RMD-08-02: Eriochloa villosa (Woolly Cup Grass)

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

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

Date Issued: 2009-09-18

This Risk Management Document (RMD) was first published in 2009 to announce the Canadian Food Inspection Agency (CFIA)'s decision to regulate Eriochloa villosa as a pest under the Plant Protection Act. The RMD was revised in September 2013 to include updated information on the distribution of Eriochloa villosa in Canada, its regulatory status as well as the risk assessment of this species.

Table of Contents

Executive Summary

Eriochloa villosa, commonly known as woolly cup grass, is a tall, annual invasive grass weed of the millet tribe (Paniceae, family Poaceae), native to temperate Asia and introduced into the United States in the mid-1900s. It was first detected in Canada, in southern Quebec, in 2000. Since then, Eriochloa villosa established and is now found in 32 sites all located in the province of Quebec.

Eriochloa villosa reduces corn and soybean yields through competition, and increases the cost of weed control. Particularly problematic is its tolerance to several of the herbicides commonly used to control annual grass weeds and its flexible growth habit, emerging early and germinating in a series of flushes over the course of a growing season (Darbyshire et al. 2003).

In 2009, the Canadian Food Inspection Agency (CFIA) consulted affected stakeholders to determine the best approach to limit the risks posed by Eriochloa villosa to acceptable levels. All respondents recommended that the CFIA regulates Eriochloa villosa under the Plant Protection Act and continue regulating it as a prohibited noxious weed seed under the Seeds Act.

Preface

As defined by the International Plant Protection Convention (IPPC), Pest Risk Analysis (PRA) includes three stages: pest risk assessment, pest risk management and pest risk communication. Pest risk assessment provides the scientific basis for the overall management of risk. Pest risk management is the process of identifying and evaluating potential mitigation measures which may be applied to reduce the identified pest risk to acceptable levels and selecting appropriate measures.

This Risk Management Document (RMD) includes a summary of the findings of a pest risk assessment and records the pest risk management process for the identified issue. It is consistent with the principles, terminology and guidelines provided in the IPPC standards for pest risk analysis.

1.0 Purpose

To record the final risk management decision with regard to regulation of Eriochloa villosa.

2.0 Scope

This Risk Management Document summarizes the Canadian Food Inspection Agency (CFIA)'s decision to regulate Eriochloa villosa (Thunb.) Kunth (woolly cup grass) as a pest for Canada.

Information pertaining to current import requirements for specific plants or plant products may be obtained from the CFIA Automated Import Service System.

Additional points for consideration:

  1. Prior to use as human food, new plants and/or derived products that fit the definition of a novel food require approval under the authority of the Food and Drugs Act from Health Canada.
  2. Prior to use as livestock feed, new plants and/or derived products must be assessed and approved by the Animal Feed Division, CFIA under the authority of the Feeds Act and Regulations. A positive list of approved ingredients can be found in Schedules IV and V of the Feeds Regulations, 1983.
  3. Release (e.g. cultivation) of plants with novel traits into the Canadian environment may require prior approval under the authority of the Seeds Act and the Seeds Regulations from the Field Crops Division, CFIA.
  4. The importation and sale of seed in Canada must meet the requirements of the Seeds Act, Seeds Regulations and Weed Seeds Order. Seed for propagation sold, imported into or exported from Canada must conform to the Seeds Act and Regulations.
  5. All imported material must meet phytosanitary requirements for all applicable regulated organisms, as stated in CFIA's Plant Protection Policies and Directives.

3.0 Definitions

Definitions for terms used in the present document can be found in the Plant Health Glossary of Terms or the IPPC Glossary of Phytosanitary Terms.

4.0 Background

  • Invasive plants are those plant species that spread when introduced outside of their natural past or present distribution and cause serious and often irreversible damage to Canada's ecosystems, economy and society.
  • The CFIA prevents the introduction of invasive plants and weeds into Canada under the authorities of the Plant Protection Act and the Seeds Act.
  • A quarantine pest is a pest of potential economic importance, not yet present in Canada or present but not widely distributed and being officially controlled.

The CFIA is evaluating and, where appropriate, restricting the importation and spread of invasive plants as part of its mandate to protect Canada's plant resource base and its commitment to limit the introduction and spread of invasive plants under an Invasive Alien Species Strategy for Canada (Government of Canada, 2004). The strategy aims to reduce the risk of invasive species to the environment, economy, and society and to protect environmental values such as biodiversity and sustainability.

Eriochloa villosa was first detected in Canada in southern Quebec during 2000. The Ministère de l'agriculture, des pêcheries et de l'alimentation du Quebec (MAPAQ, Department of Agriculture, Fisheries and Food of Quebec), jointly with the Canadian Food Inspection Agency (CFIA), started an eradication pilot project and the site was placed under supervision in 2002.

In 2002, the CFIA Plant Health Risk Assessment Unit completed a Pest Risk Assessment on Eriochloa villosa. Following the completion of the Pest Risk Assessment and consultation with interested stakeholders, Eriochloa villosa was added as a prohibited noxious weed to the Weed Seeds Order (which came into effect in July 2005). In 2009, the CFIA completed the Risk Management Document, and consulted affected stakeholders on potential additional mitigation measures to reduce the risks posed by Eriochloa villosa to acceptable levels. All respondents to the consultation were in favor of regulating Eriochloa villosa as a prohibited (quarantine) pest under the Plant Protection Act.

In 2010, the CFIA informed our international stakeholders through a Word Trade Organization notification of its intention to add Eriochloa villosa to the List of Pests Regulated by Canada. In 2010, this regulation came into effect. Simultaneously, the CFIA developed, in consultation with its provincial stakeholders, the directive D-11-03 – Phytosanitary requirements to prevent the spread of Eriochloa villosa (woolly cup grass) and control of infestations in Canada. D-11-03 was adopted and implemented in the summer of 2011. At that time, the CFIA had identified twelve (12) sites infested by Eriochloa villosa, all located in the Monteregie-East region of Quebec.

In 2012, the CFIA did an extended survey in multiple regions of Quebec, and identified 14 new infested sites, mostly in Monteregie, but some sites were also identified in Lanaudière and Mauricie.

4.1 Identity of Organism

Name: Eriochloa villosa (Thunb.) Kunth, (Poaceae) (USDA-ARS, 2013).

Synonyms: Paspalum villosum Thunb. (Darbyshire et al. 2003; USDA-ARS, 2013).

English Common Names: Woolly cup grass; woolly cupgrass; Chinese cupgrass; hairy cupgrass (Darbyshire et al. 2003; USDA-ARS, 2013).

French Common Names: Ériochloé velue, ériochloé lanineuse, ériochloa velu (Darbyshire et al. 2003).

Eriochloa villosa is a tall, annual grass weed of the millet tribe (Paniceae, family Poaceae), native to temperate Asia and introduced into the United States in the mid-1900s. It is becoming an increasingly serious pest in the midwest United States, where it reduces corn and soybean yields through competition, and increases the cost of weed control. Particularly problematic is its tolerance to several of the herbicides commonly used to control annual grass weeds and its flexible growth habit, emerging early and germinating in a series of flushes over the course of a growing season (Darbyshire et al. 2003). It is considered to be spreading rapidly across the United States and is currently reported in 15 statesFootnote 1, although it is most prevalent as a weed in the Midwest (Illinois, Iowa, Minnesota and Wisconsin) (Strand and Miller, 1980; Owen 1990; Allison and Darbyshire 2001; Darbyshire et al. 2003). It is considered one of the most frequently observed and problematic grasses in Illinois (Sprague and Hager 2003), and is listed as one of the five most fecund species in Illinois, Minnesota and Wisconsin, based on relative abundance and fecundity status (Williams et al. 2008).

