Bermuda Grass | Pest Rating Proposals and Final Ratings

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.