RMD-13-04: Consolidated Pest Risk Management Document for pest plants regulated by Canada
Appendix 9B: Risk Management Considerations for Nassella trichotoma (serrated tussock)

This page is part of the Guidance Document Repository (GDR).

Looking for related documents?
Search for related documents in the Guidance Document Repository

Values at Risk

Seed Industry

In 2007, 162,200 tons of Canadian seed were exported to the U.S., for an approximate value of $197.6 million. If Nassella trichotoma becomes established in Canada, it could complicate seed trade between the U.S. and Canada (Statistics Canada in Agriculture Canada 2008). On several occasions forage grass seed lots of South American origin have been found to be contaminated with seeds of this weed. This has caused problems for the Canadian seed trade when seed lots containing serrated tussock seeds were re-exported to the U.S. It was largely to address these trade concerns that the species was added to the Weed Seed Order as a prohibited noxious weed seed in July 2005.

The potential range of Nassella trichotoma in Canada is limited to the West Coast of British Columbia, where there is almost no forage seed production (Statistics Canada 2007). Its direct impact on seed trade is thus relatively low and is limited to re-exportation to the U.S (Table 2).

Garry Oak Ecosystem

The Garry oak ecosystem is rare and irreplaceable because of its historical and ecological significance. This landscape contributes both to the sense of place and regional identity of the inhabitants of Vancouver Island.

The British Columbia Ministry of Environment, Lands and Parks has two Ecological Reserves that primarily focus on Garry oak ecosystems. The Garry Oak Meadow Preservation Society, the British Columbia Conservation Data Centre and the Canadian Forest Service have initiated programs to promote the preservation of Garry oak ecosystems in Canada.

Table 2: Value in Canadian dollars of Canadian re-exports of forage seeds to U.S. destinations
Forage crops 2004 2005 2006 2007
Alfalfa8,63569,81869,6918,699
Clover9,28616,35828,45841,981
Fescue 0000
Rye grass47,92637,04600
Timothy grass0000
Other forage plants10,497180,97488,191253,822
Total:78,348306,201188,346306,509

Source: Statistics Canada in Industry Canada 2009.

Cost of control

If Nassella trichotoma becomes established in natural ecosystems, including the Garry oak ecosystem of BC, it could be arduous and costly to eradicate.

The most effective control method in New Zealand, chipping combined with herbicide application, is expensive both in labour costs and cost of chemicals. Control costs vary with the degree of infestation and land use (arable versus non-arable) (Vere and Campbell 1984). Costs for control on moderately to heavily-infested land were estimated at $98.50 to $107.35Footnote 1 per hectare (Vere and Campbell 1984). The same authors explain that continued treatment of heavily-infested land must be continued for up to 22 years before an economic benefit can be expected.

Glyphosate seems to be the only pesticide that is currently registered in Canada that has been successful in controlling Nassella trichotoma. Glyphosate, a non-selective herbicide, kills a broad spectrum of plants. Its use would affect native species within the treated area, including endangered species (Allison 2006).

Potential Mitigation Measures for Natural Means of Dispersal

No measures are required. Nassella trichotoma is not present along the Canadian border. It is not likely to enter Canada by natural means.

Potential Mitigation Measures for Intentional Introduction Pathways

Plants for Planting excluding Seed

Previous imports

The CFIA considers Nassella trichotoma as not cultivated in Canada.

Potential risk mitigation measures

Non-regulatory measures

Regulatory measures

Trade implications

Cost-effectiveness and Feasibility

Seed of Nassella trichotoma

Previous imports

Unknown. No figures are available specifically for Nassella trichotoma.

Potential risk mitigation measures

Trade implications

The loss of market is expected to be very low (see Section V, c. Trade Implications).

Cost-effectiveness and Feasibility

The CFIA Seed Program is already in place to prevent the entry of prohibited noxious weeds. Verification of compliance is carried out through the Seed Marketplace Monitoring ProgramFootnote 7.

Potential Mitigation Measures for Non-intentional Introduction Pathways

Seed of Forage Grasses

Previous imports

Potential risk mitigation measures

  1. Maintain the regulation of Nassella trichotoma as a prohibited noxious weed (Class 1) under the Weed Seeds Order of the Seeds Act.
    • This species meets the definitions for Class 1 species under the Weed Seeds Order.
    • All imported and domestic seed lots must be free of prohibited noxious weed seeds. Imported seed lots would require a certificate of analysis stating Nassella trichotoma is absent from the seed lot before it can be imported.
  2. Regulate Nassella trichotoma as a quarantine pest under the Plant Protection Act and add this species to the List of Pests Regulated by Canada (CFIA 2009).
    • This could prevent the importation, movement, and cultivation of this species in Canada.
    • Exporters could be required to obtain a phytosanitary certificate stating freedom from Nassella trichotomaFootnote 9.
    • Phytosanitary agreements could be negotiated to certify imports from pest free areas and/or recognize noxious weed certification in countries or states of origin.
Figure 3: Imports of forage seed into Canada from countries where Nassella trichotoma (serrated tussock) is present

Figure 3. Description follows.
Description of Figure 3

This figure depicts the imports of forage seed into Canada from countries where serrated tussock is present from 1999 to 2008. These include Chile, Uruguay Argentina, New Zealand, Australia, Italy, Brazil and South Africa. In 1999, Canada received the most imports from Argentina (approximately $2,400,00 CAN worth) and in 2008 Canada received the most imports from Chile (approximately $1,250,000 CAN worth).

Trade implications

Cost-effectiveness and Feasibility

Hay and Straw

Previous imports

Potential risk mitigation measures

No measures required. The level of risk associated with imports of hay and straw into Canada is relatively low because (1) they originate primarily from areas where Nassella trichotoma is not present, and (2) Nassella trichotoma rarely occurs in cultivated crops,such as cultivated grassland.

Live Animals

Previous imports

Between 1999 and 2008, no significant numbers of live sheep or goats for reproduction have been imported into Canada from countries where Nassella trichotoma is present (CFIA internal data).

Potential risk mitigation measures

No measures are required.

Raw Wool

Previous imports

The total value of raw wool imports was around $3.1 million in 2008; 70% of this value came from Australia, New Zealand and Argentina, where Nassella trichotoma is present (Industry Canada 2009).

Potential risk mitigation measures

No measures are required.

Date modified: