bluuebunny/crossref_metadata_2025 huggingface dataset:
Nutrient Effects on Parasitism and Germination of Egyptian Broomrape (Orobanche aegyptiaca)
Authors: Jain Rakesh , Foy Chester L.
Published: March 2018

The influence of various nutrients on parasitism of tomato plants by Egyptian broomrape and on stimulation of broomrape seed germination by strigol analogs was investigated in greenhouse and laboratory experiments. Parasitism occurred most readily in potting media low in fertility. Addition of nitrogenous compounds to potting media resulted in inhibition of broomrape parasitism. Ammonium nitrate with potassium phosphate or ammonium phosphate alone was most effective in reducing parasitism and enhancing growth of tomato plants. In the laboratory, strigol analogs induced 55% germination in broomrape seeds preconditioned in distilled water. Seeds preconditioned in distilled water or various salt solutions, but not treated with strigol analogs, showed 18% germination. GR 24 (5 μM) induced higher germination in seeds preconditioned in 10 mM ammonium nitrate, with or without potassium phosphate, compared with seeds preconditioned in sodium chloride. Preconditioning of seeds in sodium nitrate (10 mM) and treating with GR 24 stimulated, whereas preconditioning of seeds in ammonium salts (1 mM ammonium sulfate or 10 mM urea) and treating with GR 24 inhibited germination significantly.
Organosilicone Adjuvant Effects on Glyphosate Efficacy and Rainfastness
Authors: Reddy Krishna N. , Singh Megh
Published: March 2018

Greenhouse studies were conducted to evaluate the effectiveness of Kinetic, a silicone adjuvant that appeared to increase the efficacy and rainfastness of the isopropylamine salt of glyphosate on velvetleaf, sicklepod, barnyardgrass, guineagrass, yellow foxtail, and yellow nutsedge. Simulated rainfall of 1.3 cm in 5 min at 15 and 60 min after herbicide treatment reduced glyphosate efficacy on all weeds. Kinetic enhanced glyphosate efficacy when yellow nutsedge and guineagrass were subjected to post-spray rainfall at 60 min. On velvetleaf, sicklepod, and yellow foxtail, Kinetic improved glyphosate efficacy when the critical rain-free period was reduced to 15 min. Kinetic failed to provide rainfastness for barnyardgrass, thereby indicating a specificity of Kinetic for certain weed species.
Pepper (Capsicum annuum) Cultivar Response to Metolachlor in Three New Mexico Soils
Authors: Schroeder Jill
Published: March 2018

Field experiments in 1988, 1989, and 1990 evaluated the response of four pepper cultivars to PPI applications of metolachlor at Las Cruces and Artesia, New Mexico. Metolachlor at ≥ 2.2 kg ai ha–1in 1988 and 4.5 kg ha–1in 1990 reduced overall green pepper yields only in a Harkey very fine sandy loam soil at Artesia. Metolachlor at ≥ 2.2 kg ha–1reduced the yield of the jalapeno cultivar ‘TAM’ and at 4.5 kg ha–1reduced the yield of New Mexico cultivar ‘NM 6-4’ and a proprietary New Mexico cultivar in 1988. Metolachlor did not reduce the yield of any cultivar in 1989 or 1990. Metolachlor bioactivity on NM 6-4 pepper was similar in the three soils regardless of irrigation water source. Emergence of peppers was ranked Belen clay loam = Rakor loam > Harkey very fine sandy loam when the greenhouse temperature approximated field conditions. Under conditions where germination and emergence of peppers was reduced by an interaction between soil factors and temperature, further stand reduction due to metolachlor treatment caused yield reductions.
Soybean (Glycine max) Response to Chlorimuron and Imazaquin as Influenced by Soil Moisture
Authors: Newsom Larry J. , Shaw David R.
Published: March 2018

Field experiments were conducted in 1989 and 1990 to evaluate differential soybean cultivar tolerance to chlorimuron and imazaquin applied PPI, as influenced by soil moisture. Natural rainfall was supplemented with irrigation to achieve three moisture regimes: low (nonirrigated), optimum (5 cm wk–1), and excessive (15 cm wk–1). Imazaquin at 140 g ai ha–1did not adversely affect height or yield of cultivars under any of the moisture regimes. Excessive moisture, regardless of herbicide treatment, reduced height and yield with many of the cultivars. Chlorimuron at 80 g ai ha–1caused additional plant height reductions of 8 cm or more with ‘Asgrow 5403% ‘Asgrow 5979’, ‘Coker 686’, ‘Asgrow 6785’, ‘Hartz 6686’, and 'Sharkey’ in the excessive moisture regime, and yield was reduced 450 kg ha–1or more with ‘Hutcheson’, ‘Terra-Vig 515’, Coker 686, Asgrow 6785, and Hartz 6686. Chlorimuron in the optimum moisture regime reduced the height of Coker 686 and ‘Deltapine 566’ 10 and 11 cm, respectively; however, no yield reductions were noted.
Effect of the Date of Initial Handweeding on the Yield of Groundnut(Arachis hypogaea)
Authors: Ambassa-Kiki Raphael , Ngongang Jean-Claude
Published: March 2018

