bluuebunny/crossref_metadata_2025 huggingface dataset:
The Influence of Weed Seed Dispersion Versus the Effect of Competition on Crop Yield
Authors: Maxwell Bruce D. , Ghersa Claudio
Published: March 2018

A theoretical model was developed to assess the relative importance of weed competition and seed dispersal in determining long-term crop yield reductions imposed by weeds. Weed seed dispersal by cultivation, natural means, and harvest machines was incorporated into a weed and crop population model. Model simulations were conducted with green foxtail and spring wheat demographic data from the literature. Simulations indicated that seed dispersal from a weed species invading a field may have a more important influence on crop yield than the relative competitive ability of the weed with respect to the crop. However, if a weed species has a uniform or a high frequency random distribution, there is less difference in the relative importance of dispersal versus competitive ability in determining crop yield reductions. Harvest machines may be an important mechanism for dispersing weed seeds that are harvested with the crop. The practical implication is to make harvesters weed seed ‘predators’ rather than dispersal agents and thereby reduce herbicide and mechanical weed control inputs.
Case History for Weed Competition/Population Ecology: Barnyardgrass (Echinochloa crus-galli) in Sugarbeets (Beta vulgaris)
Authors: Norris Robert F.
Published: March 2018

Barnyardgrass at 10 or more plants per 1 m of row caused over 80% root yield loss in spring-sown sugarbeets in California. The yield loss decreased to between 5 and 20% when barnyardgrass densities were one plant ever 2 to 3 m of crop row. The relationship between crop yield and barnyardgrass density was described by a rectangular hyperbolic function. The economic threshold density was in the range of one barnyardgrass plant every 5 to 20 m or row. Barnyardgrass plants growing at densities of less than one plant per 1 m in sugarbeets experienced only interspecific competition. Such individual barnyardgrass plants were estimated to produce from 30 000 to over 200 000 seeds, with an average of 100 000 seeds per plant. This seed production equated to a seed rain of about 4000 to nearly 20 000 seeds per m from a density of one weed every 10 m of crop row. These data suggest that using single-year economic thresholds for barnyardgrass is not a sound management practice because even low densities can produce large quantities of seed.
Tansy
Authors: Mitich Larry W.
Published: March 2018

Common tansy [Tanacetum vulgare (L.) Bernh. ♯CHYVU], a native of Europe and Asia, is a perennial herbaceous composite growing erect to 1 m. It bears finely divided leaves and, in summer, umbels of small, button-shaped yellow flowers. It has had many traditional uses as medicine, preservative, and repellent from Medieval times to modern—uses which have been validated by contemporary research.
Effects of Soil-Applied AC 263,222 on Crops Rotated with Soybean (Glycine Max)
Authors: Wixson Marshall B. , Shaw David R.
Published: March 2018

The effects of the imidazolinone herbicide AC 263,222 on crops that may be rotated with soybean were studied in the greenhouse and field. Corn, grain sorghum, cotton, rice, wheat, soybean, and Italian ryegrass were planted directly into treated soil after AC 263,222 was incorporated. In the field, AC 263,222 at rates as high as 35 g ai ha–1did not reduce shoot weight or emergence of these species. Some visual injury occurred, but was 20% or less 28 d after planting for all crops. Crops were more sensitive in the greenhouse, where reductions in both shoot and root dry weight were observed. AC 263,222 at 13, 13, and 7 g ha–1reduced corn, grain sorghum, and Italian ryegrass shoot weights, respectively. Cotton, rice, and wheat tolerated rates from 27 to 55 g ha–1. Biomass reduction occurred with all crops at 55 g ha–1and above. Because AC 263,222 will be registered for use in soybean at 9 to 18 g ha–1, and potential rotational crops were planted immediately after soil treatment, problems with injury to these crops are not expected.
Antagonism of Graminicide Activity on Annual Grass Species by Imazethapyr
Authors: Myers Paul F. , Coble Harold D.
Published: March 2018

The interaction of imazethapyr and selected graminicides on annual grass control was studied in field experiments. Tank-mix combinations of imazethapyr with clethodim, fluazifop-P, quizalofop, or sethoxydim resulted in an antagonistic interaction. Control of large crabgrass, fall panicum, and broadleaf signalgrass by each graminicide decreased when tank-mixed with imazethapyr as compared with each graminicide applied alone. Sequential applications of imazethapyr, relative to each graminicide, successfully overcame the antagonism. Imazethapyr applied 5 d before or 1 d after each of the graminicides did not decrease grass weed control compared with each graminicide alone. Imazethapyr applied 3 or 1 d before, or the same day as the graminicides, generally decreased grass weed control.
Logistic Analysis for Monitoring and Assessing Herbicide Efficacy
Authors: Turner David L. , Ralphs Michael H. , Evans John O.
Published: March 2018

Two relatively new methods for analyzing herbicide efficacy data are described. Weighted multiple regression using the logit transformation for plant mortality data is illustrated and compared with the more accurate maximum likelihood logistic regression procedure. A partial data set evaluating the effects of increasing application rates of picloram (0, 1.1, 2.2 and 4.5 kg ae ha–1) for control of tall larkspur is used to illustrate the methods. Suggestions are made for using logistic regression to monitor herbicide efficacy over several years.
Directed Sprayer for Targeting Pesticides
Authors: Morrison J. E. , Chandler J. M.
Published: March 2018

An experimental directed sprayer has been improved for use in conservation-tillage and no-tillage field conditions and variable row widths. The directed sprayer consists of a rear-mounted toolbar with individually flotational spraying units on lightweight runners which move over field surfaces without the collection of loose residues. Improvements allow convenient adjustments which combined lateral, vertical, angular, and fore-and-aft repositionings to correctly aim the hydraulic nozzles for desired pesticide targeting. Such new designs are needed to deliver pesticides to targets at minimum application rates and with minimum environmental impacts.
Science, Technology, and Systems: A Hierarchy of Inquiry
Authors: Vietor Donald M. , Cralle Harry T. , Chandler Michael
Published: March 2018

The environment for agricultural research and development, technology transfer, and production is marked by conflict among persons with diverse ideas and goals for agriculture. The objective of this analysis was to identify and compare models for researching and problem solving that can provide a conceptual framework for understanding and improving complex situations marked by conflict. The research activities of scientists involved in development of genetically-engineered-herbicide resistance were modeled as reductionist science, technology development, and optimizing systems. An analysis of these models of goal-seeking research indicated that values and assumptions implicit in goals such as greater productivity were not evaluated or questioned. Views of experts influenced development and application of technologies and systems more than concerns of producers and society. A soft systems methodology and research system is proposed to involve more diverse ideas or views of the world, to shift the role of the researcher from expert to facilitator, and to move toward consensus concerning research and technology development in agriculture.
Response of Bermudagrass (CynodonSpp.) to CGA 163935
Authors: Johnson B. Jack
Published: March 2018

CGA 163935 was evaluated for its growth regulating effect on common bermudagrass for two years and ‘Tifway’ bermudagrass for four years. The vegetative growth of mowed common bermudagrass was suppressed for 5 wk when CGA 163935 was applied at 0.2 kg ha–1followed by 0.1 kg ha–12 wk later and mowed Tifway bermudagrass was suppressed for 4 wk after application of 0.2 kg ha–1. CGA 163935 suppressed vegetative growth of non-mowed common bermudagrass for 9 wk and non-mowed Tifway bermudagrass for 2 to 8 wk at the same rates. Common bermudagrass tolerated CGA 163935 when applied initially at 0.2 kg ha–1and followed by 0.1 kg ha–1at a 2-wk interval for a total 0.3 kg ha–1rate. However, common bermudagrass was severely injured (> 30%) when CGA 163935 was applied at 0.2 kg ha–1in each of two applications for a total rate of 0.4 kg ha–1. Tifway bermudagrass tolerated CGA 163935 when applied at 0.2 kg ha–1as a single application or when the 0.2 kg ha–1was followed by 0.1 kg ha–1at a 4-wk interval. Tifway bermudagrass was severely injured (> 30%) when CGA 163935 was applied at 0.4 kg ha–1as a single application or when 0.2 kg ha–1was followed by 0.1 kg ha–1at 2- or 3-wk interval. Seedheads were suppressed in common bermudagrass for 1 to 2 wk with CGA 163935 at 0.4 kg ha–1.
Recovery, Germinability, and Viability of Leafy Spurge (Euphorbia esula) Seeds Ingested by Sheep and Goats
Authors: Lacey John R. , Wallander Rosie , Olson-Rutz Kathrin
Published: March 2018

Germinability and viability of leafy spurge seeds following ingestion by sheep and goats were evaluated. Four sheep and four goats were separated into eight pens and fed individually a known number of leafy spurge seeds. Following ingestion, goats and sheep passed leafy spurge seeds for 4 and 9 d, respectively. Eighteen percent of the seeds fed were recovered in the fecal material of both species of livestock. Number of seeds recovered, expressed as percent of total seeds fed, decreased with time (P < 0.01). Germinability and viability of the recovered seeds were less than the control (P < 0.01). Sheep were more effective than goats in reducing germinability and viability of leafy spurge seeds (P < 0.01). Results indicate that sheep and goats are effective biological tools for reducing spread of leafy spurge seeds. However, animals grazing mature leafy spurge should be confined for 5 d, until all viable seeds have passed through the digestive system, before they are rotated onto pastures that are devoid of leafy spurge.
Rationale for Developing Herbicide-Resistant Crops
Authors: Burnside Orvin C.
Published: March 2018

Herbicide-resistant crops (HRCs) have been used extensively during the past five decades, because crop tolerance is necessary for a selective herbicide. In the past, chemical company personnel screened a large number of organic compounds against a limited number of major crop and weed species to discover HRCs. Now a single herbicide can be evaluated for crop selectivity against a great number of biotypes of a single crop in tissue culture, or sometimes gene transfer can be used to produce tolerant genotypes. Thus, one can now choose an environmentally “benign” herbicide and search for or develop resistant crop cultivars. The advantages of these new HRCs are: (a) solutions may be more easily found for difficult weed management problems, (b) growers are more apt to use integrated weed management when they have effective backup weed control procedures if cultural or mechanical methods fail, (c) increased weed management options for growers of minor crops, (d) economic advantages to growers, and (e) increased use of more environmentally “benign” herbicides. Concerns about HRCs include: (a) these weed management procedures do not eliminate herbicides, (b) some believe biotechnology should not further herbicide use, (c) HRCs may become weeds, (d) this approach may facilitate less ecological diversity, (e) HRCs may increase herbicide use, (f) it could result in more herbicide carryover by facilitating the use of environmentally “harsh” herbicides, (g) HRCs may be less competitive to weeds, and (h) dependence on HRCs may decrease the weed control practices that a farmer uses. One needs to consider both the benefits and risks of HRCs to properly evaluate this technology.
Concerns a Weed Scientist Might Have About Herbicide-Tolerant Crops
Authors: Radosevich Steven R. , Ghersa Claudio M. , Comstock Gary
Published: March 2018

