Don W. Morishita

Evaluation of models predicting winter wheat yield as a function of winter wheat and jointed goatgrass densities

Abstract Three models that empirically predict crop yield from crop and weed density were evaluated for their fit to 30 data sets from multistate, multiyear winter wheat–jointed goatgrass interference experiments. The purpose of the evaluation was to identify which model would generally perform best for the prediction of yield (damage function) in a bioeconomic model and which model would best fulfill criteria for hypothesis testing with limited amounts of data. Seven criteria were used to assess the fit of the models to the data. Overall, Model 2, provided the best statistical description of the data. Model 2, regressions were most often statistically significant, as indicated by approximate F tests, explained the largest proportion of total variation about the mean, gave the smallest residual sum of squares, and returned residuals with random distribution more often than Models 1, and 3,. Model 2, performed less well based on the remaining criteria. Model 3, outperformed Models 1, and 2, in the number of parameters estimated that were statistically significant. Model 1, outperformed Models 2, and 3, in the proportion of regressions that converged on a solution and more readily exhibited an asymptotic relationship between winter wheat yield and both winter wheat and jointed goatgrass density under the constraint of limited data. In contrast, Model 2, exhibited a relatively linear relationship between yield and crop density and little effect of increasing jointed goatgrass density on yield, thus overpredicting yield at high weed densities when data were scarce. Model 2, had statistical properties that made it superior for hypothesis testing; however, Model 1s properties were determined superior for the damage function in the winter wheat–jointed goatgrass bioeconomic model because it was less likely to cause bias in yield predictions based on data sets of minimum size. Nomenclature:Jointed goatgrass, Aegilops cylindrica Host. AEGCY; winter wheat, Triticum aestivum L.

Season-long Dose–response of Potato to Sulfometuron

Abstract Field trials were conducted to determine potato response to parts per trillion (ppt) per weight concentrations of sulfometuron in soil. The herbicide was applied to achieve targeted, 0-d soil concentrations of 0, 7.5, 15, 30, 60, 120, 240, 480, and 960 ppt. Russet Burbank potatoes were planted immediately after application using standard agronomic practices. Based on midseason visual evaluations, root and tuber injury occurred with 0-d concentrations of only 7.5 ppt. Concentrations at or above 120 ppt caused a significant increase in number of tubers with deformities compared with the control. By the end of the growing season, 0-d concentrations between 120 and 240 ppt resulted in higher percentages of tubers with deformities, such as cracks, knobs, or folds. Using logistic models fit to U.S. No. 1 tuber yield and net return data, doses of 74, 156, and 324 ppt are predicted to result in 5, 10, and 20% U.S. No. 1 yield reductions, respectively. The model predicted a 20% net return loss, approximately

Managing Wicked Herbicide-Resistance: Lessons from the Field

160/ha, occurring at 262 ppt, which is near the 240 ppt concentration determined by standard ANOVAs and means comparisons with single degree of freedom contrasts causing significant tuber quality and yield reductions in our study. Growers using the 240 ppt concentration as an indicator of a no-effect level would encounter actual losses too great to withstand. This modeling approach provides an initial attempt at giving growers the tools necessary for assessing potential losses. Nomenclature: Sulfometuron; potato; Solanum tuberosum L; ‘Russet Burbank’

Potential Yield Loss in Dry Bean Crops Due to Weeds in the United States and Canada

Abstract Herbicide resistance is ‘wicked’ in nature; therefore, results of the many educational efforts to encourage diversification of weed control practices in the United States have been mixed. It is clear that we do not sufficiently understand the totality of the grassroots obstacles, concerns, challenges, and specific solutions needed for varied crop production systems. Weed management issues and solutions vary with such variables as management styles, regions, cropping systems, and available or affordable technologies. Therefore, to help the weed science community better understand the needs and ideas of those directly dealing with herbicide resistance, seven half-day regional listening sessions were held across the United States between December 2016 and April 2017 with groups of diverse stakeholders on the issues and potential solutions for herbicide resistance management. The major goals of the sessions were to gain an understanding of stakeholders and their goals and concerns related to herbicide resistance management, to become familiar with regional differences, and to identify decision maker needs to address herbicide resistance. The messages shared by listening-session participants could be summarized by six themes: we need new herbicides; there is no need for more regulation; there is a need for more education, especially for others who were not present; diversity is hard; the agricultural economy makes it difficult to make changes; and we are aware of herbicide resistance but are managing it. The authors concluded that more work is needed to bring a community-wide, interdisciplinary approach to understanding the complexity of managing weeds within the context of the whole farm operation and for communicating the need to address herbicide resistance.

