Christian J. Willenborg

University of Saskatchewan | U of S · Department of Plant Sciences

Flax is an important oilseed crop of temperate regions, and Canada been the world’s top exporter of the crop since 1994. Increasing crop yields either through breeding or better agronomy can substantially benefit the flax industry in Canada. A multi‐location study was carried out in western Canada to determine the optimum combination of several agr...

Two species of cleavers Galium aparine L. and Galium spurium L. are known to inhabit croplands in western Canada. The latter is the more abundant of the two species. An increased abundance of these species over the most recent decades warrants a more comprehensive understanding of their developmental phenology and the cause of this increase. This s...

Ground beetles (Coleoptera: Carabidae) are among the most prevalent biological agents in temperate agroecosystems. Numerous species function as omnivorous predators, feeding on both pests and weed seeds, yet the sensory ecology of seed perception in omnivorous carabids remains poorly understood. Here, we explore the sensory mechanisms of seed detec...

Integrating agronomic practices can be useful in increasing flax (Linum usitatissimum L.) yield under biotic or abiotic constraints. A study was conducted to determine the combined effect of seeding density, row spacing, fertilizer and fungicide application on no‐till flax yields at three locations (seven site‐years) in Saskatchewan and Manitoba, C...

Reduced use of chemicals in weed management has been identified as a key strategy to increase overall agricultural sustainability. Carabid (Coleoptera: Carabidae) and cricket (Orthoptera:Gryllidae) weed seed predation has shown promise, but also variability, as an additional weed management tool. Therefore, it is important that carabid activity-den...

Wild oat ( Avena fatua L.) and false cleavers ( Galium spurium ) are currently a challenge to manage in less competitive crops such as flax ( Linum usitatissimum L.). Increasing the functional diversity in crop rotations can be an option to improve weed management. Nonetheless, this strategy is not tested in flax in Western Canada. A 5-yr (2015-201...

Species of carabid (ground) beetles are among the most important postdispersal weed seed predators in temperate arable lands. Field studies have shown that carabid beetles can remove upwards of 65%–90% of specific weed seeds shed in arable fields each year. Such data do not explain how and why carabid predators go after weed seeds, however. It rema...

Increased frequency and occurrence of herbicide-resistant biotypes heightens the need for alternative wild oat management strategies. There is an opportunity to exploit the height differential between wild oat and crops by targeting wild oat between panicle emergence and seed shed timing. Two field studies were conducted either in Lacombe, AB, or L...

Mycosphaerella blight, caused by Peyronellaea pinodes (Berk. & A. Bloxam) Aveskamp, Gruyter & Verkley (syn. Mycosphaerella pinodes (Berk. et Blox.) Vesterg.), is a destructive foliar pathogen of field pea that is managed, in large part, through application of foliar fungicide at flowering. The fungicides are usually applied into dense crop canopies...

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 t...

Wild oat ( Avena fatua L.) is one of the most problematic weed species in western Canada due to widespread populations, herbicide resistance, and seed dormancy. In wheat ( Triticum aestivum L.), and especially in shorter crops such as lentil ( Lens culinaris L.), A. fatua seed panicles elongate above the crop canopy which can facilitate physical cu...

Glyphosate-resistant (GR) canola is a widely grown crop across western Canada and has quickly become a prolific volunteer weed. Glyphosate-resistant soybean is rapidly gaining acreage in western Canada. Thus, there is a need to evaluate herbicide options to manage volunteer GR canola in GR soybean crops. The present experiment was conducted to eval...

Cropping systems experiments are considered vital to devise sustainable strategies to overcome many challenges in weed management. A plethora of cropping systems studies have been carried out to develop weed management solutions for a specified weed problem, or for general weed management. Even though these studies were indispensable to develop wee...

In recent years, soybean acreage has increased significantly in western Canada. One of the challenges associated with growing soybean in western Canada is the control of volunteer glyphosate-resistant (GR) canola, as the majority of soybean cultivars are also glyphosate resistant. The objective of this research was to determine the impact of soybea...

The traditional visual rating system is labor-intensive, time-consuming, and prone to human error. Unmanned aerial vehicle (UAV) imagery-based vegetation indices (VI) have potential applications in high-throughput plant phenotyping. The study objective is to determine if UAV imagery provides accurate and consistent estimations of crop injury from h...

Acute respiratory infections (ARIs) are a major cause of morbidity among children. Respiratory viruses are commonly detected in both symptomatic and asymptomatic periods. The rates of infection, and community epidemiology of respiratory viruses in healthy children needs further definition to assist interpretation of molecular diagnostic assays in t...