There are three primary activities that characterize the discipline of Weed Science. These activities are weed technology, weed biology, and the ethics of weed control. Each of these activities needs to be considered as herbicide-tolerant crops (HTCs) are introduced. HTCs are the most recent refinement in the existing technology to control weeds. The potential benefits from the improved weed control must be weighed against possible increased costs of production and potential for genes that control herbicide tolerance to escape into non-tolerant plant populations. These questions about herbicide resistance are primarily technological and biological. They demonstrate the paucity of information in Weed Science on weed genetics, gene flow, fitness, and other aspects of weed-crop population dynamics. Other questions about HTCs are ethical. They require that we ask who benefits from the technology and what are the economic, ecological, and social consequences of it.
Concerns of Seed Company Officials with Herbicide-Tolerant Cultivars
Authors: Duvick Donald N.
Published: March 2018

The primary aim of seed companies is to provide products that the customer wants to buy, and to sell them at a profit. Future demands for improved cultivars of major field crops will continue to be primarily for those with reliably high yield and desirable quality. Herbicide tolerance will not be a primary determinant in cultivar choice for most customers. Therefore, seed companies probably will move with caution in development of herbicide-tolerant cultivars.
Epa's Response to Resistance Management and Herbicide-Tolerant Crop Issues
Authors: Horne Diana M.
Published: March 2018

The regulation of transgenic plants is at the very early stages of dialog between the U.S. Environmental Protection Agency (EPA), the Food and Drug Administration (FDA), and the U.S. Department of Agriculture (USDA). Herbicide resistance is discussed in the broader terms of resistance management and of the cooperative efforts underway involving governments, industry, academia, and the environmental community on an international level. A new body, the International Organization for Resistant Pest Management (IOPRM) was formed to implement pesticide resistance management programs worldwide. The research base for integrated pest management programs which form the context for pesticide resistance management programs is in need of expansion. Public and private efforts to expand this base converge in an ambitious collaborative program between the U.S. EPA and USDA entitled the National Integrated Pest Management Forum. Finally, the potential role of EPA in the regulation of resistance management is discussed.
Use of Modeling in Developing Label Restrictions for Agricultural Chemicals
Authors: Jones Russell L.
Published: March 2018

The movement and degradation of agricultural chemicals in soil and groundwater is a complex process, influenced by climatic conditions, site characteristics, chemical properties, and agricultural practices. Because of this complexity, mechanistic models are useful tools in evaluating environmental fate. Although currently available unsaturated zone models often do not provide accurate concentration profiles when compared with field measurements, they can be used to estimate the depth and extent of movement. Another application of modeling is to compare predicted movement under different simulation conditions to determine the significance of the various factors affecting the behavior of agricultural chemicals. When properly designed and interpreted, modeling studies can contribute to the understanding of the environmental fate of agricultural chemicals. When necessary, modeling can also be useful in developing management practices included on the label or in state regulations. Modeling has been a frequently used tool in developing restrictions for minimizing the movement of aldicarb residues into groundwater and preventing residues in drinking water. Examples of model use include optimizing application timing, estimating well setback distances, and identifying vulnerable soils.
Environmental Risk Assessment of Pesticides: Improving Simulation Model Credibility
Authors: Wauchope R. Don
Published: March 2018

Registrant use of computer simulation modeling is generally accepted by regulators in lieu of some experimental data for risk assessment, provided worst-case assumptions and extremely conservative criteria for negligible risk are used. These requirements taken together mean that only extreme cases escape the requirement for actual environmental data. This conservatism reflects the uncertainty in both exposure estimates by the models and in the hazard estimates from toxicologists. Until the credibility of estimated environmental concentrations given by models is improved by more experimental data and experience on the part of both registrants and regulators, the models will continue to be considered not-validated by many. There are four current developments that provide a compromise between the two impossible extremes of total model validation and total field measurement: (1) as models develop more process detail the parameters become more fundamental in nature and these are generally more amenable to independent estimation or measurement; (2) the reporting of probabilistic analyses and probable errors of results by modelers will enhance credibility; (3) the development of data sets for specific crop/site/pesticide/weather scenarios will allow users to modify those parts of the input they are concerned with while retaining confidence that parameters with which they are unfamiliar will have reasonable values; and (4) meso-scale and micro-scale physical simulation experiments can fill the gap between laboratory and field results. The most important need for enhancing model credibility is full access by the pesticide science community to all the information available, so that we may increase our understanding. Legal mechanisms should be considered for longer ownership of exclusive marketing rights of active ingredients, in exchange for complete public disclosure of the environmental fate and toxicology data submitted to regulatory agencies.
International Organization for Resistant Pest Management (IOPRM) - A Step Toward Rational Resistance Management Recommendations
Authors: Lebaron Homer M. , Gressel Jonathan , Smale Bernard C. , Horne Diana M.
Published: March 2018

A group of scientists from academia, government, and industry, along with ecologists, regulators, conservationists, and grower representatives have formed an International Organization for Resistant Pest Management (IOPRM) to review and delineate proactive and retroactive management strategies for specific cases of pesticide resistance. Within IOPRM, technical working groups were appointed to deal with each pest group. The Weed Resistance Management Working Group (WRMWG) is chaired by Drs. Jonathan Gressel and Leonard Saari, and will deal with the analysis and promoting of alternative control strategies for case studies where a high risk of herbicide resistant weeds exists. Based on our experience to date, crops such as wheat, corn, and soybeans and weeds such as kochia, annual ryegrass and blackgrass, will be used as models to develop optimum weed resistance management programs. The group is especially looking for herbicide and weed control data on negative-cross resistance, econometric models, novel management procedures, and quantitative data from weed scientists and other research and extension communities that could facilitate reaching optimal management decisions. All recommendations and experiences will be communicated through a worldwide network.
Horsetail
Authors: Mitich Larry W.
Published: March 2018

