported only in San Francisco Bay Area, Mendocino, Yosemite National Park and San Diego Counties. 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:

Score: -2

-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.

Final Score:

The final score is the consequences of introduction score minus the post entry distribution and survey information score: Medium (12)

Uncertainty:

Cytisus striatus entered California long ago, although it has not yet spread widely, there is nothing to stop it spreading in the appropriate habitats. So, there is low uncertainty.

Conclusion and Rating Justification:

Conclusions of the harm(s) associated with this pest to California using all of the evidence presented above: Proposed Rating: based on the score listed above the pest is a medium risk. A “B” rating is recommended, as the plant is invasive in 12 counties but has not spread as far as it is likely to without management.

References:

1. Alvarez, Maria. 2000. Cytisus striatus In: Bossard, Carla C.; Randall, John M.; Hoshovsky, Marc C., eds. Invasive plants of California’s wildlands. Berkeley, CA: University of California Press: 150-154. Accessed January 05, 2017. https://www.fs.fed.us/database/feis/plants/shrub/cytspp/all.html#4

2. Encyclopedia of Life. Hairy-fruited broom. Accessed January 05, 2017 http://eol.org/pages/703580/details

3. Invasive Plant of California’s Wildland. Cal-IPC News. Accessed January 05, 2017 http://www.cal-ipc.org/ip/management/ipcw/pages/detailreport.cfm@usernumber=40&surveynumber=182.php

4. Invasive weeds in Forest land. EC 1598-E September 2008 Oregon State University. Accessed January 05, 2017 http://ir.library.oregonstate.edu/xmlui/bitstream/handle/1957/19804/ec1598-e.pdf

5. Inaturalist.org- hairy fruited broom – Accessed January 05, 2017 http://www.inaturalist.org/taxa/76598

6. Invasive Species information. Accessed January 05, 2017 http://www.weedcenter.org/resources/state.html

7. Michail Belov. 2005-2009 – Chile flora – Article. Accessed January 05, 2017 http://www.chileflora.com/Florachilena/FloraEnglish/HighResPages/EH0297.htm

8. Chater, A. O. & D. A. Webb. 1971. Orobanchein Flora Europaea Vol. 3: Diapensiaceae to Myoporaceae. T. G. Tutin, V. H. Heywood, N. A. Burges, D. H. Valentine, S. M. Walters, & D. A. Webb, eds. Cambridge University Press. United Kingdom.

9. Hrusa, F., B. Ertter, A. Sanders, G. Leppig, and E. Dean. 2002. Catalog of non-native vascular plants occurring spontaneously in California beyond those addressed in The Jepson Manual. Part I. Madroño 49: 61-98.

10. Pest and Damage Record Database, California Department of Food and Agriculture, Plant Health and Pest Prevention Services. http://phpps.cdfa.ca.gov/user/frmLogon2.asp