Wildmustard (Sinapis arvensis) is prevalent weed that is found widespreadthroughout Canada and north central United States (Christoffers et al., 2006).Considered to be native to Europe, the Middle East and western Asia, reports ofwild mustard populations in western Canada go back as far as 1860 in FortGarry, Manitoba and 1875 in Dufferin, Manitoba (Mulligan and Bailey, 1975).Since then, wild mustard has become an important weed of agricultural crops inthe Canadian prairies (Friesen et al., 2009; Warwick et al.
, 2005).In 2003, wild mustard was ranked 15th out of 124 weeds in aSaskatchewan survey of cereal, oilseeds, and pulse crops (Leeson et al., 2003)and 11th of 101 weeds in a 2002 survey of cereal and oilseed cropsin Manitoba (Leeson et al., 2002).Wildmustard is a broad-leafed annual weed species with indeterminate growth (Warwick et al.
, 2000).It is self-incompatible, grows in locations with high light intensity and isreadily killed by frost (Warwick et al., 2000).
Wild mustard can be easily identified by several of its distinguishingfeatures. This includes kidney shaped cotyledons; coarsely hairy stems withpetiolate lower leaves and sessile upper leaves; bright yellow, four-petalledflowers; pods are generally hairless and terminated by a flattened beak; valvessplit lengthwise at maturity; and the seeds are black-purplish (Mulligan and Bailey, 1975).Often confused with several yellow-flowered annuals, such as Brassica rapa,Brassica napus, and Sinapis alba, Wild mustard is distinctive from theses as inaddition to having seeds within the valves, there is also seed in the beak ofthe pod (Warwick et al., 2000).Wildmustard is a potentially very problematic weed within the Canadian prairies.
Due to its high reproductivity, competitive growth habit, and persistent seedbank, the yield loss of agriculture field crops can become serious. Forexample, in spring rapeseed, yield can be reduced by 20% with populationdensities of wild mustard being as low as 10 plants per m-2 (Buchanan,2016). Although there are many available herbicides to control wild mustard infield crops, biotypes of wild mustard resistant to Group 2, Group 4, and Group5 herbicides have been reported in Canada in the 1980s and 1990s (Warwick et al., 2000).Acetolactate synthase (ALS) inhibitors (Group 2) resistant wild mustard wasinitially discovered in Manitoba in 1992 (Morrison and Devine, 1994)and was later discovered in 2002 in Saskatchewan (Warwick et al.
, 2005).Kochia(Kochia scoparia) is one of the most prevalent summer annual broadleaf weed. Itis located throughout Canada, except for the maritime provinces and coastalBritish Colombia (Royer and Dickinson, 2006).Initially categorized as rare in Saskatchewan and Alberta in 1948 (Friesen et al.
, 2009),kochia was the 10th most prevalent weed across the Canadian prairies(Leeson et al., 2005). Kochia is present in 13% of surveyed Canadian prairiesfields, and is most common in Saskatchewan (8th in Provincialranking) occurring in 17% of fields with a mean density of 4.2 plants m-2(Friesen et al., 2009).Kochiais described as a bushy, pyramid-shaped plant with potential to reach heightsof 2m (Royer and Dickinson, 2006).
Kochia has a potentially large tap root (up to 5m long) and its stem is erect,branched, green or red tinged, and can somewhat be hairy (Friesen et al., 2009).It has a high tolerance of saline soils (Friesen et al., 2009),early emergence, and low seed dormancy (Kumar and Jha, 2015).
It is also an abundant seed producer, were a single plant will produce morethan 14,000 seeds (Schwinghamer and Van Acker, 2008).Kochiahas built up resistant to several modes of action including acetolactatesynthase (ALS) inhibitors. Group 2 resistant kochia was first discovered inSaskatchewan and Manitoba in 1988 (Morrison and Devine, 1994).Due to its tumbleweed mobility and ability to cross pollinate, populations ofgroup 2 resistant kochia has become increasingly common.
In 2007, Beckie et al.found that 90% of the 109 prairie fields surveyed, had widespread resistance toALS inhibitors (2013).This increased spread of resistant kochia may be in part caused by transmissionthrough pollen movement, however seed dispersal by mature plants moving throughthe prairie landscape is likely responsible for the long-distance transport ofgroup 2 resistant kochia (Beckie et al., 2016; Hall et al., 2014; Stallings etal., 1995).Although the spread of group 2 resistant kochia is difficult to prevent,management practices including crop rotation (Government of Saskatchewan, 2017)and rotation of broadleaf herbicide (Government of Manitoba, 2015) should beused to delay the development of ALS inhibitors resistance.