A select few of our present-day weeds are descended from much grander primeval forms. Field horsetail (Equisetum arvense L. ♯ EQUAR) and related species are “degenerate” herbaceous plants whose tree-sized ancestors dominated forests in the Carboniferous period about 300 million years ago. Indeed, early equisetums contributed significantly to the formation of coal beds (12).
Weeds, Crops, and Herbicides: A Modern-Day “Neckriddle”
Authors: Radosevich Steven R. , Ghersa Claudio M.
Published: March 2018

The agricultural community is currently involved in a debate with other members of society concerning many of the tools and tactics used to grow food. The discipline of weed science represents a microcosm of this larger societal debate, and thus is indicative of many other applied agricultural disciplines. Weed science comprises six fundamental disciplines, which have been arranged to depict its three major areas of research: weed technology, weed biology, and the ethics of weed control. Insight into those components of the debate that involve weed science is gained by examining each area. It seems unlikely that solutions to the “neckriddle” can be found through traditional research because of the integrative nature of agriculture, which involves environmental, economic, and social components. It is hoped that movement toward more holistic approaches to research will lead to resolution of the debate between society and the agricultural community.
Influence of Seed Vigor, Herbicide Rates, and Incorporation Depths on Emergence and Seedling Development of Soybean (Glycine max)
Authors: Ratnayake Sunil , Shaw David R.
Published: March 2018

Imazaquin at 140, 280, and 420 g ai ha-1did not negatively affect seedling emergence from high vigor (98% germination) soybean seed but, coupled with a 5.0-cm herbicide incorporation depth, reduced seedling emergence from low vigor (67% germination) seed at all rates. Imazaquin at 420 g ha-1incorporated 5.0 cm deep reduced low and high vigor seedling height 36 and 28%, respectively. Imazaquin at all rates reduced root length from high vigor seed, whereas only the high rate reduced root length of seedlings from low vigor seed. Although 420 g ha-1metribuzin did not affect seedling emergence or root length, emerged seedlings were severely damaged when herbicide was incorporated to 5.0 cm. Trifluralin at 840 and 1680 g ai ha-1reduced emergence of low vigor seed when incorporated 5.0 cm deep. Trifluralin at 840 g ha-1did not affect seedling height or root length, but 1680 g ha-1reduced height of seedling from low and high vigor seed by 86 and 66% when incorporated 5.0 cm deep. Trifluralin at 1680 g ha-1reduced shoot dry weight of both types of seedlings only at the 5.0-cm incorporation depth.
Common Bermudagrass (Cynodon dactylon) Suppression inZoysiaspp. with Herbicides
Authors: Johnson B. Jack
Published: March 2018

During 1989 and 1990, herbicides were applied to suppress common bermudagrass in a mixed stand of common bermudagrass and ‘Emerald’ zoysiagrass. When the mixed stand was treated with fluazifop at 0.2 kg ha-1mid-May and 0.1 kg ha-11 mo later for two consecutive years, the common bermudagrass cover was reduced from 35 to 7% and the zoysiagrass cover increased from 65 to 85%. Similar results were achieve when fenoxaprop was applied at 0.2 kg ha-1mid-May and repeated at monthly intervals for a total of four applications each year for 2 yr. The quality of mixed common bermudagrass and zoysiagrass turf was reduced immediately after each treatment; however, zoysiagrass recovered and treatments did not result in permanent damage. Sethoxydim suppressed common bermudagrass during the second year of treatment, but reduced the zoysiagrass stand each year. Ethofumesate applied along or with flurprimidol severely reduced the zoysiagrass stand with an increase of common bermudagrass.
Effect of Rye (Secale cereale) Mulch on Weed Control and Soil Moisture in Soybean (Glycine max)
Authors: Liebl Rex , Simmons F. William , Wax Loyd M. , Stoller Edward W.
Published: March 2018

A four-year experiment was conducted near Urbana, IL to evaluate the effect of a rye cover crop on weed control, soybean yield and soil moisture. Soybeans were planted into either a rye mulch or corn stubble (with and without spring tillage). Giant foxtail, velvetleaf, smooth pigweed and common lambsquarters control in the rye mulch plots was generally greater than 90% and better than the corn residue treatments five weeks after planting. Weed control was generally better, except for lambsquarters, in the corn residue without spring tillage plots compared to the spring-tilled plots. Herbicides improved weed control in the corn residue plots but not in the no-till rye treatment, due to the excellent control by the rye mulch. Soil water content was lowest during June under the late-killed (killed at planting) rye during dry periods due to water depletion caused by the growing rye. During wet periods the rye mulch resulted in a wetter soil profile compared to the corn residue treatments. Soybean yields were reduced in late-killed rye compared to early-killed rye (killed 2 wk prior to planting) due to soybean stand reductions in the late killed rye. Yields in early-killed rye and spring-tilled treatments were similar to or better than soybeans planted in corn residue without spring tillage.
Nolina texanaControl with Soil-Applied Herbicides
Authors: Petersen Joseph L. , Ueckert Darrell N.
Published: March 2018