The effect of two dates of initial manual weeding, i.e., before flowering and after flowering, and of no weeding on yield of a local groundnut variety was studied during 1988 and 1989 at Minkoameyos, Yaounde, Cameroon, in comparison with chemical weed control method or control. The use of herbicides ametryn plus promotryn for weed control gave the best mean yield, followed by handweeding after flowering, and handweeding before flowering, in that order. The no weeding treatment had the lowest yield throughout the trial period.
Density ofCarduusandCirsiumThistles in Selected Areas of Maryland
Authors: Tipping Philip W.
Published: March 2018

In a three county area, the density of musk thistle was higher than plumeless thistle in pastures in the easternmost county, equivalent in the central county, and lower in the westernmost county. Bull thistle was detected frequently, but density was always low. Detection of Canada thistle decreased from east to west.
Addressing Public Fears Over Pesticides
Authors: Major Christopher S. , William Ray D.
Published: March 2018

Organizer's comments: Systems inquiry represents an array of research-based problem-solving approaches. European experience with the pesticide debate suggests several simple messages contained in this paper. As weed scientists, we have everything to gain by considering a global sphere of views, practices, logic, experience, and message. Read this paper for the essence, the message, the systems thinking, the research framework, and the interface between society and weed science. Read it because science and society must communicate.
Safening of Corn (Zea mays) from Clomazone Injury with Naphthalic Anhydride
Authors: Krausz Ronald F. , Kapusta George
Published: March 2018

Field studies were conducted in 1989 and 1990 to determine if corn seed treated with naphthalic anhydride (NA) at 0.5% (w/w) would result in a reduction in corn injury caused by clomazone applied preplant incorporated (PPI) or preemergence (PRE) at 0.56 and 0.70 kg a.i. ha–1. NA significantly reduced corn injury, especially where clomazone was incorporated. Plant population, height, ear number, and grain yield also were higher in plots where NA was used. In most instances, corn injury was less and plant population, height, ear number, and grain yield were higher in plots where clomazone was applied PRE compared with PPI.
Corn (Zea mays) Response to Post-directed Sethoxydim Under Irrigated and Dryland Conditions
Authors: Smart James R. , Mortensen David A. , Roeth Fred W.
Published: March 2018

Four corn hybrids were evaluated for tolerance to sethoxydim at 110 and 220 kg ha–1applied post-directed at two growth stages (V6–7 and V10–11). Dryland corn grain yields did not respond to sethoxydim, while irrigated corn yields were sensitive to sethoxydim treatments. Sethoxydim at 220 g ha–1reduced the grain yield of hybrid 3377 by 12% at both growth stages. Sethoxydim at the same rate reduced grain yield of hybrid 3379 by 15% when applied to V6–7 corn. Hybrid 3475 had an 11% grain yield reduction from sethoxydim applied at either dosage to V10–11 corn. Under irrigated conditions, a trend toward reduced grain yield was observed for hybrid 3183 at all application times and sethoxydim rates. Corn ear weights and kernel weights differed among hybrids but did not exhibit a response to sethoxydim within hybrids. Visual evaluation for crop injury and measured corn heights did not indicate a response to sethoxydim. There was no yield response in any hybrid to 110 g ha–1applied to V6–7 stage corn indicating this treatment was safe to use on all hybrids evaluated.
Environment Influences Green Foxtail (Setaria viridis) Competition with Wheat (Triticum aestivum)
Authors: Peterson Dallas E. , Nalewaja John D.
Published: March 2018

Temperature, soil moisture, green foxtail density, relative emergence dates, and soil fertility effects on green foxtail and spring wheat competition were evaluated in controlled environments. Green foxtail competition was highest at 30 C and without moisture stress. Early green foxtail emergence increased competition with wheat more than changes in temperature, soil moisture, or green foxtail density. At 30 C, wheat fresh weight was reduced 50% by green foxtail seeded 4 d before wheat, but only 13% by foxtail seeded 4 d after wheat. Doubling the nitrogen and total nutrient concentration did not increase wheat growth, but increased foxtail weight 41 and 75%, respectively.
Future Impact of Crops with Modified Herbicide Resistance
Authors: Wyse Donald L.
Published: March 2018