4.2 Presence / Absence in Canada

Eriochloa villosa was first detected in Canada in southern Quebec during the summer of 2000. In the fall of 2001 it was confirmed that the population had survived the winter and continued to spread (Darbyshire et al. 2003). In 2002 the site was placed under supervision, and a joint eradication program was initiated by the CFIA and the Department of Agriculture, Fisheries and Food of Quebec (Ministère de l'agriculture, des pêcheries et de l'alimentation du Québec (MAPAQ)). Between 2003-2007, five imported seed lots of Japanese millet contaminated with Eriochloa villosa were intercepted and reported through the CFIA's monitoring programs; all five originated from the same exporter in Minnesota. In 2007, one new population was found growing near the original site in Quebec, and one additional site was reported in a different municipality. By the fall of 2011, the CFIA had identified eighteen (18) sites infested by Eriochloa villosa, all located in the Monteregie-East region of Quebec, and by the fall of 2012, the total number of sites had risen to 32, mostly in Monteregie, but with some sites also identified in Lanaudière and Mauricie. Eriochloa villosa is not reported to occur elsewhere in Canada.

Eriochloa villosa is not known to be cultivated in Canada. While historical records indicate that it may have been included in forage trials in the United States (Weintraub 1953; Stubbendieck et al. 1995; Darbyshire et al. 2003), and possibly grown for ornamental purposes there (Bailey et al. 1976; Griffiths 1994), no evidence was found to indicate this is the case in Canada.

Based on this information, Eriochloa villosa is considered present, subject to official control in Canada.

4.3 Current regulatory status

Eriochloa villosa is regulated under Canada's Seeds Act and Regulations. The Seeds Act provides authority for the testing, inspection, quality and sale of seeds in Canada. Eriochloa villosa is listed as a Class 1 Prohibited Noxious Weed under the Weed Seeds Order. Its presence in domestic and imported seed is prohibited (Seeds Act).

Prior to the first publication of the present decision document in 2009, Eriochloa villosa was not regulated as a pest under the Plant Protection Act. Regulatory measures under the Plant Protection Act to control Eriochloa villosa were taken in 2011. The Plant Protection Act provides authority to prevent the importation, exportation and spread of pests injurious to plants, and provides for control and eradication methods and for the issuance of certificates.

At the provincial level, Eriochloa villosa is regulated as a prohibited weed under the Saskatchewan Weed Control Act, and Ontario, Manitoba and British Columbia are evaluating the possibility of regulating Eriochloa villosa under their provincial weed control acts in future.

Eriochloa villosa is not currently regulated as a pest by any foreign countries.

5.0 Pest Risk Assessment Summary

The information in this section is summarized from the pest risk assessment (PRA # 2001-42) and biological information update (PRA # 2011-78) conducted by C. Wilson, Plant and Biotechnology Risk Assessment Unit (CFIA 2002; 2011). The risk assessment summarizes the available information on Eriochloa villosa and evaluates the probability of entry, establishment, and spread in Canada, and the potential economic and environmental consequences. The factors considered in each of these sections, along with the guidelines used to assign risk and uncertainty ratings, are shown in Appendix 1. Overall risk and uncertainty is summarized in terms of probability and consequences.

5.1 Probability of Entry

The most likely pathway of entry of Eriochloa villosa into Canada is the unintentional introduction of seeds as contaminants in seed or grain commodities from countries where Eriochloa villosa is present, such as the United States. The first population of Eriochloa villosa reported in Canada was discovered on cultivated land owned by a seed company, suggesting the likelihood that it was introduced with seed, and unknowingly planted. The population was growing with a variety of associated crops, including soybean, corn and barley (Darbyshire et al. 2003).

Between 2003-2007, CFIA import records indicate that five seed lots contaminated with Eriochloa villosa were intercepted from the United States; all five were Japanese millet and originated from the same exporter in Minnesota. In 2009, Allison and Darbyshire (2009) reported the presence of Eriochloa villosa seeds in soybean grain originating from the United States. They documented the contaminants found in a 0.25 kg sample of screenings from #2 yellow soybeans produced in North Dakota. The sample was from a shipment of over 60,000 tons of soybeans on a Malaysian cargo ship bound for China that went aground in Alaska in 2004. Eriochloa villosa was detected in the sample, even though it has not naturalized in North Dakota (Darbyshire and Allison 2009). In 2012, the CFIA made one additional interception of Eriochloa villosa in organic soybean grain from China. These records show that Eriochloa villosa moves as a contaminant of seed and grain of certain species, and suggest it is most likely to enter Canada from the United States. This would also be expected due to the prevalence of Eriochloa villosa as an agricultural weed in the Midwestern United States, and the large volume of corn, soybeans, and other agricultural commodities imported to Canada from the United States each year.

It is also possible that Eriochloa villosa could enter Canada with the movement of contaminated farm equipment and other vehicles. Contaminated farm machinery is considered the most common source of new infestations in agricultural fields in the United States (Hartzler 2001; Darbyshire et al. 2003), and the movement of people and vehicles across the U.S.-Canada border is constant with about 30 million vehicles making the crossing from the United States to Canada each year (TBWG 2013). It is not clear to what extent this includes agricultural machinery.

The seeds of Eriochloa villosa are ovate-elliptic and relatively large (3.9 - 5.5 mm long x 2.0 - 2.8 mm wide, and 1 mm thick), suggesting they might be more likely than seeds of some other weed species to pass undetected through standard seed cleaning measures. Seeds are smaller than typical corn kernels, but may be similar in size to some soybeans, for example. The seeds of Eriochloa villosa are also dormant at physiological maturity when they fall from the plant and are protected by a hard shell making them likely to survive transit with crop seeds or grain, or on vehicles and farm equipment.

Risk Rating for Probability of Entry: Likelihood of introduction is rated "high" as entry into Canada is considered very likely or certain given the combination of factors described above.

Uncertainty and Information Gaps: Uncertainty is considered "negligible" as Eriochloa villosa is already present and spreading in western Quebec, and has been intercepted as a contaminant in several imported seed lots. It is unclear exactly how it was introduced to Quebec in the first instance, and why the majority of the interceptions have been in Japanese millet seed when it is considered most prevalent as a weed in corn and soybeans in the United States. Additional information gaps include: Details about the prevalence of the weed in individual states, the likelihood of contamination of various crops at source, the likelihood of contamination in storage or transport, the likelihood of movement of seed on vehicles and farm equipment through the Canada-U.S. border, and details about natural dispersal mechanisms including vectors and distances covered.

5.2 Probability of Establishment

Eriochloa villosa is native to temperate and subtropical Asia, occurring in China (Anhui, Fujian, Guangdong, Guizhou, Heilongjiang, Henan, Hubei, Jiangsu, Jiangxi, Jilin, Nei Monggol, Shaanxi, Shandong, Sichuan, Yunnan, Zhejiang), Japan (Honshu, Kyushu, Ryukyu Islands, Shikoku), North and South Korea, parts of Mongolia, eastern Russia (Amur, Primorye), Taiwan and Indochina (Darbyshire et al. 2003; USDA-ARS 2013). It is also reported to be introduced in the Caucasus region, western Siberia, South Asia and Iran (Tsvelev 1984; Darbyshire et al. 2003), as well as European Russia (Sukhorukov (Suchorukow) 2011), the Ukraine (Clayton 1980), Hungary (Partosfalvi et al. 2008; Solymosi 2010), France (Rivière et al. 1992) and Romania (Sike et al. 2006; Farcasescu et al. 2008; Ardelean et al. 2009; Daraban et al. 2012).

In the United States, Eriochloa villosa is typically reported from thirteen states (California, Colorado, Florida, Illinois, Iowa, Kansas, Minnesota, Mississippi, Missouri, Nebraska, Oregon, Pennsylvania, Wisconsin) (e.g., Kartesz 1999; USDA-NRCS 2013), although reports from Florida were investigated and appear to be based on cultivated material (Darbyshire et al. 2003). Two new state records include South Dakota, where it is reported to have become more common and widespread since an original collection in 1983 (Larson 2010) and Virginia, where it was collected recently along the open edge of a railroad bed in Bath County (presumed to have been introduced along the active railway) (Belden et al. 2004).

