RMD-13-04: Consolidated Pest Risk Management Document for pest plants regulated by Canada
Appendix 1A: Pest Risk Assessment Summary for Aegilops cylindrica (jointed goat grass)
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- Identity of Organism
- Organism Status
- Regulatory Status
- Probability of Entry
- Probability of Establishment
- Probability of Spread
- Potential Economic Consequences
- Potential Environmental and Social Consequences
Identity of Organism
Name: Aegilops cylindrica Host (1802), family Poaceae
Synonyms: Triticum cylindricum (Host) (1869), Cylindropyrum cylindricum (Host) (1982), Aegilops caudata
English Common Names: Jointed goat grass (Darbyshire, 2003), jointed goat grass, (Randall, 2002)
French Common Names: Égilope cylindrique (CFIA 2008)
Taxonomic Note: The taxonomy of the Triticeae tribe is notoriously difficult and unstable (Gould and Shaw, 1983). Due to its similarities with wheat, some authors have in the past renamed jointed goat grass Triticum cylindricum (Host) (Gould and Shaw 1983; Donald and Ogg 1991), although the currently accepted name is Aegilops cylindrica Host (e.g. Tutin et al. 1980; Tsvelev 1984; USDA ARS, 2006). Donald and Ogg (1991) describe the genus Aegilops as distributed worldwide and comprising at least 23 species. Holm et al. (1991) report Aegilops cylindrica as a weed in the United States and Turkey, and other Aegilops species as weeds in Morocco, Portugal, Iran, Jordan and Israel. Donald and Ogg (1991) note that two varieties (or subspecies) of Aegilops cylindrica are recognized by some authors (Aegilops cylindrica var. cylindrica and var. rubiginosa) and Tsvelev (1984) lists three more (var. pauciaristata, var. aristulate and var. prokhanovii), all distinguished based on morphological differences of glumes and spikelets. Most studies fail to describe which varieties are studied, and it is not known whether they differ in their susceptibility to control mechanisms (Donald and Ogg 1991).
Description: Aegilops cylindrica is a winter annual grass that is very similar in appearance to winter wheat (Wicks et al. 2004). Individual plants consist of up to 50 erect flowering stalks (Donald and Ogg 1991). The root system of the plant is shallow and fibrous. Leaves are alternate and 2 to 5 mm wide, and vary from 3 to 15 cm in length (Barkworth 2006). The leaves are glabrous or sparsely hairy (Tutin et al. 1980) and the hairs are evenly spaced along the leaf blade margin (NJGRP 2006). The seed head, or spike, is a narrow cylinder 5-10 cm long with alternately arranged spikelets on opposite sides of the main axis of the spike. Spikelets are 8-10 mm long and contain 2-4 florets each. Glumes on the lower spikelets do not have awns, or have one awn. Glumes of apical spikelets have long awns (3.0 – 9.0 cm). Each spikelet contains on average 2 seeds (Hitchcock 1950; Donald and Ogg 1991; Lyon et al. 1995-2000; Barkworth 2006).
Seeds are reddish-brown caryopses, 6.5-9 mm long, 2 mm wide, and grooved. The lemma and palea adhere to the seed. Aegilops cylindrica plants produce an average of 130 seeds, and up to 3000 seeds under optimal conditions (Donald and Ogg 1991).
At maturity, some selections of Aegilops cylindrica may be distinguished from winter wheat by purple-coloured spikes (Donald and Ogg 1991). Spikes of Aegilops cylindrica are also much narrower and more cylindrical than those of wheat. In the field or in harvested seed lots, disarticulated Aegilops cylindrica spikelets are sometimes mistaken for small pieces of wheat straw (Donald and Ogg 1991).
The first occurrence of Aegilops cylindrica in Canada was likely a small non-persistent population in New Westminster, British Columbia in 1997 (Haber 2006). In 2002, there were four unconfirmed reports of Aegilops cylindrica present in shipments of Canada Western Red Spring wheat destined for Mexico.
