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Allergic rhinitis (AR) impacts around 25% of the worldwide population. However, cost, safety, and a high dissatisfaction rate with numerous conventional medications continues to be an issue in the largest patient surveys, due primarily to a lack of efficacy on nasal congestion. Our previously published randomized trial demonstrated a significant reduction in cold and flu-like symptoms, and a secondary potential observation of a decrease in nasal congestion with an oral yeast-derived compound; therefore, the objective of this study was to test the effects of this same product on nasal congestion and other notable AR symptoms.A 12-week, randomized, double-blind, placebo-controlled clinical trial of 96 healthy subjects with a recent clinically documented history of seasonal allergies and AR was conducted. Participants received once-daily supplementation with 500 mg of a dried, modified Saccharomyces cerevisiae oral fermentation product (EpiCor, Embria Health Sciences, Ankeny, Iowa, USA) or placebo during the 12-week period of the highest recorded concentrations of total pollen counts for this Midwest geographic area. Clinical outcome measurements included in-clinic examinations, validated questionnaire and standard diary, and serologic analysis at baseline, 6 and 12 weeks.During the highest pollen count period (weeks 1-6), EpiCor significantly reduced the mean severity of specific AR symptoms, including a significant reduction in nasal congestion (P=0.04), rhinorrhea (P=0.005), and a nonsignificant reduction in ocular discharge symptoms. A significantly (P=0.04) reduced total number of days with nasal congestion (12.5 fewer days) favored EpiCor compared with placebo, as did the nasal congestion section of the quality of life questionnaire (P=0.04). Subjects receiving the intervention also experienced significantly (P=0.03) higher salivary IgA levels. Adverse events were similar to placebo.This yeast-derived product appeared to be safe and efficacious, and should receive more clinical research with and without standard medications to reduce the impact of seasonal allergies, especially AR-induced nasal congestion. more...

Background: The common cold has a profound impact on employee attendance and productivity. Seasonal influenza is responsible for approximately 200,000 hospitalizations and 36,000 deaths per year in the United States alone. Over-the-counter medication efficacy has been questioned, and seasonal vaccination compliance issues abound. Our previously reported randomized trial of an oral fermentation product found an adjuvant benefit for vaccinated individuals in terms of a significantly reduced incidence and duration of cold and flu-like symptoms. Methods: A concurrent 12-week, randomized, double-blind, placebo-controlled clinical trial of 116 subjects with no recent history of seasonal influenza vaccination was conducted. Participants received once-daily supplementation with 500 mg of a dried modified Saccharomyces cerevisiae oral fermentate (EpiCor) or placebo. Clinical outcome measurements included periodic interval-based in-clinic examinations and serologic analysis at baseline, 6 weeks, and 12 weeks. Participants utilized a standardized self-report symptom diary. Results: Subjects receiving the intervention experienced a statistically significant reduction in the incidence (p = 0.01), a nonsignificant reduction in duration (p = 0.10), and no impact on the severity (p = 0.90) of colds or flu-like symptoms, but a more favorable safety profile compared with subjects receiving placebo. Conclusions: This nutritional-based fermentate appeared to be safe and efficacious in a unique at-risk population and should receive more clinical research as a potential method to reduce the incidence of cold and flu-like symptoms, in individuals with and without a history of influenza vaccination. more...

Allergic rhinitis (AR) impacts around 25% of the worldwide population. However, cost, safety, and a high dissatisfaction rate with numerous conventional medications continues to be an issue in the largest patient surveys, due primarily to a lack of efficacy on nasal congestion. Our previously published randomized trial demonstrated a significant reduction in cold and flu-like symptoms, and a secondary potential observation of a decrease in nasal congestion with an oral yeast-derived compound; therefore, the objective of this study was to test the effects of this same product on nasal congestion and other notable AR symptoms. A 12-week, randomized, double-blind, placebo-controlled clinical trial of 96 healthy subjects with a recent clinically documented history of seasonal allergies and AR was conducted. Participants received once-daily supplementation with 500 mg of a dried, modified Saccharomyces cerevisiae oral fermentation product (EpiCor®, Embria Health Sciences, Ankeny, Iowa, USA) or placebo during the 12-week period of the highest recorded concentrations of total pollen counts for this Midwest geographic area. Clinical outcome measurements included in-clinic examinations, validated questionnaire and standard diary, and serologic analysis at baseline, 6 and 12 weeks. During the highest pollen count period (weeks 1–6), EpiCor significantly reduced the mean severity of specific AR symptoms, including a significant reduction in nasal congestion (P=0.04), rhinorrhea (P=0.005), and a nonsignificant reduction in ocular discharge symptoms. A significantly (P=0.04) reduced total number of days with nasal congestion (12.5 fewer days) favored EpiCor compared with placebo, as did the nasal congestion section of the quality of life questionnaire (P=0.04). Subjects receiving the intervention also experienced significantly (P=0.03) higher salivary IgA levels. Adverse events were similar to placebo. This yeast-derived product appeared to be safe and efficacious, and should receive more clinical research with and without standard medications to reduce the impact of seasonal allergies, especially AR-induced nasal congestion. more...

Control of weeds growing around field edges to limit seed production is an important component of preventative weed management. POST herbicide rates that are effective on weeds growing within a dense corn or soybean canopy may not be high enough to control weeds at the edge of a field. A study was conducted from 2004 through 2006 to compare velvetleaf growth and fecundity at the edge of the field as opposed to within the crop in response to a range of glyphosate rates. Treatments included position (plot center or edge), time of emergence (VE or V4 crop growth stage) and glyphosate rate (0 to 900 g ae ha−1). Without herbicide application, velvetleaf plants grown on the edge flowered earlier, had thicker stems, and produced more seed capsules than plants grown in the center of the plots. At glyphosate application rates of 200 to 900 g ha−1, the percentage of plants surviving and reproducing was higher on the edge than within the crop. Edge plants treated with 900 g ha−1of glyphosate produced more seeds than center plants that received no herbicide. Dose–response curves were used to estimate the glyphosate rate that would reduce seed production of surviving plants to 80% of the untreated plants. Plants emerging at the VE stage were estimated to require 300 g ha−1within the corn or soybean canopy and 668 g ha−1on the crop edge, whereas plants emerging at the V4 stage would require 0 g ha−1within the canopy and 280 g ha−1on the crop edge. more...