Tebuthiuron, picloram, hexazinone, and bromacil were evaluated at 0.5, 1.0, and 2.0 g ai or ae per plant for sacahuista control on gravelly loam soils in western Texas. Tebuthiuron applied at 2.0 g per plant killed 87% of the sacahuista, which was significantly greater mortality than that achieved with the same rate of bromacil (62%) and hexazinone (44%). The 2.0 g plant-1rate of tebuthiuron, bromacil, and hexazinone reduced live canopies of sacahuista 88 to 98%. Picloram did not control sacahuista. Sacahuista mortality increased curvilinearly with increasing rates of tebuthiuron and bromacil, whereas the response to hexazinone was linear.
Response of Four Soybean Cultivars to Metribuzin
Authors: Ivany Jerry A. , Macleod John A. , Sanderson J. Brian
Published: March 2018

The effect of metribuzin at six rates of application was evaluated on four soybean (Glycine maxL.) cultivars and on common hempnettle (Galeopsis tetrahitL.) over a three-yr period (1985 to 1987). The cultivars Maple Amber and Baron were susceptible to metribuzin whereas the cultivars Maple Isle and KG-20 were tolerant of metribuzin. Metribuzin caused progressively greater reductions in plant stands and loss in yield in the susceptible cultivars as rate of application increased. Metribuzin at 0.5 kg ha-1or higher controlled over 90% of common hempnettle.
Annual Grass Control in Alfalfa (Medicago sativa) with Postemergence Graminicides
Authors: Foy Chester L. , Witt Harold L.
Published: March 2018

Field experiments were conducted during 1982 to 1988 in Virginia to evaluate BAS 517, CGA 82725, clethodim, cloproxydim, fenoxaprop, fluazifop, fluazifop-P, haloxyfop, paraquat, quizalofop, SC-1084, sethoxydim, sethoxydim plus thifensulfuron, and terbacil for control of annual grasses in alfalfa. Herbicides were applied to alfalfa and grasses 2 to 30 cm in height after the first and/or second cuttings. Overall, the herbicides were highly effective in controlling fall panicum, giant foxtail, barnyardgrass, and large crabgrass. Alfalfa yields were not increased with herbicide treatments in several experiments. Only paraquat, applied later than recommended after cutting in one experiment, and sethoxydim plus thifensulfuron at one location reduced alfalfa yields.
Re-Seeding Wheat (Triticum aestivum) Following Preplant Treatments of Atrazine
Authors: Bolton Floyd E. , Appleby Arnold P. , Case Scott
Published: March 2018

When applied correctly, atrazine can be used safely in certain areas of the United States for weed control in winter wheat, but persistence in the soil may injure wheat replanted after crop failure. Studies were conducted at Moro, OR, in 1989–90 and 1990–91 to determine the effect of September preplant applications of atrazine at 0.56, 1.12, and 2.24 kg a.i. ha-1 (1X, 2X, and 4X label rates) on wheat seeded at that time and on wheat re-seeded 2 or 6 mo later. Yield of winter wheat re-seeded in November following September atrazine applications was not reduced at any rate. The September-planted wheat was killed with glyphosate in the spring to simulate winter killing, then plots were re-seeded to spring wheat. The commercial rate of atrazine, 0.56 kg ha-1, caused only minor injury to spring wheat, but injury at the 2X and 4X rates was excessive.
Oxyfluorfen for Directed Postemergence Weed Control in Chile Peppers (Capsicum annuum)
Authors: Schroeder Jill
Published: March 2018

Field experiments were conducted in 1990 and 1991 near Artesia and Las Cruces, NM to evaluate directed POST treatments of oxyfluorfen for the control of broadleaf weeds that emerge after thinning chile peppers. At Artesia, Wright groundcherry and prostrate pigweed reduced red pepper yield by 33% in untreated plots in 1990 and clusterflower reduced yield by 19% in 1991. At Las Cruces, Wright groundcherry, Palmer amaranth and common lambsquarters reduced yield by 61% in 1990 and by 76% in 1991. A sequential treatment of oxyfluorfen at 0.14 kg ai ha-1 2 wk after thinning, when the peppers were 15 cm tall, followed by 0.14 kg ha-1 4 wk after thinning controlled all species except common lambsquarters without injuring the peppers.
Effect of Ethalfluralin and Other Herbicides on Trifluralin-Resistant Green Foxtail (Setaria viridis)
Authors: Beckie Hugh J. , Morrison Ian N.
Published: March 2018

The response of trifluralin-susceptible (S) and -resistant (R) green foxtail biotypes to herbicides belonging to several chemical groups was compared to determine the cross-resistance pattern of the R-biotype. Dose-response experiments conducted in the growth chamber indicated that R-green foxtail was resistant to other dinitroanilines and a chemically unrelated mitotic disrupter herbicide, but not to nine other herbicides belonging to seven chemical families. The response of S- and R-green foxtail to increasing dosages of ethalfluralin, applied PPI in rapeseed, was investigated in a field experiment in 1989 and 1990. The R-biotype was 7 times more resistant to ethalfluralin than the S-biotype based on density determinations 4 wk after emergence. Seven times higher dosage was required to reduce R-seed production by 50% than to reduce S-seed production by the same amount. The initial reductions in density of R- and S-plants at the recommended dosage of ethalfluralin in rapeseed (1.4 kg ha−1) was 35% and 95%, respectively. The effective kill (seed yield reduction) of R- and S-biotypes was 55% and 99%, respectively. The results indicate that ethalfluralin will not effectively control R-green foxtail. However, several other herbicides with different mechanisms of action can be used to effectively control R-foxtail, thereby reducing any adverse effects of their interference on crop production.
Persistence of Chlorsulfuron and BAY SMY 1500 in Air Dry Soil at Room Temperature
Authors: Kinfe Birhanu , Peeper Thomas F.
Published: March 2018

Persistence of BAY SMY 1500 and chlorsulfuron during storage for 0 to 6 mo at room temperature in air-dry clay loam soil with pH 7.6 and sandy loam soil with pH 6.6 was determined with conventional wheat bioassay procedures. BAY SMY 1500 had predicted half-lives greater than 6 mo in both soils. Half-lives of chlorsulfuron were 6.0 and 3.2 mo in the clay loam soil and sandy loam soil, respectively.
Herbicide Efficacy and Tolerance in Sweet White Lupin
Authors: Penner Donald , Leep Richard H. , Roggenbuck Frank C. , Lempke James R.
Published: March 2018

The successful introduction of a new crop depends upon the availability of economical, safe, and effective herbicides for that crop. Greenhouse trials identified PRE herbicide applications of 4.5 kg ai ha−1 of metolachlor and of alachlor, 2.2 kg ai ha−1 of linuron and of pendimethalin, and 1.1 kg ai ha−1 of desmediphan as noninjurious to sweet white lupin. POST applications of 0.28 kg ai ha−1 of sethoxydim and of fluazifop and 0.22 kg ai ha−1 of haloxyfop also did not injure the sweet white lupin. Field trials indicated that safe and effective weed control could be obtained with combinations of linuron with metolachlor, alachlor, or pendimethalin depending on weed species present.
Quackgrass (Elytrigia repens) Interference and Control in Seed Alfalfa (Medicago sativa)
Authors: Moyer James R. , Schaalje G. Bruce
Published: March 2018

Alfalfa seed yield and quackgrass density were measured in seven irrigated fields in southern Alberta to assess the effect of quackgrass on seed yield. Six herbicides were tested to determine their effect on quackgrass growth and accompanying alfalfa seed yield. The effect of quackgrass on seed yield was adequately described by a hyperbolic model. Quackgrass densities of 50 and 100 heads per m2reduced seed yields by 56 and 74%, respectively. The economic threshold density was 3 quackgrass heads per m2. The most effective herbicide treatments, quizalofop and propaquizafop, resulted in good initial quackgrass suppression and yield increases similar to those predicted by the hyperbolic model.
Response of Common Bean (Phaseolus vulgaris) Cultivars to Metobromuron
Authors: Park Soon J. , Hamill Allan S.
Published: March 2018

Metobromuron is a major preemergence herbicide controlling mainly broadleaf weeds in common bean production in Ontario. Rainstorms at the seedling stage may splash metobromuron on the plants which results in serious injury, reduced plant stand, and low seed yield. This study determined the appropriate rates of metobromuron for identification of germplasm tolerant to the herbicide. Metobromuron of 0, 0.28, and 0.56 kg ai ha−1 in the glasshouse and 0, 0.28, 0.42, and 0.56 kg ha−1 in the field were applied POST at the unifoliolate stage of 30 bean cultivars. A significant linear effect of herbicide rate on plant injury and recovery was detected. Plant growth was reduced significantly on sensitive cultivars. Two cultivars, Taylor Hort’ and ‘UI 51’, and several plant introductions were tolerant to metobromuron. A rate range of 0.42 to 0.56 kg ha−1 of metobromuron would be appropriate to separate tolerant from sensitive bean lines.
Effect of 2,4-D on Leafy Spurge (Euphorbia esula) Viable Seed Production
Authors: Al-Henaid Jamal S. , Ferrell Mark A. , Miller Stephen D.
Published: March 2018

Leafy spurge viable seed production and germination were reduced by 2,4-D applied during flower development and seed formation, in the field. Viable seed production was reduced when 2,4-D was applied at all growth stages after the start of flower bud development. The number of viable seed from untreated plants was 173, while, the number of viable seed from plants treated 0, 7, 14, 21, 28, or 35 d after the start of flower bud development was <1, 4, 7, 31, 53, and 62; respectively. Leafy spurge seed germination was higher in gibberellic acid than in water for seed collected from untreated plants and from plants treated with 2,4-D 7, 14, and 21 d after bud initiation. This research shows that 2,4-D must be applied prior to flower bud development to prevent seed production.
Response of Southern Wax Myrtle (Myrica cerifera) to Herbicides in Florida
Authors: Kalmbacher R. S. , Eger J. E. , Rowland-Bamford A. J.
Published: March 2018

Triclopyr (0.28, 0.56, and 1.12 kg ai ha−1); triclopyr + 2,4-D (0.56 + 1.12 kg ha−1); and dicamba (1.12 kg ha−1) were evaluated over 2 yr at two locations in Florida for southern wax myrtle control following spring (Mar. to Apr.) or summer (Aug. to Sept.) applications. All treatments were applied twice, 1 yr apart, except 1.12 kg ha−1triclopyr, which was applied once in the initial year. In the first year, defoliation with triclopyr was quadratic with > 90% at 0.56 kg ha−1. In the second year, a single application of 1.12 kg ha−1triclopyr resulted in similar (P > 0.05) defoliation compared with two applications of 0.56 kg ha−1triclopyr. After 1 yr, increasing triclopyr rate resulted in a linear increase in mortality. After 2 yr, two applications of triclopyr at 0.56 kg ha−1and triclopyr + 2,4-D caused lower (P < .01) mortality (45%) than a single application of 1.12 kg ha−1triclopyr (63%). Addition of 2,4-D to triclopyr did not increase mortality. After 2 yr, two applications of 0.28 kg ha−1triclopyr resulted in 21% mortality while two applications of dicamba were ineffective. Defoliation was often greater with spring, compared with summer applications, but often depended on treatment and location. Mortality was greater (P < 0.01) at 1 and 2 yr after summer application compared with spring application at one location, but not the other. Roots of wax myrtle were sampled on 28-d intervals in the first year and analyzed for total non-structural carbohydrate (TNC). Starch composed 630 g kg−1of TNC in myrtle roots, with highest concentration of TNC (120 g kg−1) in March and lowest (30 g kg−1) in August.
Effect of Chemical Treatments on Bahiagrass (Paspalum notatum) Suppression
Authors: Nelson Linda S. , Getsinger Kurt D. , Luu Kien T.
Published: March 2018

