Physical: Manual or mechanical extraction as well as mowing, burning or covering are all management techniques that can work effectively on small populations of Spartina densiflora but have complications in areas with a large population.
Chemical: A combination of the aquatic herbicides imazapyr or glyphosate and surfactant is applied through various means directly to S. densiflora to eradicate and control populations of the invasive cordgrass. These two herbicides are currently the only aquatic chemicals approved for use in estuarine environments in the state of California by the USEPA and the California Department of Pesticide Regulation (CDPR) see (San Fransisco Estuary Invasive Spartina Project, undated).
Location Specific Management Information
The California Invasive Plant Inventory categorizes
non-native invasive plants that threaten
the state’s wildlands. Spartina densiflora is rated as 'High' based on an evaluation which considers ecological impacts, invasion potential and ecological distribution. (High: These species have severe ecological impacts on physical processes, plant and animal communities, and vegetation structure. Their reproductive biology and other attributes are conducive to moderate to high rates of dispersal and establishment. Most are widely distributed ecologically). S. densiflora scores a 'High' for impacts, 'Moderate' for invasiveness and 'Limited' for distribution.
It has invaded the San Francisco and Humboldt Bay salt marshes.
Please follow this link for California-county distributional map for Spartina densiflora
Studies on Spartina densiflora have shown that mowing can be an effective method for control on a large scale while hand digging on a smaller scale (Tatum, undated) .
Spartina densiflora is listed as a "A" designated' and 'Quarantine' weed in the state of Oregon.
Definitions: “A” Designated Weed – a weed of known economic importance which occurs in the state in small enough infestations to make eradication or containment possible; or is not known to occur, but its presence in neighboring states make future occurrence in Oregon seem imminent.
Recommended action: Infestations are subject to eradication or intensive control when and where found.
Please follow this link for Oregon-county distributional map for Spartina densiflora
San Francisco Bay (Estuary)
The San Francisco Estuary Invasive Spartina Project has developed a management and control program that includes both mechanical and chemical treatments to the invasive Spartina densiflora. The aquatic herbicides imazapyr and glyphosate are currently being used exclusively in conjunction with other non-chemical methods. Mechanical removal of S. densiflora can be costly and time consuming but has proven to be more effective than hand removal methods. The covering or blanketing method involves draping fabric that seals out sunlight and kills off the S. densiflora trapped underneath. This method is only effective when used on smaller populations of cordgrass that are limited in area (San Fransisco Estuary Invasive Spartina Project, undated).
Spartina densiflora is listed as 'Class A Noxious weed' and comes under the 'Wetland and aquatic weed quarantine' in the state of Washington. (Class A noxious weeds are those noxious weeds not native to the state that are of limited distribution or are unrecorded in the state and that pose a serious threat to the state). The Wetland and aquatic weed quarantine is established against nonnative, aggressive weeds that threaten Washington waters and wetlands: Washington waters and wetlands are threatened by nonnative, aggressive weeds that destroy the commercial, aesthetic, fish and/or wildlife habitat, and recreational value of these areas. These rooted or freely floating plant species, when established, form dense stands or mats that clog irrigation systems and waterways, displace native species, alter fish and wildlife habitat, and/or seriously impact recreational use of the waterways.
1. Ayres, Debra R.; Debra L. Smith, Katy Zaremba, Shannon Klohr & Donald R. Strong., 2004. Spread of exotic cordgrasses and hybrids (Spartina sp.) in the tidal marshes of San Francisco Bay, California, USA Biological Invasions 6: 221–231, 2004.
Summary: A study that looked at the spread of Spartina densiflora and other non-native Spartina species. The researchers also examined the ability of the non-natives to colonize a given habitat.
4. Daehler, Curtis C. & Donald R. Strong., 1996. Status, prediction and prevention of introduced cordgrass Spartina spp. invasions in Pacific estuaries, USA. Biological Conservation
Volume 78, Issues 1-2, October-November 1996, Pages 51-58
Summary: A study that analyzed the ways in which Spartina species invade in order to make predictions about ways to protect habitat from the invasives.
5. Kittelson, Pamela M.; Milton J. Boyd ., 1997. Mechanisms of Expansion for an Introduced Species of Cordgrass, Spartina densiflora, in Humboldt Bay, California. Estuaries, Vol. 20, No. 4. (Dec., 1997), pp. 770-778.
Summary: A study done in Humboldt Bay, California that looked at the mechanisms for expansion for Spartina densiflora.
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