Two greenhouse trials were conducted over a 2 year period (2004 and 2005) to compare the relative growth potential and fitness of triazine-susceptible (TS) and triazine-resistant (TR) waterhemp biotypes. Waterhemp plants from each biotype were grown in 6 L pots in the greenhouse in a completely randomized design. There was no difference in leaf number, plant height, plant biomass, time to bud or time to flower between the two biotypes. The TR female waterhemp plants produced 30% less reproductive biomass and 39% less seed than the TS biotype. The fitness penalty associated with triazine resistance was related to reproductive capability, not to vegetative growth. more...

Spreading orach is an annual weed that colonizes roadsides, field edges, and increasingly, no-till agricultural fields. It produces dimorphic seeds with different levels of physiological dormancy, but little is known about the germination ecology of the two seed types. Field and controlled-environment studies were conducted to determine seed responses to light and stratification, the pattern of seedling emergence in the field, and the effect of soil water content on the length of cold stratification required to break dormancy for each seed type. The large, brown seeds have three times the mass of the smaller, black seeds, primarily because of a larger embryo, but have a thinner seed coat. Germination of brown and black seeds in petri dishes was 98 and 90%, respectively, after stratification for 3 mo at 5 C, whereas germination of unstratified seeds was 19 and 12%, respectively. Light stimulated germination of both stratified and unstratified black seeds but did not increase germination in stratif... more...

Common waterhemp was first identified in Ontario in 2002. Eight trials were conducted ove r a 3-yr period (2003-2005) at Cottam and Petrolia, Ontario to determine the efficacy of various preemergence and postemergence herbicides for the control of herbicideresistant waterhemp in soybean [ Glycine max (L.) Merr.]. Waterhemp was resistant to the a cetolactate synthase-inhibiting herbicides at both locations and to the photosystem II-inhibiting herbicides at Petrolia; therefore, results varied by location. Results at Petrolia also varied across years. Waterhemp interference resulted in soybean yield losses of up to 73% in weedy versus weed-free checks. Preemergence-applied metolachlor, dimethenamid, and linuron provided greater than 80% control and metolachlor plus metribuzin 94% or greater control of waterhemp 70 d after emergence at both locations. Acifluorfen, fomesafen, imazamox plus fomesafen, and glyphosate applied postemergence resulted in 87% or greater waterhemp control 70 d after application at Cottam in 2003 and 2004 and at Petrolia in 2004; however, waterhemp control with these herbicides was only 60 to 66% at Petrolia in 2005 due to prolonged weed emergence. Multiple herbicide applications per season may be required for effective waterhemp control in soybean. Key words more...

Amaranthus tuberculatus var. rudis (common waterhemp) was first identified in Ontario, Canada in 2002. Eight trials were conducted over a 2-year period (2003 and 2004) at two locations to determine the efficacy of pre-emergence and post-emergence herbicides for the control of A. tuberculatus in maize (Zea mays L.). A. tuberculatus was resistant to the acetolactate synthase inhibiting herbicides at both locations and was resistant to the photosystem II inhibiting herbicides at one location; therefore, results varied by location. A. tuberculatus interference in maize resulted in yield loss of up to 38%. Isoxaflutole plus atrazine, s-metolachlor/atrazine, mesotrione, or S-metolachlor/atrazine plus mesotrione when applied pre-emergence all resulted in greater than 96% control of A. tuberculatus at both locations at 70 days after emergence. Dicamba, dicamba/atrazine, and mesotrione plus atrazine when applied post-emergence all provided greater than 90% control of A. tuberculatus at both locations at 70 days after application. Herbicide treatments which effectively controlled A. tuberculatus resulted in maize yields which were equivalent to the weed-free check. Herbicide selection will have to be site-specific depending on the resistance pattern of A. tuberculatus at each site. more...

Prickly lettuce is an annual weed that germinates in both the fall and the spring. It is often found in no-till soybeans and winter wheat in Ontario, Canada, as well as along the edges of fields. Field studies were conducted from 2001 to 2004 to estimate crop yield losses, and to characterize the phenology and seed production of prickly lettuce in relation to time of emergence. Prickly lettuce had a large impact on soybean yield, with losses of 60 to 80% at densities of 50 plants m−2 or more. Prickly lettuce density estimated to cause a 10% soybean yield loss varied from 0.2 plants m−2 in 2002 to 1.2 plants m−2 in 2003 and 2004. In winter wheat, prickly lettuce at densities up to 200 plants m−2 caused no detectable yield loss in this study. Plants that emerged in the fall generally were larger, flowered earlier. and produced more seeds than those emerging in spring, but size and fecundity were strongly density-dependent. The number of flowers produced per plant could be estimated from the height ... more...

Field studies were conducted over 3 yr at two locations to evaluate the effects of glyphosate rate and application timing on barnyardgrass control, seed production, seed viability, and seedbank density the year after herbicide application in glyphosate-resistant corn. Glyphosate was applied at 0, 112, 225, 450, 675, or 900 g ai/ha when barnyardgrass was at the two-, four-, or six-leaf stage of growth. Visual estimates of percent control increased whereas density, dry weight, seed production, and seedbank density the year after treatment decreased as the rate of glyphosate was increased from 0 to 450 g/ha. Increasing the rate of glyphosate from 450 to 900 g/ha (registered rate) had no further effect on any measured parameter. Seed viability was not affected by glyphosate rate nor application timing. Corn yield declined only at a glyphosate rate of 225 g/ha and below. Barnyardgrass control improved as application was delayed to the six-leaf stage because this weed had an extended period of emergence. There ... more...

