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RMD-16-02: Pest Risk Management Document for Arundo donax (giant reed) in Canada

November 2017

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Executive Summary

This Risk Management Document (RMD) is part of the risk analysis process examining the risk associated with importation, cultivation and trade of Arundo donax (giant reed) in Canada. The RMD includes the pest risk assessment, risk management considerations and potential risk management measures which may be applied to reduce the identified risk to acceptable levels. It identifies potential risk management approaches, examines regulatory policy options and is used to seek input from a range of potentially affected stakeholders.

Arundo donax is a tall, fast-growing perennial reed grass native to warm temperate and subtropical regions of the Old World. It has been cultivated for a variety of purposes, including biofuel, pulp and paper, light construction material, animal fodder, reed and pipe making, windbreaks, erosion control, and medicinal and ornamental use. However, A. donax has become highly invasive in riparian and wetland areas of some countries outside of its native range, including the United States and Mexico. It is recognized by some scientists as one of the World's Top 100 plant invaders (Lowe et al. 2000). It is not known to have naturalized in Canada and its distribution may be limited to garden and small-scale research plantings.

A weed risk assessment was completed in 2006 by the Canadian Food Inspection Agency (CFIA), concluding that A. donax presents a phytosanitary risk to Canada. A preliminary stakeholder consultation was undertaken in 2007. Renewed interest in planting A. donax as a biofuel crop led the CFIA to re-examine its regulatory status. Two risk management options, as detailed in this RMD, were presented to stakeholders for comments. Under Option 1, A. donax would be regulated as a pest under the Plant Protection Act. Under Option 2, A. donax would not be regulated as a pest under the Plant Protection Act.

The CFIA has decided to regulate A. donax as a plant pest under the Plant Protection Act. Importation, domestic use and movement of A. donax is prohibited and any imported commodity must be free propagative parts of A. donax. This decision is based on the outcomes of the risk analysis and the responses from the stakeholder consultation.

Preface

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, and as such is responsible for conducting pest risk analyses to support decisions about the management of phytosanitary risk.

Pest risk analysis (PRA) involves three processes; risk assessment, risk management and risk communication. Pest risk assessment provides the scientific basis for the overall management of risk. It involves identifying hazards and characterizing the risks associated with those hazards by estimating their probability of introduction and establishment as well as the severity of their economic impact. 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. Pest risk communication is an additional component of PRA that is common to all stages of the PRA process.

This risk analysis follows the format and terminology used by the IPPC. For further information on the IPPC standards for PRA, refer to the International Standards for Phytosanitary Measures.

1.0 Purpose

This risk management document (RMD) records the final risk management decision with regard to regulation of Arundo donax.

2.0 Scope

This RMD examines the phytosanitary risks associated with the introduction of Arundo donax into Canada, outlines potential risk management options and summarizes the CFIA's decision to regulate Arundo donax as a regulated pest for Canada.

Information pertaining to current import requirements for specific plants or plant products may be obtained from the Canadian Food Inspection Agency (CFIA) Automated Import Reference System (AIRS).

Additional points for consideration:

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

3.0 Definitions

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

4.0 Background for Risk Management Documents

This RMD describes the environmental, economic and social risk associated with A. donax and the management options available to mitigate that risk.

It is well-recognized that the risk posed by invasive species in Canada is a shared risk and therefore a shared responsibility among government jurisdictions and stakeholders. Once it is determined that a particular plant is a pest, the CFIA develops and enforces domestic regulatory measures to mitigate the risks associated with the plant species. The CFIA's regulatory approach is based on the principles of Pest Risk Analysis using the most up-to-date science, consultation and regular review.

5.0 Pest Risk Assessment

Pest risk assessment provides the scientific basis for the overall management of the risk posed by a potential pest. This section addresses the probability of entry, establishment and spread of A. donax in Canada as well as the potential economic and environmental impacts.

The following information is based on the CFIA Weed Risk Assessment for A. donax initiated in 2006 (CFIA 2006) and updated in, 2011 (CFIA 2011), 2014 and 2016.

Guidelines for rating the risk assessment and uncertainty elements are available upon request.

5.1 Identity of Organism

Name: Arundo donax L. (Poaceae)

English common names: giant reed, bamboo reed, giant cane, Spanish reed, wild cane (Rojas-Sandoval et al. 2014)

French common names: canne de Provence, grand Roseau (USDA-ARS 2016)

Description of organism: Arundo donax is a perennial grass with strong, fleshy rhizomes, deeply-penetrating fibrous roots and tall stems (2-10 m) (Rojas-Sandoval et al. 2014). It is the tallest and largest ornamental grass species after bamboo (GISD 2016). Individual stems (culms) are usually erect, 1-3.5 cm thick, and have glabrous nodes and hollow internodes (Barkworth et al. 2003). The outer stem tissue is hard, brittle and glossy (Rojas-Sandoval et al. 2014). Leaves are blue-green, 30-100 cm long and arranged alternately in two vertical rows on opposite sides of the stalk (Barkworth et al. 2003). Inflorescences are plume-like panicles, 30-65 cm long, found at the upper tips of stems (Rojas-Sandoval et al. 2014; Barkworth et al. 2003). The flowering unit is a spikelet 10-15 mm long with 2-4 florets (Barkworth et al. 2003). Seeds are light brown, oblong caryopses 3-4 mm long (Barkworth et al. 2003).

Variegated strains have originated from bud variations that have been isolated and further propagated (Shamel 1917). Selection of such off-shoots has led to the propagation of a number of variegated forms that, with the exception of variegated leaves, do not differ significantly from the green form (Rojas-Sandoval et al. 2014; Perdue 1958). The common variegated varieties and cultivars that are currently available in the horticultural trade are referred to as A. donax var. versicolor, A. donax var. variegata; A. donax 'Variegata', A. donax 'Variegata Superba', A. donax 'Peppermint Stick', and A. donax 'Golden Chain'. Most of the variegated varieties/cultivars have white and green-striped leaves and are shorter in stature (i.e., 1-5 m tall as compared to 3-10 m tall) than the typical green form of A. donax (Barkworth et al. 2003; Huxley et al. 1999; Oakes 1990; Perdue 1958; Shamel 1917). In the case of 'Golden Chain', leaves are yellow and green-striped. Other than the shorter stature and variegated foliage, variegated A. donax is identical in shape, texture, and growth habit to the green form of the plant (Oakes 1990). An additional ornamental cultivar with wide leaves is known as A. donax 'Macrophylla'. This cultivar has grey-green to blue-green leaves that are wider than the green form (i.e., 100 x 9 cm as compared to 60 x 6 cm) (Huxley et al. 1999; Griffiths 1994).

