Bromus tectorum | Pest Rating Proposals and Final Ratings

California Pest Rating for

Cheatgrass Bromus tectorum

Pest Rating: C | Proposed Seed Rating: None

PEST RATING PROFILE

Initiating Event:

This plant is implicated in changing fire regimes in western states.

History & Status:

Cheatgrass is an annual grass. It is a tufted annual; although not large, it can colonize preferred habtat in large numbers, especially after disturbance. The spikelets consist of several florest that are pendent at maturity. Cheatgrass can be grazed early in the year, but as it matures the spikey awns render it less suitable for this purpose. As such it is inferior to perennial grasses in regards to livestock production. A survey of 11 western states in 1964 showed that cheatgrass was present on at least 60 million acres. Its range is larger now.

California Distribution: Cheatgrass has been collected in all counties of California exept the driest deserts in the southeast of the state.

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

United States: Cheatgrass was introduced to North America independently several times via ship ballast, contaminated crop seed, and packing material. Cheatgrass now occurs throughout most of the United States, Canada, Greenland, and northern Mexico.

International: Cheatgrass is native to northern Africa, Europe, and western Asia. It is introduced in North and South America, Australia, New Zealand, Japan, and Iceland.

This risk Cheatgrass would pose to California is evaluated below.

Consequences of Introduction:

1) Risk is high (3), as Cheatgrass is naturalized in the drier regions throughout western North America and is still 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: Cheatgrass seeds are light and produced prolifically. The awns on Cheatgrass fruits allow for long-distance dispersal in animal skin and fur. Motor vehicles also disperse Cheatgrass fruits. Cheatgrass can begin producing seeds at 3 weeks from germination or, given available water and nutrients, can bloom later in the season with many more flowers. It can germinate in the fall or winter depending on the year and the climate. Therefore, Cheatgrass 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: Cheatgrass has been used as forage in arid environments in the Intermontane West, and this is a positive economic value. It is less nutritious than the perennial bunchgrasses that it often replaced. When Cheatgrass invades new habitats, there is often an increase in fire that removes perennials, including grasses and sagebrush steppe shrubs from the area. Livestock browse shrubs as a source of protein in the late season. As shrubs are eliminated by fire, fall and winter digestible protein sources are lost. Cheatgrass is also a row crop weed, although this is less of an issue than its effects on rangeland.

Cheatgrass receives a High (3) in this category.

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

The pest could lower crop yield.

A. The pest could lower crop value (includes increasing crop production costs).

B. The pest could trigger the loss of markets (includes quarantines).

C. The pest could negatively change normal cultural practices.

D. The pest can vector, or is vectored, by another pestiferous organism.

E. The organism is injurious or poisonous to agriculturally important animals.

F. The organism can interfere with the delivery or supply of water for agricultural uses.

– Low (1) causes none of the above to occur.
– Medium (2) causes 2 of these impacts.
– High (3) causes 3 or more of these impacts.

5) Environmental Impact: Cheatgrass invades and dominates a variety of vegetation types, especially sagebrush steppe. In natural areas, it tends to form dense swards that exclude native vegetation and increase the ability of fire to spread. In some arid regions, Cheatgrass can transform native sagebrush scrub into non-native grasslands. This, in turn, decreases the native biodiversity and removes habitat for wildlife including birds such as the species of concern Greater Sage Grouse (Centrocercus urophasianus) and its distinct population segment, the Bi-state Sage Grouse, as well as other sagebrush steppe endemics. Therefore, Cheatgrass 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 Cheatgrass: 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: Cheatgrass is regionally common 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 (12)

Uncertainty:

This plant has been known in SW North America for over 100 years and it has proved highly invasive. So, there is low uncertainty.

Conclusion and Rating Justification:

Proposed Rating: based on the score listed above, cheatgrass is still spreading but has occupied the majority of its potential habitat in California. This plant has been invasive; in California it is already known from most counties. Because this plant is so widespread, a rating of C 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

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

Pellant, M. 1996. Cheatgrass: the Invader That Won the West. Bureau of Land Management, Boise Idaho.

U.S. Forest Service. Cheatgrass. Accessed 8/20/2015:

http://www.fs.fed.us/database/feis/plants/graminoid/brotec/all.html

Young, J. A. & C. D. Clements. 2007. Cheatgrass and Grazing Rangelands. Rangelands, 29:15-20.

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.

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