The development of crop cultivars with resistance to selected herbicides has the potential to impact environmental quality, food safety, consumers, and crop producers in either a positive or negative manner. The technology that makes it possible to develop herbicide-resistant crops is neither good nor bad, it is rather how the products of this technology are used that will determine whether or not the introduction of herbicide-resistant crops is ultimately a good or bad decision. The introduction of herbicide-resistant crops will have diverse impacts leading to redundancy, diversity, and confusion in crop production systems. Often the introduction of herbicide-resistant cultivars will have the same impact on cropping systems as the introduction of a new herbicide that has the same mode-of-action and use pattern of herbicides already in use. This may add diversity of herbicide options for a given crop but will cause redundancy of product use over several years. This redundancy could lead to weed resistance and water quality concerns. Confusion at the user level will exist because not all cultivars of a crop will be resistant to the herbicide; this could be the major deterrent to widespread adoption of herbicide-resistant crops. Steps must be taken to provide information to crop producers that will insure that herbicide-resistant crops are used effectively and safely. Weed scientists will determine whether this technology will be used to improve food safety, water quality, crop production systems, and farmer profitability or have a negative impact on agriculture and the whole of society.
Developing Computer Simulation Models for Estimating Risks of pesticide use: Research vs. user Needs
Authors: Donigian Anthony S. , Carsel Robert F.
Published: March 2018

The use of models for regulatory purposes requires accurate descriptions of important chemical fate processes, techniques for applying models for specific regulatory issues, techniques for parameterizing the model, and sufficient model distribution and support. Researchers (i.e. model developers), on the other hand, want to conceive more and more complex, sophisticated models in order to better represent the important environmental processes; unfortunately this invariably tends to lead to models with greater data requirements, parameters that are difficult to evaluate, greater expertise needed for application, and greater computational requirements, all of which makes for more difficult model application and use. The development of usable models for both current needs and future regulatory requirements demands that we achieve a balance between these ‘research needs' and ‘user needs'. Software engineering and code development issues can help to establish the needed bridge between research and user needs so that future models can more quickly escape the research arena and satisfy user needs as effective regulatory tools.
Developing Models with More Detail: Do More Algorithms Give More Truth?
Authors: Decoursey Donn G.
Published: March 2018

Do quasi-physically based models with more detail perform better than regression or other empirical models? This is a question that was raised many years ago and still remains. In an effort to respond to this question, the author reviews the needs and concerns of users and then divides the large number of models into three classes: (1) screening, (2) research, and (3) planning, monitoring, and assessment. Empirical and causal (physically based) models are contrasted and the advantages and disadvantages of each described. Sources of model uncertainty (properties of data bases, model structure, parameter estimation methods, algorithmic implementation, verification and validation, and future users) that lead to skepticism about models' performance are investigated. Simulation scale and spatial variability are also important considerations. The leading question is then discussed from the perspective of screening, research, and planning, monitoring, and regulatory models.
Winds of Change
Authors: Abernathy John R.
Published: March 2018

I, too, would like to add my welcome to each of you on behalf of the 32nd annual Weed Science Society of America meeting. I would especially like to recognize our special guest this morning, Dr. C. Everett Koop. I know each of you will find the Clarion Plaza facilities and the program to be excellent due to an outstanding effort by Joe Antognini and the Program Committee and Joan Dusky and the Local Arrangements Committee. We owe all of these folks a tremendous debt of gratitude for the success of this meeting.
Weed Control in Oat (Avena sativa)-Alfalfa (Medicago sativa) and Effect on Next Year Corn (Zea mays) Yield
Authors: Moomaw Russell S.
Published: March 2018

Field experiments were conducted from 1985 through 1989 to evaluate herbicide selectivity and impact on seeding-year yields of spring oat and underseeded alfalfa, and carryover weed control benefits from increased legume-fixed N for second-year dryland no-till corn. PRE metolachlor, pendimethalin, and prodiamine controlled green foxtail and POST bromoxynil or 2,4-DB controlled broadleaf weeds. These herbicides caused 0 to 20% alfalfa injury and 0 to 17% oat injury, and increased oat yield one of three years but did not increase the yield of underseeded alfalfa. POST pyridate, thifensulfuron, and tribenuron were too injurious to either oat, alfalfa, or both crops. Forage yields of annual ‘Nitro’ and perennial ‘Wrangler’ alfalfa seeded alone were greater than when they were underseeded in oat, with herbicides applied in both systems. As a result of drought in 1988 and 1989, yield of second-year corn planted after one-year alfalfa was not increased from potentially greater legume-fixed N. Dryland corn yield following monoculture oat or corn was 254% higher than corn following alfalfa.
Flurtamone for Wild Mustard (Sinapis arvensis) Control in Canola (Brassica napusandB. campestris)
Authors: Wall David A.
Published: March 2018

The tolerance of canola to soil applied flurtamone was investigated in greenhouse and field studies. In the greenhouse, the dosage of flurtamone required to reduce canola fresh weight by 50% was 7.1- to 8.4- and 4.4- to 6.1-fold higher forB. napusandB. campestriscultivars, respectively, than that required to reduced wild mustard fresh weight by 50%.B. campestriscultivars tended to be more sensitive to flurtamone thanB. napuscultivars. In the field, flurtamone applied at 0.4 to 0.5 kg ai ha-1controlled 80% of wild mustard in canola (B. napuscv. ‘Westar’). In 1991 canola plant densities were reduced by increasing rate of flurtamone, but seed yields were unaffected by rate of application in either year.
Red Horned Poppy (Glaucium corniculatum) Control in Winter Wheat (Triticum aestivum)
Authors: Baughman Todd A. , Peeper Thomas F.
Published: March 2018

Fourteen field experiments were conducted from 1988 to 1991 in Oklahoma to evaluate herbicides for red horned poppy control in winter wheat. Chlorsulfuron applied alone PRE at 9 to 26 g ai ha-1 or with metsulfuron controlled red horned poppy 90 to 100% in four of five locations. MCPA at 420 g ae ha-1 and MCPA + bromoxynil at 140 + 140 g ae ha-1 applied POST in mid November controlled red horned poppy 100%. All herbicides applied POST in mid March failed to control the weed consistently.
Interaction of Terbufos and Nicosulfuron on Corn (Zea mays)
Authors: Kapusta George , Krausz Ronald F.
Published: March 2018

Field studies were conducted in 1989 and 1990 to determine the potential interaction of terbufos and nicosulfuron on corn. Terbufos applied in-furrow at planting interacted with nicosulfuron applied POST to cause significant injury 25, 30, 40, 50, and 60 d after planting in 1989 and 1990. Injury decreased significantly when nicosulfuron was applied at later growth stages of corn. Plant population was not affected by terbufos and nicosulfuron regardless of the growth stage of corn at application of nicosulfuron in either year. Corn ear number and grain yield in 1989 and 1990 were lower in plots treated with terbufos at planting and nicosulfuron applied at the three leaf stage than in plots treated with only nicosulfuron. There were no differences in the height of corn, ear number, or grain yield when nicosulfuron was applied at the seven-leaf stage regardless of terbufos application in 1989 or 1990.
Longevity of Yellow Starthistle (Centaurea solstitialis) Achenes in Soil
Authors: Callihan Robert H. , Prather Timothy S. , Northam Francis E.
Published: March 2018

Yellow starthistle achenes were placed in 80-mesh nylon packets, buried in the field at depths of 2.5, 5, and 15 cm, and retrieved over 10 yr. No effects of burial depth on longevity were detected. Viability decreased faster for plumeless achenes than for plumed achenes. Average longevity of plumeless and plumed achenes was 6 and 10 yr, respectively.
Total Postemergence Herbicide Programs in Cotton (Gossypium Hirsutum) with Sethoxydim and DPX-PE350
Authors: Jordan David L. , Frans Robert E. , McClelland Marilyn R.
Published: March 2018

Weed control and cotton yield with a herbicide program of sethoxydim and DPX-PE350 applied postemergence over-the-top was compared with that of a standard herbicide program of trifluralin applied PPI plus fluometuron applied PRE plus methazole and MSMA applied postemergence-directed. Control of pitted and entireleaf morningglory, smooth pigweed, and prickly sida was similar with the postemergence over-the-top program and the standard herbicide program when DPX-PE350 was applied to cotton in the V2 or V4 growth stages. Less weed control and lower yield were observed when DPX-PE350 was applied to V6-stage cotton. Good control of annual grasses was obtained with all herbicide programs.
Germination and Root Dynamics of Range Weeds and Forage Species
Authors: Sheley Roger L. , Larson Larry L. , Johnson Douglas E.
Published: March 2018

Rapid germination and root growth have been identified as important plant characteristics for establishment in arid environments. This study evaluates germination, radicle elongation, and root growth rates of two annual grasses, two forage species, and yellow starthistle. Yellow starthistle germination, radicle elongation, and root growth were faster than those of medusahead and hedgehog dogtailgrass. Subterranean clover possessed rapid seedling growth characteristics similar to those of yellow starthistle, whereas Palestine orchardgrass was most delayed.
GPS and GIS for Weed Surveys and Management
Authors: Lass Lawrence W. , Callihan Robert H.
Published: March 2018

Global positioning systems (GPS) technology, developed by the Department of Defense, enable accurate documentation of Cartesian coordinates anywhere on the earth's surface. Surveying, mapping, positioning, and subsequent management of weed infestations can be expedited with this technology. Positions and boundaries of infestation may be located with 10-m or better accuracy while the GPS receiver is continuously moving, and with 2-m or better accuracy with brief stops for repeated sampling. GPS data agreed closely with U.S. Geological Survey data. Coordinates for a weed infestation may be relocated for treatment, evaluation or other purposes. Basic geographic information systems (GIS) map features from Digital Line Graph (DLG), Topologically Integrated Encoding and Reference Systems (TIGER) and other sources of information may be used to fully integrate delimiting survey results from GPS readings in order to develop weed management plans.
A System for Morningglory (Ipomoeaspp.) Control in Cotton (Gossypium hirsutumL.)
Authors: Savoy Bryan R. , Holshouser David L. , Smith Kenneth L. , Chandler James M.
Published: March 2018

Research was conducted to determine an effective morningglory control system for cotton grown in central Texas, Prometryn applied PRE or directed-POST applications of methazole or methazole + MSMA did not always adequately control ivyleaf, entireleaf, and seedling sharppod morningglories. However, adequate control of the above species plus pitted morningglory was achieved with a management system that used a dinitroaniline applied PPI or PRE, prometryn applied PRE (0.9 kg ai ha−1), followed by methazole (0.56 kg ha−1) or methazole + MSMA (0.56 + 1.80 kg ha−1) directed POST to cotton 10 to 15 cm high.
Differential Bentazon Response in Cowpea (Vigna unguiculata)
Authors: Harrison Howard F. , Fery Richard L.
Published: March 2018

The U. S. Plant Introduction Collection of cowpea germplasm and a collection of cowpea cultivars were evaluated for bentazon tolerance in the field. Most accessions were intermediate in bentazon tolerance; however, several highly tolerant and highly susceptible accessions were identified. Tolerant and susceptible selections from the field experiment were evaluated in greenhouse experiments. The most susceptible selections were killed or severely injured by bentazon at 2 kg ae ha−1; the most tolerant selections were not severely injured by bentazon at 16 kg ha−1.
Tropical Soda Apple (Solanum viarum): A New Weed Threat in Subtropical Regions
Authors: Mullahey J. Jeffrey , Nee Michele , Wunderlin Richard P. , Delaney Kris R.
Published: March 2018

In 1990, a broadleaf weed growing on a cattle ranch in Hendry County in southwest Florida was identified as tropical soda apple (Solanum viarum Dunal), a species native to Argentina and Brazil (5) (Figure 1). Tropical soda apple (TSA) was apparently collected in Florida from Glades County in 1988 (University of Florida Herbarium) but was observed on the Hendry County ranch as early as 1987. Having foliage unpalatable to livestock, this noxious weed can infest a pasture or rangeland within one to two years resulting in lower stocking rates (animals per hectare). However, livestock and wildlife (feral hogs, deer, raccoons) will eat the fruit and disseminate the seed via feces. Fruit production occurs throughout the year (primarily September through May) thus providing high numbers (40000 to 50 000 per plant) of viable seed (75% germination) for seed dispersal. Our objectives are to alert those concerned with weed control of the presence of TSA in subtropical regions of the U.S., to discuss the ecology and taxonomy of this weed, and to indicate areas for future research.
Yellow Toadflax
Authors: Mitich Larry W.
Published: March 2018

There are about 130 species of Linaria, a genus of hardy herbs with whorled or opposite leaves; a few species are sub-shrubs. The genus, native to Eurasia, is widely dispersed. Closely related but separated from Linaria are the genera Kickxia and Cymbalaria.
Postemergence Grass Control in Sweet Potatoes (Ipomoea batatas)
Authors: Porter Wayne C.
Published: March 2018

Fluazifop-P, sethoxydim, and quizalofop were evaluated over two years for postemergence annual grass control in sweet potatoes. All treatments controlled broadleaf signalgrass and large crabgrass, but in 1987 only rates of at least 0.14 kg/ha of fluazifop-P and quizalofop and 0.28 kg/ha of sethoxydim controlled large crabgrass. No. 1 grade and total yield were greater from plots treated with herbicides compared with the weedy check in 1986. In 1987, No. 1 grade and total yield were greater in plots treated with fluazifop-P at 0.14 kg/ha or higher and sethoxydim or quizalofop at 0.28 kg/ha or higher.
Herbicide Systems in Stale Seedbed Soybean (Glycine max) Production
Authors: Oliver Lawrence R. , Klingaman Tracy E. , McClelland Marilyn , Bozsa Robert C.
Published: March 2018