In its native range, Eriochloa villosa is reported to grow in moist meadows, open grassy places in lowlands and on hillsides, with a strong tendency towards disturbed habitats such as roadsides and waste areas (Darbyshire et al. 2003). It is also reported as a weed in rice and soybeans, and a weed of arable land (Tsvelev 1984; Darbyshire et al. 2003; Dushko et al. 2012). In the United States, Eriochloa villosa is primarily a weed of agricultural fields, occurring mostly in corn-corn and corn-soybean rotations (Owen 1990; Darbyshire et al. 2003). It also readily invades adjacent lands such as field edges, hedgerows, terraces, and water courses (Hartzler 2001; Darbyshire et al. 2003).

Based on its native distribution and records of introduction, Eriochloa villosa is capable of surviving and becoming established in at least NAPPFAST plant hardiness zones 2 - 10 (e.g., Heilongjiang; Vietnam), and possibly 1 - 10 (e.g., Amur; Vietnam) (see www.nappfast.org), covering most, if not all of Canada (Figure 2). According to Darbyshire et al. (2003), "The occurrence of Eriochloa villosa in Asia from the boreal region of eastern Russia to subtropical areas of Taiwan and in California, Oregon and the northern Great Plains of North America indicates that it is adapted to a wide variety of climatic conditions and is successful as a weed in temperate climates". Its potential range covers all areas of agricultural production in Canada, including the main corn and soybean production zones in southern Ontario and Quebec. Populations of Eriochloa villosa in Quebec currently fall in NAPPFAST zone 4.

a. Image - North Carolina State University Animal and Plant Health Inspection Service Plant Pest Forecasting System Plant Hardiness Zones 2 - 10

b. Map - North Carolina State University Animal and Plant Health Inspection Service Plant Pest Forecasting System Plant Hardiness Zones 1 - 10

Figure 2: Potential range of Eriochloa villosa in Canada, showing (a) NAPPFAST Plant Hardiness Zones 2-10, and (b) NAPPFAST Plant Hardiness Zones 1-10.

The first image is a map in which the majority of Canada covered in red except parts of the Arctic in order to display NAPPFAST Plant Hardiness Zone's 2-10 as the potential range of Eriochloa villosa in Canada.

The second image is a map of Canada which is completely covered in red showing NAPPFAST Plant Hardindess Zones 1-10 as the potential range of Eriochloa villosa in Canada.

Risk Rating for Probability of Establishment: Probability of establishment is rated "high" for Eriochloa villosa, as it has the potential to survive in more than five plant hardiness zones in Canada (i.e., NAPPFAST Plant Hardiness Zones 2-10 or 1-10), and its worldwide distribution suggests a climatic tolerance that could allow it grow in almost all or all of Canada.

Uncertainty and Information Gaps: Uncertainty is considered "negligible" as the presence of Eriochloa villosa in Quebec indicates that it is capable of establishment in Canada and there is direct evidence from reliable sources that it has the potential to survive in at least nine plant hardiness zones. Information gaps include details about the habitats of Eriochloa villosa in its native range, in particular specific habitat preferences or restrictions, as well as its prevalence in the northeastern parts of its range in Asia, which might lead to more specific predictions of the northern limits of its range in Canada.

5.3 Probability of Spread

Eriochloa villosa is an annual species that reproduces and disperses naturally by seed. Seeds are large and tend to germinate earlier in the season than most other grass weeds, from a wide range of soil depths and temperatures. Eriochloa villosa also undergoes several germination flushes in the course of a season (Owen 1990; Bello et al. 2000; Allison and Darbyshire 2001; Darbyshire et al. 2003). In North America, emergence begins in mid-April to early May and flowering begins in mid-July to early August, continuing until frost kills the plants (Owen 1990; Hartzler et al. 1999; Hartzler et al. 2000; Darbyshire et al. 2003; Hilgenfeld et al. 2004b; Simard and Bégin 2010). Plants produce stolons early in the growing season, and branch extensively later in the season, so that single plants occupy and disperse seed over a large area. Adventitious roots produced at the nodes of stolons also support axillary branching, shoot production and tillering, which in turn increases seed production (Darbyshire et al. 2003). Fertile flowers are bisexual but do not open (cleistogamous) and appear to be entirely self-fertilizing. This is a reproductive strategy that facilitates spread and establishment of new populations, as only one viable seed is required to start a new infestation (Darbyshire et al. 2003). Eriochloa villosa is a prolific seed producer, with a single plant capable of producing up to 164,000 seeds in a season under ideal conditionsFootnote 2, some of which will germinate the following spring and some of which will enter the seed bank (Owen 1990). Plants that emerge late in the season tend to yield less as they have less time to complete their life cycle. However, late-emerging plants may still produce many viable seeds (e.g., 2600) (Owen 1990; Bello et al. 2000). No evidence was found for vegetative reproduction, at least in North America (Darbyshire et al. 2003).

Little is known about mechanisms of natural seed dispersal for Eriochloa villosa. Species in the genus Eriochloa do not appear to possess specialized dispersal structures, and it is generally assumed that seeds fall close to the parent plant. It is possible that the callus at the base of the spikelets evolved as an elaiosome, a specialized structure facilitating dispersal by insects (usually ants) (Darbyshire et al. 2003). Recent work by Darbyshire et al. (2013) supports this, showing lipids present in the callus of Eriochloa villosa, which may attract animals. Most insect predators in North America would be too small to effectively disperse the large seeds of Eriochloa villosa, but other vectors could include birds and rodents. Work by Simard et al. (2013) indicates that Eriochloa villosa seeds are predated upon by both invertebrates (mostly crickets and beetles) and vertebrates (birds and rodents) in Quebec, although invertebrates mostly consumed seeds in situ, and vertebrate predators were not monitored so dispersal distances are not estimated. Work by Nurse et al. (unpublished) indicates that water is an unlikely vector for Eriochloa villosa, as the seeds are not buoyant for long. When placed in water-filled beakers the seeds germinated rapidly, clumped together, and sank (R. Nurse, AAFC, pers. comm.). Overall, while a number of possible vectors for natural dispersal do exist, human agency is still considered the most likely mechanism for spread in North America (see below).

There are no reports of Eriochloa villosa hybridizing with natural relatives (Darbyshire et al. 2003). Shaw and Webster (1987) suggest that hybridization may occur among the annual tetraploid Eriochloa species in North America. This may include E. contracta, which has been reported as a rare historical occurrence in Ontario, and E. acuminata which has spread as far north as New York state. However, Eriochloa villosa is hexaploid. Natural hybridization with wild relatives in Canada is considered unlikely.

Human-mediated spread of Eriochloa villosa may occur in several ways. Long-distance spread may occur with intentional movement of seed and plants for cultivation, or with the unintentional contamination of seed, grain, and other agricultural commodities or conveyances. Eriochloa villosa has been shown to spread through the latter pathway as indicated by interception records in imported seed and grain (see discussion under "Probability of Entry", above). Local spread of Eriochloa villosa in the United States is typically attributed to the movement of contaminated farm machinery (Darbyshire et al. 2003).

Risk Rating for Probability of Spread: Probability of spread is rated "medium" for Eriochloa villosa, as it has a high reproductive potential (up to 164,000 seeds/plant), but little is known about natural dispersal mechanisms or the mobility of its propagules. It should be noted that Eriochloa villosa has spread extensively in the United States since its introduction in the 1940s, and new sites continue to be found in southwestern Quebec since its discovery in 2000.