Flax yield can be severely reduced by weeds. The combination of limited herbicide options and the spread of herbicide-resistant weeds across the prairies has resulted in a need for more weed control options for flax producers. The objective of this research was to evaluate the tolerance of flax to topramezone, pyroxasulfone, flumioxazin, and fluthi...

Three Galium species are believed to be present across western Canada: Galium aparine, Galium spurium and Galium boreale. Galium spurium and G. aparine are very difficult to distinguish morphologically, which is problematic for crop consultants and weed surveyors, and could have implications for control measures. Molecular techniques could potentia...

With the increasing resistance of wild oat (Avena fatua L.) to herbicides, there is a need to evaluate the potential of alternative cropping systems based on integrated weed management principles. A 5-yr field study at eight sites across Canada was used to evaluate the profitability of alternative cropping systems that have the potential to control...

The escalating evolution of weed species resistant to acetolactase synthase (ALS)-inhibitor herbicides makes alternative weed control strategies necessary for field crops that are dependent on this herbicide group. A fully integrated strategy that combined increased crop seeding rates (2X or 4X recommended), mechanical weed control with a minimum-t...

Concern over the development of herbicide-resistant weeds has led to interest in integrated weed management systems that reduce selection pressure by utilizing mechanical and cultural weed control practices in addition to herbicides. Increasing crop seeding rate increases crop competitive ability and thus can enhance herbicide efficacy. However, it...

Competition is a key feature that structures the composition of plant communities. A growing body of evidence is showing that the presence of neighbours, especially belowground neighbours, induces varied morphological responses in plants. However, in many species, it is not known whether neighbour identity also influences plant morphological respon...

Most red lentil produced worldwide is consumed in dehulled form, and post-harvest milling and splitting qualities are major concerns in the secondary processing industry. Lentil producers in northern temperate regions usually apply pre-harvest desiccants as harvest aids to accelerate the lentil crop drying process and facilitate harvesting operatio...

Raw data used the first experimental run of the greenhouse trial (Figs 2 and 3). (XLSX)

Raw data used the second experimental run of the greenhouse trial (Figs 2 and 3). (XLSX)

Olfactory ability is an element of fitness in many animals, guiding choices among alternatives such as mating partners or food. Ground beetles (Coleoptera; Carabidae), exhibit preferences for prey, and some species are well-known weed seed predators. We used olfactometer-based bioassays to determine if olfactory stimuli are associated with detectio...

Raw data used for analyses of residence time for dry seeds (Fig 3a). (XLSX)

Raw data used for analyses of residence time for imbibed seeds (Fig 3b). (XLSX)

Raw data used for chi-square tests on dry and imbibed seed (Fig 2). (XLSX)

Raw data used for two-choice bioassay chi-square tests (Fig 4). (XLSX)

Soil seedbanks contribute to development of weed communities in agroecosystems and thus, understanding their regulation contributes to weed management strategies. In this context, the impacts of beneficial seed-consuming arthropods like carabids may contribute to sustainable long-term weed management. We were interested in assessing the spatial rel...

Canola (Brassica napus L.) is the most widespread profitable cash crop in Canada. In 2014 and 2015, direct-seeded experiments were conducted in 16 western Canada environments. “Small” canola seed (average 3.32–3.44 g 1000⁻¹) was compared to “large” canola seed (average 4.96–5.40 g 1000⁻¹) at five seeding rates (50, 75, 100, 125 or 150 seeds m⁻²). L...

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 20...

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...

Canola (Brassica napus L.) is the main oilseed crop grown in the northern Great Plains (Canada). This species, however, also is associated with significant seed losses before and during harvest. To determine the factors that contribute to on-farm harvest losses in B. napus, an extensive on-farm survey was conducted in four regions across the northe...

Desiccants are currently used to improve lentil dry-down prior to harvest. Applying desiccants at growth stages prior to maturity may result in reduced crop yield and quality, and leave unacceptable herbicide residues in seeds. There is little information on whether various herbicides applied alone or as a tank-mix with glyphosate have an effect on...

We describe an outbreak of respiratory syncytial virus (RSV) infection on a haematology ward without allogeneic stem cell transplant patients. Twelve patients and one staff member infected with RSV were identified from the laboratory database. Five patients had lower respiratory tract infection, seven had upper respiratory tract infection, one was...

Understanding the factors that determine college students' success could enhance the university experience for students and could help direct resources at students who most require them. This study was conducted to determine the factors that influence students' course performance in two upper-year agronomy courses at the University of Saskatchewan....