'Nile Fiber' is a patented cultivar of A. donax grown for landscape and biomass production (Carroll and Volotin 2014). Derived from a natural cane sport of A. donax, this cultivar may be distinguished from standard ecotypes in having a purple band below each node section and in lacking serrated leaf margins (Carroll and Volotin 2014). It is also characterized by increased growth, greater wall thickness, higher germination rates of propagules, extreme vigour and superior fiber for pulp and paper when compared to standard ecotypes of this species (Carroll and Volotin 2014). Plant height can reach as much as 15 m in 2-3 years (Carroll and Volotin 2014).

The Bio-G clone is an improved ecotype of A. donax, also developed for biomass production (Galiltec 2014). It is uniformly produced through tissue culture technology and is described as a resilient and high-yielding energy crop that "augments the positive qualities of A. donax" (Galiltec 2014). This clone is being promoted for biomass production in Honduras (La Prensa 2013).

5.2 Organism Status

Arundo donax is not reported to occur in natural ecosystems in Canada (Brouillet et al. 2010; Barkworth et al. 2003; Scoggan 1979). It has been available from some garden centres and nurseries in southern British Columbia, southern Ontario, Quebec, Nova Scotia, and possibly elsewhere in Canada. In a 2009 CFIA Ornamental Grass Inventory, A. donax was available at one of 42 Canadian nurseries visited. This species has also been grown in botanical gardens in Canada (e.g., Vancouver, BC, Niagara Falls, ON, and Montreal, QC). Several small-scale research trials for biomass production have also been planted in Nova Scotia and Ontario in recent years. As well, propagules of A. donax have been produced in greenhouses in Ontario for export. Based on this information, A. donax is considered present in Canada in cultivation only and not in natural ecosystems.

Arundo donax is found throughout the southern United States, with fewer, scattered occurrences in the central and northern United States (USDA-NRCS 2016). The most northerly reports are from the states of Washington, Oregon, Nebraska, Indiana, West Virginia, Maryland and Delaware (Kartesz 2015).

5.3 Current Regulatory Status

Arundo donax is not regulated federally in Canada. However, while it is undergoing a risk analysis process, regulatory measures are in place to control further introduction until the process is completed. It is not regulated provincially; however, the province of British Columbia has proposed to add it to the British Columbia Prohibited Noxious Weed List (BCIMISWG 2015).

In the United States, A. donax is not regulated as a Federal Noxious weed; however it is listed as a noxious weed in California, Colorado, Nevada and Texas (USDA-NRCS 2016; CWMA 2016; CDFA 2015; State of Nevada 2003). It is also on the State of Washington Department of Agriculture's (2015) quarantine list, with the exclusion of variegated cultivars, and is on the monitor list of the Washington State Noxious Weed Control Board (WSNWCB 2010). In Oregon, A. donax has been designated as a quarantine species; however, rules have been established to allow A. donax to be grown as a biofuel under permit conditions and variegated varieties to be grown for ornamental use (Oregon Secretary of State 2013). In addition, it is listed as a potential aquatic invasive species by the Nebraska Game and Parks Commission (NGPC 2015).

5.4 Probability of Entry

Intentional importation of plants for planting is the most significant pathway of entry for A. donax. There are reports of it having already been imported into Canada and planted for ornamental and biofuel purposes (e.g., Peters et al. 2016). There has also been interest in cultivating A. donax for pulp and paper production in Canada.

Intentional importation of plant parts not for propagation is another potential introduction pathway for A. donax as it used for such a wide variety of purposes (e.g. biofuel, musical reed making, basket making, decorative arrangements, and medicines). The risk posed by this pathway would be from the importation of fresh plant material rather than dry material.

Most other introduction pathways for A. donax, including non-intentional introduction pathways and natural means of dispersal, are unlikely as there are no populations near the Canadian border (USDA-NRCS 2016) and because this species is not reported to produce viable seed in most locations where it is apparently well-adapted (Perdue 1958). It has not been known to produce viable seed in the United States (Bell 1997; Else 1996).

Risk Rating for Probability of Entry: Probability of entry is "High" because A. donax has already entered Canada. The primary pathway is intentional importation of plants for planting.

Uncertainty and Information Gaps: Uncertainty is considered "Negligible" because it is known that A. donax is present in Canada to a limited extent in cultivation.

5.5 Probability of Establishment

Arundo donax is native to warm temperate and subtropical regions of the Old World. Its centre of origin is likely Asia (Mariani et al. 2010) or the Mediterranean (Perdue 1958). It has been cultivated for millennia in southern Europe, North Africa, the Middle East and Asia (Lambert et al. 2010; Perdue 1958). Arundo donax has also been widely introduced in the New World, where it has naturalized in many countries from the United States south to Argentina and Chile (Rojas-Sandoval et al. 2014). Arundo donax has also been introduced into South Africa, Australia, New Zealand, and many islands of the Pacific and Atlantic oceans (Rojas-Sandoval et al. 2014). In the United States, it has naturalized below 40°N (USDA-NRCS 2016). The densest infestations in the United States are found along coastal rivers of southern California and the Rio Grande River in Texas (Yang et al. 2011). A plantation at Prosser, WA (46°N) has overwintered successfully (S. Fransen, pers. comm.). In Canada, A. donax has survived winters in gardens in Niagara Falls, ON and Vancouver, BC. The plants are able to survive very low temperatures when dormant (Perdue 1958) but prefer areas where regular or prolonged periods of freezing do not occur (Rojas-Sandoval et al. 2014; DiTomaso and Healey 2007). In colder climates, the plants are killed to ground level, but new stems emerge from the crowns the following spring (Oakes 1990). In Virginia, in areas of USDA Plant Hardiness Zones 6 or 7, culms go dormant in winter and sprout new culms from above-ground nodes in spring (Barney 2014; Mann et al. 2013).