Uncertainty and Information Gaps: Uncertainty is considered "medium" as there is evidence that Eriochloa villosa can spread in Canada, but considerable uncertainty around predicting the rate and extent of spread, as well as the most likely mechanisms. There is limited information available about natural dispersal mechanisms so that potential distances for natural dispersal cannot be estimated. It is generally assumed that Eriochloa villosa entered Canada in contaminated seed and is now being spread in Quebec by the movement of vehicles and farm equipment.

5.4 Potential Economic and Environmental Consequences

The primary economic impacts of Eriochloa villosa are reduced crop yields caused by competition with corn and soybeans, and increased cost of control. Impacts are more pronounced in corn than in soybeans, as Eriochloa villosa is most competitive with annual crops of similar growth habit. While its effects cannot generally be separated from those of other grass weeds, it has been estimated that season-long competition from uncontrolled grass weeds like Eriochloa villosa can reduce corn yields by up to 50% (Staniforth 1957; Hall et al. 1992; Rabaey and Harvey 1997a; Tapia et al. 1997). A similar estimate can be reached using the WEEDSOFT Yield Loss Calculator, a model developed by the University of Nebraska-Lincoln (University of Nebraska - Lincoln 2001-2009). This is a computer-based tool used to estimate yield loss in corn and soybeans, based on parameters such as weed species and density, crop spacing, and expected ‘weed free' yield and selling price. Using weed density data for Eriochloa villosa reported from experimental corn plots in Illinois (207 plants m–2; Hart and Wax 1997) and expected ‘weed free' yield of corn (150 bu/acre) and selling price ($5.25/bu) from the Ontario Ministry of Agriculture and Food (OMAFRA 2012), the model estimates that Eriochloa villosa left uncontrolled in corn could result in a loss of 83.80 bu/acre ($439.97/acre) over the course of a season. This represents a yield loss of about 55%.

Weed control is a standard component of any crop production system, but Eriochloa villosa is more difficult to control than many other grass weeds. It is less susceptible to soil-applied herbicides and can also survive exposure to some foliar-applied herbicides (Harvey 1974; Owen et al. 1993; Mickelson and Harvey 2000; Bunting et al. 2004). It is not clear to what extent this is due to biochemical factors such as an ability to quickly metabolize herbicides (e.g., Jensen et al. 1977; Hinz and Owen 1996; Hinz et al. 1997), and/or evasion through growth patterns, for example germinating from soil depths where herbicides are not concentrated, or after herbicides have dissipated (Owen 1990; Darbyshire et al. 2003; Hilgenfeld et al. 2004a). A wide range of herbicide combinations and application regimes have been tested in the United States with variable results; they generally show that control is easier to achieve in soybean than in corn, and that a strategy of sequential control with both soil-applied pre-emergence herbicides and foliar-applied post-emergence herbicides, is the most effective (Owen 1990; Rabaey et al. 1996; Hart and Wax 1997; Rabaey and Harvey 1997b; Tapia et al. 1997; Young and Hart 1999; Mickelson and Harvey 2000; Hartzler 2001; Darbyshire et al. 2003). In 1997, the cost of additional herbicide applications required to control Eriochloa villosa in corn in the Midwest United States was estimated at US$63/ha, representing about an 18% increase in production costs. Complete management recommendations for Eriochloa villosa in the United States include an integrated approach, combining sequential herbicide applications with sanitation of machinery and equipment, crop rotation, and mechanical control, the costs of which are not estimated (Owen 1990; Hartzler 2001; Darbyshire et al. 2003).

There is no evidence that Eriochloa villosa has direct impacts on natural ecosystems or native species in its introduced range in the United States. It is not reported to have established in natural areas, nor are there any reports of invasive behavior outside agricultural fields. There are no reports of toxicity to livestock or humans, or impacts on recreation, aesthetics or property. Eriochloa villosa is most likely to affect the environment indirectly, through the impacts of increased tillage and herbicides used in control programs.

Risk Rating for Potential Economic and Environmental Consequences: Potential economic and environmental consequences are rated "medium" for Eriochloa villosa as it has the potential to cause at least two economic impacts (i.e., crop yield reduction and increased cost of control) primarily in corn-corn and corn-soybean rotation systems (i.e., in a relatively narrow range of crops). However, it should be noted that the areas where Eriochloa villosa is most likely to establish in Canada include southern Ontario and Quebec, where most corn and soybean production occurs, so it could have a significant impact on those industries.

Uncertainty and Information Gaps: Uncertainty is considered "low" as there is evidence from primary and secondary sources that Eriochloa villosa causes economic impacts in corn and soybean production systems. However, it should be noted that these are difficult to quantify, and difficult to separate from the impacts of other grass weeds. Calculations presented in this section are estimates based on the information available. Information gaps include: actual (quantified) yield losses and costs of control in corn and soybeans, and whether Eriochloa villosa also causes impacts in other crops.

5.5 Summary

The following table summarizes the risk and uncertainty ratings for Eriochloa villosa, assigned in each section of the risk assessment as outlined above. The overall probability of introduction and spread, and associated uncertainty rating, were calculated following the guidance in Appendix 1.

Table 1: Risk and Uncertainty Ratings for Eriochloa villosa
Probability Risk Rating Uncertainty
Probability of Entry High Negligible
Probability of Establishment High Negligible
Probability of Spread Medium Medium
Overall Probability of Introduction and Spread High Low
Consequences Risk Rating Uncertainty
Potential Economic and Environmental Consequences Medium Low

5.6 Conclusion

The evidence examined in this risk assessment suggests that Eriochloa villosa has the potential to establish and spread in many parts of Canada, particularly in areas where corn and soybean are grown. Its potential economic consequences include considerable yield losses and increased costs of weed control. It is reported as an important agricultural weed in the United States where it is naturalized and spreading. It is not likely to hybridize with natural relatives in Canada, and there is no evidence that it poses a threat to natural environments or native species.

6.0 Risk Management

6.1 Introduction

In this section, potential risk mitigation measures to control Eriochloa villosa are provided. The effectiveness and feasibility of those measures are discussed, including impacts on the CFIA, practicality of implementation, impacts on Canadian stakeholders, impacts on trading relationships, and short-term and long-term sustainability.

This document summarizes the rationale in determining the regulatory status of Eriochloa villosa. It outlines the possible phytosanitary requirements for traded commodities. The commodities may be the plant under consideration for regulation itself (intentional introduction) or a product contaminated with the plant (unintentional introduction).

6.2 International Responsibilities, Government of Canada Priorities and CFIA Objectives

Canada is a contracting party to the International Plant Protection Convention (IPPC), and is a member of the World Trade Organization (WTO). The IPPC is formally identified in the WTO Sanitary and Phytosanitary (SPS) Agreement as the international standard setting organization for phytosanitary measures. The IPPC is an international treaty to secure action to prevent the spread and introduction of pests of plants and plant products (including plants as pests), and to promote appropriate measures for their control.

The CFIA is recognized under the IPPC as Canada's official National Plant Protection Organization. The CFIA is correspondingly invested with a number of responsibilities set out in the IPPC, and plays an important role in protecting Canada's plant resource base from pests and diseases. In that regard, the objectives of the CFIA's plant protection program are to: (1) prevent the introduction and spread within Canada of plant pests of quarantine significance, including invasive plants; (2) detect and control or eradicate designated plant pests in Canada; and (3) certify plants and plant products for domestic and export trade.

In 1996, as a party to the United Nations Convention on Biological Diversity (CBD), Canada developed the Canadian Biodiversity Strategy, which recognized the need to conserve biological diversity and promote the sustainable use of biological resources through increased understanding, legislation, incentives and other means. In addition, in September 2004 Canada introduced An Invasive Alien Species Strategy for Canada, aimed to minimize the risk of IAS to the environment, economy, and society, and to protect environmental values such as biodiversity and sustainability. The CFIA provides leadership in the implementation of the national IAS strategy as it relates to invasive plants and plant pests.

As party to these international and national instruments, Canada has a strong commitment to addressing the deleterious impacts of invasive plants.