This annual dioecious weed was found in 2002 and 2003 infesting soybean fields in southwestern Ontario, and it was collected in 1992 from waste places in British Columbia. It is a major weed problem in field crops in the mid-western United States, where it has become increasingly difficult to control during the past 10 yr. Morphological differences between Amaranthus tuberculatus var. rudis and var. tuberculatus are presented. A review of the biological information published is provided. Plants exhibit high phenotypic plasticity and genetic variability. Emergence is prolonged, growth rapid, and female plants produce a large number of viable seeds that contribute to a persistent seed bank. Amaranthus tuberculatus var. rudis has developed multiple resistance to triazine and acetolactate synthase- and protoporphyrinogen-inhibiting herbicides. Airborne pollen can travel significant distances and A. tuberculatus var. rudis may hybridize with other noxious Amaranthus spp. transferring herbicide resistance or other traits. Key words: Amaranthus tuberculatus var. rudis, AMATA, Amaranthus rudis, common waterhemp, weed biology, invasive alien more...

Root traits and growth of spreading orach and common lambsquarters were compared in response to soil compaction, drought, and waterlogging under controlled environment conditions. On the basis of the typical habitats occupied, the hypothesis was that spreading orach would be more tolerant of compaction and waterlogging and common lambsquarters more tolerant of drought. When grown in buckets with two soil bulk densities (1.2 and 1.6 g cm−3) for 8 wk, the two species responded similarly to compaction, with the fraction of fine roots reduced by 10%, total root length by 70%, root and shoot dry weight and leaf area by 50 to 60%, and plant height by 30% at the high compared with the low bulk density. When grown for 6 wk in soil columns 1 m long, which were watered daily or allowed to dry, common lambsquarters was deeper rooted than spreading orach at both moisture levels and better able to sustain growth in the drying columns. The watering regime did not alter the rooting depth of either species. Tota... more...

Field studies were conducted over 3 yr at two locations to evaluate the effect of glyphosate rate and time of application on common lambsquarters control, density, dry weight, seed production, and the number of seedlings emerging from soil cores taken the year after herbicide application in glyphosate-resistant corn. Glyphosate was applied at 0, 112, 225, 450, 675, or 900 g ai/ha when common lambsquarters were at the two-, four-, or six-leaf stage of growth. Nicosulfuron was applied to all experimental areas to control annual grasses. Visual estimates of percent control increased, whereas density, dry weight, seed production, and seedlings emerging the year after treatment decreased as the rate of glyphosate was increased from 0 to 450 g/ha. Increasing the glyphosate rate above 450 g/ha had little effect on these parameters. Corn yield declined only at glyphosate rates below 450 g/ha. Time of application had no effect on common lambsquarters control and corn yield because little emergence occurred after the first glyphosate application. There was no interaction between glyphosate rate and time of application for any of the parameters evaluated. In these studies, the application of glyphosate at half the manufacturer's registered rate provided control of common lambsquarters equivalent to the full-registered rate with no measured increase in weed seed production and no increase in weed seedlings emerging from soil cores the year after herbicide application. The results suggest that in some cases the use of reduced herbicide rates can provide excellent weed control and maintain crop yields, while reducing the cost of production and the environmental impact of herbicides. The use of extremely low rates (112 or 225 g/ha), however, resulted in reduced corn yields, increased common lambsquarters seed production and seedlings emerging the year after application, and possibly increased weed management costs in subsequent years. more...

A 3-yr study was conducted on nine farms across southern Ontario to evaluate the risks and benefits of different approaches to weed management in corn and soybean. Weed control decisions were based on field scouting and recommendations from the Ontario version of HADSS™, the herbicide application decision support system. Treatments were selected to maximize profit (economic threshold approach) or to maximize yield (highest treatment efficacy). Reduced rates of the high efficacy treatment for each field also were included. Weed density before and after treatment, crop yields, weed seed return, and the effect of weed control decisions on weed density 1 yr after treatment were assessed. Crop yield varied among years and farms but was not affected by weed control treatment. Weed control at 28 d after treatment (DAT) was often lower and weed density, biomass, and seed production 70 DAT were often higher with the profit maximization approach compared with the yield maximization approach. However, weed density 1 yr later, after each cooperator had applied a general weed control program, did not vary significantly among the previous year's weed control treatments. Reduced rates of the high efficacy treatments did not lead to increased weed problems the next year, despite lower weed control and increased weed seed production in some years. During the 3 yr of the study, weed control costs with the profit maximization approach were approximately Can$45/ha less than with the yield maximization approach. more...

Horseweed is a winter annual weed that has evolved resistance to multiple herbicide modes of action in 11 countries worldwide. A paraquat-resistant horseweed population in an Ontario orchard that was being managed by a rotation of herbicides began to show increased tolerance to the herbicide linuron. Experiments were conducted in the greenhouse to compare the response of this population and several paraquat-susceptible populations to linuron, diquat, and oxyfluorfen. Plants were sprayed with a range of doses of each herbicide when they were from 5 to 10 wk old, and the ED50, or dose at which shoot dry weight was reduced by 50%, was estimated. There was a sevenfold difference in the ED50values of the paraquat-resistant and -susceptible populations in response to diquat and a threefold difference in response to linuron. The response to oxyfluorfen was age dependent. The ratio of resistance to susceptible ED50values was estimated as 57 for 5-wk-old plants and 11 for 8-wk-old plants in response to oxyfluorfen. Ten-week-old plants from both populations showed no response to oxyfluorfen at rates up to 4.8 kg ai ha−1. more...

A review of the biological information published after 1980 is provided for three species of the genus Amaranthus: A. retroflexus L., A. powellii S. Watson and A. hybridus L. The three species are noxious weeds introduced to Canada from southern North America. Their geographical distribution has remained almost unchanged since the original paper published in 1980. The plants exhibit a high phenotypic plasticity and genetic variability and they easily adapt to a multitude of agrestal and ruderal habitats. The seeds contribute to a persistent seed bank; they exhibit a variable dormancy and polymorph germination as a result of maternal, genetic and environmental factors. Growth is rapid and plants produce a large number of viable seeds. The three species have developed multiple resistance to triazine and acetolactate-synthase-inhibiting herbicides. They are alternate hosts to many insects, nematodes, viruses, bacteria and fungi that affect cultivated plants. Key words: Amaranthus retroflexus, Amaranthus powellii, Amaranthus hybridus, weed biology, ecology, taxonomy, herbicide resistance more...