Arundo donax is a hydrophyte that grows best in moist, well-drained soils along ditches, streams, rivers, lakes and floodplains (GISD 2016; Weber 2003). However, it tolerates a wide range of environmental conditions, including low light levels, saline soils and areas affected by drought (Quinn and Holt 2008; Hoshovsky 1986; Perdue 1958). Additional habitats of this species include agricultural areas, open forests, grasslands, scrublands, coastlands, deserts, roadsides and urban areas (Rojas-Sandoval et al. 2014). It grows well under cultivation. Availability of suitable habitats would not likely be a limiting factor for A. donax establishment in Canada.

A map of the predicted distribution of A. donax in North America is shown in Figure 1. The map was produced for the USDA-APHIS (2012) weed risk assessment for A. donax and is based on the species' distribution elsewhere in the world, including occurrence records from the Global Biodiversity Information Facility (GBIF 2011). It represents the joint distribution of USDA Plant Hardiness Zones 6-13, areas with 0-100+ inches of annual precipitation, and the following Köppen-Geiger climate classes: tropical rainforest, tropical savanna, steppe, desert, Mediterranean, humid subtropical, humid continental warm summers, humid continental cool summers, and marine west coast (USDA-APHIS 2012). Plant hardiness zones are based on 10-year averages and follow procedures outlined in Magarey et al. (2008). Based on the map, it is estimated that about 2 percent of Canada and 57 percent of the United States is suitable for the establishment of A. donax. In Canada, the suitable areas include southern and coastal British Columbia, southern Ontario, most of Nova Scotia, and parts of Prince Edward Island and Newfoundland (Figure 1). The cultivar 'Nile Fiber' is reported to be hardy to zone 4 (Carroll and Volotin 2014), which would include most of the productive agricultural land in southern Canada, including the Prairie provinces. It may, therefore present a greater probability of establishment in Canada than the standard ecotypes of this species.

Figure 1. Predicted distribution of Arundo donax in Canada and the United States (map insets for Hawaii and Puerto Rico are not to scale) (USDA-APHIS 2012)
Figure 1. Predicted distribution of Arundo donax in Canada and the United States. Description follows.
Description for photo - Figure 1. Predicted distribution of Arundo donax in Canada and the United States

This figure is a map of North America and shows the areas where Arundo donax could survive in Canada and the United States in red. Areas in Canada include the portions of the provinces of BC, ON, NL, NS, PE. Much of the United States is included, with the exception of Alaska, the colder inner continental region, and parts of the northeast.

Climate change may affect the potential distribution of A. donax in Canada in the future. Warming temperatures, especially in winter, may increase its probability of establishment in areas where cold temperatures are currently too severe, and improve its growth and competitiveness in areas that are currently tolerable (Glaser and Glick 2012; Hellmann et al. 2008). Winter temperatures in Canada are expected to increase significantly by the middle of this century (Government of Canada 2013). In most of the provinces with areas currently estimated to be suitable for A. donax (BC, ON, NL, NS, PE), summer temperatures, as well as winter and summer precipitation, are also projected to increase (Environment and Climate Change Canada 2016). These changes represent shifts toward more favourable climate conditions for A. donax. Furthermore, A. donax responds favourably to increased atmospheric CO2 concentrations, with increased biomass production and improved water use efficiency (Nackley et al. 2014).

Risk Rating for Probability of Establishment: Probability of establishment is rated "Medium" for A. donax, as it has the potential to become established in five Plant Hardiness Zones in Canada (i.e., USDA Plant Hardiness Zones 6-10). Note that some cultivars may have a higher potential for establishment than the standard ecotypes (e.g., 'Nile fiber' is reported to be hardy to Zone 4) (Carroll and Volotin 2014).

Uncertainty and Information Gaps: Uncertainty is considered "Low" because the distribution of A. donax is well studied and documented in reliable sources.

5.6 Probability of Spread

In its native range, A. donax is reported to produce seeds that develop on the large plume-like inflorescences and are dispersed by the wind (Rojas-Sandoval et al. 2014). However, A. donax does not appear to produce viable seed in places where it has been introduced and is apparently well-adapted (Weber 2003; Perdue 1958). Most natural spread is vegetative and occurs by means of stem and rhizome pieces, layering, and clump expansion. Stem and rhizome pieces are successful as long as they contain a bud (Witje et al. 2005; Boose and Holt 1999; Else 1996); they can sprout at any time of the year (Mann et al. 2013). Stem and rhizome fragments disperse downstream along watercourses following disturbance and initiate new colonies (Bell 1997). In established plants, rhizomes extend approximately 0.5 m per year (Rojas-Sandoval et al. 2014). Layering occurs when a stem develops roots while attached to the parent plant and then subsequently detaches to become an independent plant. This has been observed in flood zones, and can lead to much faster expansion (7.4 times faster in a California study, or 3.7 m per year) (Boland 2006). Arundo donax also exhibits a remarkable growth rate, with a photosynthetic rate similar to that of C4 species, even though it is a C3 species (Rossa and Tueffers 1998). Under favourable conditions, it can grow as much as 10 cm per day (Perdue 1958). In a California study, A. donax grew 3-4 times faster than native woody riparian plants, which combined with its ability to resprout quickly after fire and to respond favourably to nutrient enrichment, promoted its spread and dominance after wildfires (Coffman et al. 2010). Arundo donax is not known to hybridize (Gordon and Gantz 2008).

Human-mediated dispersal has been the most important factor contributing to the introduction and spread of A. donax in many parts of the world. A. donax is intentionally planted for a variety of purposes, which leads to opportunities for its escape from cultivation. Of particular concern is its cultivation near water sources. Non-intentional dispersal of stem or rhizome fragments can result from human disturbance and mechanical damage in or along waterways and wetlands, such as by motor boats and other water equipment, as well as by bulldozers and heavy equipment used for its removal (Rojas-Sandoval et al. 2014; Saltonstall et al. 2010; Boland 2008).