6.3 Values at Risk

Risk assessment anticipates the impact to the Canadian economy and environment from the introduction of Eriochloa villosa to be significant. Eriochloa villosa is a weed of row crops, particularly affecting corn-soybean and corn-corn rotations. The following table shows the Canadian production of corn and soybean by region.

Table 2: Corn and soybean production by regions in 2012
Corn for grain
Harvested area (1000 ha)
Corn for grain
Production (1000 tonnes)
Corn for fodder
Harvested area (1000 ha)
Corn for fodder
Production (1000 tonnes)
Soybean
Harvested area (1000 ha)
Soybean
Production (1000 tonnes)
Maritimes 15.0 105.8 10.2 341.1 28.4 71.3
Quebec 385.0 3505.0 72.5 2430.3 279.5 825.0
Ontario 894.4 8598.3 119.0 4898.8 1046.1 3274.0
West 123.5 851.0 63.5 2399.5 323.7 759.3
Canada 1417.9 13060.1 265.2 10069.7 1677.7 4929.6

Eriochloa villosa is reported to be a good competitor with other plants in cultivation, especially row-crops. Eriochloa villosa is difficult to suppress as it is tolerant to several herbicides commonly used to control annual grass weeds. It also has a flexible growth habit, emerging early and germinating in a series of flushes over the course of a growing season (Darbyshire et al. 2003). It is also known to impact non-agricultural areas as it has been found in roadside ditches, disturbed areas and on pond banks in eastern Nebraska (Stubbendieck et al 1995 Weeds of Nebraska and the Great Plains).

Eriochloa villosa is not known to have direct consequences on the environment. However, it could have indirect consequences through the impacts of increased tillage and herbicides used in control programs.

Canada imports grains from a number of different countries, some of which have reported populations of Eriochloa villosa. Between 2003 and 2012, the CFIA has intercepted six imported commodities infested with Eriochloa villosa. It has been found as a contaminant in Japenese millet seed lots and organic soybean grain.

Since it is not regulated as a quarantine pest by any other country, it is unlikely that the presence of Eriochloa villosa in the field would make Canadian corn, soybean or other field crop commodity less marketable on an international scale. However, Eriochloa villosa is regulated as a prohibited noxious weed in Saskatchewan, and is likely to be added to the Ontario, Manitoba and British Columbia provincial lists of prohibited weeds. Domestic trade with these provinces may be affected.

6.4 Pest Risk Management Options

6.4.1 Option 1: Do Not Regulate Eriochloa villosa

  1. Re-classify Eriochloa villosa from Class 1, Prohibited Noxious Weed, to a lower class of the Weed Seeds Order.
  2. Discontinue involvement in the Quebec pilot project and do not require any control measures in the event that new infestations are discovered.
Advantage:
  • No additional costs for the CFIA.
Disadvantages:
  • The dispersal of Eriochloa villosa will result in added production costs for Canadian farmers. The Table 2 and Figure 2 show the potential impact for Canadian farmers, using the example of corn crops. According to Statistics Canada (2007), more than 6,000 farms earn income from corn production and around 1.65 million hectares are under grain and feed corn cultivation in Canada.
  • The initial investment of around $110,000 that the CFIA has already invested for controlling and monitoring Eriochloa villosa in Quebec would be wasted.
  • The CFIA would have no authority to require mitigation measures for commodities contaminated with Eriochloa villosa or to eradicate established populations.
Figure 1: Potential Financial Impact of Eriochloa villosa on Annual Corn Crop Revenues in Canada (overall). Description follows.
Description of Image - Potential Financial Impact of Eriochloa villosa on Annual Corn Crop Revenues in Canada (overall)

This graph illustrates the potential increase in production costs ($ million/year) for corn due to additional herbicide application for controlling severe infestations of Eriochloa villosa in Canada. The increase in production costs would increase linearly with the percentage of corn crops severely affected by Eriochloa villosa in Canada. The increase in production costs would be of $20 million/year when 20% of the conventional corn crops in Canada are severely affected by Eriochloa villosa and ends up close to $100 million/year when 100% are affected. The increase in production costs would be of around $18 million/year when 20% of the glyphosate-tolerant corn crops in Canada are affected and ends up around $73 million/year when 100% are affected.

6.4.2 Option 2: Continue to Regulate Eriochloa villosa under the Seeds Act (Status Quo)

  1. Continue to regulate Eriochloa villosa in the Weed Seeds Order (under the Seeds Act) as a prohibited noxious weed.
  2. Do not regulate Eriochloa villosa under the Plant Protection Act as a quarantine pest.
  3. Continue involvement in the Quebec pilot project at Site 1a-c, without requiring phytosanitary measures against any other infestations.
Advantage:
  • The CFIA can prevent the entry and spread of Eriochloa villosa as a contaminant of seed. Eriochloa villosa, as a prohibited noxious weed species, is not permitted in imported or domestic seed. Verification of compliance can easily be carried out through the Marketplace Monitoring Program without additional cost.
Disadvantages:
  • The CFIA cannot control the presence of Eriochloa villosa in other commodities such as grain not intended for propagation.
  • The CFIA would have no authority to require phytosanitary measures to eradicate Eriochloa villosa from infested sites. To date, stakeholders have been diligent in applying the voluntary precautionary measures suggested by CFIA inspectors and the MAPAQ crop advisors. However, if new infestations were discovered in Canada, the CFIA would not be involved.
  • Without adequate mitigation measures, the species could be re-introduced by commodities other than seed or escape from infested sites with grain or farm machinery and spread into several Canadian crops, substantially increasing production costs.

6.4.3 Option 3: Regulate Eriochloa villosa under the Seeds Act and the Plant Protection Act

  1. Maintain Eriochloa villosa in the Weed Seeds Order (under the Seeds Act) as a prohibited noxious weed.
  2. Add Eriochloa villosa to the List of Pests Regulated by Canada (under the Plant Protection Regulations) (CFIA, 2009).
  3. Add Eriochloa villosa to existing and future Directives. These directives currently specify the pests regulated in the host commodity material (i.e. propagative and non-propagative):
    • D-99-01: Barley, Oats, Rye, Triticale and Wheat - Phytosanitary Requirements on Import, Transshipped, In-Transit and Domestic Movement (CFIA, 2007);
    • D-96-03: Plant Protection Import Requirements for Hemp (Cannabis sativa) (CFIA, 2006a);
    • D-96-08: Import and Domestic Movement Requirements, Sorghum spp. (CFIA, 2006b);
    • D-95-28: Plant Protection Import and Domestic Movement Requirements for Corn, Zea mays. Directive D-95-28 (CFIA, 2006c);
    • D-94-17: Plant Protection Phytosanitary Import Requirements for Soybean Seed. (CFIA, 2006d).
    • New directives will be developed to specify the import restrictions for regulated invasive plant species as well as to outline the import requirements for commodities currently not regulated.
  4. Continue CFIA's involvement in the Quebec pilot project at Site 1a-c and the control plan at Site 2, and implement a control plan at Sites 3 and 4.
Advantages:
  • By maintaining Eriochloa villosa in the Weed Seeds Order as a prohibited noxious weed, the CFIA limits its spread through seed.
  • Adding Eriochloa villosa to the List of Pests Regulated by Canada and amending relevant directives would give the CFIA the authority to control both import and domestic movement of the species. The CFIA would have the necessary authority to impose control measures for any infested sites discovered in Canada, and to require phytosanitary measures for any commodity or article found containing viable seeds of Eriochloa villosa.
  • While the costs to individuals or companies may be high, when balanced with the costs to Canadian growers if Eriochloa villosa were to become established on Canadian farmland regulation would generally be cost-effective.
  • At this time, eradication is still feasible. Eriochloa villosa is only known to occur at four confined sites in Canada. Up to 4000 ha at risk were inspected in Quebec for the presence of Eriochloa villosa in 2007 and 2008. If the CFIA delays action, this opportunity may be lost and control costs in the long term would increase significantly.
Disadvantages:
  • Minor additional extra resources would be needed to increase the frequencies of regular import audits for commodities imported from origins where Eriochloa villosa is present. Currently, the resources that have been allocated to the verification of grain imports (for the presence of a number of other invasive plant seeds) are estimated at 2 FTEs. Corresponding resources have been allocated to conduct laboratory analyses of the samples. Substantial resource requirement increases are not anticipated.
  • Any commodity containing seed or plants of Eriochloa villosa would be refused entry or movement in Canada, re-routed to another country, treated or destroyed at the importer's expense. These expenses also include, but are not limited to, costs associated with quarantine actions resulting from accidental contamination and any seizure, confiscation and forfeiture of shipments.
  • The CFIA could require risk-based phytosanitary measures to eradicate any Eriochloa villosa infestation and prevent its spread. This could include, but is not exclusive to: restricting or prohibiting movements and activities on the infested area, requiring herbicide and/or cultural treatments, and requiring treatment or destruction of the crop harvested on the infested area, including screenings. Treatments include heat treatment, pelletizing, grinding and milling. Incineration or deep burial are acceptable means of destruction.