Impact of glyphosate-resistant sugar beet

Abstract 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

The Influence of Foliar Ethephon Application on Economic Returns of Red LaSoda Potatoes

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

Determining Physiological Maturation of Jointed Goatgrass (Aegilops cylindrica Host) Caryopses1

622 and US

Confirmation of Glyphosate-Resistant Kochia (Kochia scoparia) from Sugar Beet Fields in Idaho and Oregon

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.

SPATIAL STATISTICAL ANALYSIS FOR THE AREA-OF-INFLUENCE EXPERIMENTS

Glyphosate-resistant (GR) sugar beet became commercially available to US sugar beet growers in 2008 and was rapidly adopted. Prior to the availability of GR sugar beet, growers would commonly make 3-5 herbicide applications. This often resulted in some crop injury, but was accepted to reduce the impact of weeds. In addition, non-GR sugar beet was cultivated 1-3 times and often followed by hand weeding. The introduction of GR sugar beet drastically reduced the complexity of weed management. Concerns about GR weeds in the United States also apply to sugar beet growers. Changes in weed management strategies will be required to keep this technology. Sugar beet is arguably one of the most suitable crops for GR technology because: (1) none of the herbicides registered for use in this crop was very effective without risking crop injury; (2) sugar beet cannot be grown in the same field year after year owing to disease concerns and thus requires a 3-4 year rotation; (3) pollen-mediated gene flow is negligible from the sugar beet crop because it is a biennial and harvested before it flowers; (4) the processing of harvested roots to extract the sucrose rapidly degrades the DNA in the extracted raw juice and subsequent refining so that no DNA is present in the finished sugar; (5) studies have shown that processed GR beet sugar is identical to non-GR beet sugar, as well as cane sugar.

SITE-TO-SITE AND YEAR-TO-YEAR VARIATION IN TRITICUM AESTIVUM-AEGILOPS CYLINDRICA INTERFERENCE RELATIONSHIPS

The successful marketing of fresh potatoes is heavily reliant upon tuber appearance. Past attempts to improve the color and appearance of fresh potatoes have included the adoption of new cultivars, application of waxes during packing, control of skin damaging diseases, and foliar application of growth regulators. An analysis of the potential economic impact of the use of the plant growth regulator ethephon(2-chloroethylphosphonic acid) was conducted. Data on the influence of ethephon application rate on tuber size distribution and yield was collected from field trials on the red-skinned cultivar Red LaSoda during 2011 and 2012. These data were then used in conjunction with records of red potato prices for the most recently available five crop years to calculate gross returns. Production costs, chemical and application costs, and packing costs were then subtracted to calculate net economic returns. No adjustment in market value was made to account for the improved skin color measured due to ethephon application, as there are no data to support this assumption. Ethephon rate did not significantly affect total yield in either year, but did influence the distribution of various market classes (A, B and Creamers) in 2012. There was some influence in net value by size class, but total net return was not significantly affected in either year. While ethephon is not a very expensive addition to the total cost of production, it does not appear to provide a significant economic benefit based on the change in tuber size distribution alone.ResumenEl mercadeo exitoso de papa fresca se confía fuertemente en la apariencia del tubérculo. Los intentos pasados para mejorar el color y la apariencia de papa fresca han incluido la adopción de nuevas variedades, aplicación de ceras durante el empaque, el control de enfermedades dañinas de la piel y la aplicación foliar de reguladores del crecimiento. Se condujo un análisis del impacto económico potencial del uso del regulador de crecimiento etefon (ácido 2-chloroetilfosfonico). Se colectaron datos de la influencia del nivel de la aplicación del etefon en la distribución del tamaño de tubérculo y rendimiento, de ensayos de campo en la variedad de piel roja Red La Soda durante 2011 y 2012. Se usaron después estos datos junto con los registros de los precios de papa roja de los cinco años más recientemente disponibles del cultivo para calcular retornos brutos. Se sustrajeron los costos de producción, los costos de los agroquímicos y de su aplicación y del empaque, para calcular las ganancias económicas netas. No se hizo ajuste en el valor del mercado para que contara para el mejoramiento del color de la piel medido debido a la aplicación del etefon, porque no hubo datos para respaldar esta suposición. El nivel de etefon no afectó significativamente al rendimiento total en ningún año, pero si influenció la distribución de varias clases de mercado (A, B, y pequeñas prematuras Cremer) en 2012. Hubo alguna influencia en el valor neto por clase de tamaño, pero la ganancia total neta no se afectó significativamente en ningún año. Mientras que el etefon no es un agregado muy caro al costo total de producción, no parece suministrar un beneficio económico significativo con base solo en el cambio en la distribución del tamaño de tubérculo.