Despite extensive research, reduced corn (Zea mays L.) performance is still encountered using conservation tillage on fine-textured soils in cool humid temperate climates. These problems are intensified when corn is planted into residue from a previous crop such as winter wheat (Triticum aestivum L.). The objective of this 4-yr study was to determine the influence of fall zone tillage (ZT), no tillage (NT), and conventional moldboard plow tillage (CT) (fall plowing) on corn performance and soil physical quality under a winter wheat-corn-soybean (Glycine max L. Merr.) rotation with and without red clover (Trifolium pratense L.) (RC) underseeded in the wheat phase of the rotation. A randomized complete block design (3 x 2 factorial, 4 replicates) was established on three adjacent fields in the fall of 1996 on a Brookston day loam soil (fine loamy, mixed, mesic, Typic Argiaquoll) at Woodslee, ON Canada, and measurements were collected during 1997 to 2000. Over both wet and dry growing seasons from 1998-2000, zone tillage following underseeded RC produced average corn grain yields (7.23 Mg ha -1 ) that were within 1% of those obtained using conventional tillage (7.33 Mg ha -1 ), and 36% higher than those obtained using no tillage and RC (5.33 Mg ha -1 ). Zone tillage also improved soil quality as evidenced by generally lower soil strength than no tillage, and near-surface soil physical quality parameters that were equivalent to, or more favorable than, those of the other treatments. It was concluded that corn production using zone tillage and RC underseeding is a viable option in Brookston clay loam soil, as it retains much of the soil quality benefit of conventional tillage but still achieves most of the yield benefit of conventional moldboard plow tillage. more...

A study was undertaken to determine whether the relative leaf stages of common annual weeds and crops could serve as a reliable indicator of the time of weed emergence. Ten annual broadleaved and grass weeds were sown at successive intervals in field corn and soybean at Harrow, ON, Canada, in 1997, 1998, and 1999. All weeds emerging at a particular crop leaf stage were assigned to a cohort. Leaf numbers of the crop and different weed cohorts were recorded at 2- to 3-d intervals up to the eight-leaf stage of corn and the fourth trifoliate of soybean. For each weed species, categorical data analysis revealed a high degree of association between the leaf stage of a crop and the leaf number expected for an individual weed of a given cohort. For example, by the third trifoliate of soybean, most of the weeds emerging with the crop (VE cohort) had 8 to 10 leaves, whereas weeds in the V1, V2, and V3 cohorts averaged about seven, four, and two leaves, respectively. Year to year variation in the correspond... more...

Conyza canadensis (L.) Cronq. (Canada fleabane, horseweed, mare’s-tail) is a winter or summer annual, native to North America, and found in all provinces of Canada except Newfoundland. It is a weed of orchards, vineyards, roadsides, and arable fields where tillage has been reduced or eliminated. Most seedlings emerge from late August through October and form rosettes which overwinter. Large numbers of small, wind-dispersed seeds, ranging to over 200 000 seeds per plant, are produced in late summer. Populations of C. canadensis in more than ten countries have evolved resistance to herbicides such as paraquat, atrazine, chlorsulfuron or glyphosate. Several paraquat resistant populations were found in orchards in Essex Country, Ontario. It serves as a wild host of the tarni shed plant bug, and of aster yellows, a mycoplasma disease transmitted by the aster leaf hopper. Key words: Canada fleabane, ERICA, Conyza canadensis, Erigeron canadensis, horseweed more...

Field studies were conducted in Harrow, Ontario, from 1990 to 1993 to quantify the relationship between yield of field corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] and density of lamb’s-quarters (Chenopodium album L.), common ragweed (Ambrosia artemisiifolia L.), and green foxtail [Setaria viridis (L.) Beauv.]. Experiments were conducted separately for each weed and crop combination. Weeds emerged at the same time as or within a week of the crop. Coefficients of the rectangular hyperbolic damage function were estimated for each year and pooled over years. In both crops, lamb’s-quarters was the most competitive of the three weed species, and green foxtail was the least competitive at low densities. Maximum yield loss at high weed density varied with weed species in field corn, but not in soybean. The estimated competition coefficients of the damage function have been incorporated in a decision support system for integrated weed management in Ontario. Key words: Weed interference, yield loss more...

The objectives of this study were to determine the efficacy and risk of controlling weeds at reduced herbicide rates under various environmental and biotic conditions, through analysis of published data on the use of below-labeled rates of herbicides. A database was established by extracting information from previously published papers on weed control at below-labeled rates of herbicides in crop production systems over large geographical and temporal scales. The database was then analyzed to evaluate the efficacy and risk of using herbicides at various reduced rates under different management systems. Using below-labeled herbicide rates in conjunction with interrow cultivation is an effective way of reducing herbicide input in agricultural systems while maintaining satisfactory weed control. There are greater opportunities for herbicide reduction using preemergence (PRE) than preplant incorporated (PPI) or postemergence (POST) herbicides, in coarse-textured than in fine-textured soils, and in co... more...

Crop rotation is thought to reduce weed density and maintain species diversity, thus preventing the domination of a few problem weeds. Because cropping sequence dictates other agricultural management practices, variations in weed populations between cropping systems may be the direct result of crop rotation, the result of different weed management practices associated with crop rotation, or both. Studies that fail to separate the effects of crop rotation from weed management may generate misleading results. A 10-yr crop rotation study was undertaken to study the dynamics of the standing weed vegetation inZea maysL.,Glycine maxL., andTriticum aestivumL. The present paper compared total weed density and diversity between monocultures and rotations under three levels of weed management. Weed management accounted for 37.9% of the variation in total weed density, whereas crop rotation accounted for only 5.5%. Weed density varied between monocultures and rotations in plots where herbicides were applied. The effectiveness of rotations in reducing weed density was dependent upon the crop. Margalef's species richness index (DMG), a measure of diversity, varied among weed management strategies, with 38.4% of the variance attributed to this factor. In the 10th year, when all plots were sown withZ. mays, few cumulative effects of crop rotation were apparent, with two exceptions. In weedy and herbicide-treated plots, weed density was higher on plots cropped withZ. maysthe previous year. Also, under these weed management treatments, including a cereal in the crop rotation reduced weed density. Crop rotation, when used in combination with herbicides, provides additional weed control and is therefore an effective tool in integrated weed management. more...

