2012 weed survey of Saskatchewan canola fields

Non-Peer Reviewe

Alternative cropping systems alter residual weed community composition

Non-Peer ReviewedWeed community composition was assessed in 1994 through 2000 in the Alternative Cropping System Project at Scott, SK. Weeds were counted during July after in-crop management practices had been used. The weed community was composed of 67 species. The nine arable cropping systems in the project were compared in terms of weed frequency, density, and diversity. Changes in weed community composition over time are displayed as a principal response curve (PRC). This method compares the weed community in the cropping systems to a reference system. PRCs are based on redundancy analysis, a constrained form of principal components analysis. Weed densities are constrained to be linear combinations of the interaction of system and year. Seven years and initial spatial variation (4 replicates and 36 sub-plots) are removed as covariables. The PRC analysis identified problematic weed species associated with the cropping systems after six years. Green foxtail, lamb’s-quarters and stinkweed were abundant in the three organic input systems. Wild oats, shepherd’s-purse and narrow-leaved hawk’s-beard were abundant in the reduced input systems. The three organic systems appear to have reached equilibrium after a three-year transition period. The problematic weed species in the reduced systems still appear to be increasing after six years

Identification and distribution of barnyard grass (Echinochloa crus-galli and E. muricata)

Non-Peer ReviewedBarnyard grasses (Echinochloa spp.) have become increasingly prevalent in agricultural fields of the Prairie Provinces during the past 30 years. The taxonomy and identification of the barnyard grasses has been controversial and difficult. At least two annual species occur as weeds in arable fields; the Eurasian Echinochloa crus-galli and the native E. muricata. Although they are relatively easy to distinguish from other Canadian grass weeds by the absence of a ligule, both exhibit considerable morphological variation and are often confused or simply reported as a single species, E. crus-galli. The two species can be most readily distinguished using characteristics of the mature fertile lemmas and paleas. In E. crus-galli the top of the body of the lemma is broadly rounded with an irregular row of hairs. The short acute tip is abruptly different in colour and texture from the body of the lemma. The top of the lemma in E. muricata gradually and smoothly tapers into a pointed tip, without a sharp contrast in texture, colour or pubescence. An examination of about 100 plants collected in 2006-8 and over 240 herbarium specimens suggests that the Eurasian E. crus-galli is less common in the Prairie Provinces than the native E. muricata. The distribution of the species was found to overlap and the two species were occasionally found at the same site. In order to understand any ecological differences that may be important in their effective management, it is critical to be able to recognize the differences between the species in research and control programs. Inconsistencies in reported behaviours and responses, within Canada and other parts of the world, may be at least in part due to the confusion of these two species

Residual weed populations in Saskatchewan – 1976 to 2003

Non-Peer ReviewedThe comparison of the relative abundance of weeds in Saskatchewan in 2003 with results from previous provincial surveys enables the identification of recent shifts in species ranks, life form density and relative abundance. In 2003, 2046 fields of spring wheat, barley, durum, oat, canary seed, canola, flax, mustard, lentil and pea were surveyed. These fields were selected using a stratified random sampling procedure based on ecodistricts. In each field, weeds were counted in 20 quadrats (50 by 50 cm) in late summer. Weed data are summarized using a relative abundance index based on frequency, field uniformity and density. Green foxtail was the most abundant weed, wild oats ranked second, wild buckwheat third and Canada thistle fourth. The results from the 2003 survey are compared to results from surveys of 1178 fields in 1995, 1149 fields in 1986 and 4423 fields in 1976-1979. Twelve species have been ranked amongst the top 20 most abundant species in each survey. Seven species, ranked in the top 20 species in the 1970’s and/or 1986, have since declined: rose, prostrate pigweed, night-flowering catchfly, cow cockle, bluebur, pale smartweed, flixweed. Six species have appeared in the top 20 list for the first time in 1995 and/or 2003: cleavers, barnyard grass, wheat, dandelion, quack grass, canola. Relative abundance of annual grass and perennials has increased, while relative abundance of annual broad-leaved species and facultative winter annuals has decreased. Densities of all life forms have decreased since the 1970’s

Alberta field survey of herbicide-resistant weeds

Non-Peer ReviewedIn 2001, 236 fields were randomly selected throughout the ecoregions of Alberta and surveyed for grass and broadleaf weeds resistant to Group 1 (ACCase inhibitor) or Group 2 (ALS inhibitor) herbicides. Nearly 20% of surveyed fields had a herbicide-resistant weed biotype. Only 5% of producers with resistant biotypes were aware of their occurrence. This survey serves as a baseline for determining future trends in weed resistance in Alberta