Arundo donax spreads less in drier upland areas than in riparian or wetland habitats, as it is limited to slow lateral spread by culm expansion (Barney 2014; Boland 2006), and lack of moisture can act as a natural control measure to prevent the species from spreading. For example, A. donax is not likely to spread beyond irrigated areas into dry soils that lack irrigation (Steve Fransen, pers. comm.). In a study by Smith et al. (2015a), spread by layering was not observed to occur in an agricultural setting in Virginia. However, in cultivated areas, the species can still spread when plant fragments are caught up in garden waste, soil or agricultural machinery and transported to more favourable locations (Rojas-Sandoval et al. 2014). Rapid spread by earth-moving equipment is evident from its proliferation in construction sites and newly graded restoration areas, even in some areas far from the water table (Rieger and Kreager 1989). An introduced subspecies of Phragmites australis provides an interesting parallel because it is closely related, exhibits low seed production, and has spread dramatically throughout eastern Canada along roadsides with construction and maintenance activities (S. Darbyshire, pers. comm.). Similarly, A. donax has been observed to colonize several kilometres of roadsides in places such as California and southern Europe (Pilu et al. 2013).

Risk Rating for Probability of Spread: Probability of spread is rated "Medium" for A. donax. Its potential for natural spread is limited (i.e., it is unlikely to produce seed in Canada, clump expansion is local and propagule dispersal is limited to riparian habitats and is dependent on disturbance), though its potential for human-mediated spread is significantly higher (i.e., through intentional planting and non-intentional movement of plant parts through construction, maintenance and agricultural activities).

Uncertainty and Information Gaps: Uncertainty is considered "Medium" for probability of spread because the extent of human-mediated spread that would occur in Canada is unknown, and depends on many factors (e.g. how much and where it would be planted).

5.7 Potential Economic and Environmental Consequences

Arundo donax has become invasive in many parts of the world, including southern Africa, Spain, Portugal, Italy, the southern United States, Mexico, the Caribbean, South America, Australia, New Zealand and many of the Pacific Islands (Rojas-Sandoval et al. 2014; Mascia et al. 2013; Holmes et al. 2005; Wittenberg 2005; Weber 2003). It falls within a subset of invasive plants known as "transformer" species, which not only naturalize and spread outside their native ranges, but cause clear ecosystem impacts and change ecosystems over substantial areas (Csurhes 2009; Spencer 2005; Richardson et al. 2000). A. donax meets these criteria because it is an excessive user of resources (water, light) (Watts and Moore 2011; Richardson et al. 2000) and because it alters the hydrology, nutrient cycling, fire regime, community structure and biodiversity of riparian and wetland areas (GISD 2016, USDA-APHIS 2012; McWilliams 2004; Bell 1997). It forms dense, tall monocultures that can cover hundreds of acres (Rojas-Sandoval et al. 2014; Weber 2003) or tens of thousands of acres (e.g., southern California) (Bell 1997). Stands are estimated to consume as much as 2000 litres of water per square meter of plants per year, or three times more water than native plants, potentially reducing groundwater availability (DiTomaso and Healy 2007; McWilliams 2004; Bell 1997; Iverson 1994). Its large root masses trap sediments and alter flow regimes (Bell 1997). Dominated areas tend to have warmer warmer temperatures, lower oxygen concentrations and higher pH (Bell 1997). The dead shoots are highly flammable, increasing the susceptibility of riparian corridors to fire and allowing fires to spread quickly (Giessow et al. 2011; Coffman et al. 2010; DiTomaso and Healy 2007; Weber 2003). It acts as a "ladder fuel" by providing vertical fuel continuity from the surface to the crowns of shrubs and trees and facilitating the spread of fire from one layer to the other (Brooks et al. 2004).

The impacts of A. donax on plant biodiversity in riparian and wetland areas are significant. Arundo donax forms monocultures that crowd out native plant species (GISD 2016; Csurhes 2009). In California, it often displaces cottonwood/willow riparian forests (Bell, 1997). In Italy (Sardinia), it threatens populations of a rare, congeneric species, Arundo micrantha (Mascia et al. 2013). In Spain, it was observed that habitat features differed between invaded and non-invaded areas, with the largest leaf litter deposition and soil carbon stock in the invaded areas, as well as the poorest herbaceous understory (Maceda-Veiga et al. 2016).

Dense colonies of A. donax offer little food or habitat to native fauna. In southern California, A. donax is responsible for habitat loss for birds such as the endangered least Bell's vireo and the threatened willow flycatcher (Bell 1997), and its invasion is associated with reduced bird diversity and abundance in general (D'Antonio et al. 2011). This species has also reduced habitat for the endangered arroyo toad in California (Lawson et al. 2005). Furthermore, it is associated with a reduction in the abundance and diversity of aerial arthropods in riparian systems of central California (Herrera and Dudley 2003). Aquatic insect growth is also negatively impacted by A. donax litter, as compared to native litter, as it is characterized by a high silica content, the presence of toxic compounds (alkaloids), and low nutritional quality (D'Antonio et al. 2011; Going and Dudley 2008). A negative relationship between A. donax presence and soil macro-arthropod diversity, abundance and body size has been demonstrated in Spain as well (Maceda-Veiga et al. 2016). Due to the effects of this species on water quality, riverine areas dominated by A. donax also have lower diversity of aquatic animals, including fishes (Bell 1997; Dunne and Leopold 1978).

Several authors provide estimates of costs related to A. donax infestations. For example, over $2 million was spent to remove A. donax from a dam in Ventura County, California, prior to deconstruction of the dam (D'Antonio et al. 2011). Removal costs vary but can exceed $10,000 (US) per hectare and can lead to rapid re-infestation if efforts are not continued over many years (Rojas-Sandoval et al. 2014). In the Santa Margarita river system in California, it cost almost $10,000 (US) per hectare to treat A. donax using a foliar spray of glyphosate in the first year alone and required 150 hours per hectare of labour (Lawson et al. 2005). Costs were lower in subsequent years, such that over four years, treatment costs totalled $13,550 per hectare and required just under 200 hours of labour per hectare (Lawson et al. 2005). These costs did not include manipulation or removal of the huge quantities of dead biomass that resulted from treatment nor the costs associated with program management and reporting (Lawson et al. 2005). A report by Giessow et al. (2011) stated that over a period of 15 years, $71 million (US) was spent on A. donax control in a 2,863 ac (1158 ha) study area between Monterey and San Diego, California, indicating a cost of about $25,000 per acre ($61,300 per ha) over that period.