Field studies were conducted at Charleston, SC to evaluate the effects of six chemical treatments on bahiagrass and the potential of these treatments to reduce mowing operations. Sulfometuron, maleic hydrazide, and imazethapyr plus imazapyr, in decreasing order of effectiveness, were the most consistent treatments evaluated during the 2-yr study. Sulfometuron reduced bahiagrass vegetative height (23%) for 6 to 8 WAT and suppressed 87 to 92% of seedheads without adversely affecting turf quality. All treatments temporarily discolored turf; however, effects were not objectionable for medium- to low-quality turf settings. Sulfometuron, maleic hydrazide, and imazethapyr plus imazapyr controlled growth and maintained acceptable turf quality for an average of 9, 9, and 8 wk, respectively; thereby reducing mowing operations by an average 29%. Mefluidide plus fluazifop-P, mefluidide plus sulfometuron, and chlorosulfuron were the least effective and/or consistent treatments evaluated.
Canada Thistle (Cirsium arvense) Control with Disking and Herbicides
Authors: Zimdahl Robert L. , Foster Gus
Published: March 2018

Studies from 1985 to 1989 showed that disking 3, 7, 10, 14, or 30 d after applying chlorsulfuron, clopyralid, dicamba, glyphosate, picloram, or 2,4-D did not improve Canada thistle control in uncropped, dryland fields. Disking after a fall or after a fall plus a spring herbicide application did not influence Canada thistle control for any herbicide regardless of the time of herbicide application or the time between application and disking.
Spray Carrier Salts Affect Herbicide Toxicity to Kochia (Kochia scoparia)
Authors: Nalewaja John D. , Matysiak Robert
Published: March 2018

Calcium chloride in the spray carrier antagonized the toxicity of diethanolamine 2,4-D and sodium 2,4-D, dimethylamine MCPA, sodium bentazon, dimethylamine dicamba and sodium dicamba, sodium acifluorfen, imazamethabenz, ammonium imazethapyr, and isopropylamine glyphosate to kochia in greenhouse experiments. Diammonium sulfate overcame calcium chloride antagonism of the above herbicides, except for glyphosate and imazethapyr. Diammonium sulfate or ammonium nitrate adjuvants overcame calcium chloride and sodium bicarbonate antagonism of dicamba toxicity to kochia and enhanced toxicity of sodium dicamba to nearly equal that of dimethylamine dicamba.
Protection from Primisulfuron Injury to Corn (Zea mays) and Sorghum (Sorghum bicolor) with Herbicide Safeners
Authors: Simarmata Marulak , Penner Donald
Published: March 2018

Greenhouse studies were conducted to evaluate and compare herbicide safeners for protection of corn and sorghum from herbicidal injury from metolachlor, primisulfuron, and the interaction of primisulfuron with terbufos, an insecticide. With the exception of CGA-133205 which killed corn, the safeners oxabetrinil, flurazole, naphthalic anhydride, dichlormid, and R-29148 protected against significant injury from the interaction between primisulfuron (40 g ai ha−1) and terbufos (9.8 kg ha−1equivalent to 750 g per 1000 m of row) and from metolachlor (6.7 kg ai ha−1). No primisulfuron-terbufos interaction was observed in sorghum and none of the safeners protected sorghum from primisulfuron injury. PRE application of the antioxidants, piperonyl butoxide and metyrapone, increased primisulfuron injury to corn. Piperonyl butoxide by itself did not influence the growth of corn seedlings, but metyrapone caused slight injury. The increased injury from piperonyl butoxide plus primisulfuron applied at 40 g ha−1was protected by naphthalic anhydride, flurazole, and R-29148, whereas at 80 g ha−1protection was provided by flurazole and R-29148. None of the safeners tested protected against increased injury from metyrapone. Naphthalic anhydride was also an effective safener against increased corn injury when 3000 ppm piperonyl butoxide was applied foliarly 3 d prior to primisulfuron application.14C-Primisulfuron absorption by corn was not influenced by piperonyl butoxide or the safener, naphthalic anhydride. However, metabolism of14C-primisulfuron was inhibited by piperonyl butoxide. This inhibition was not totally reversed by the safener, naphthalic anhydride.
Growth Response of Wild Poinsettia (Euphorbia heterophylla) Following Foliar Herbicide Applications
Authors: Willard Teresa S. , Griffin James L.
Published: March 2018