In 2006, a small population of this species was discovered in the Regional Municipality of Niagara, Ontario. A small satellite population was discovered approximately 2.5 km away in 2007. In 2009 CFIA took some pre-emptive control measures to limit the further spread of these two populations.
As part of the CFIA import monitoring program, Aegilops cylindrica was found in eight samples of wheat and barley grain imported from the United States in 2008 and destined for British Columbia flour mills.
In 2005, the CFIA added Aegilops cylindrica to the Weed Seeds Order under the authority of the Seeds Actand Seeds Regulations, as a Class 1 Prohibited Noxious Weed Seed, prohibiting its movement as seed and as a contaminant in seed.
Provincially, Aegilops cylindrica is listed as a Provincial Noxious Weed in British Columbia, under the British Columbia Weed Control Act. The Province of Saskatchewan completed consultation on the revision of their Noxious Weed Act early in 2009, which includes the addition of Aegilops cylindrica to a prohibited noxious weeds list.
In the United States, Aegilops cylindrica is not included on the USDA's Federal Noxious Weed List, but it is regulated by Arizona, California, Colorado, Idaho, New Mexico, Oregon, and Washington (USDA, NRCS 2006).
Probability of Entry
The most likely pathway for the introduction of Aegilops cylindrica into Canada is general range expansion of the weed from infested states in the United States that share a border with Canada. General range expansion is a risk because Aegilops cylindrica is present in counties adjacent to the Canadian border in Washington, Idaho, Montana, and New York (Figure 1). Seeds of Aegilops cylindrica float and can be dispersed by runoff water in agricultural fields. However, the spiklets are large and unlikely to be moved great distances by wind. It has been suggested that Aegilops cylindrica seed can be dispersed by birds and mammals, after ingestion; however, it is not clear whether seeds remain viable after passing through the digestive tract in animals other than cattle (WSU Extension 2007).
The occurrence of Aegilops cylindrica in eight separate shipments of wheat and barley from the United States destined to Canada for milling and malting in 2008 provides evidence that the importation of grain for consumption is also a viable pathway for this species. If grains imported for consumption are contaminated with Aegilops cylindrica there is potential for some seeds to enter favourable environments and establish (Table 6). Examples include spillage along railway tracks, or dispersal of viable seeds by livestock that consume contaminated grain.
The listing of Aegilops cylindrica as a Class 1 Prohibited Noxious Weed in the Weed Seeds Order in 2005 provides a sufficient risk mitigation measure for preventing new incursions of this species through the seed pathway. Seed containing prohibited noxious weed seeds may not be sold, offered for sale, or imported into Canada.
|Type of Potential Introduction||Specific Pathway||Description|
|Natural Means of Dispersal||Wind||Aegilops cylindrica reproduces only by seed, which have no obvious adaptations for long-range dispersal.|
|Water||Seeds float and will be dispersed by water runoff in agricultural fields|
|Bird||Unclear if seeds can remain viable after passing through the digestive tracts of birds.|
|Animal (external or internal)||Aegilops cylindrica has no obvious adaptations for this kind of dispersal.|
|Intentional Introduction Pathways||Seed||Prohibited under Seeds Actand Seeds Regulations|
|Plants for planting (excluding seed)||None identified.|
|Field crops not intended for propagation||None identified.|
|Decorative arrangements and branches||None identified.|
|Unintentional Introduction Pathways||Field crops not intendedfor propagation||Aegilops cylindrica could enter Canada as a contaminant in grain from areas where Aegilops cylindrica is established. Aegilops cylindrica is primarily a problem in cereal crops, particularly winter wheat.|
|Seed||Aegilops cylindrica is a Class 1 Prohibited Noxious Weed in the Weed Seeds Order, 2005 (Seeds Act) which provides sufficient risk mitigation.|
|Hay and Straw||Straw originating from the U.S. and used for livestock bedding or packing material could contain seedsof Aegilops cylindrica.|
|Livestock||High viability and seedling emergence can be expected from seeds after passage through cattle.|
|Raw wool and raw hides||Aegilops cylindrica has no obvious adaptations for this kind of dispersal.|
|Motorized vehicles||Custom combine harvesters typically follow the winter wheat harvest northward, even across the Canada/U.S. border and is a potential mechanism of Aegilops cylindrica spred into Canada.
