Category Archives: Weeds

Plants (weeds)

Chrysanthemoides monilifera: Bitou bush

California Pest Rating for
Chrysanthemoides monilifera: Bitou bush
Asterales: Asteraceae
Pest Rating: A  |  Proposed Seed Rating: R

 


PEST RATING PROFILE
Initiating Event:

This plant has been recently discovered spreading from a single population in Orange County.

History & Status:

Background:  Bitou bush is a small shrub (to 2 meters) native the Cape Region of South Africa. It is a semi-succulent plant with ascending candelabra-like branches and elliptical leaves without a petiole about 80 mm long. The flowers heads are borne in summer through fall. The ray flowers and disk flowers are bright yellow. Although it most likely arrived in CA as a garden plant, it is no longer available in the trade (except rarely as seed). Its distribution is limited by cold, as it is intolerant of frost.

Official Control: Bitou bush has not been subject to official control.

California Distribution:  Known from 3 historic populations in Orange and San Diego Counties. These most likely are or were persisting from cultivation.

California Interceptions:  None.

United States:  Bitou bush has been reported from California only.

International:  Bitou bush is native to South Africa. It is reported as naturalized and as an environmental weed in Australia and New Zealand where millions of dollars have been spent on control efforts.

This risk Bitou bush would pose to California is evaluated below.

Consequences of Introduction:

1)  Climate/Host Interaction: The plant has had at least 3 introductions in CA. One of these populations is beginning to spread. It is very invasive in eastern Australia in areas with a similar climate to parts of California. Therefore Bitou bush receives a 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 weeds do not require any one host, but grow wherever ecological conditions are favorable.

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:  Bitou bush produces via numerous achenes (“seeds”) that are enclosed in a fleshy fruit dispersed by birds. Bird dispersal is an efficient means of plants establishing new populations. The seed bank is moderately persistent. Known populations have not spread until recently. Bitou bush receives a Medium (2) 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:  Bitou bush does not persist well in grazed areas due to browsing and trampling. Bitou bush receives a Low (1) in this category.

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

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.

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:  Chrysanthemoides monilifera out competes native vegetation in coastal environments in Australia and New Zealand, and invasion can lead to a decline in both floral and faunal diversity, changing ecosystem composition. It changes ecosystem processes by altering nutrient cycling, particularly nitrogen cycling, at the expense of native species and creating heavy shade in normally high light areas. It is considered a “weed of national significance” in Australia and has replaced entire stands of native species. This species is tolerant of saline conditions near coastal areas. In addition, it can create a favorable environment for other invasive weeds. Rare taxa that might be affected include strand species such as Laguna Beach dudleya (Dudleya stolonifera) and sagebrush scrub species such as California gnatcatcher (Polioptila californica). Because it forms dense patches, it could interfere with recreation along the coast and invade expensive coastal properties requiring control. Bitou bush receives a High (3) in this category.

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

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.

Score the pest for Environmental Impact. Score:

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 Bitou bush: Medium (12)

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:  Bitou bush is very local in CA. It receives a Low (-1) 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.

Final Score:

The final score is the consequences of introduction score minus the post entry distribution and survey information score: Medium (11)

Uncertainty:

As Bitou bush has invaded Australia and is beginning to spread in CA, uncertainty is low.

Conclusion and Rating Justification:

A potentially bad weed in CA.  Bitou bush merits an “A” rating to prevent its further spread in California. It has a low risk as a potential seed contaminant, so it should be restricted in seed for planting.

References:

Adamson, R. S. & T. M. Salter 1950. Flora of the Cape Peninsula. Juta & Co. Cape Town.

Baldwin, B. G., D. H. Goldman, D. J. Keil, R. Patterson, T. J. Rosatti, & D. H. Wilken, editors. 2012. The Jepson manual: vascular plants of California, second edition. University of California Press, Berkeley.

Bond, P. & P. Goldblatt 1984. Plants of the Cape Flora: A descriptive catalogue. National Botanic Gardens of South Africa, Kirstenbosch.

Consortium of California Herbaria accessed 1/21/2015: ucjeps.berkeley.edu/consortium/

Coutts-Smith, A. J., & P. O. Downey. 2006. Impact of weeds on threatened biodiversity in NSW. CRC for Australian Weed Management, Adelaide, Australia.