Greenhouse and field studies were conducted to characterize wild poinsettia growth response to imazaquin (140 g ai ha−1), fomesafen and acifluorfen (420 g ai ha−1), and chlorimuron (9 g ai ha−1) applied at 5 to 7 cm (POST1), 8 to 10 cm (POST2), and 15 to 20 cm (POST3). Based on reductions in weed height and lateral branch number 28 DAT, wild poinsettia was controlled more effectively in both greenhouse and field studies for all herbicides applied at POST1 than at POST3. In the greenhouse studies, reduction in wild poinsettia biomass with the herbicides 28 DAT was similar when applied at POST1 and POST2 and, with the exception of chlorimuron, was higher at POST2 than at POST3. In the field study, weed biomass reduction measured approximately 4 mo after herbicide application was higher for imazaquin, acifluorfen, and chlorimuron applied at POST2 than at POST1. Wild poinsettia biomass was reduced more with imazaquin applied at POST3 than at POST1. Increased lateral branch production, indicative of decreased weed control, was often manifested in higher seed production per plant. With application of all herbicides at POST3 seed production was equal to the untreated check.
Leafy Spurge (Euphorbia esula) Control and Grass Injury with Sulfometuron
Authors: Beck K. George , Lym Rodney G. , Becker Roger L. , Ferrell Mark A. , Finnerty Deane W. , Frank Ronald J. , Henson M. Ann , Peterson Mark A.
Published: March 2018

Leafy spurge control with four herbicides was evaluated at nine sites in six Great Plains states. Sulfometuron alone did not control leafy spurge satisfactorily 12 mo after treatment (MAT). Sulfometuron plus dicamba at 105 plus 2240 g ai ha−1, when spring- or fall-applied, averaged 26 and 89% control and 31 and 86% grass injury, respectively, 12 MAT. Sulfometuron plus picloram at 105 plus 560 g ai ha−1, when spring- or fall-applied, averaged 63 and 92% control and 19 and 89% grass injury, respectively, 12 MAT.
Proso Millet (Panicum miliaceum) Tolerance to Several Postemergence Herbicides
Authors: Lyon Drew J. , Baltensperger David D.
Published: March 2018

The tolerance of two proso millet cultivars to atrazine preemergence and postemergence applications of bromoxynil, clopyralid, dicamba, or metsulfuron plus amine formulations of 2,4-D was studied in the field. Proso millet grain yield, test weight, seed weight, moisture content, and plant height at harvest were not affected by any of the herbicide treatments, despite some early-season injury observed in 1990.
Weed Eradication Using Geographic Information Systems
Authors: Prather Timothy S. , Callihan Robert H.
Published: March 2018

A Geographic Information System (GIS) was developed to evaluate its utility in an eradication program of common crupina. Infested areas were recorded in the GIS along with information normally found on United States Geological Survey topographic maps. Infested areas were separated into management areas according to possible treatment method and special environmental or health requirements such as proximity to streams or inhabited buildings. The location, size, and type of each management area were recorded in the database. The database was constructed to maintain treatment and efficacy data for tracking the process of eradication for each infestation. Areas were identified for detection surveying, including coordinates for navigating with a global positioning system (GPS).
Rice (Oryza sativa) Weed Control with Soil Applications of Quinclorac
Authors: Street Joe E. , Mueller Thomas C.
Published: March 2018

Field studies were conducted from 1988 to 1990 on a Sharkey clay to evaluate residual weed control in rice with quinclorac applied PPI, PRE to dry soil, and PRE to moist soil. Quinclorac applied at 0.4 or 0.6 kg ai ha−1PPI or PRE to dry or moist soil controlled more than 80% of barnyardgrass, pitted morningglory, and hemp sesbania without rice injury. Quinclorac applied at 0.3 kg ha−1controlled these three weed species substantially but inconsistently. No rice injury was observed from any quinclorac treatment. Except for one of three years when irrigation was delayed for 7 d after PRE application to dry soil, application timing did not consistently affect weed control or rice yield.
Influence of Application Variables on Efficacy of Postemergence Applications of DPX-PE350
Authors: Jordan David L. , Frans Robert E. , McClelland Marilyn R.
Published: March 2018

Experiments were conducted to compare control of entireleaf morningglory with POST applications of DPX-PE350 applied with no adjuvant, a nonionic surfactant, or crop oil concentrate in spray volumes of 94, 235, and 375 L ha−1. Control was greater with a nonionic surfactant or crop oil concentrate than with no adjuvant and control with crop oil concentrate exceeded control with the nonionic surfactant. Spray volume had no effect on efficacy. DPX-PE350 was more effective when applied to foliage only or to soil plus foliage than when applied to soil only after emergence of entireleaf morningglory. Control from soil-only applications was lower on a silty clay soil than on a silt loam soil. Except for sicklepod, mixing DPX-PE350 with fluometuron or MSMA had little effect on weed control.
Soybean (Glycine max) Herbicide Carryover to Grain and Fiber Crops
Authors: Walsh Joseph D. , Defelice Michael S. , Sims Barry D.
Published: March 2018

Experiments were conducted in 1988, 1989, and 1990 at two locations in Missouri to study the influence of fall tillage on the soil persistence of several soybean herbicides and subsequent injury to the rotational crops winter wheat, corn, cotton, and grain sorghum. Chlorimuron, clomazone, imazaquin, imazethapyr, and metribuzin plus chlorimuron were applied at their label and double label rate (2X) in soybean. Fall chisel plowing did not influence the carryover potential of these herbicides on any of the crops, in any year, or at either location of the research. However, herbicides injured several of these rotational crops. The 2X-label rate of clomazone reduced winter wheat grain yield at both locations. None of the herbicide treatments at either location reduced corn yield. Imazaquin applied at the 2X rate caused greater than 30% visible injury to cotton in 1989; however, cotton yield was not affected. The 2X rate of chlorimuron caused a reduction of grain sorghum yield in 1989, but not in 1990 or 1991 at Novelty.