No-tillage systems on fine-textured soil are not well suited for corn (Zea mays L.) because of problems with excess water, lower temperatures, and residue management during the early stages of corn growth. This is a problem, as corn is commonly used in rotation with wheat (Triticum aestivum L.) and soybean [Glycine max (L.) Merr.]. Furthermore, when corn follows winter wheat there may be additional problems associated with residue management during the early stages of corn growth. Hence, the objectives of this study were to measure the effect of the red clover (Trifolium pratense L.) cover crop underseeded in wheat and no-tillage on soil temperature, water content, corn emergence, surface residue, and yields in a wheat-corn-soybean rotation in southwestern Ontario. Treatments included con ventional vs. no-tillage both with and without underseeded red clover in a wheat-corn-soybean rotation in a clay loam soil. A no-tillage and red clover treatment that had the wheat straw baled was also included. No-tillage (with arid without red clover) increased soil water content by 2 to 5% and reduced soil temperatures by 1 to 2°C during early corn emergence. Soil drying occurred along the planting slot of the no-tillage treatments, which enabled the soil seed furrow to open and the corn seedlings to become water stressed even though the no-tillage treatments were wetter in the spring. Corn emergence in the no-tillage treatment without red clover was delayed by 3 to 4 d and the final plant stand was reduced by 24% compared with the conventional tillage treatment. The no-tillage treatment without red clover had 13% lower corn grain yield than the conventional tillage treatment averaged over three years. However, when red clover was included with no-tillage, corn emergence was increased and corn grain yields were not significantly different from conventional tillage in both 1994 and 1996, There was also 15% less dry weight of surface plant residue present in the no-tillage treatments when red clover was included. Hence, red clover alleviated some of the problems of no-tillage for corn production. more...

Field experiments were conducted to determine the influence of time of emergence and density of single and multispecies populations of pigweed and barnyardgrass on soybean yield and competitive abilities of pigweed and barnyardgrass. Pigweed and barnyardgrass were established at selected densities within 12.5 cm on either side of the soybean row. Pigweed and barnyardgrass seeds were sown concurrently with soybean and at the cotyledon stage of soybean growth. Time and density of pigweed and barnyardgrass seedling emergence relative to soybean influenced the magnitude of soybean yield loss. Maximum soybean yield loss ranged from 32 to 99%, depending upon time of emergence relative to soybean. Pigweed was more competitive than barnyardgrass across all locations, years, and time of weed emergence. When pigweed was assigned a competitive index of 1 on a scale from 0 to 1, the competitive ability of barnyardgrass ranged from 0.075 to 0.40 of pigweed, depending upon location and time of emergence. This is the first multiple weed species study to include time of weed emergence relative to the crop. Competitive index values for multiple weed species must be calculated from field experiments in which weeds are grown with the crop under differing environmental conditions. more...

Populations of horseweed and Virginia pepperweed resistant to the herbicide paraquat were found in several fruit orchards in Essex County, Ontario, Canada, where paraquat had been applied four to five times per year for at least 10 yr. Dose–response experiments were conducted in the greenhouse for each species, using 2-to 4-mo-old plants from populations that had received repeated exposure to paraquat and those that had not. The paraquat dose that reduced shoot dry weight by 50% (ED50) was estimated for each population. Resistant populations of horseweed had ED50 values 25 to 35 times higher than susceptible populations. A resistant population of Virginia pepperweed had an ED50 10 times higher than susceptible populations. more...

Eastern black nightshade is a problem weed in soybeans primarily due to interference with harvesting operations and reductions in crop quality. Field and greenhouse studies were conducted in 1990 and 1991 at Harrow, Ontario, to determine whether sublethal rates of imazethapyr and metolachlor could suppress growth and berry production by eastern black nightshade. In the greenhouse, plants treated with metolachlor PRE at 0.8 kg ai ha−1or imazethapyr POST at 30 g ai ha−1(1/3 to 1/2 the labelled rates) produced significantly fewer berries in the first flower cluster, with fewer seeds per berry, than untreated plants. When a surfactant was added to the imazethapyr, almost all flower buds in the first cluster were aborted. Treated plants recovered from the damage, however, and did not differ significantly from control plants in dry weight or berry production 110 DAP. In the field, application of 50 g ai ha−1imazethapyr POST (2/3 of the lowest labelled rate), with or without a surfactant, resulted in delayed flowering, abortion of most of the flower buds in the first cluster, and greatly reduced growth and total berry production between soybean leaf abscision and harvest. Application of metolachlor + metribuzin PPI in the field at 2/3 of the labelled rate (1.6 + 0.25 kg ai ha−1) was not sufficient to reduce nightshade growth and berry production after soybean leaf abscision. Sublethal rates of imazethapyr and metolachlor did not reduce seed viability in either the greenhouse or the field. more...

A synthetic data set was created by incorporating results from previously published papers on antagonistic and synergistic herbicide interactions between two herbicides applied as a tank mixture or sequentially, and then analyzed on the basis of various properties of the herbicides and target plants. Generally, interactions between herbicides were antagonistic more frequently than synergistic. This trend held no matter whether the interacting herbicides were absorbed by the same or different parts of the plant, had the same or different translocating abilities, had the same or different modes of action, and regardless of whether the target plants were annual or perennial plants, or crops or weeds. Antagonistic interactions occurred much more frequently when the target plants were monocot than dicot, and in the Compositae, Gramineae, or Leguminosae than in the Chenopodiaceae or Convolvulaceae families. more...