Multiple studies have examined the potential net economic benefits of A. donax control programs, and all resulting benefit to cost ratios have been positive (Giessow et al. 2011). In the most intensive of these analyses, Seawright et al. (2009) estimated a benefit-cost ratio of $4.38 (US) for every dollar invested in a proposed 50-year A. donax biological control project over a 170 mile river section of the Texas Lower Rio Grande Valley. The analysis estimated the benefits of water saved from reducing the A. donax infestation and used for agricultural purposes.

Arundo donax can also negatively impact tourism, outdoor recreation, fishing, irrigation, hydroelectric power generation, property values and law enforcement. This species affects water usage related to many of these industries and activities by constricting or obstructing waterways, re-routing overflow, reducing visibility and drying out water channels (Rojas-Sandoval et al. 2014; USDA-APHIS 2012). During storm events, large interconnecting root mats accumulate behind bridges and culverts, affecting their function and sometimes causing damage to, or even loss of the structure (GISD 2016; Csurhes 2009; Coffman et al. 2004). Damage or loss can also occur to properties when stream water is diverted into new paths by A. donax stands as they collect sediments and cause the sediment surface beneath them to rise (Rojas-Sandoval et al. 2014). Along the United States-Mexico border, tall, impenetrable stands of A. donax also interfere with law enforcement activities (Goolsby et al. 2016). Most of these impacts are related to A. donax infestations in riparian areas and wetlands, although this species could also be of potential concern along roadsides and in other disturbed areas where conditions are favourable.

Arundo donax, which is often grown under cultivation, is not generally considered to be an agricultural weed. Crop yields may be affected indirectly from invasions of A. donax in nearby ditches and irrigation canals, where water flow is impeded or water quantity is reduced by the uptake from the plant. Costs of herbicide or mechanical control in field margins and ditches could lead to lower crop returns. By promoting wildfire, it could also put nearby commodities in danger and cause significant economic losses. It could potentially invade wild rice, which grows in shallow lakes and rivers in Canada (Oelke 1993). Since it is unlikely to produce seed in Canada, it would not likely contaminate Canadian seed or grain commodities. It is not toxic to livestock (Cheatham and Johnston 1995). Along the Rio Grande River in Texas, infestations of A. donax facilitate the introduction of cattle fever ticks from Mexico (Gooslby et al. 2016; Esteve-Gassent et al. 2014).

Risk Rating for Potential Economic and Environmental Consequences: Potential economic and environmental consequences are rated "High" for A. donax, as it has the potential to cause major damage to the environment (i.e., changes to ecosystem processes, community structure and function, loss of biodiversity), it is difficult and costly to control, and it can negatively impact a variety of water-based industries.

Uncertainty and Gaps: Uncertainty is considered "Low" as the species is well studied and there is direct scientific evidence on environmental effects of this species from the United States and other countries where A. donax has been introduced.

5.8 Summary

The following table summarises the risk and uncertainty ratings for A. donax, assigned in each section of the risk assessment, above.

Table 1. Risk and uncertainty ratings for the A. donax risk assessment
Risk Rating Uncertainty
Probability of Entry High Negligible
Probability of Establishment Medium Low
Probability of Spread Medium Medium
Overall Probability of Introduction and Spread Medium Low
Potential Economic and Environmental Consequences High Low

5.9 Technical Issues for Consideration

5.10 Conclusions

Arundo donax is a tall, fast-growing perennial reed grass native to warm temperate and subtropical regions of the Old World. This species has a history of cultivation and has been used for a wide variety of purposes. Its rapid growth makes it attractive for production of biofuel, fibre and pulp. A. donax is currently present in Canada in limited areas under cultivation. The evidence examined in this risk assessment suggests that A. donax has the potential to establish and spread in some parts of Canada, particularly parts of British Columbia, Ontario, Nova Scotia, Prince Edward Island and Newfoundland. Within these provinces, riparian and wetland areas in USDA Plant Hardiness Zones 6 and above are particularly at risk. Some cultivars which are hardier than the standard ecotypes may place additional parts of Canada at risk (e.g., the cultivar 'Nile Fiber" is reported to be hardy to Zones 4 and above). The potential economic and environmental impacts of A. donax are high. It has a history of invasiveness elsewhere, in the United States, Australia, South Africa and Europe. Arundo donax has been described as a "transformer" species as it is a heavy resource user and has the potential to dramatically alter habitats and ecological processes. Control of A. donax is difficult and expensive.

6.0 Risk Management Considerations

6.1 Pest Risk Assessments from Other Jurisdictions

Weed risk assessments have also been conducted on A. donax at the federal level for the United States and at the state or similar administrative level for Oregon, Florida and Hawaii (U.S.), Queensland (Australia) and the Bonin Islands (Japan).

Results or conclusions of the various weed risk assessments were as follows:

6.2. Environmental Consequences

Values potentially at risk due to the presence of A. donax in Canada include plant and animal diversity in riparian and wetland areas, water quality, water use for recreational activities (e.g., tourism, boating, fishing), irrigation, navigation or hydroelectric power generation, property values in infested areas, visibility along roadsides, flood control, and fire control (see Section 5.7). Commercial production could also potentially affect land use through the conversion of large tracts of marginal land to monocultures.

From the pest risk assessment, it is apparent that A. donax poses the greatest risk to riparian and wetland ecosystems. Riparian ecosystems are "among the world's most productive and richest in biodiversity" (Coote and Gregorich 2000). They consist of the vegetated areas along water bodies that form transitions between the water bodies and the upland vegetation (Hilliard and Reedyk 2014). Although an estimate of the percentage of Canada's land area consisting of riparian areas was not found, these areas are commonly found throughout Canada along ditches, canals, creeks, rivers, sloughs, lakes, wetlands and in coulees (Coote and Gregorich 2000). They serve numerous ecological functions, such as reducing the incidence of flooding, reducing sediment and nutrient runoff, facilitating groundwater recharge and discharge, providing food, shelter and/or travel corridors for many wildlife species and aquatic organisms, and improving water quality in general (Hilliars and Reedyk 2014; Coote and Gregorich 2000). Wetlands consist of highly productive areas covered with shallow water on a seasonal or permanent basis, and form many similar functions to riparian areas (Coote and Gregorich 2000). Wetlands include marshes, swamps, bogs, fens and other shallow waters (Coote and Gregorich 2000). They are characterized by hydrophytic plants such as reeds, cattails, rushes, sedges and willows, and support an abundance of wildlife, including waterfowl, amphibians, reptiles, fish, mammals and thousands of invertebrates (Coote and Gregorich 2000).