Seasonal weed response to integrated crop management systems

Non-Peer ReviewedWeed plant density was monitored to determine the effect of various integrated crop management systems on weed population levels and evaluate the efficacy of the various management practices. The management systems studied primarily varied tillage and herbicide inputs. Weed plant density was determined in spring, prior to in-crop management and after in-crop management in each year of the study. Also, weeds were counted after in-crop management prior to the establishment of the management systems. Multivariate analyses were used to determine the response of the weed communities to the management systems. Principal response curves were used to illustrate seasonal fluctuations and trends in weed densities. Stinkweed, lamb’s-quarters, wild buckwheat, redroot pigweed, wild mustard and Russian thistle are best controlled with in-crop herbicide applications. These species increased over time in the no herbicide high tillage system and low herbicide systems. Winter annuals, perennials and early spring annuals were found to increase in the lower herbicide zero-tillage systems. These species tended to be found in high densities in the spring and not effectively controlled in-crop

Seedbank response to integrated crop management systems

Non-Peer ReviewedSix integrated crop management systems varying primarily in terms of tillage and herbicide inputs were maintained for four years at two locations in the Moist Mixed Grassland ecoregion in Saskatchewan. The seedbank was sampled in each plot in the spring of 1997 prior to the initiation of the experiment and the spring of 2001 following the completion of the experiment to determine if cropping system had changed seedbank composition. Redundancy Analysis (RDA) was used to directly quantify the change in weed seedbank attributable to cropping system at each location. The RDA was constrained by cropping system for the 2001 data and year for the 1997 data. Initial spatial variation observed in the 1997 weed seedbank was removed from the analysis by using plot number and replicate block as binary covariables. The majority of species increased in the seedbank in all systems studied at both locations. The seedbank from the no herbicide high tillage systems was distinguishable from the other systems by large increases in lamb’s-quarters and stinkweed at both locations. While similar species tended to increase in all the systems with herbicides, the systems with lower levels of herbicides applied had larger increases in the seedbank than those with high herbicide inputs

Weed survey and management practices used in alfalfa (Medicago sativa) seed fields in 1997

Non-Peer ReviewedA weed survey in alfalfa seed fields, located primarily in northeast Saskatchewan, was conducted in 1997. Following the weed survey, a farm management questionnaire was used to determine the influence of farm management practices on the surveyed weed community. Results from the weed survey and farm management questionnaire were compared to a similar survey and questionnaire conducted in 1989-90. Wild oats and green foxtail were the most abundant annual grass weeds and their relative abundance did not change significantly. Narrow-leaved hawk’s beard generally decreased in relative abundance while perennial weed species usually increased. Herbicides were the most common weed management practice used in Saskatchewan alfalfa seed fields and their use increased compared to the previous questionnaire. Group 1 herbicide use exceeded the recommended frequency to delay the onset of resistance in wild oats and green foxtail in over half of the fields surveyed. The increase in herbicide use may account for the reduction in relative abundance of some annual broad-leaved weed species between 1989-90 and 1997. The decrease in annual weed competition may have allowed some perennial weeds, which are harder to control with herbicides, to increase in relative abundance

Seasonal weed response to integrated crop management systems

Non-Peer ReviewedWeed plant density was monitored to determine the effect of various integrated crop management systems on weed population levels and evaluate the efficacy of the various management practices. The management systems studied primarily varied tillage and herbicide inputs. Weed plant density was determined in spring, prior to in-crop management and after in-crop management in each year of the study. Also, weeds were counted after in-crop management prior to the establishment of the management systems. Multivariate analyses were used to determine the response of the weed communities to the management systems. Principal response curves were used to illustrate seasonal fluctuations and trends in weed densities. Stinkweed, lamb’s-quarters, wild buckwheat, redroot pigweed, wild mustard and Russian thistle are best controlled with in-crop herbicide applications. These species increased over time in the no herbicide high tillage system and low herbicide systems. Winter annuals, perennials and early spring annuals were found to increase in the lower herbicide zero-tillage systems. These species tended to be found in high densities in the spring and not effectively controlled in-crop

Manitoba field survey of herbicide-resistant weeds

Non-Peer ReviewedIn 2002, 150 fields were randomly selected throughout the ecoregions of Manitoba and surveyed for grass and broadleaf weeds resistant to Group 1 (ACCase inhibitor) or Group 2 (ALS inhibitor) herbicides. One-third of surveyed fields had a herbicide-resistant weed biotype. Two biotypes new to western Canada are Group 2-resistant green foxtail and redroot pigweed. Of producers with resistant biotypes, 10% or fewer were aware of their occurrence