Soybean seed yield losses due to interference from common cocklebur, velvetleaf, and jimsonweed, with and without a PPI application of 0.42 kg ai ha-1 metribuzin, were determined in 1986, 1987, and 1988. Damage functions were calculated based on weed density, weed leaf density, and relative weed leaf area index, respectively. Functions relating crop yield losses to weed density varied significantly among treatments and years for each species. Weeds which escaped soil-applied metribuzin were shorter with fewer leaves at 3 wk after planting, and caused lower crop yield losses than control plants at equal densities. Yield loss estimates based upon relative weed leaf area at 3 wk after planting showed least variation between years and treatments. Nomenclature: Metribuzin, 4-amino-6-(1,1-dimethylethyl)-3-(methylthio)-1,2,4-triane-5(4H)-one; soybean, Glycine max (L.) Merr. 'Premier'; common cocklebur, Xanthium strumarium L. #3 XANST; jimsonweed, Datura stramonium L. # DATST; velvetleaf, Abutilon theophrasti Medik. # ABUTH. Additional index words: Abutilon theophrasti, Datura stramonium, Xanthium strumarium, ABUTH, DATST, XANST. more...

A yeast-based product (EpiCor, a dried Saccharomyces cerevisiae fermentate) was compared to placebo to determine effects on the incidence and duration of cold and flu-like symptoms in healthy subjects recently vaccinated for seasonal influenza. In a 12-week, randomized, double-blind, placebo-controlled clinical trial, 116 participants received daily supplementation with 500 mg of EpiCor or placebo for 12 weeks. Data collected included periodic in-clinic examinations and serologic evaluations at baseline, 6- and 12-weeks. Subjects also utilized a standardized self-report symptom diary during the study. Participants receiving the yeast-based product had significantly fewer symptoms and significantly shorter duration of symptoms when compared with subjects taking a placebo. more...

Reductions in yields of processing tomatoes (Lycopersicon esculentumMill. ‘H2653’ and ‘Earlirouge′) caused by interference from eastern black nightshade (Solanum ptycanthumDun. # SOLPT) and hairy nighthsade (S. sarrachoidesSendt. # SOLSA) were estimated for transplanted and seeded tomatoes at two locations in southern Ontario. Tomato yield losses were significantly greater in seeded than in transplanted tomatoes. Stomatal conductance and transpiration rates of seeded tomatoes decreased more rapidly with increased nightshade density than did those of transplanted tomatoes. Percent yield losses also differed between sites. Seeded tomatoes grown at high density in twin rows (33 300 and 45 000 plants/ha) had higher yields and lower percent yield losses than did tomatoes grown at low density in single rows (12 500 to 22 500 plants/ha). Nightshade dry weight and seed production decreased per plant but increased per unit area with increasing nightshade density. Nightshade dry weights and seed production did not vary with site or method of tomato establishment. A hyperbolic model provided an excellent fit to data on both tomato yield losses and nightshade seed production as a function of nightshade density. more...

Convolvulus arvensis L., field bindweed, is an introduced weed which occurs in the agricultural regions of all provinces of Canada with the exception of Newfoundland and Prince Edward Island. Its twining growth habit and extensive root and rhizome system make it exceptionally difficult to control. It spreads by both seeds and root or rhizome fragments. Details of its morphology, reproductive biology, response to parasites, and methods of control are presented. more...

The critical period of weed interference in transplanted tomatoes (Lycopersicon esculentumMill. 'Springset’) was from 28 to 35 days after transplanting. A single weeding during this period was sufficient to prevent yield reductions. A growth analysis revealed that significant differences in plant dry weight and fruit number between tomatoes from weed-free and weed-infested plots were not apparent until 56 to 70 days after transplanting. The shorter the initial weed-free period, or the longer weeds were allowed to remain in the plots before removal, the earlier reductions in tomato dry weight and fruit number appeared. Weed interference was due primarily to shading rather than water stress. Tomatoes from weed-infested plots had significantly lower stomatal conductances than those from weed-free plots, but did not differ in xylem-pressure potential or in canopy temperature. If tomatoes were kept weed-free for more than 28 days, or when weeds were present for less than 28 days after transplanting, stomatal conductances were not significantly reduced. more...

Populations of the colonizing weeds Rumex crispus L. and R. obtusifolius L. were initiated from seed following disturbance on three occasions between May and September 1976. Three distinct cohorts were followed within each population. Cohorts which had the same order of emergence within a population but different dates of emergence had similar mortality rates. On the other hand, when cohorts of different emergence order and similar emergence dates were compared, those cohorts which emerged first had the lower mortality rates. For both species, the population arising latest in the season had the lowest percentage emergence but the greatest percentage survival of emerged plants to the time of flowering. These populations also had the best reproductive performance. The latest emerging population of R. crispus was the only one to produce as many seeds as had originally been sown, despite the fact that less than 10% of the emerged seedlings survived the winter and less than 1% of the seed pool gave rise to flowering plants. These results suggest that the timing of land management practices such as cultivation can have a profound effect on the success of weed populations. more...

Effects of soil pH on growth, competitive ability, and leaf nutrient content of corn (Zea maysL.), Powell amaranth (Amaranthus powelliiS. Wats. ♯ AMAPO), velvetleaf (Abutilon theophrastiMedic. ♯ ABUTH), and green foxtail [Setaria viridis(L.) Beauv. ♯ SETVI] were measured in the field. Corn yields were significantly reduced by weed competition at all pH levels, but leaf nutrient content, as a percentage of dry weight, was not affected. Aboveground dry weights of Powell amaranth and velvetleaf were significantly lower at pH 4.8 than at pH 6.0 or 7.3, whereas growth of green foxtail was greater at pH 4.8 than at pH 7.3. Weed competitive ability, as evidenced by reductions in dry weight, varied with soil pH and companion plant. Powell amaranth and velvetleaf had higher levels of S, Zn, and especially Mn, at pH 4.8 than at pH 7.3. N and K in the leaf tissue were greater in the weed species than in corn at all soil pH levels. The dicot species had higher percentages of Ca and Mg in leaf tissue at all soil pH levels and accumulated higher percentages of Mn at low pH than the monocot species. more...

