Weed management is a challenge in all agroecosystems. Given the negative consequences associated with herbicide-based weed management, it is important to consider integrated weed management options with emphasis on strategies such as biological control. Postdispersal weed seed predation by granivorous and omnivorous carabid beetles results in substantial natural suppression of weed populations. Although the role of ground beetles as “generalist predators” in various agroecosystems is known, their contribution to weed management is not well recognized. In this context, this review presents an account of carabids and their granivorous nature, the importance of a seed diet in the life histories of different carabid groups, factors affecting granivory, and their potential role in weed seed management. Below, we discuss the interrelationships among various factors influencing weed seed consumption by carabids, its consequences for weed management, and the need for future research.

Ashraf and Abu-Shakra, 1978; Hao and de Jong, 1988). Several studies have indicated that germination is de-Oat (Avena sativa L.) yield and quality on the northern Great layed and reduced by low water potential (Rao and Plains are consistently reduced by frequent drought and wild oat Dao, 1987; Hao and de Jong, 1988), low temperature (Avena fatua L.) competition. Wild oat cannot be selectively removed (Livingston and de Jong, 1990; Willenborg et al., 2004), from oat with herbicides. Identifying genotypes or seed size(s) with high germination potential under moisture stress may facilitate im-high salinity (Romo and Haferkamp, 1987), and combiproved seedling vigor, stand establishment, and crop competitiveness.nations of these factors (Willenborg et al., 2004; Living-Therefore, a germination study was conducted to determine the effects ston and de Jong, 1990; Hao and de Jong, 1988). The of genotype and seed size on the germination of oat seed subjected resulting late and inadequate germination and subseto moisture stress. Large, medium, and small seeds of six common quent seedling establishment critically affect crop prowestern Canadian oat genotypes were germinated in polyethylene duction this region (Livingston and de Jong, 1990). glycol (PEG 8000) solutions with initial osmotic potentials rangingOat is one of the major economic grain crops grown from 0 to Ϫ0.4 MPa at 5؇C. Generalized linear mixed models fit to in the northern Great Plains region, planted annually the data provided a statistically valid, appropriate, and convenient on 1.7 million hectares of land in western Canada alone method to analyze germination data. In all genotypes examined, de-(Statistics Canada, 2004). Oat is a crop that normally creasing seed size and osmotic potential increased median germination time (MGT) and lowered final germination percentage (FGP). Among produces seed of varying size as a result of the multigenotypes, CDC Bell had the fastest MGT while AC Mustang had floret habit of the oat spikelet (Doehlert et al., 2002, the highest FGP. Delays in MGT and reductions in FGP resulting 2004). Oat seed size is inherently nonuniform because oat from increased moisture stress were similar to those observed in other may produce one, two, or three seeds per spikelet. The cereals, suggesting that oat may be as capable of germinating under innermost seed, called the primary seed, is the largest low spring soil moisture conditions as wheat and barley. The results and seed size and mass decrease with increasing seed of this study also indicate that large seed of genotypes such as AC order (Doehlert et al., 2002). This relationship results Mustang and CDC Bell appear better suited to germinate under the from reduced sink strength and photoassimilate acquirange of osmotic potentials in this study. Although differences in sition of higher order seeds (Palagyi, 1983; Doehlert et MGT and FGP between seed sizes in this study were statistically al., 2002).significant, they were generally small and thus, oat germination characteristics may not be...

The increasing occurrence of herbicide resistance, along with no new herbicide modes of action developed in over 30 yr, have increased the need for nonherbicidal weed management strategies and tactics. Harvest weed seed control (HWSC) practices have been successfully adopted in Australia to manage problematic weeds. For HWSC to be effective, a high proportion of weed seeds must be retained on the plant at crop maturity. This 2-yr (2014, 2015) study evaluated seed shatter of wild oat, green foxtail, wild mustard, and cleavers in both an early (field pea) and late (spring wheat) maturity crop in field experiments at Scott, Saskatchewan. Seed shatter was assessed using shatter trays collected once a week during crop ripening stage, as well as at two crop maturation or harvest stages (swathing, direct-combining). Seed shatter differed among weed species, but was similar between crops at maturity: ca. 30% for wild oat, 5% for cleavers, < 2% for wild mustard, and < 1% for green foxtail. Overall, seed shatter of wild oat occurred sooner and at greater levels during the growing season compared with the other weed species. Viability of both shattered and plant-retained seeds was relatively high for all species. The small amount of seed shatter of cleavers, wild mustard, and green foxtail suggests that these species may be suitable candidates for HWSC. Due to the amount and timing of wild oat seed shatter, HWSC may not reduce population abundance of this grassy weed.

and reduce germination and plant establishment (Sharma, 1976;Hegarty, 1977; Schneider and Gupta, 1985). Polymer coatings have recently been developed to prevent germi-To avoid some of these problems in canola producnation and thereby reduce undesirable emergence of fall-seeded ca-Polymer seed coats have been shown to decrease im-

Seed shatter of wild oat (Avena fatua L.), green foxtail [Setaria viridis (L.) P. Beauv.], wild mustard (Sinapis arvensis L.), cleavers (Galium spurium L. and G. aparine L.), wild buckwheat (Polygonum convolvulus L.), and kochia [Kochia scoparia (L.) Schrad.] was evaluated in field pea, spring wheat, and canola fields in Saskatchewan in 2014 and 2015. Seed shatter was assessed using shatter trays collected once a week during the crop ripening stage, as well as at swathing or direct-harvest (direct-combining). Seed shatter differed among weed species in field pea and wheat at maturity: 22%-30% for wild oat, and generally ≤10% for the other species. Seed shatter of investigated weeds in canola at swathing, including that of wild oat, was uniformly low (<5%). The relatively low level of seed shatter for cleavers, wild mustard, green foxtail, and wild buckwheat suggests that these species may be suitable candidates for harvest weed seed control (HWSC). Because of the amount and timing of wild oat seed shatter, HWSC may not reduce population abundance of this grassy weed, except in canola when swathed.