Farm trucks are commonlyused for multiple purposes , including hauling seed, fertilizer and harvested grain, and can lead to contamination and spread.
|Nursery stock with soil||None identified.|
|Used recreational equipment and clothing (excluding motorized vehicles)||None identified.|
The Seed Science & Technology Section of the CFIA Saskatoon laboratory analyze submitted samples of domestic and imported seed for contaminants, and have no record of Aegilops cylindrica being found in monitored samples of seed.
The level of risk associated with imports of hay and straw into Canada is relatively high when they originate from areas where Aegilops cylindrica is established and when Aegilops cylindrica has gone to seed in hay crop.
Other potential pathways considered to be of lesser importance include the movement of livestock with ingested seed across the border and used farm machinery potentially contaminated with soil which may carry seeds of Aegilops cylindrica.
Probability of Establishment
Aegilops cylindrica could potentially invade crops, pastures, and disturbed areas up to Canada Plant Hardiness Zone 2b, which includes the majority of Canada's agricultural land (Figure 2). Within this range, it is most likely to become a serious weed in winter wheat production areas; these include southern Ontario and in the southern Prairie Provinces where the majority of Canadian winter wheat is sown.
Probability of Spread
While seed production is moderate, Aegilops cylindrica could easily spread through both natural and man-made dispersal mechanisms if introduced into Canada.
Its biological and physical similarities to winter wheat make Aegilops cylindrica difficult to remove from dispersal pathways. Aegilops cylindrica spikelets measure approximately 8 to 10 mm long, and can be difficult to separate from wheat seed, which typically measure 5 to 7 mm. (Donald and Ogg 1991).
There is also risk of hybridization of Aegilops cylindrica with wheat and other closely related species. Hybridization of Aegilops cylindrica with other species could result in increased weediness. The transfer of herbicide resistance traits from wheat into Aegilops cylindrica has already been documented in the United States (S. Darbyshire, 2006, pers. Comm.)
Potential Economic Consequences
In the United States, losses in winter wheat crop yield and quality due to Aegilops cylindrica are estimated at $150 million annually (Mallory-Smith 2001). Yield reductions are dependent on a variety of factors, notably rainfall, soil moisture and the severity of previous infestations. Field experiments in Washington State for instance, demonstrated that a first year infestation of one to five plants per square metre led to yield loss from 3% to 30 % in the following year (Young et al. 2000). This weed can also cause dockage losses in wheat. In non-herbicide resistant winter wheat varieties, costs of controlling Aegilops cylindrica are mostly indirect due to lack of selective control options. The presence of Aegilops cylindrica in Canadian seed could have negative trade impacts within Canada as well as with Mexico, certain U.S. states, Australia (although it is primarily a wheat-exporting nation), China, and possibly other countries.
Potential Environmental and Social Consequences
Aegilops cylindrica is primarily an agricultural weed, rather than an environmental weed, and its greatest environmental impacts are to sustainable agricultural practices. The presence of Aegilops cylindrica can discourage the cultivation of winter wheat, which is a relatively environmentally friendly crop, as it is an important component in reduced tillage systems and it provides nesting areas for waterfowl (Hamill 2005).
Additional phytosanitary measures may be necessary to prevent Aegilops cylindrica from further introduction into Canada, and to preventits spread. Eradication and subsequent monitoring of the Regional Municipality of Niagara populations should be a high priority, as should surveys in this and other potential high risk areas, particularly where winter wheat is grown, adjacent to railway lines, and along the Canada-United States border. Prevention of further introductions into Canada should be sought through activities such as public education, prevention of entry into Canada of contaminated farm equipment, vehicles, and straw, and possibly grain car inspections. Early control of Aegilops cylindrica, should it be introduced into Canada, would prevent negative economic and environmental consequences for Canada. Therefore, it is recommended that Aegilops cylindrica be considered for inclusion on the List of Pests Regulated by Canada.
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