Xanthium strumarium L. is an annual weed found in all provinces of Canada except Newfoundland, and throughout the temperate and subtropical regions of the world. It occurs in ruderal habitats, waste places, agricultural fields, and along watercourses, beaches and coastal dunes. Throughout its range, populations vary widely in fruit size and morphology and in photoperiodic requirements. It has been used extensively as an experimental plant in studies of floral induction, leaf development, stomatal control, seed germination, and biological control.Key words: Cocklebur, reproductive biology, weed, Xanthium more...

Summary: Resume: Zusammenfassung The effects of soyabean Glycine max (L.) Merr. row width, date of planting and year on threshold levels of jimsonweed (Datura stramonium L.) and on jimsonweed seed production were examined over 3 years. Natural infestations of jimsonweed were employed and densities were determined at 3 weeks after planting and also at soyabean harvest. Date of planting affected emergence of both soyabean and jimsonweed seedlings, whereas row width affected weed seedling mortality. Percentage soyabean yield losses attributable to jimsonweed, over all treatments, were greater in the 2 years with above-average rainfall than in the one dry year. Slopes of regression equations and estimates of threshold densities varied significantly among years and between initial and final density counts. The number of jimsonweed seed capsules produced per plant and the number of seeds per capsule declined with jimsonweed density, but the mean number of seeds produced per m2 remained fairly constant over a wide density range. Jimsonweed seed production did not decline significantly until well below the threshold densities determined for soyabean yields. Les facteurs du seuil de nuisibilite et de la production de graines chez Datura stramonium L. dans les cultures de soja (Glycine max. (L.) Merr.) L'influence de l'ecartement des rangs de soja, Glycine max (L) Merr., de la date de semis, et de l'annee, sur le seuil de nuisibilite et la production de graines chez le Datura stramonium L., a eteetudiee durant 3 annees. Les etudes ont ete effectuees sur des infestations naturelles de datura, dont les densites ont ete determinees 3 semaines apres le semis ainsi qu'a la recolte. La date du semis influence a la fois la levee du soja et celle du datura, alors que l'ecartement des rangs influe sur la mortalite des graines de l'adventice. Dans tous les traitements, les pertes de rendement attribuables au datura ont ete plus importantes durant les 2 annees ou les precipitations on ete superieures a la moyenne que durant une annee seche. Les pentes des equations de regression et les estimations de seuils de nuisibilite variaient d'une maniere significative selon les annees et entre les comptages initiaux et finaux. Le nombre de capsules par plane et le nombre de graines par capsule diminuaient avec la densite des datura, mais le nombre moyen de graines produites par m2 est reste assez constant dans une large gamme de densite. La production de graines de datura n'a decline significativement que pour une densite de plantes situee bien en dessous du seuil de nuisibilitea l'egard des rendements du soja. Faktoren, welche die Schadigungsschwelle und Samenproduktion von Stechapfel (Datura Stramonium L.) in Sojabohnen (Glycine max (L.) Merr.) beeinflussen Wahrend drei Jahren wurde in Sojabohnen der Einfluss von Reihendistanz und Saatzeitpunkt auf die Schadigungsschwelle und Samenproduktion von Stechapfel (Datura stramonium L.) untersucht. Diese Studie basierte auf den naturlichen Stechapfelpopulationen; die Zahlungen der Populationsdichten erfolgten drei Wochen nach der Sojasaat und bei der Ernte. Der Saattermin beeinflusste das Auflaufen der Sojabohnen und der Stechapfelsamlinge, wahrend die Reihendistanz die Mortalitat der Unkrautsamlinge veranderte. Die Steigung der Regressionsgeraden und die Schatzungen der schadigenden Populationsdichte variierten signifikant in den einzelnen Jahren und zwischen der ersten und letzten Zahlung. Die Anzahl der von den Stechapfelindividuen produzierten Samenkapseln pro Pflanze und Samenmenge pro Kapsel nahm mit zunehmender Populationsdichte ab; die pro m2 gebildete Samenzahl blieb jedoch uber einen weiten Bereich verschiedener Populationsdichten relativ konstant. Die von der Stechapfelpopulation produzierte Samenmenge nahm bis weit unter die fur die Sojabohen schadigende Populationsschwelle nicht signifikant ab. more...

Between- and within-population variation for 21 quantitative characters was estimated for five populations of Datura stramonium originating along a climatic gradient ranging from southern Ohio, U.S.A., to Elgin County, Ont., Canada. Datura stramonium is a predominantly inbreeding, annual species with a distribution which is expanding northward in Ontario. Plants were grown from seed to maturity in the greenhouse under uniform conditions. The five populations differed significantly in the mean values of all measured characters. Canonical variates analyses were used to distinguish the populations on the basis of combined groups of characters. Canonical means of the five populations differed significantly for both seedling and mature plant characters, but the relative distance between populations varied for the two character sets. Levels of between- and within-family variation differed significantly among populations and from one character to another. Percent germination, seedling dry weight, and leaf area were strongly correlated with initial seed weight. Seed weight and cotyledon length increased and days to anthesis decreased with a decreasing length of the growing season. more...

A summary of biological information is provided on Amaranthus retroflexus L., A. powellii S. Wats. and A. hybridus L. These three pigweed species are annual weeds of cultivated fields and other open, disturbed habitats. A. retroflexus is found in all provinces of Canada except Newfoundland. A. powellii is found in British Columbia and in southern Ontario. A. hybridus occurs in southwestern Ontario. more...

Datura stramonium L. (Solanaceae) is an annual weed found in most temperate and subtropical regions of the world. It has been recorded from all the provinces of Canada except Newfoundland, but is most common in Ontario and Quebec. It occurs in waste places, gardens, barnyards and, increasingly, in cultivated fields. Datura stramonium serves as an alternate host for many insect pests and diseases of Solanaceous crops, such as tomatoes, tobacco and potatoes, and has both narcotic and medicinal properties due to its production of a variety of alkaloids. It has been used extensively as an experimental plant in studies of genetics, chromosome morphology and embryonic development.Key words: Weed biology, jimsonweed, Datura stramonium, distribution more...