Over 14% of Canada's area, or over 127 million hectares, consists of wetlands (Coote and Gregorich 2000). If introduced into Canada, A. donax has the potential to put riparian and wetland habitats in areas which are climatically suitable (i.e., plant hardiness zones 6 and higher) at risk.

6.3 Economic Opportunities

Notwithstanding its potential economic and environmental impacts, A. donax may also provide economic opportunities for Canada as it is been cultivated for a variety of purposes, including biofuel, pulp and paper, light construction material, animal fodder, reed and pipe making, windbreaks, erosion control, and medicinal and ornamental use (Mack 2008, Coelho et al. 2007; Barkworth et al. 2003, Perdue 1958).

This document focuses on its use in the biofuel and horticultural industries as these are where the greatest interest currently lies for the cultivation of A. donax in Canada.

6.3.1 Biofuel

The uncertainty of long-term fossil fuel supplies and increasing carbon dioxide emissions has generated interest in alternative fuel sources such as biofuels. Canada is signatory to international agreements to reduce greenhouse gas (GHG) emissions. Biofuels such as ethanol are being promoted as an alternative to fossil fuels and are perceived as one measure to reduce GHG emissions in Canada and meet international and national targets (see Ngo et al. 2008 for a review). Numerous biofuel crops are currently available in Canada.

The Renewable Fuels Regulations (Government of Canada 2010) are a key component of the Government's broader Renewable Fuels Strategy, which is intended to reduce GHG emissions from liquid petroleum fuels. The Renewable Fuel Regulations require an average of 5% renewable content in gasoline across Canada. The Government of Canada has established a number of programs which provide financial incentives to industry to assist in developing biofuels which include next generation, cellulosic, fast-growing grasses (see Ngo et al. 2008 for a review). Over the past few years, there has been interest in importing and planting A. donax for use as a biofuel feedstock. Arundo donax has higher or similar biomass and bioenergy yields to miscanthus, a well-known C4 bioenergy crop (Ge et al. 2016; Smith et al. 2015b). Its rapid growth rate; tolerance to pests, drought and saline conditions; suitability for marginal lands; ability to decontaminate soils; high yielding above-ground biomass production; and positive energy balance make it an attractive candidate for biofuel production (Accardi et al. 2015; Lemons e Silva et al. 2015; Angelini 2009; Barney and DiTomaso 2008). Many of these same attributes are also characteristic of invasive species (Barney and DiTomaso 2008). Any potential new crop should be introduced in an environmentally responsible manner in order to minimize risk of invasion by avoiding planting in or near high risk habitats and having management plans in place to prevent the potential for escape into the environment.

In 2013, the U.S. Environmental Protection Agency (EPA) issued a ruling that approved the use of A. donax as a cellulosic biofuel (US EPA 2013), despite the U.S. Department of Agriculture having assessed it as a high risk species (USDA-APHIS 2012) and working to develop biological control agents to manage invasions (Quinn et al. 2015; USDA-APHIS 2010). Based on the ruling, planting of A. donax is subject to a set of registration, recordkeeping and reporting requirements in order to reduce the risk of it behaving as an invasive species (US EPA 2013). Renewable fuel producers are required to demonstrate that the growth of A. donax will not pose a significant likelihood of spreading beyond the planting area or that such a risk will be minimized through an EPA-approved Risk Mitigation Plan (RMP). The RMP includes best management practices on the production, monitoring, management, transport, collection and processing of the feedstock, as well as mitigation strategies to minimize escape and early detection and rapid response plans for unintended spread. The RMP also includes plans for site closure and identifies a third party auditor who will evaluate the RMP on an annual basis. Biofuel producers using A. donax are further required to provide information on the financial resources or mechanisms available to cover remediation costs should A. donax spread beyond the intended planted area (US EPA 2013).

In 2010, the Australian Government Rural Industries Research and Development Corporation issued a report on the commercial potential of A. donax for pulp, paper and biofuel production (Williams and Biswas 2010). The results of the project indicated that A. donax "produced more cellulosic biomass and sequestered more carbon per annum, using less land and pesticides than any other alternative crop reported in the literature, for warm temperate to subtropical environments and for marginal lands under similar water input regimes (either irrigated with wastewaters or grown dryland with over 450 mm of annual precipitation)". The marginal lands referred to in the report were affected by saline ground water. Similarly, it produced advantageous amounts of dry pulp production per hectare when grown under irrigation. The authors estimated a 22% per year internal rate of return on funds employed for bioethanol production and 18% for pulp and paper production. A weed risk assessment included in the report concluded that A. donax posed a negligible weed risk to terrestrial natural ecosystems in Australia but a very high risk to riparian areas, and that it should not be grown or allowed to spread in riparian areas (Virtue et al. 2010).

In Europe, A. donax is considered to be one of the most promising species for biofuel production (Cavallaro et al. 2014). There is strong interest in its cultivation in Italy, for instance, where A. donax biofuel producers have access to double the incentives from the Government compared to those for wheat or corn (AEEG 2015, cited in TCS 2016). Arundo donax is one of the feedstocks of the Crescentino biofuel facility in Italy, which is the world's largest cellulosic biofuels plant and the first to produce ethanol at a commercial scale using enzymatic conversion of crop residues and energy crops (McGrath 2014; Lane 2013). Although large scale cultivation of A. donax has not yet been realized because vegetative propagation and/or in vitro propagation is very expensive and time-consuming (Pilu et al. 2013), research on in vitro propagation is in progress to overcome this limitation (e.g., Cavallaro et al. 2014).

6.3.2 Horticulture

Several variegated cultivars of A. donax and a cultivar with wide leaves are available in the horticultural industry. They are grown as specimen plants or as accents for borders in gardens. A search of online plant lists and catalogues from garden centers and nurseries across Canada suggests that they are available from a limited number of these facilities, mainly in the warmest parts of Canada including British Columbia, southern Ontario, Quebec and Nova Scotia, but they are not widely available. Ornamental cultivars of A. donax are also grown in botanical gardens in British Columbia, Ontario, Quebec, and possibly elsewhere.