Flora of North America Editorial Committee, eds. 1993+. Flora of North America North of Mexico. 16+ vols. New York and Oxford.

Grice, A. C., S. Campbell, R. Breaden, F. Bebawi, & W. Vogler. 2008. Habitat management guide-Rangelands: Ecological principles for the strategic management of weeds in rangeland habitats. CRC for Australian Weed Management, Adelaide, Australia.

Lindsay, E. A., & K. French. 2005. Litterfall and nitrogen cycling following invasion by Chrysanthemoides monilifera ssp. rotundata in coastal Australia. Journal of Applied Ecology 42: 556-566.

USDA Weed Risk Assessment of Chrysanthmoides monilifera accessed 1/21/2015: http://www.aphis.usda.gov/plant_health/plant_pest_info/weeds/downloads/wra/Chrysanthemoides_monilifera_WRA.pdf

Responsible Party:

Dean G. Kelch, Primary Botanist; California Department of Food and Agriculture; 1220 N Street, Sacramento, CA 95814; Tel. (916) 654-0312; plant.health[@]cdfa.ca.gov.


Comment Period: CLOSED

The 45-day comment period opened on Monday, March 16, 2015 and closed on Thursday, April 30, 2015.


Pest Rating: A  |  Proposed Seed Rating: R


Posted by ls

Bermuda grass (Cynodon dactylon)

California Pest Rating
Bermuda grass (Cynodon dactylon)
Pest Rating: D  |  Proposed Seed Rating: None

 


PEST RATING PROFILE
Initiating Event:

A new find of this plant submitted to the Plant Laboratory for identification.

History & Status:

Background:  Bermuda grass is a long-lived, warm season turf grass. It is a densely spreading perennial, with deeply penetrating roots and low stems to 25 cm tall. It was introduced from Africa in 1751 and is widely spread throughout the southwest and southern United States. It is found in most areas of California at elevations below 3,000 feet and is common in gardens, landscapes, turf areas, orchards, roadsides, vineyards, and industrial areas. Bermuda grass is listed as a noxious weed in Arkansas and Utah. It previously was listed as a “C” rated weed in California, but it was removed from the list, as it is listed as an official crop in state seed regulation.

California Distribution:  Bermuda grass has been collected in most counties in California except for the exteme NE part of the state (Modoc County). Many of these collections represent plants persistng from horticulture, but many are naturalized as well.

California Interceptions:  Several vouchers have been submitted to CDFA for identification.

United States:  Because Bermuda grass has a long history of use in North America as a turf or range grass, it occurs in all but the most northern states and in all but the coldest regions of states where it occurs.

International:  Bermuda grass is native to Africa, India, and western Asia. It is introduced in North and South America and in Australia, as well as to other areas with warm temperate climates.

The risk Bermuda grass would pose to California is evaluated below.

Consequences of Introduction:

1)  Climate/Host Interaction:  Risk is High (3), as the Bermuda grass is naturalized throughout Southwestern North America and is spreading.

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 weeds do not require any one host, but grow wherever ecological conditions are favorable.

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:  Bermuda grass seeds are light, and dispersed primarily by wind and water. Seeds eaten by animals are widely dispersed. Motor vehicles also disperse Bermuda grass seed. The plant spreads quickly via long rhizomes and stolons and can regenerate from small pieces. Therefore, Bermuda grass 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:  Bermuda grass has been used widely as a turf grass and for forage in warm environments. Bermuda grass seed is produced by many seed companies and newer sterile cultivars are sold in flats; this is a positive economic value. When Bermuda grass invades areas, it can compete with or exclude other valuable species. Bermuda grass receives a Low (1) in this category.

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

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.

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:  In the southwestern United States, Bermuda grass occurs in riparian areas and in grasslands adjacent to streams and marshes. It is a frequently encountered understory grass in mesquite woodlands in the desert. On Santa Rosa Island, Bermuda grass is a common understory plant in riparian woodland dominated by willows and cottonwoods. In the Sacramento River valley, Bermuda grass occurs on gravel bars where the willow canopy is not too dense. As it is a common garden weed, especially in vegetable gardens, Bermuda grass causes problems for home gardeners at the same time it is useful as a warm season turf for lawns. Therefore, Bermuda grass receives a High (3) in this category.

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

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.

Score the pest for Environmental Impact. Score:

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 Bermuda grass: High (13)

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:  Bermuda grass is widespread in CA. It receives a High (-3) 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.

Final Score:

The final score is the consequences of introduction score minus the post entry distribution and survey information score: Medium (10)

Uncertainty:

This plant has been known in SW North America for over 200 years and spreading populations are common. Therefore, there is low uncertainty.

Conclusion and Rating Justification:

Proposed Rating: The pest has invaded much of California. Further spread within these areas is possible. As bermuda grass is an official crop in California, a rating of “D” is justified.

References:

Baldwin, B. G., D. H. Goldman, D. J. Keil, R. Patterson, T. J. Rosatti, & D. H. Wilken, editors. 2012. The Jepson manual: vascular plants of California, second edition. University of California Press, Berkeley.

CalFlora: Accessed 2/9/2015: http://www.calflora.org/cgi-bin/species_query.cgi?where-calrecnum=2570

Carey, Jennifer H. 1995. Cynodon dactylon in Fire Effects Information System,
U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, accessed 1/29/2015:  http://www.feis-crs.org/beta/

Clark, R. A., W. L. Halvorson, A. A. Sawdo, & K. C. Danielsen. 1990. Plant communities of Santa Rosa Island, Channel Islands National Park. Tech. Rep. No. 42. University of California, Davis, Institute of Ecology, Cooperative National Park Resources Studies Unit. Davis, CA.

Conard, S. G., R. L. MacDonald, & R. F. Holland. 1980. Riparian vegetation and flora of the Sacramento Valley. In: A. Sands ed. Riparian forests in California: Their ecology and conservation. University of California, Division of Agricultural Sciences: 47-55.

Consortium of California Herbaria:  cjeps.berkeley.edu/consortium/

Cudney, D. W., C. L. Elmore, & C. E. Bell. Cynodon dactylon in UC IM Online accessed 1/29/2015: http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7453.html

Stubbendieck, J., S. L. Hatch, & K. J. Hirsch. 1986. North American range plants. 3rd ed. University of Nebraska Press. Lincoln, NE.

Responsible Party:

Dean G. Kelch, Primary Botanist; California Department of Food and Agriculture; 1220 N Street, Sacramento, CA 95814; Tel. (916) 654-0312; plant.health[@]cdfa.ca.gov.


Comment Period:  CLOSED

The 45-day comment period opened on Monday, March 16, 2015 and closed on Thursday, April 30, 2015.


Pest Rating:  D  |  Proposed Seed Rating:  None


Posted by ls

Buffel grass (Pennisetum ciliare)

California  Pest Rating
Buffel grass (Pennisetum ciliare)
Pest Rating:  D  |  Proposed Seed Rating:  None

 


PEST RATING PROFILE
Initiating Event:

A new find of this plant submitted to the Plant Laboratory for identification.

History & Status:

Background:  Buffelgrass is a long-lived perennial bunchgrass. It is a densely tufted perennial, with deeply penetrating roots and erect stems to 60 cm tall. It was introduced into North America as livestock foage in arid areas. Its weedy qualities suit it for desert range conditions. It is listed as a noxious weed in Arizona.

California Distribution: Buffelgrass has been collected in Imperial, Orange, Riverside and San Bernadino Counties.

California Interceptions: Several vouchers have been submitted to CDFA for identification.

United States:  Buffelgrass was introduced into Texas and Arizona in the 1930s and 1940s to stabilize overgrazed rangelands and provide livestock forage. Buffelgrass also established in Arizona from seed dispersed from Sonora, Mexico where over 1,000,000 acres of native desert and thornscrub vegetation was converted to buffelgrass pasture. Buffelgrass also was introduced into Hawaii.

International:  Buffelgrass is native to Africa, India, and western Asia. It is introduced in North and South America and in Australia.

The risk Buffelgrass would pose to California is evaluated below.

Consequence of Introduction:

1)  Climate/Host Interaction:  Risk is High (3), as buffelgrass is naturalized in the desert throughout Southwestern North America and is spreading.

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 weeds do not require any one host, but grow wherever ecological conditions are favorable.