6.5 Recommendation

The CFIA recommended Option 3 for the following reasons:

  • The CFIA already regulates seeds, one of the major pathways of introduction, for the presence of Eriochloa villosa. All imported and domestic seed must be free of prohibited noxious weed seeds. Imported seed lots must have a laboratory certificate of analysis certifying freedom from Eriochloa villosa prior to import release. The CFIA monitors compliance with this requirement through the marketplace monitoring program.
  • The CFIA will be able to control the other potential pathways of introduction of Eriochloa villosa into Canada by regulating it as a quarantine pest under the Plant Protection Act, and by amending relevant existing import directives and developing new ones.
  • The control of Eriochloa villosa populations is feasible.
  • The control of Eriochloa villosa populations is cost-justifiable. The cost of regulating Eriochloa villosa is considerably lower than the costs that would ensue from its spread into Canadian crops.

7.0 Pest Risk Management Decision

7.1 Decision

By way of this Risk Management Decision Document, the CFIA is announcing its decision to proceed with the regulation of Eriochloa villosa as a pest under the Plant Protection Act. Consultation on the Risk Management Document and the recommended option was conducted between December 2008 and January 2009. Stakeholder comments received were all generally supportive of the recommended risk management Option 3: regulate Eriochloa villosa as a quarantine pest, under the Plant Protection Act. A list of the consulted stakeholders is provided at the Appendix II.

8.0 References

Allison, K. and Darbyshire. S. J. 2001. Identification of Eriochloa villosa. Seed Technology 23(2): 169-172.

Ardelean, A., Karacsonyi, K. and Negrean. G. 2009. Eriochloa villosa - a new alien Graminaceae species for Arad County (Romania). Studia Universitatis Vasile Goldis Arad, Seria Stiintele Vietii 19(2): 281-282 [Romanian; English abstract]

Bailey, L.G., and Bailey, E. Z. 1976. Hortus Third: A Concise Dictionary of Plants Cultivated in the United States and Canada. McMillan Publishing Co., New York, NY.

Belden, A. J., Fleming, G. P., Ludwig, J. C., Townsend, J. F., Van Alstine, N. E., Stevens, C. E. and Wieboldt, T. F. 2004. Noteworthy Collections. Castanea 69(2): 144-153.

Bello, I. A., Hatterman-Valenti, H. and Owen, M. D. K. 2000. Factors affecting germination and seed production of Eriochloa villosa. Weed Science 48: 749-754.

Canadian Food Inspection Agency (CFIA). 2002. Weed Risk Assessment: Woolly cupgrass (Eriochloa villosa (Thunb.) Kunth.) PHPD Request No. 2001-42. Canadian Food Inspection Agency, Ottawa (unpublished).

Canadian Food Inspection Agency (CFIA). 2009. Pests Regulated by Canada. Canadian Food Inspection Agency. [cited July 2009].

Canadian Food Inspection Agency (CFIA). 2008. Directive D-95-26: Phytosanitary requirements for soil and related matter, alone or in association with plants. Canadian Food Inspection Agency, Ottawa.

Canadian Food Inspection Agency (CFIA). 2007. Directive D-99-01: Barley, Oats, Rye, Triticale and Wheat - Phytosanitary Requirements on Import, Transshipped, In-Transit and Domestic Movement. Canadian Food Inspection Agency, Ottawa.

Canadian Food Inspection Agency (CFIA). 2006a. Directive D-96-03: Plant Protection Import Requirements for Hemp (Cannabis Sativa). Canadian Food Inspection Agency, Ottawa.

Canadian Food Inspection Agency (CFIA). 2006b. Directive D-96-08: Import and Domestic Movement Requirements, Sorghum spp. Canadian Food Inspection Agency, Ottawa

Canadian Food Inspection Agency (CFIA). 2006c. Directive D-95-28: Plant Protection Import and Domestic Movement Requirements for Corn, Zea mays. Canadian Food Inspection Agency, Ottawa.

Canadian Food Inspection Agency (CFIA). 2006d. Directive D-94-17: Plant Protection Phytosanitary Import Requirements for Soybean Seed. Canadian Food Inspection Agency, Ottawa.

Canadian Food Inspection Agency (CFIA). 2011. Request for Biological Information: Eriochloa villosa (Thunb.) Kunth. (woolly cup grass). PRA Request No. 2011-78. Canadian Food Inspection Agency, Ottawa (unpublished).

Clayton, W. D. 1980. 136. Eriochloa Kunth. Pages 262 in T. G. Tutin, V. H. Heywood, N. A. Burgess, D. M. Moore, D. H. Valentine, S. M. Walters and D. A. Webb (Eds.), Flora Europaea, vol. 5. Alismataceae to Orchidaceae (Monocotyledones). Cambridge University Press, Cambridge, UK.

Crop Health Protection Act. R.S.Q., chapter 16. Assented to 12th June, 2008.

Darbyshire, S.J., C.E. Wilson and K. Allison. 2003. The Biology of Invasive Alien Species in Canada. 1. Eriochloa villosa (Thunb.) Kunth. Canadian Journal of Plant Science, 83: 987-999.

Farcasescu, A. M., Arsene, G. G. and Neacsu, A. G. 2008. Eriochloa villosa (Thunb.) Kunth - a new invasive weed in Romania. Journal of Plant Diseases & Protection Special Issue 21: 333-334.

Government of Canada. 2004. An Invasive Alien Species Strategy for Canada. Government of Canada. [Online].

Griffiths, M. 1994. The New Royal Horticultural Society Dictionary. Index of Garden Plants. Timber Press, Portland, OR. lxi + 1234 pp.

Hall, M. R., Swanton, C. J. and Anderson, G. W. 1992. The critical period of weed control in grain corn (Zea mays). Weed Science 40:441-447.

Hart, S. E. and Wax, L. M. 1997. Utilization of herbicide resistant crops for weed management in midwestern United States corn and soybean production. Proceedings of the 1997 Brighton Crop Protection Conference - Weeds, Volume 3. British Crop Protection Council, Surrey, U.K.

Industry Canada. 2009. Trade Data Online (TDO). Data from Statistics Canada and the United States Census Bureau (United States Department of Commerce). [cited May 2009].

Kartesz, J. T. 1999. Synthesis of the North American Flora Version 1.0 - A synonomized checklist and atlas with biological attributes for the vascular flora of the United States, Canada, and Greenland. North Carolina Botanical Garden, Chapel Hill, NC.

Larson, G. E. 2010. New vascular plant records for South Dakota. Journal of the Botanical Research Institute of Texas 4(1): 467-470.

Mickelson, J.A., Boergoom, C.M. and R.G. Harvey. 2000. Eriochloa villosa and Wild Proso-Miller Management. Department of Agronomy, University of Wisconsin, Madison.