Field experiments were conducted using a stale seedbed production system to determine the effect of herbicide application time on preplant, preplant incorporated (PPI), and at-planting treatments on weed control and soybean yield. Herbicides were applied on the surface preplant (PPL) or PPI at 6 to 7, 4 to 5, and 2 to 3 wk before planting and just prior to planting. The differences in weed control and soybean yield among years were due to rainfall patterns 2 wk after herbicide application and during the growing season. Preplant treatments applied 2 to 5 wk before planting generally controlled common cocklebur and pitted morningglory better than preplant treatments applied 6 to 7 wk before planting due to persistence of herbicide activity or treatments at planting due to a greater chance of obtaining adequate rainfall for herbicide activation, more uniform seedbed at planting, and larger weeds at application. Metribuzin plus chlorimuron was less suited than imazaquin as a preplant treatment when applied more than 2 weeks before planting.
Integration of Airborne Video, Global Positioning System and Geographic Information System Technologies for Detecting and Mapping Two Woody Legumes on Rangelands
Authors: Everitt James H. , Escobar David E. , Villarreal Ricardo , Alaniz Mario A. , Davis Michael R.
Published: March 2018

Blackbrush acacia and huisache, two troublesome woody legumes on Texas rangelands, could be distinguished on conventional color aerial video imagery. The integration of a global positioning system with the video imagery permitted latitude/longitude coordinates of blackbrush acacia and huisache infestations to be recorded on each image. Global positioning system coordinates were entered into a geographic information system to map blackbrush acacia and huisache populations over an extensive rangeland area.
Reduced Rates of Postemergence Herbicides for Weed Control in Sweet Corn (Zea mays)
Authors: O'Sullivan John , Bouw William J.
Published: March 2018

The efficacy of reduced rates of POST herbicides for weed control in sweet corn was evaluated over a three-year period in field studies conducted at the Horticultural Experiment Station, Simcoe, Ontario. POST applications of metolachlor/cyanazine, cyanazine/atrazine and metolachlor/atrazine at 1/2X and 1/4X of labelled rates controlled broadleaf weeds comparable to that of standard labelled rates. Control exceeded 94% each year. Annual grass control was reduced with below-label rates, especially for cyanazine/atrazine and metolachlor/atrazine. A 1/2X application of nicosulfuron/rimsulfuron, following the 1/4X rate of cyanazine/atrazine, significantly improved grass control, compared to cyanazine/atrazine applied alone. Below-label rates did not result in decreased sweet corn yields.
On-Farm Evaluation of Mechanical and Chemical Weed Management Practices in Corn (Zea mays)
Authors: Hartzler Robert G. , Van Kooten Brad D. , Stoltenberg David E. , Hall Elaine M. , Fawcett Richard S.
Published: March 2018

Combinations of rotary hoeing, cultivation, and band- or broadcast-applied herbicides were compared for weed management in corn at 64 locations in Iowa from 1987 to 1991. Cultivation alone resulted in denser weed populations than herbicide treatments at 41% of the locations; however, corn yields were reduced at only 22% of the locations when weeds were controlled mechanically rather than with herbicides. Compared with broadcast applications, herbicides applied in a band resulted in increased weed populations at 8% of the locations; however, corn yields were reduced at only 1% of the locations.
Cogongrass,Imperata cylindrica, in the United States
Authors: Bryson Charles T. , Carter Richard
Published: March 2018

Cogongrass [Imperata cylindrica(L.) Beauv. # IMPCY] is an aggressive, pernicious, rhizomatous perennial in the Poaceae (Graminae). It is native to tropical and subtropical areas of the eastern hemisphere. Introductions of cogongrass into the southeastern United States have been tracked to several separate sources, both accidental and intentional, in southern Alabama, southern Mississippi, and Florida. It was found to be unacceptable for use as a forage and in erosion control. Cogongrass is a highly variable species and has adapted to a variety of environmental conditions in its native and introduced range. Today cogongrass infests 200 million ha in Asia, several thousand ha in the Southeastern United States, and over 500 million ha worldwide. It has been reported to be a weed problem in many annual and perennial crops. In addition to competing for light, water and nutrients, cogongrass interference is caused by alleopathy and physical injury when rhizome apices penetrate crop roots, bulbs, and tubers. Holm et al. designated cogongrass as the world's seventh worst weed.
Postemergence Weed Control in Potatoes (Solanum tuberosum) with Rimsulfuron
Authors: Eberlein Charlotte V. , Whitmore James C. , Stanger Charles E. , Guttieri Mary J.
Published: March 2018

Greenhouse and field studies were conducted to examine weed control with, and potato tolerance to, rimsulfuron or rimsulfuron + metribuzin applied POST. In greenhouse trials, hairy nightshade control with rimsulfuron applied POST at 9 to 35 g/ha was ≥ 90%, but cutleaf nightshade control was < 30%. In field studies, rimsulfuron at 18 to 35 g/ha provided ≥ 85% control of hairy nightshade, redroot pigweed, tumble pigweed, and shepherd's-purse; 75 to 82% control of volunteer oats; and 25 to 87% control of common lambsquarters. Common lambsquarters control was increased to 92 to 100% when rimsulfuron at 18 to 35 g/ha was applied in combination with metribuzin at 280 g/ha. Hairy nightshade and redroot pigweed control usually were not improved by adding metribuzin to the rimsulfuron spray mixture and tumble pigweed and shepherd's-purse control were improved only slightly. Volunteer oat control with rimsulfuron sometimes was antagonized by the addition of metribuzin to the spray mixture. In weed-free trials, yield of potatoes grown for the fresh market or to produce seed tubers was not reduced by rimsulfuron at rates as high as 70 g/ha.
Preharvest Applications of Glyphosate for Canada Thistle (Cirsium arvense) Control
Authors: Darwent A. Lloyd , Kirkland Kenneth J. , Baig Mirza N. , Lefkovitch Leonard P.
Published: March 2018

The effectiveness of single and repeated annual preharvest glyphosate applications (1 to 2 wk before crop harvest) to reduce Canada thistle populations was evaluated in field experiments near Bezanson, AB, Scott, SK, and St. Albert, AB. Single applications of glyphosate at 0.45 to 1.8 kg/ha at Bezanson and St. Albert reduced Canada thistle shoot density by more than 75% but in the three experiments at Scott 1.8 kg/ha was required to consistently obtain a similar reduction. Four consecutive, annual applications of glyphosate at 0.45 kg/ha or more did not eliminate Canada thistle but reduced shoot densities by more than 98% at Bezanson. At Scott, similar reductions occurred in two of three sites following two consecutive, annual preharvest applications of glyphosate at the same rates. In the third Scott site the 1.8 kg/ha rate of glyphosate provided a similar reduction but lower rates did not. At Bezanson, barley yields following the first, second, and third applications of glyphosate at 0.45 kg/ha or more were 14% greater than check plots where MCPA was applied in the spring. Yields of wheat seeded 1 yr after a single application of glyphosate at St. Albert were 26% greater than from unsprayed checks. Barley yields seeded 1 yr after each glyphosate application at Scott were not affected because Canada thistle populations were sparse.
Soil Insecticide and Placement Influence Corn (Zea mays) Tolerance to Nicosulfuron
Authors: Bailey John A. , Kapusta George
Published: March 2018

Field experiments were conducted in 1991 and 1992 to evaluate corn tolerance to nicosulfuron following in-furrow or surface-band applications of seven soil-applied insecticides. The organophosphate insecticides evaluated included terbufos (15G and 20CR formulations), phorate, chlorpyrifos, fonofos, and DPX-43898, as well as the synthetic pyrethroid tefluthrin. Potential for a nicosulfuron/ insecticide interaction to injure corn was ranked as follows: terbufos 15G = phorate > terbufos 20CR > fonofos. Chlorpyrifos, DPX-43898, or tefluthrin followed by nicosulfuron caused no significant corn injury. Corn injury and yield reduction were greater in corn treated in-furrow compared with surface-band. Soil moisture at nicosulfuron application was more influential in causing corn injury and loss of yield than growth stage of corn at nicosulfuron application.
Effect of Nicosulfuron Applied Postemergence and Post-Directed on Sweet Corn (Zea mays) Tolerance
Authors: Robinson Darren K. , Monks David W. , Schultheis Jonathan R.
Published: March 2018