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:  Buffelgrass seeds are light, umbrella-like, and dispersed primarily by wind and water. Barbed bristles on buffelgrass fruits allow for long-distance dispersal in animal skin and fur.  Motor vehicles also disperse buffelgrass seed.  Buffelgrass can begin producing seeds at 3 months from germination and continue seed production for more than 10 years. Therefore, buffelgrass 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:  Buffelgrass has been used as forage in arid environments, and this is a positive economic value. But when buffelgrass invades new habitats, there is often a loss of soil fertility, an increase in soil erosion that increases surface water runoff, and this results in degraded water quality. Buffelgrass receives a Low (1) in this category.

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

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.

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:  In Hawaii, buffelgrass invades and dominates a variety of vegetation types. In natural areas, it tends to form dense swards that exclude native vegetation, decreasing biodiversity and altering successional processes. In upland arid regions, buffelgrass can transform native desert shrub and thornscrub into grasslands. For instance, in Arizona buffelgrass excludes native shrubs such as creosote (Larrea tridentata), saltbush (Atriplex spp.), and bursage (Ambrosia spp.) and their associated native grasses and forbs. In Hawaii, buffelgrass displaces native pili grass (Heteropogon contortus) communities and discourages the succession of native woody species. In lowland riparian areas, buffelgrass can replace native riparian vegetation along riverbanks. In the arid areas of Queensland, Australia, buffelgrass outcompetes and displaces native grasses and riparian vegetation. By dominating riparian areas and their moist refuges within arid regions, buffelgrass threatens keystone habitats that are vital to the survival of many plant and animal species. Buffelgrass could negatively affect sensitive desert riparian species such as the federally endangered Southwestern Willow flycatcher (Empidonax traillii extimus). Therefore, buffelgrass receives a High (3) in this category.

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

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.

Score the pest for Environmental Impact. Score:

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 buffelgrass: High (13)

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:  Buffelgrass is regional in CA. 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.

Final Score:

The final score is the consequences of introduction score minus the post entry distribution and survey information score:  Medium (11)

Uncertainty:

This plant has been known in SW North America for over 80 years and spreading colonies have been detected. So, there is low uncertainty.

Conclusion and Rating Justification:

Proposed Rating: based on the score listed above, the pest is medium risk for further invasions of California. This plant shows invasive qualities; in California it is already known from 5 counties. Nevertheless, as buffelgrass is an official crop in California, a “D” rating is justified.

References:

Baldwin, B. G., D. H. Goldman, D. J. Keil, R. Patterson, T. J. Rosatti, & D. H. Wilken, editors. 2012. The Jepson manual: vascular plants of California, second edition. University of California Press, Berkeley.

CalFlora: http://www.calflora.org/cgi-bin/species_query.cgi?where-calrecnum=12041

Collinette, S. 1999. Wildflowers of Saudi Arabia. National Commission for Wildlife Conservation, Kingdom of Saudi Arabia. Riyadh.

Consortium of California Herbaria:  cjeps.berkeley.edu/consortium/
Daehler, C.C. & D.A. Carino. 1998. Recent replacement of native pili grass (Heteropogon contortus) by invasive African grasses in the Hawaiian Islands. Pacific Science 53: 220-227.

Hauser, A. S. 2008. Pennisetum ciliare. In: Fire Effects Information System. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory. Accessed 1/25/2015:
http://www.fs.fed.us/database/feis/plants/graminoid/pencil/all.html

Tu, M. Pennisetum ciliare in Bugwood Wiki accessed 1/27/2015: http://wiki.bugwood.org/Pennisetum_ciliare

Ward, J. P.; S. E. Smith, & M. P. McClaran. 2006. Water requirements for emergence of buffelgrass (Pennisetum ciliare). Weed Science. 54: 720-725.

Responsible Party:

Dean G. Kelch, Primary Botanist; California Department of Food and Agriculture; 1220 N Street, Sacramento, CA 95814;
Tel. (916) 654-0312; plant.health[@]cdfa.ca.gov.


Comment Period:  CLOSED

The 45-day comment period opened on Monday, March 16, 2015 and closed on Thursday, April 30, 2015.


Pest Rating: D  |  Proposed Seed Rating: None


Posted by ls