Ford, G. 2015. Glyphosate-resistant kochia (Kochia scoparia L. Schrad.) in Saskatchewan and Manitoba. Can. J. Plant Sci. 95: 345Á349. Previous surveys have documented the occurrence of glyphosate-resistant (GR) kochia in Alberta in 2011 and 2012. To determine the incidence of GR kochia in Saskatchewan and Manitoba, a stratified-randomized survey of 342 sites (one population per site) in southern and central regions of Saskatchewan and a similar survey of 283 sites in southern Manitoba was conducted in the fall of 2013. Mature plants were collected, seed threshed, and progeny screened by spraying with a discriminating glyphosate dose of 900 g ae ha Á1 under greenhouse conditions. Screening confirmed 17 GR kochia populations in nine municipalities in west-central or central Saskatchewan, but only two GR populations from different municipalities in the Red River Valley of Manitoba. While the majority of GR kochia populations in Saskatchewan originated in chemicalfallow fields, some populations were found in cropped fields (wheat, Triticum aestivum L.; lentil, Lens culinaris Medik.; GR canola, Brassica napus L.) and non-cropped areas (oil well, roadside ditch). In Manitoba, the two populations occurred in fields cropped to GR corn (Zea mays L.) and soybean (Glycine max L. Merr.). Agronomic and economic impact of this GR weed biotype is compounded because of consistent multiple resistance to acetolactate synthase-inhibiting herbicides. However, GR kochia is susceptible to dicamba, an increasingly important auxinic herbicide used for control of this multiple-resistant weed biotype. Pour e´tablir l'incidence de cette adventice GR en Saskatchewan et au Manitoba, les auteurs ont proce´deá`u ne enqueˆte ale´atoire stratifie´e a`342 sites (un peuplement par site) dans le sud et le centre de la Saskatchewan, puis ont effectue´une enqueˆte similaire a`283 sites dans le sud du Manitoba, a`l'automne 2013. Ils ont recueilli des plants matures, en ont re´colte´les graines et ont pre´se´lectionne´la proge´niture en la pulve´risant avec 900 g de glyphosate par hectare, en serre, aux fins de discrimination. La pre´se´lection a confirme´la pre´sence de 17 peuplements de kochie GR dans neuf municipalite´s du centre-ouest ou du centre de la Saskatchewan, mais seulement deux populations GR dans des municipalite´s diffe´rentes de la valle´e de la rivie`re Rouge, au Manitoba. Bien que la majorite´des peuplements de kochie GR de la Saskatchewan aient e´te´observe´s dans des jache`res chimiques, quelques-uns ont e´te´retrouve´s dans des cultures (ble´, Triticum aestivum L.; lentille, Lens culinaris Medik.; canola GR, Brassica napus L.) et sur des terrains en friche (puits de pe´trole, fosse´d'une route). Au Manitoba, les deux populations ont e´te´de´couvertes dans des champs de maı¨s GR (Zea mays L.) et de soja (Glycine max L. Merr.). L'impact agronomique et e´conomique de cette adventice GR est complexe, car la kochie pre´sente une re´sistance multiple aux herbicides qui inhibent l'ace´tolactate synthase. Ne´anmoins, la kochie GR est sen...

Carabid beetles can greatly contribute to biocontrol in agroecosystems, reducing both insect pests and weed seeds. However, insect foraging and feeding behavior can be highly dependent on the interaction network and spatial structure of the environment, which can make their biocontrol contributions variable. In the present article, we explore how the interaction network of carabids can affect their behavior and how spatial vegetation structure and specific agronomy practices can, in turn, affect the strength of interactions in their network. We suggest that research on carabid biocontrol should move toward an approach in which the network of interactions among pests, carabids, and other organisms within its spatial structure is evaluated, with equal focus on direct and indirect interactions, and provide examples of tools to do so. Overall, we believe this approach will improve our knowledge of carabid networks, help to elucidate the underlying mechanisms of biocontrol, and lay the foundation for future biocontrol strategies.

Wild oat is a serious weed in cultivated oat because there are no herbicides to selectively control it. Considering the effect of time of emergence on weed–crop interference is critical for the development of accurate crop yield loss models and weed density thresholds. Therefore, field experiments were conducted at two locations in Saskatchewan, Canada, in 2002 and 2003 to determine the effect of wild oat density and time of emergence on cultivated oat yield and quality. Wild oat was planted at 50 growing degree day (GDD) intervals ranging from 100 GDD before to 100 GDD after crop planting. Wild oat density ranged from 0 to 320 plants m−2. High densities of early emerging wild oat greatly reduced cultivated oat yield and increased wild oat contamination, with observed oat yield losses as great as 70% and wild oat contamination levels of 15%. Wild oat that emerged before cultivated oat caused considerably more yield and quality loss and had higher reproductive output than wild oat that emerged after cultivated oat. The yield loss caused by individual wild oat plants at low densities (parameter I) ranged from 0.40 to 0.49%. The effect of relative time of wild oat emergence (parameter C) always varied significantly between site-years. However, little variation in absolute values within site-years was observed for cultivated oat yield loss, wild oat seed production, and wild oat contamination, suggesting that relative time of wild oat emergence influences all similarly. The results of this study emphasize both the need to control early emerging wild oat, as well as the importance of time of emergence in the prediction of crop yield loss. Furthermore, our approach of conducting an emergence study based on thermal time is novel and demonstrates a robust, mechanistic method of estimating crop yield losses due to relative time of emergence.