The invasiveness of ornamental cultivars of A. donax has not been tested, however, variegated A. donax cultivars are shorter and are considered less hardy than the regular green form of this species (Huxley et al. 1999; Perdue 1958; Shamel 1917). Despite this, the variegated form appears to be no different in growth form, expansion capability and ecological effects than the normal form. Variegated plants have been observed in river systems in southern California, mostly near residential areas where it has been planted and escaped (A. Lambert, pers. comm.). In Canada, variegated A. donax is known to have overwintered in Niagara Falls, ON and Vancouver, BC, which are in plant hardiness zones 6 and 8, respectively.

The likelihood of variegated plants, or at least portions of plants, reverting back to the normal, green form over time is high. Gardeners are generally advised to prune out green portions of plants in order to maintain a variegated plant; otherwise, the green portions tend to dominate.

6.4 Control

Efficacy of control methods for A. donax has not been tested in Canada. It is extremely difficult and expensive to control in areas where it has become invasive. Although herbicides are the most commonly used management technique in the United States, federal and provincial legislation in Canada restrict the use of herbicides in or near aquatic areas or ditches, etc. Several products are registered by the Pest Management Regulatory Agency (PMRA) for restricted use in and/or near aquatic areas, however these products would also need to comply with other applicable federal and provincial legislation such as the Fisheries Act. In addition, provincial government permits may be required for use of these products. Control by manual methods including hand-pulling, excavating, chopping, cutting or mowing or combinations of these methods is often unsuccessful as rhizome fragments re-sprout and it is extremely difficult to remove all of them. A brief review of the main control methods for A. donax is provided below. As with many other invasive species, integrated control that includes a suite of methods can be more successful than any single method alone (Rojas-Sandoval et al. 2014).

6.4.1 Herbicides

Herbicides are the most common technique for controlling invasive populations of A. donax and may require continued applications over several years. The key to eradicating A. donax is killing the root mass with systemic herbicides (Bell 1997). Foliar spray or cut stem treatments using glyphosate or fluaziprop are effective (DiTomaso and Healy 2007; Weber 2003). In an A. donax removal project in California, both foliar and cut stem treatments were challenging to perform due to the very tall, dense stands which made access difficult and led to huge volumes of dead biomass (Lawson et al. 2005). Aerial application of herbicide using helicopters may be the most efficient application method for large, pure stands of A. donax (Bell 1997). Follow-up assessments and treatments are necessary to kill any regrowth. These types of treatments and applications may not be practical or feasible in Canada.

Herbicide options in or near water sources are more restricted than in upland areas due to environmental and water quality concerns. Puértolas et al. (2010) studied the effect of glyphosate on the structure and function of a river ecosystem in Spain following its use in an A. donax control program. The abundance and number of pollution-tolerant macroinvertebrate species did not change after herbicide application in the already degraded ecosystem; however, specific toxic effects such as feeding inhibition and oxidative stress were observed on two invertebrate species. Currently, there are no products available in Canada that are labelled for control of A. donax and permitted for use in and/or near aquatic areas.

6.4.2 Mechanical Control

Mechanical control using an excavator or bulldozer over large areas is prohibitively expensive and leads to concerns about viable stem and rhizome fragments left over at the control site or accidentally moved in association with vehicles and equipment (USDA-APHIS 2010; Mack et al. 2008; Lawson et al. 2005). In a project in California, the cost of mechanical removal of A. donax was approximately $20,000 ha-1 (Lawson et al. 2005).

For small infestations, plants may be hand-pulled or dug with care to remove all the rhizomes (DiTomaso and Healy 2007; Weber 2003). Cutting or burning the stems to the ground alone are not effective as they do not kill the rhizomes (Weber 2003).

6.4.3 Biological Control

Biological control might be the only feasible and comprehensive solution to large infestations of A. donax (Mack et al. 2008). It is a management tool that may be considered should eradication efforts fail. A biological control program targeting A. donax has been established in the United States, where the USDA Agricultural Research Service is evaluating four insects including the Arundo wasp, Tetramesa romana (Hymenoptera: Eurytomidae), the Arundo scale, Rhizaspidiotus donacis (Hemiptera: Diaspididae), the Arundo fly, Cryptonevra sp. (Diptera: Chloropidae), and the European leaf sheath mining midge, Lasioptera donacis (Diptera: Cecidomyiidae) (Seawright et al. 2009).

The Arundo wasp, Tetramesa romana Walker, was released in 2009 and the Arundo scale insect, Rhizaspidiotus donacis, was released in 2011 (Goolsby et al. 2016; 2013; 2011). It is believed that the impact of the two organisms on A. donax may be complementary (Cortes et al. 2011). A recent evaluation of the wasp indicated that above-ground biomass of A. donax has decreased by 22% across 10 sites (Gooslby et al. 2016). Populations of the scale insect were reported to be increasing in 2013, although it was not equally effective among different A. donax genotypes (Gooslby et al. 2013). It is anticipated that Lasioptera donacis will be released in 2016 (J. Gooslby, pers. comm.).

The biological control program in North America could potentially come into conflict with efforts to establish plantations for biofuel feed stocks.

6.5 Introduction by Natural Dispersal

Arundo donax disperses naturally by water, which carries rhizome and stem fragments downstream, and to a lesser extent, by clump expansion. It is not known to produce viable seeds in North America.

There are currently no populations of A. donax adjacent to the Canadian border (USDA-NRCS 2016; Barkworth et al. 2003). Therefore, given the current range of A. donax, natural dispersal is an unlikely pathway for entry into Canada; and, no mitigation measures for this pathway are required at this time.

6.6 Introduction by Intentional Importation

This is considered the most likely pathway of introduction due to the interest in A. donax as a commercial crop and ornamental plant. Research trials for biofuel production have taken place in Nova Scotia and Ontario and cultivation as an ornamental has occurred to a limited extent in Canada. While a regulatory decision is being made, the CFIA has imposed conditions on importation, cultivation and use, in order to prevent environmental release.