Mickelson, J. A., Midthun-Hensen, A. and Harvey, R. G. 2004. Fate and persistence of woolly cupgrass (Eriochloa villosa) seed banks. Weed Science 52(3): 346-351.

Molenhuis, J. 2008. Grain Corn Conventional Till Enterprise Budget. Ontario Ministry of Agriculture, Food and Rural Affairs. Last updated: May 22, 2007 [cited July 2007].

Néron, R. 2003. Bulletin no. 11 (22 août 2003) - Grandes cultures - L' Ériochloé velue. Réseau d'avertissements phytosanitaires.

Ontario Ministry of Agiculture and Food (OMAFRA). 2012. Grain corn conventional enterprise budget. [Online] Available: http://www.omafra.gov.on.ca/english/busdev/bear2000/Budgets/Crops/Grains/grcorn_static.htm [cited 2013].

Owen, M. D. K. 1990. Woolly cupgrass biology and management. Proceedings of the Crop Production Conference of Iowa State 2: 61-72.

Partosfalvi, P., Madarasz, J. and Dancza, I. 2008. The first occurrence of Eriochloa villosa (Thunb.) Novenyvdelem 44(6): 297-304 [Hungarian; English abstract].

Plant Protection Act. Canada Gazette. Part III, Vol. 22, No. 1 (June 19, 1990).

Plant Protection Regulations (SOR/95-212).

Rabaey, T. L. and Harvey, R. G. 1997. Annual grass control in corn (Zea mays) with primisulfuron combined with nicosulfuron. Weed Technology 11: 171-175.

Rivière, G., Guillévic, Y. and Hoarher, J. 1992. Flore et végétation du Massif Armoricain. Supplément pour le Morbihan. Erica [Conservatoire Botanique National de Brest] 2: 6–78.

Seeds Act, RSC, 1985, c. S-8

Seeds Regulations (C.R.C., c. 1400)

Shaw, R. B. and Webster, R. D. 1987. The genus Eriochloa (Poaceae: Paniceae) in North and Central America. Sida 12(1): 165-207.

Sike, M., Goga, N. and Fritea, T. 2006. Eriochloa villosa (Thunb.) Kunth. (Poaceae), new species of Romanian flora and new weed of field crops in North-West of Romania. Analele Institutului National de Cercetare-Dezvoltare Agricola Fundulea 73: 167-171 [Romanian; English abstract].

Solymosi, P. 2010. New adventive grass weeds in the Hungarian flora Novenyvdelem 46(3): 117-120. [In Hungarian; English abstract].

Sprague, C. L. and Hager, A. G. 2003. Weeds to watch for in 2003. University of Illinois Extension. [Online] Available: www.ag.uiuc.edu/cespubs/pest/articles [Cited 2011].

Staniforth, D. W. 1957. Effects of annual grass weeds on the yield of corn. Agronomy Journal 49: 551-555.

Statistics Canada. 2007. Field and Specialty Crops (Seeded Area). Statistics Canada. Last updated: June 26, 2007 [cited July 2007].

Strand, O. E. and Miller, G. R. 1980. Weedwatch: Woolly cupgrass – A new weed threat in the midwest. Weeds Today 11(3): 16.

Stubbendieck, J., Friisoe, G. Y. and Bolick, M. R. 1995. Weeds of Nebraska and the Great Plains. 2nd ed. Nebraska Department of Agriculture, Lincoln, NE. 621 pp.

Tapia, L. S., Bauman, T. T., Harvey, R. G., Kells, J. J., Kapusta, G., Loux, M. M., Lueschen, W. E., Owen, M. D. K., Hageman, L. H. and Strachan, S. D. 1997. Postemergence herbicide application timing effects on annual grass control and corn (Zea mays) grain yield. Weed Science 45: 138-143.

Tsvelev, N. N. 1984. Grasses of the Soviet Union. Amerind Publishing, New Delhi, India [English translation published for the Smithsonian Institution and the National Science Foundation, Washington, DC]. 1196 pp.

University of Nebraska – Lincoln. 2001-2009. WeedSOFT Yield Loss Calculator. [Online] [cited 2013].

USDA-ARS. 2013. Germplasm Resources Information Network - (GRIN) [Online Database]. [Online] [cited 2013].

USDA-NRCS. 2013. The PLANTS Database. [Online] [cited 2013].

Weed Seeds Order, 2005 (SOR/2005-220).

Weintraub, F. C. 1953. Grasses introduced into the United States. USDA Agric. Handb. 58. 79 pp.

Williams, M. M., Rabaey, T. L. and Boerboom, C. M. 2008. Residual weeds of processing sweet corn in the North Central region. Weed Technology 22(4): 646-653.

9.0 Endorsement

Approved by:

Chief Plant Health Officer

Appendix 1: Risk Assessment Rating Guidelines

Weed risk assessment considers the probability of introduction (entry, establishment) and spread of a potential weed, as well as the potential economic and environmental consequences. The following guidelines explain what factors are considered under each of these headings, and outline the methods for assigning and calculating ratings for risk and uncertainty.

Guidelines for Rating Probability of Entry

This rating reflects the probability that the weed will enter the PRA area. The probability of entry of a pest depends on the pathways from the exporting country to the destination, and the frequency and quantity of pests associated with them. The higher the number of pathways, the greater the probability of the pest entering the PRA area. Note that the ratings are designed to reflect the risk of entry through unintentional pathways of introduction. If the primary pathway of introduction is the intentional importation of plants for planting, a rating of "high" is automatically assigned, and the assessment continues with probability of establishment (below).

Rating = negligible (numerical score is 0): The probability of entry is extremely low given the combination of factors including the distribution of the weed at source, management practices applied, low commodity volume, low probability of weed survival in transit, low probability of transfer to a suitable habitat, or low probability of distribution in the PRA area given the intended use of the commodity.

Rating = low (1): The probability of entry is low but clearly possible given the expected combination of factors necessary for entry described above.

Rating = medium (2): Weed entry is likely given the combination of factors necessary for entry described above.

Rating = high (3): Weed entry is very likely or certain given the combination of factors necessary for entry described above.

Guidelines for Rating Probability of Establishment

This rating reflects the probability of establishment and potential range of a weed or invasive plant introduced into the PRA area. Factors considered include the climatic and habitat requirements of the species and the ease with which it may obtain these in the PRA area, as well as adaptabilty and other factors affecting its life cycle and survival. Introduced plants can be expected to behave as they do in their native area (or in other areas where they have been introduced) if suitable habitats and climatic conditions are present. Analysis may involve the use of geographic information systems (GIS) and other computerized systems such as CLIMEX to model and map potential distributions in PRA area.

Rating = negligible (numerical score is 0): The weed has no potential to survive and become established in the PRA area.

Rating = low (1): The weed has potential to survive and become established in 0-3 Plant Hardiness Zones (e.g. NAPPFAST zones 7-9) if the PRA area is all of Canada, or; the weed has potential to survive and become established in approximately one third of the PRA area, if that area is not all of Canada.

Rating = medium (2): The weed has potential to survive and become established in 4-5 Plant Hardiness Zones (e.g. The area up to and including NAPPFAST zones 5 and/or 6) if the PRA area is all of Canada, or; the weed has potential to survive and become established in approximately one third to two thirds of the PRA area, if that area is not all of Canada.

Rating = high (3): The weed has the potential to survive and become established in more than 5 Plant Hardiness Zones (e.g. The area up to and including NAPPFAST zone 4 and beyond) if the PRA area is all of Canada, or; throughout most or all of the PRA area, if that area is not all of Canada.

Guidelines for Rating Probability of Spread

This rating reflects the probability and potential rate of spread of the weed, both into and within the PRA area. A pest with a high potential for spread may also have a high potential for establishment, and possibilities for its successful containment and/or eradication are more limited. Natural means of spread may include wind, water, soil, and live vectors, all of which can transport seed, pollen, and vegetative plant parts, sometimes over great distances. Human-mediated spread may include both intentional and unintentional movement. In the case of plants intended for cultivation, this section will also consider the probability of escape and spread outside of cultivated environments.