POST broadleaf weed control options in chickpea are very limited on the Northern Great Plains. Field experiments were conducted in 2012 and 2013 in Saskatchewan to evaluate the response of chickpea cultivars to imidazolinone (IMI) herbicides applied at different growth stages. Conventional cultivars 'CDC Luna' and 'CDC Corinne' were compared with I...

Chickpea (Cicer arietinum L.) production in the Northern Great Plains is limited by very few broadleaf weed control options. Field experiments were conducted at two locations in 2012 and at three locations in 2013 in Saskatchewan, Canada, to examine the performance of the conventional and the imidazolinone (IMI) resistant chickpea cultivars to post...

Applying harvest aid herbicides can dry down lentil (Lens culinaris Medik.) crops evenly and quickly, and can help control late-emerging weeds. However, improper application timing may reduce yield and quality, and leave unacceptable herbicide residues in seed, which can cause commercial issues when marketing lentil. The objective of this research...

Previous research has demonstrated that late and sequential applications of glyphosate and glufosinate can have adverse effects on glyphosate- and glufosinate-resistant canola. Similarly, imidazolinone (IMI)-resistant canola may be affected negatively by late applications of imidazolinone herbicides. Field trials were established across the Norther...

We used laboratory and field feeding trials to investigate adult carabid beetle preferences for three brassicaceous weed species (rapeseed, wild mustard, and field pennycress) that are pests in canola. All carabid species preferred seeds of rapeseed most and those of field pennycress least and showed intermediate preference for wild mustard seeds....

The inclusion of competitive crop cultivars in crop rotations is an important integrated weed management (IWM) tool. However, competitiveness is often not considered a priority for breeding or cultivar selection by growers. Field pea (Pisum sativum L.) is often considered a poor competitor with weeds, but it is not known whether competitiveness var...

Much of what is known about the seasonality of human rhinovirus (hRV) infections has been learned from the study of acute asthma exacerbations presenting to emergency care, including those among children at the start of the school term. Much less is known about the patterns of hRVs in the community. In this study, viruses and day-to-day symptoms of...

Ground beetles are postdispersal weed seed predators, yet their role in consuming buried seeds is not well studied. We conducted greenhouse experiments to investigate how seed burial affects consumption of weed seeds (volunteer canola) by adult ground beetles (Coleoptera: Carabidae). Seed burial depth influenced seed consumption rates as demonstrat...

High-frequency canola (Brassica napus L.) rotations increase canola production risks. From 2008 to 2013, direct-seeded experiments involving several variations of continuous canola were compared with wheat (Triticumaestivum L.) and field pea (Pisumsativum L.) rotated with canola at five western Canada locations. Continuous canola rotations involved...

The development of glyphosate-resistant canola has provided improved weed-management options for growers, but crop tolerance to glyphosate may be inadequate at later growth stages. In this study, glyphosate-resistant canola 45H28 (RR) was used to determine the effects of glyphosate application timing on yield and yield components at several sites i...

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 subst...

Canola (Brassica napus L.) is the most common dicotyledonous crop in Canada. Here we determine the effect of canola seed size and seeding rate on canola emergence, development, yield and seed weight. In 2013, direct-seeded experiments were conducted at nine western Canada locations. Four canola seed sizes (1000-seed weights ranging from 3.96 to 5.7...

Previous research has shown that glyphosate applied to glyphosateresistant canola (Brassica napus L.) at later growthstages can reduce yield, particularly if applications are made beyond the six-leaf stage. We questioned whether similar effects could occur in glufosinateresistant canola and therefore, our objective was to characterize the effects o...

Domestication is the process by which a wild plant evolves into a cultivated plant by undergoing morphological, physiological or molecular changes. These changes may be due to conscious selection (primary cultivated plant) or unconscious selection (secondary cultivated plant) by man. These evolutionary changes need to be studied to understand the t...

Viruses are frequently associated with acute exacerbations of asthma, but the extent to which they contribute to the level of day-to-day symptom control is less clear. We sought to explore the relationship between viral infections, host and environmental factors, and respiratory symptoms in children. Sixty-seven asthmatic children collected samples...

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 Man...

Field pea breeding programs have been very successful at improving plant and disease resistance; however, limited success has been achieved in improving the competitive ability of field pea. A study was conducted to determine whether growing field pea in two-way genotypic mixtures could improve the crop’s yield and competitive ability. A second obj...

Efficacy of soil-applied herbicides can be influenced by edaphic factors including soil organic matter (OM) content, as well as by interactions with herbicide tank-mix partners. Field trials were conducted over 6 site-years in 2011 and 2012 across western Canada to examine the interaction of pyroxasulfone and sulfentrazone when co-applied for contr...

The ground beetles (Coleoptera: Carabidae) constitute the largest family of adephagan beetles. Their role as arthropod predators is well known in various agro-ecosystems, and carabids are considered important biological control agents of important agriculture pests. Some recent studies also emphasized their potential in the biological control of we...

Weed management in chickpea (Cicer arietinum L.) in Canada has been restricted by limited options of registered herbicides. Only metribuzin and sulfentrazone are registered for use in chickpea in Canada. The chickpea breeding program at the Crop Development Centre, University of Saskatchewan, has developed chickpea cultivars with tolerance to imida...

There has been keen interest in the development of cow cockle (Vaccaria hispanica (Mill.) Rauschert) as a medicinal and industrial crop in North America. However, very limited agronomic information exists regarding the cultivation of cow cockle as a crop. The objective of this study was to determine how seeding date and rate affected stand establis...

The bed is commonly regarded as the main site of house dust mite exposure; however this has not been directly established by continuous measurements. The objective of this study was to determine the pattern of personal exposure to mite aeroallergen over 24 hours. 12 adults each collected 9 sequential samples (8 during the day, mean 115 mins, and on...

Average personal exposure (pg/m3) for each of the 12 subjects. Each symbol represents the average exposure (pg/m3) for the nine different sampling periods over the 24 hours. Periods P1-P8 were of approximately 2 hours each, between 7am and 10:30 pm and P9 was overnight (~8 hrs). Subject 5 collected samples on 2 days in different locations during th...

The 39 observed activities that were further summarised into 14 categories of activity. In total 39 activities were identified from a post hoc review of the diary records kept for each sample and from viewing the automated pictures taken by the iPod camera running Timelapse Pro worn by the subject. These were further summarised into 14 categories o...

A field study was conducted at eight sites in western Canada to determine the influence of agronomic inputs on fatty acid profiles and biodiesel quality of canola. Protein and chlorophyll concentration and fatty acid profiles were determined from seed samples at all sites. Oil was extracted from canola seed samples from three sites, converted to bi...

Asthma is a common, chronic disease of the airways. Asthmatics can suffer exacerbations (worsening symptoms) due to a range of environmental and occupational factors. At least half of all asthma exacerbations are caused by respiratory viruses. In this article we examine some of the microbiolog-ical causes of asthma development and exacerbations.

Relatively high prices and increasing demand for canola (Brassica napus L.) have prompted growers to produce more canola on more cropland. Here we determine if canola seed yield and oil concentration can be increased over current levels with high levels of crop inputs. From 2008 to 2010, direct-seeded experiments involving two seeding rates (75 vs....

We report the effects of redbacked cutworm Euxoa ochrogaster (Guenée) on cow cockle [Vaccaria hispanica (Mill.) Rauschert] plant height, seed yield, and 1000-seed weight (TSW). Euxoa ochrogaster damage to plots varied considerably among genotypes, with some genotypes exhibiting<10% damage and others >45%. Seed yield also varied significantly among...

Mycosphaerella blight, caused by Mycosphaerella pinodes, is a destructive disease of field pea that is managed using foliar fungicides. Strobilurin fungicides have been used in western Canada for disease management since 2003. To assess the baseline sensitivities of M. pinodes isolates to the strobilurin fungicide pyraclostrobin, the effective conc...

Asfirst-generationgeneticallymodified/trans - geniccropswithnovelagronomictraitshave� beengrowncommerciallyinanumberof� countriessincethemid-1990s,� second-gen- erationcropswithnoveltraits� (CNTs)� arenow� beingtestedinconfinedfieldtrialsaroundthe� world.� Postreleasemonitoring� (PRM)� ofabiotic� stress-tolerantandothersecond-generation� CNTswillst...

Gene flow exposed by genetically engineered crops Gene flow is the transfer of genes between populations of the same or related species. The exchange between crop cultivars of genes selected by traditional breeding that confer characteristics such as shorter stems, higher yield, or increased seed quality will attract little attention. In the same w...

Wheat (Triticum aestivum L.) is one of many crops into which novel traits have been incorporated using recombinant DNA technology, and thus may require segregation from nontransgenic wheat. Volunteer wheat populations, which cannot be selectively removed from wheat crops, pose a challenge to segregation because they may serve to facilitate trait mo...

Transgenic wheat (Triticum aestivum L.) with improved agronomic traits is currently being field-tested. Gene flow in space is well-documented, but isolation in time has not received comparable attention. Here, we report the results of a field experiment that investigated reductions in intraspecific gene flow associated with temporal isolation of fl...