6.6.1 Previous Imports

The CFIA has issued several import permits for Arundo species. Available data make it difficult to identify exactly which species are being imported into Canada as only genus information is required on import permits. The majority of import permits are for horticultural use as rooted plants for planting, and a few are for scientific research or personal use in the form of plant fiber, rhizomes, or in vitro (tissue culture). Based on this information about previous imports and from online gardening and nursery catalogues, there is limited interest in Arundo species for ornamental purposes in Canada.

6.7 Introduction by Non-intentional Importation Pathways

The pest risk assessment for A. donax indicated that non-intentional introduction was unlikely, therefore risk mitigation measures for specific non-intentional pathways have not been identified. The general measure that; under the Plant Protection Regulations, imported commodities must be free from species on the List of Pests Regulated by Canada; will apply to A. donax if it is added to the List of Pests Regulated by Canada.

7.0 Risk Management Options

Risk management involves identifying appropriate management or mitigation options to reduce the risk identified in the risk assessment stage to an acceptable level. The effectiveness and feasibility of each option is discussed including practicality of implementation, impacts on Canadian stakeholders, impacts on the CFIA, impacts on trade relationships, and short-term and long-term sustainability.

The following section addresses each potential pathway of introduction for A. donax and presents potential management options.

7.1 Summary of Risk Management Options

Table 2 summarizes the risk management options considered for A. donax.

Table 2. Summary of risk management options and requirements.
Option Rationale Impacts and Requirements

Option 1: Regulate as a pest under the Plant Protection Act and Regulations

Add A. donax to the List of Pests Regulated by Canada

The CFIA would prohibit the importation of live plants, plant parts and seeds of A. donax, from all sources.

Arundo donax would be considered present in Canada however with a limited distribution and under official control.

  • Option would provide the highest risk based level of protection for Canada.
  • It is more economical to prevent the introduction and spread of an invasive species than control it once it is established.
  • Import would be allowed only under Section 43 permits for scientific research, educational, processing, industrial use or exhibition purposes. However, large scale commercial production would not be permitted.
  • The CFIA would have jurisdictional control over all of the pathways of introduction and domestic movement.
  • The CFIA would have the authority to respond to incursions or existing plants or populations by applying official control measures.
  • Option would protect natural ecosystems (i.e., riparian and wetland areas), biological diversity and species at risk.

Impacts on the CFIA

  • The CFIA would add A. donax to its on-going surveillance efforts for invasive plants.
  • If detected, the CFIA would implement regulatory control measures
  • Known populations would be placed under official control (e.g. eradication, containment) and monitored.
  • The CFIA would develop an education and awareness program targeting ornamental trade and biofuel crops.

Impacts on Stakeholders

  • Parks and recreational users, producers, landowners and the general public would be protected from the potential uncontrolled spread of this species.
  • Arundo donax would not be permitted to be grown commercially as a biofuel or for other uses in Canada, potentially resulting in a loss of opportunity for these industries.
  • Horticultural varieties would be prohibited from import which could result in potential lost opportunities for the horticultural industry.
  • Federal regulation would avoid a province by province approach to legislation, which could be less consistent across Canada and more difficult for Canadians to understand and comply with.

Option 2: Do not regulate as a pest under the Plant Protection Act and Regulations

There would be no phytosanitary restrictions on plant materials being imported into or moving within Canada, regardless of end use.

  • Option would allow for opportunities for use of A. donax as feedstock for commercial biofuel production.
  • The CFIA would have no control over the pathways of introduction or domestic movement.
  • The CFIA would have no authority to respond to incursions or existing plants or populations.
  • Option would not provide federal protection of natural ecosystems (i.e., riparian and wetland areas), biological diversity or species at risk against introductions of A. donax.

Impacts on the CFIA

  • No impact as the CFIA would have no authority in relation to A. donax.

Impacts on Stakeholders

  • Parks and recreational users, producers, landowners and the general public could be negatively affected by the potential uncontrolled spread of this species.
  • Arundo donax would be permitted to be grown commercially as a biofuel or for other uses in Canada. Other stakeholders and jurisdictions would be responsible for controlling and managing new potential populations of A. donax if needed.
  • Horticultural varieties would be allowed for import.

7.2 Further Considerations

If the decision is made to regulate A. donax, the CFIA may consider allowing the import and production of live plants, plant parts and seeds for specific uses under strict phytosanitary conditions. For example, plantings (and storage) as a biofuel feedstock crop may be allowed under conditions which would include the development of and adherence to an acceptable risk management plan with the provision of buffer zones from high risk areas (e.g. waterways, riparian and wetland areas).

There are existing measures in place to prevent the intentional introduction of pests. However, allowing import and domestic activities with restrictions for specific end uses would require additional CFIA resources to:

As a result, these activities would need to be delivered collaboratively with other organizations and jurisdictions (e.g., provinces, municipalities). This would be a longer term consideration that would depend on the development of a program that would necessitate formal agreements between the CFIA and its partners that are not yet in place. At this time, the CFIA is not considering this approach.

7.3 CFIA Recommendation

The CFIA recommended Option 1: Regulate Arundo donax as a pest under the Plant Protection Act for the stakeholder consultation.

8.0 Risk Management Decision

The CFIA has decided to regulate Arundo donax as a pest under the Plant Protection Act. This means that importation of live plants, plant parts and seeds of A. donax – from all sources – as well as domestic use and movement is prohibited. Imported things must be free from species on the List of Pests Regulated by Canada, including A. donax.

The CFIA made this regulatory decision after evaluation of Arundo donax, the risks associated with its potential introduction into Canada and feedback from the stakeholder consultation. The CFIA consulted its federal, provincial and territorial partners, affected Canadian stakeholders, the scientific community and the general public in the consultation process. The CFIA issued a World Trade Organization notification to inform international partners and stakeholders of the decision to regulate A. donax. The List of Pests Regulated by Canada and Automated Import Reference System were updated to include the phytosanitary requirements for A. donax.

8.1 Re-evaluation of a Risk Management Decision

The CFIA will review the risk management decision as new information becomes available (e.g. regarding A. donax invasiveness or distribution) to ensure that the action being taken is still appropriate. The extent of the review and potential amendments will be determined by the nature of the new information. In some instances, additional consultation with stakeholders will be required.

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