Rating = negligible (numerical score is 0): The weed has no potential for spread in the PRA area.

Rating = low (1): The weed has potential for spread locally in the PRA area within a year (some reproductive potential and/or some mobility of propagules)

Rating = medium (2): The weed has potential for spread throughout a physiographical region of the PRA area within a year (e.g., It has either high reproductive potential or highly mobile propagules).

Rating = high (3): The weed has potential for rapid spread throughout its potential range in the PRA area (e.g., It has high reproductive potential and highly mobile propagules).

Guidelines for Rating Potential Economic and Environmental Consequences

This stage of the assessment considers the potential economic and environmental consequences of the weed's introduction in the PRA area. Economic and environmental consequences are considered together as it is not always possible to fully separate them. Information from areas where the pest currently occurs is compared with conditions in the PRA area to estimate the potential importance of the pest. Case histories concerning comparable pests, and intrinsic biological traits that may contribute to pest impacts (e.g., parasitism, allelopathy, thorns, etc.) may also be considered.

Consequences may be direct or indirect, and both should be evaluated as much as is possible. Sometimes indirect effects may be more difficult to evaluate as they require the consideration of side effects of a pest's establishment that may not be immediately apparent. Care should be taken not to take the evaluation of indirect effects to extremes, but to keep them limited to one or two orders of separation away from the direct effects. Probably some of the most common indirect effects are social consequences, secondary habitat consequences of control / eradication efforts and secondary habitat consequences of ecological changes induced by the pest.

Economic factors considered include impacts on crop production costs, yield, quality, and marketability, and variability of impacts among crop cultivars or varieties. Crops considered include cultivated and forest species, but only those that are managed.

Environmental factors considered include impacts on non-agricultural host(s) and natural ecosystems. This may include subjective consideration of direct biotic effects on endangered or threatened natural species and reduction of biodiversity. Examples of abiotic impacts considered include ecosystem destabilisation, environmental degradation, fire, and impacts on recreation and aesthetic values. Also considered are impacts on human and animal health, and indirect environmental effects of risk management options (e.g., pesticides).

A more detailed economic assessment than provided here may be required in some cases.

Rating = negligible (numerical score is 0): The weed has no potential economic impact and no potential to degrade the environment or otherwise affect ecosystems (e.g., causes none of the above-listed impacts).

Rating = low (1): The weed has a limited potential to cause economic impacts or affect the environment (e.g., causes one of the above-listed impacts unless there is potential to reduce populations of threatened or endangered species, in which case rating should be high).

Rating = medium (2): The weed has moderate potential to cause economic impacts (e.g., causes two of the above-listed economic impacts or any one of these impacts on a wide range of economic plants, plant products, or animals (over 5 types)) or it has potential to cause moderate changes in the environment, such as obvious change in the ecological balance (affecting several attributes of the ecosystem), as well as moderate recreation or aesthetic impacts. (e.g. Causes two of the above-listed environmental impacts).

Rating = high (3): The weed has significant potential to cause economic impacts (e.g., Causes all the above-listed impacts, or causes any two of these impacts on a wide range of economic plants, plant products, or animals (over 5 types) or it has potential to cause major damage to the environment with significant losses to plant ecosystems and subsequent physical environmental degradation (eg. has potential to reduce populations of threatened or endangered species, or affects three or more of the above-listed impacts).

Guidelines for Rating Uncertainty

Risk ratings are subjective, and based on interpretation of available information. Therefore, risk assessors are not always completely confident of the ratings assigned to risk elements. Uncertainty ratings are designed to give the reader an indication of the level of confidence associated with a particular risk rating. The level of confidence depends largely on the quality or nature of the evidence available. In general, quantitative data, multiple independent sources or expert information will lower uncertainty. By contrast, low-quality sources, conflicting information or a lack of evidence will raise uncertainty. In cases where evidence is lacking for a species and information about congeners is used to support risk ratings, uncertainty will also be higher.

Uncertainty Interpretation / Meaning Examples to justify the uncertainty rating
Negligible There is very little doubt about the risk rating. Additional or better information is very unlikely to change the risk rating.
  • all of the evidence pertaining to the risk element comes from primary sources (e.g. original research papers published in peer-reviewed journals, a survey conducted by an NPPO with methodology approved by CFIA, a request to import, etc.)
  • available information is consistent
  • the risk rating is based on area- or species-specific data
  • the species is well-studied or known
  • the situation can be easily predicted
  • the risk assessor is an expert on the pest or has communicated directly with an expert on the pest
Low There is little doubt about the risk rating. Additional or better information will probably not change the risk rating.
  • the evidence pertaining to the risk element comes from primary and secondary sources (e.g. books, reviews, pest survey data for which methodology is uncertain or unknown, etc.)
  • available information is straightforward and any controversies are historical only
  • the risk rating is based on area- or species-specific data
  • the species is well-studied or known and a lack of evidence suggests the issue is not relevant
Medium There is some doubt about the risk rating. Additional or better information may change the risk rating.
  • the evidence pertaining to the risk element comes from moderate- or low-quality sources (e.g. gardening websites, local journals, dated agricultural bulletins, non-rfereed sources, etc.)
  • some of the available information is ambiguous or contradictory
  • the risk rating is based on examples from other related, well-known species in the same genus
  • the species is moderately well-studied or known and a lack of evidence suggests the issue is not relevant
High There is considerable doubt about the risk rating. Reliable information is lacking. Additional information could significantly change the rating.
  • there is no direct evidence for the risk element and sources are of poor quality
  • most of the available information is ambiguous or contradictory
  • the risk rating is based on examples from other related, well-known species in the same family
  • the species is poorly studied or known

Guidelines for Calculating Overall Risk and Uncertainty Ratings for Probability of Introduction and Spread

The individual risk ratings given in examining the three probability factors, (i.e., probability of entry, probability of establishment and probability of spread) are taken into consideration to produce an overall rating for the probability of introduction and spread of the weed. This is done by translating the individual risk ratings into numerical scores (negligible = 0; low = 1; medium = 2; high = 3), and multiplying the numerical scores to produce a product score, as follows:

Probability of introduction and spread = Probability of entry x Probability of establishment x Probability of spread

Depending on the resulting overall score, the consequences of introduction will be rated as negligible (0), low (1-3), medium (4-12) or high (>12). The underlying assumption behind this approach is that the three factors are dependant, that is, all three would need to occur for there to be a risk. A parallel process is not necessary for potential economic and environmental consequences, because in that case there is only one rating. The table below is provided as a guide.

Product Scores (Probability of Entry X Probability of Establishment X Probability of Spread) Overall Rating for Probability of Introduction and Spread
0 Negligible
1 - 3 Low
4 – 12 Meduim
>12 High

As with the risk ratings, the individual uncertainty ratings are also combined for the three probability factors (i.e., probability of entry, probability of establishment and probability of spread) to produce an overall uncertainty rating for the probability of introduction and spread of the weed. This is done by translating the individual uncertainty ratings into numerical scores (negligible = 0; low = 1; medium = 2; high = 3), and adding the numerical scores. Depending on the resulting overall score, the uncertainty will be rated as negligible (0), low (1-3), medium (4-6) or high (7-9). The underlying assumption behind this approach is that the three uncertainty scores are additive, not dependant. As with the risk ratings, a parallel process is not necessary for potential economic and environmental consequences, because in that case there is only one rating. The table below is provided as a guide.

Additive Scores for Uncertainty of Overall Probability of Introduction and Spread Overall Rating Uncertainty of Probability of Introduction and Spread
0 Negligible
1 - 3 Low
4 – 6 Medium
7-9 High
Date modified: