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Earlier reports have summarized crop yield losses throughout various North American regions if weeds were left uncontrolled. Offered here is a report from the current WSSA Weed Loss Committee on potential yield losses due to weeds based on data collected from various regions of the United States and Canada. Dry bean yield loss estimates were made by comparing dry bean yield in the weedy control with plots that had >95% weed control from research studies conducted in dry bean growing regions of the United States and Canada over a 10-year period (2007 to 2016). Results from these field studies showed that dry bean growers in Idaho, Michigan, Montana, Nebraska, North Dakota, South Dakota, Wyoming, Ontario, and Manitoba would potentially lose an average of 50%, 31%, 36%, 59%, 94%, 31%, 71%, 56%, and 71% of their dry bean yield, respectively. This equates to a monetary loss of US $36, 40, 6, 56, 421, 2, 18, 44, and 44 million, respectively, if the best agronomic practices are used without any weed management tactics. Based on 2016 census data, at an average yield loss of 71.4% for North America due to uncontrolled weeds, dry bean production in the United States and Canada would be reduced by 941,000,000 and 184,000,000 kg, valued at approximately US $622 and US $100 million, respectively. This study documents the dramatic yield and monetary losses in dry beans due to weed interference and the importance of continued funding for weed management research to minimize dry bean yield losses. Nomenclature: dry bean, Phaseolus vulgaris L.

Chemical weed control remains a widely used component of integrated weed management strategies because of its cost-effectiveness and rapid removal of crop pests. Additionally, dicamba-plus-glyphosate mixtures are a commonly recommended herbicide combination to combat herbicide resistance, specifically in recently commercially released dicamba-tolerant soybean and cotton. However, increased spray drift concerns and antagonistic interactions require that the application process be optimized to maximize biological efficacy while minimizing environmental contamination potential. Field research was conducted in 2016, 2017, and 2018 across three locations (Mississippi, Nebraska, and North Dakota) for a total of six site-years. The objectives were to characterize the efficacy of a range of droplet sizes [150 μm (Fine) to 900 μm (Ultra Coarse)] using a dicamba-plus-glyphosate mixture and to create novel weed management recommendations utilizing pulse-width modulation (PWM) sprayer technology. Results across pooled site-years indicated that a droplet size of 395 μm (Coarse) maximized weed mortality from a dicamba-plus-glyphosate mixture at 94 L ha–1. However, droplet size could be increased to 620 μm (Extremely Coarse) to maintain 90% of the maximum weed mortality while further mitigating particle drift potential. Although generalized droplet size recommendations could be created across site-years, optimum droplet sizes within each site-year varied considerably and may be dependent on weed species, geographic location, weather conditions, and herbicide resistance(s) present in the field. The precise, site-specific application of a dicamba-plus-glyphosate mixture using the results of this research will allow applicators to more effectively utilize PWM sprayers, reduce particle drift potential, maintain biological efficacy, and reduce the selection pressure for the evolution of herbicide-resistant weeds.

Core Ideas Model fit increased by predicting optimum droplet sizes for site‐specific scenarios. Generally, an Extremely Coarse spray would be recommended for a 2,4‐D choline plus glyphosate application. Site‐specific weed management using PWM sprayers was both manageable and effective. Weed control reductions were observed as droplet size increased at several site‐years. Alternative drift reduction efforts must be identified to avoid weed control losses. The delivery of an optimum herbicide droplet size using pulse‐width modulation (PWM) sprayers can reduce potential environmental contamination, maintain efficacy, and provide more flexible options for pesticide applicators. Field research was conducted in 2016, 2017, and 2018 across three locations (Mississippi, Nebraska, and North Dakota) for a total of 6 site‐years. The objectives were to evaluate the efficacy of a range of droplet sizes (150 µm [Fine] to 900 µm [Ultra Coarse]) using a 2,4‐D choline plus glyphosate pre‐mixture and to create novel weed management recommendations using PWM sprayer technology. A pooled site‐year generalized additive model explained less than 5% of the model deviance, so a site‐specific analysis was conducted. Across the Mississippi and North Dakota sites, a 900‐µm (Ultra Coarse) droplet size maintained 90% of the maximum weed control. In contrast, at the Nebraska sites, droplet sizes between 565 and 690 µm (Extremely Coarse) were almost exclusively required to maintain 90% of the maximum weed control, likely due to weed leaf architecture. Severe reductions in weed control were observed as droplet size increased at several site‐years. Alternative drift reduction practices must be identified; otherwise, weed control reductions will be observed. This research illustrated that PWM sprayers paired with appropriate nozzle–pressure combinations for 2,4‐D choline plus glyphosate pre‐mixture could be effectively implemented into precision agricultural practices by generating optimum herbicide droplet sizes for site‐specific management plans. To fully optimize spray applications using PWM technology, future research must holistically investigate the influence of application parameters and conditions.

Increased use of dicamba and/or glyphosate in dicamba/glyphosate-tolerant soybean might affect many sensitive crops, including potato. The objective of this study was to determine the growth and yield of ‘Russet Burbank’ potato grown from seed tubers (generation 2) from mother plants (generation 1) treated with dicamba (4, 20, and 99 g ae ha-1), glyphosate (8, 40, and 197 g ae ha-1), or a combination of dicamba and glyphosate during tuber initiation. Generation 2 tubers were planted near Oakes and Inkster, ND, in 2016 and 2017, at the same research farm where the generation 1 tubers were grown the previous year. Treatment with 99 g ha-1dicamba, 197 g ha-1glyphosate, or 99 g ha-1dicamba + 197 g ha-1glyphosate caused emergence of generation 2 plants to be reduced by up to 84%, 86%, and 87%, respectively, at 5 wk after planting. Total tuber yield of generation 2 was reduced up to 67%, 55%, and 68% when 99 g ha-1dicamba, 197 g ha-1glyphosate, or 99 g ha-1 dicamba + 197 g ha-1 glyphosate was applied to generation 1 plants, respectively. At each site year, 197 g ha-1 glyphosate reduced total yield and marketable yield, while 99 g ha-1 dicamba reduced total yield and marketable yield in some site-years. This study confirms that exposure to glyphosate and dicamba of potato grown for potato seed tubers can negatively affect the growth and yield potential of the subsequently grown daughter generation. Nomenclature: Dicamba; glyphosate; potato, Solanum tuberosum L; soybean, Glycine max (L.) Merr

The discipline of weed science is at a critical juncture. Decades of efficient chemical weed control have led to a rise in the number of herbicide-resistant weed populations, with few new herbicides with unique modes of action to counter this trend and often no economical alternatives to herbicides in large-acreage crops. At the same time, the world population is swelling, necessitating increased food production to feed an anticipated 9 billion people by the year 2050. Here, we consider these challenges along with emerging trends in technology and innovation that offer hope of providing sustainable weed management into the future. The emergence of natural product leads in discovery of new herbicides and biopesticides suggests that new modes of action can be discovered, while genetic engineering provides additional options for manipulating herbicide selectivity and creating entirely novel approaches to weed management. Advances in understanding plant pathogen interactions will contribute to developing new biological control agents, and insights into plant–plant interactions suggest that crops can be improved by manipulating their response to competition. Revolutions in computing power and automation have led to a nascent industry built on using machine vision and global positioning system information to distinguish weeds from crops and deliver precision weed control. These technologies open multiple possibilities for efficient weed management, whether through chemical or mechanical mechanisms. Information is also needed by growers to make good decisions, and will be delivered with unprecedented efficiency and specificity, potentially revolutionizing aspects of extension work. We consider that meeting the weed management needs of agriculture by 2050 and beyond is a challenge that requires commitment by funding agencies, researchers, and students to translate new technologies into durable weed management solutions. Integrating old and new weed management technologies into more diverse weed management systems based on a better understanding of weed biology and ecology can provide integrated weed management and resistance management strategies that will be more sustainable than the technologies that are now failing.

Pyroxasulfone (KIH-485) is a seedling growth-inhibiting herbicide developed by Kumiai America that has the potential to control weeds in sunflower. However, little is known about how this herbicide will interact with various soil types and environments when combined with sulfentrazone. The objective of this research was to evaluate sunflower injury and weed control with pyroxasulfone applied with and without sulfentrazone across the Great Plains sunflower production area. A multisite study was initiated in spring 2007 to evaluate sunflower response to pyroxasulfone applied PRE at 0, 167, 208, or 333 g ai ha−1. In 2008, pyroxasulfone was applied alone and in tank mixture with sulfentrazone. In 2007, no sunflower injury was observed with any rate of pyroxasulfone at any location except Highmore, SD, where sunflower injury was 17%, 4 wk after treatment (WAT) with 333 g ha−1. In 2008, sunflower injury ranged from 0 to 4% for all treatments. Adding sulfentrazone did not increase injury. Sunflower yield was only reduced in treatments in which weeds were not effectively controlled. These treatments included the untreated control and pyroxasulfone at 167 g ha−1. Sunflower yield did not differ among the other treatments of pyroxasulfone or sulfentrazone applied alone or in combination. The addition of sulfentrazone to pyroxasulfone improved control of foxtail barley, prostrate pigweed, wild buckwheat, Palmer amaranth, and marshelder, but not large crabgrass or green foxtail. The combination of pyroxasulfone and sulfentrazone did not reduce control of any of the weeds evaluated. Nomenclature: Pyroxasulfone (KIH-485); sulfentrazone; foxtail barley, Hordeum jubatum L. HORJU; green foxtail, Setaria viridis (L.) Beauv. SETVI; large crabgrass, Digitaria sanguinalis (L.) Scop. DIGSA; marshelder, Iva xanthifolia Nutt. IVAXA; Palmer amaranth, Amaranthus palmeri S. Wats. AMAPA; prostrate pigweed, Amaranthus blitoides S. Wats AMABL; wild buckwheat, Polygonum convolvulus L. POLCO; sunflower, Helianthus annuus L

Field trials using sublethal doses of glyphosate, dicamba, or mixtures of both herbicides on dry edible pea ( Pisum sativum ), dry edible bean ( Phaseolus vulgaris ), and potato ( Solanum tuberosum ) were conducted at six locations to determine the injury potential if spray drift were to occur. All studies used three increasing sublethal doses of glyphosate and dicamba, which were labeled as low, medium, and high. The doses for each herbicide varied for the three crops because of expected sensitivity differences. Herbicide doses were targeted for the reproductive stage 1 with dry edible pea and dry edible bean, and at tuber initiation for potato. Visible injury 20 days after the treatment ranged from 0% to 13% for dry edible pea, 0% to 53% for dry edible bean, and 0% to 50% for potato. Compared with the nontreated, yield was least when doses included dicamba, regardless of the crop. Dry edible bean was the most sensitive crop to sublethal doses of dicamba, followed by dry edible pea and potato. Results from these six studies suggested that drift injury potential to dry edible pea, dry edible bean, and potato will be greater if a dicamba-resistant soybean ( Glycine max ) crop is adjacent and upwind compared with a glyphosate-resistant crop. Results also reinforce the need for diligence in the application of these herbicides in proximity to susceptible crops and the need to thoroughly clean sprayers before spraying a sensitive crop.

Lack of consistent regulation and marketing of adjuvants and complexity of the interaction among plant, herbicide, environment, water quality, and adjuvant have caused general confusion in adjuvant selection among growers. Choosing the best adjuvant is difficult. Growers must chose from thousands of commercial products and are confused by product descriptions with unfamiliar ingredients and functions. Confusing recommendations, aggressive marketing, and lack of unbiased research and educational information make matters even worse. Manufacturer lists of approved adjuvant products, guidelines that set minimum requirements to qualify adjuvants for use with herbicides, and packaging effective adjuvants with herbicides either in the herbicide formulation or packaged in a different container help reduce grower confusion. University adjuvant research and education have aided grower knowledge and understanding of adjuvants by field testing adjuvants and have influenced herbicide label wording and recommendations. Abbreviations: HLB, hydrophilic–lipophilic balance; NDSU, North Dakota State University; NIS, nonionic surfactant.

A field experiment was conducted over five years to determine the effect of season-long kochia interference on oat yield and quality. Kochia interference did not affect oat height, test weight, 500-kernel weight, or groat percentage. Similarly, ash, starch, and total β-glucan percentages in oat groat were not affected by kochia interference. Oat grain yield was reduced in 1991 and 1994 by 30 kochia$\\text{plants}/{\\rm m}^{2}$, the highest density. Lipid and protein content were not affected by kochia except in 1992 where protein content was reduced and lipid content was increased by kochia.