Percent germination and germination rates of seeds of atrazine (6-chloro- N-ethyl-N' -(1 -methylethyl)- 1,3,5 -triazine- 2,4-diarnine)-resistant and -susceptible bio - types of redroot pigweed (Amaranthus retroflexus L. #3 AMARE) and Powell amaranth (A. powellii S. Wats. # AMAPO) from southern Ontario were compared in petri dishes using a 100-cell germination plate. The plate pro- vided 100 separately controlled, altemating temperature combinations ranging from 0 to 45 C in increments of 5 C. The experiment was conducted under alternating light and dark conditions for 21 days and under constant dark con- ditions for 7 days. Initial seed viabilities exceeded 90% for all four biotypes. Under alternating light and darkness, the resistant biotype of Powell amaranth had significantly lower total germination and a slower rate of germination than the susceptible biotype, whereas the biotypes of redroot pigweed did not differ in germination response. Germina- tion rate and total germination were positively correlated for all four biotypes. In constant darkness, the atrazine- resistant biotypes of both species had significantly lower germination percentages compared to the susceptible bio- types. In general, percent germination of Powell amaranth was greater than that of redroot pigweed for day and night temperatures more...

Abstract This paper describes a heuristic approach to Production Facility siting and optimal pipeline routing to connect wells to Production Facilities. The pipe sizes for the production, lift gas and water injection systems were calculated and included in the optimization. Production Facility siting, based on production lines alone, is not Production Facility siting, based on production lines alone, is not optimal. Introduction Sohio's involvement in the development of an oil field of large areal extent led to this study. Once the location of wells and their production schedules had been estimated, the number of Production Facilities, their locations, and the routing of pipelines connecting wells to the Production Facilities had to be developed. A Production Facility is defined as one where production is separated into its phases and each phase is treated as required. These Facilities may also contain lift gas compressors and injection water pumps. The connections to wells consist of single three-phase production lines, trunk and lateral lift gas and injection water lines, electrical power transmission lines and roads. These connections between adjacent power transmission lines and roads. These connections between adjacent wells or a well to a Production Center are shown in Figure 1. Since the production schedule (hence the probable revenue) was fixed, the objective was to develop a gathering/distribution system to handle the projected rates at a minimum total cost. projected rates at a minimum total cost. Optimal trunk and lateral systems for the lift gas and injected water cannot be designed by standard network algorithms. As is demonstrated in the following section, this is because basic assumptions inherent in standard network algorithms are invalid for trunk and lateral pipeline systems. The problem is further complicated by the fact that the solution being sought is one that minimizes the total cost of all the interconnections in the field; or .............(1) where Tg = total cost of the lift gas trunk and lateral system Tw = total cost of the injected water trunk and lateral system Tp = total cost of individual production lines from each well Tr = total road cost (function of distance only)Te = total power transmission cost (function of distance only)Ts = total pipe support costs and T = total cost of all interconnections A heuristic procedure has been developed by the authors to solve this problem. problem. The algorithm developed helps determine:The number of Production Facilities required in a field.The routing of pipelines, roads and electric power transmission lines to the wells.The sizes of the pipelines for each service to each well.The effect of increasing lift gas compressor discharge pressures, and injection water pump discharge pressures. THEORY AND DEFINITIONS Trunk and lateral systems are also commonly referred to as dendritic and telescoped systems. In a trunk and lateral system, wells distant from the Production Facilities can "share" pipes to intermediate wells. Hence larger flow rates exist in portions of trunk and lateral systems closer to the Production Facility. Direct enumeration is a method where all possible alternative solutions are evaluated to find the optimal solution. For practical problems where several options exist, this solution method becomes too time problems where several options exist, this solution method becomes too time consuming even for high speed computers. p. 257 more...

La compétition entre les cultures et les mauvaises herbes est un phénomène complexe. Des modèles de simulation exhaustifs, orientés vers les processus et traitant la compétition selon une approche systématique plutôt qu'empirique, peuvent offrir un aperçu des relations qui existent entre la compétition, la densité des cultures et des mauvaises herbes, les périodes relatives d'émergence, les divers caractères morphologiques et physiologiques, ainsi que les niveaux de ressources. Ils peuvent aussi être utilisés pour la prévision en tant que composante d'une approche systémique de lutte contre les mauvaises herbes. Cet article passe en revue les caractéristiques de quelques modèles de simulation récents de compétition entre les cultures et les mauvaises herbes, les espèces pour lesquelles leurs paramètres ont été adaptés, ainsi que leurs applications. Jusqu'à maintenant, ces modèles ont été principalement utilisés afin de prédire les pertes de rendement attribuables à la compétition exercée par les mauvaises herbes. Leur aptitude à simuler la production de graines de mauvaises herbes en réponse à certains facteurs environnementaux n'a pas été exploitée. La prochaine étape consistera à relier les modèles de simulation de compétition cultures-adventices aux modèles de dynamique des populations de mauvaises herbes, pour améliorer notre aptitude à prédire dans le temps les effets de diverses stratégies de lutte contre les mauvaises herbes. Les avantages et inconvénients de l'approche par modèles pour résou dre les problèmes de lutte contre les mauvaises herbes sont discutés., Competition between crops and weeds is a complex phenomenon. Comprehensive, process-oriented simulation models which treat competition in a mechanistic rather than an empirical fashion, can offer insight into relationships among competition, crop and weed density, relative time of emergence, various morphological and physiological traits, and resource levels. They can also be used for prediction as part of a Systems approach to weed management. This paper reviews the features of a number of recent simulation models of crop-weed competition, the species for which they have been parameterized, and their applications. To date, these models have been used primarily to predict crop yield losses due to weed competition. Their ability to simulate weed seed production in response to the environment has not been exploited. The next step is to link simulation models of crop-weed competition to weed population dynamics models, in order to improve our ability to predict the effect of various weed management strategies over time. Advantages and drawbacks of a modeling approach to weed management problems are discussed. more...