In 1991 and 1993, tolerance of ‘Zenith’ and ‘Merit’ sweet corn to 35 g ai/ha nicosulfuron post-directed (PDIR) 0, 5, 10, and 15 cm up the corn stalk or applied POST was determined. In 1991, nicosulfuron applied POST to Zenith caused approximately 30% visible injury, 30% height reduction, and 50% reduction of U.S. No. 1 marketable ear weight. In 1991 no visible injury was observed in the PDIR treatments. Zenith was not injured by any treatment in 1993. Both years, Merit was killed by nicosulfuron applied POST. In 1991 and 1993, nicosulfuron PDIR 0 and 5 cm up the corn stalk of Merit caused approximately 5% and 65% visible injury, respectively, and resulted in yield loss. PDIR application increased nicosulfuron tolerance of moderately tolerant Zenith but did not improve that of least tolerant Merit.
Common Sunflower (Helianthus annuus) Interference in Soybean (Glycine max)
Authors: Geier Patrick W. , Maddux Larry D. , Moshier Loren J. , Stahlman Phillip W.
Published: March 2018

An in-row competition study was conducted in 1991 and 1992 near Silver Lake, KS to determine the relationship of noncultivated common sunflower density to soybean yield, PAR at the soybean canopy, and common sunflower dry matter production. Because of environmental differences, year main effect interactions occurred, so results are presented by year. For example, 0.3 common sunflower plant/m2produced 4030 kg/ha of aboveground dry matter in 1991 and 1300 kg/ha in 1992. Soybean yield reduction ranged from 19 and 17% with 0.3 common sunflower plant/m2to 97 and 95% with 4.6 plant/m2, in 1991 and 1992, respectively. Assuming a treatment cost of $35/ha and a soybean market price of $0.21/kg, economic threshold levels were 0.1 common sunflower plant/m2in 1991, and 0.07 in 1992. Common sunflower at 0.3 plant/m2reduced PAR at the soybean canopy by 390 and 300 μE/m2/s, or 24 and 18% in 1991 and 1992, respectively. We conclude that the ability of common sunflower to intercept PAR above the soybean canopy is an important component in its interference with soybean.
What Are Working Groups and Why Should Scientists Be Involved
Authors: Svejcar Tony J.
Published: March 2018

The conflicts over management of natural resources, especially on public lands, have resulted in a high level of frustration among many of the interested parties. There are many underlying causes of the conflicts, but I think several major societal trends must be considered. During the past several decades, there has been increased emphasis on participatory democracy, with the public seeking more involvement in decision making and policy formulation. A related trend is the decline in the public image of science and lack of trust in state and federal agencies. Individual members of society desire to be included in decision making, and may not necessarily view scientists as capable of providing the answers to natural resource issues. One response to natural resource conflicts is to form a group of interested individuals from diverse backgrounds to develop solutions. These groups may also work toward policy development. Coalitions or working groups may take many forms. There are two basic types of groups I will mention: 1) those formed to address a specific issue over a set time period, and 2) those formed to foster communication, interaction, and education. Many working groups have been formed over controversies, but effective use of the groups might also keep controversies from arising. In my opinion, scientists should be active participants in natural resource working groups. Participation provides the opportunity to incorporate science in decision-making and may also guide research efforts insuring that the results are of value to a wider cross-section of society.
Phytotoxicity of Flumetsulam on Peanut (Arachis hypogaea)
Authors: Johnson W. Carroll , Mullinix Benjamin G.
Published: March 2018

Field studies were conducted at Tifton, GA to quantify phytotoxicity of flumetsulam on peanut as influenced by application rate and timing in a weed free experiment. Flumetsulam PPI at rates up to 0.14 kg ai/ha visibly injured peanut and reduced canopy width, but injury from PPI flumetsulam at 0.07 kg/ha or less was no worse than a standard early postemergence (EPOST) treatment of bentazon (0.6 kg ai/ha) plus paraquat (0.14 kg ai/ha). Flumetsulam EPOST at rates up to 0.07 kg/ha visibly injured peanut and reduced peanut canopy width. Flumetsulam injury at rates of 0.035 kg/ha EPOST was similar to that caused by bentazon plus paraquat. Interactive effects of PPI and EPOST flumetsulam reduced early and mid-season pod and foliage biomass more than either application alone. However, peanut recovered with final yields not affected by flumetsulam, regardless of rate or time of application.
Nicosulfuron Tolerance in Sweet Corn (Zea mays) as Affected by Hybrid, Rootworm Insecticide, and Nicosulfuron Treatment
Authors: Williams Bill J. , Harvey R. Gordon
Published: March 2018

Sweet corn tolerance to nicosulfuron as affected by interactions between nicosulfuron applied postemergence (POST), sweet corn hybrid, and rootworm insecticide applied at planting was determined in 1992 and 1993 field experiments. Sweet corn vigor was reduced as nicosulfuron rate increased from 35 to 140 g ai/ha. Sweet corn vigor was reduced 4% more by nicosulfuron with oil emulsifier mixture than nicosulfuron with non-ionic surfactant one week after treatment (WAT). Adjuvant selection did not influence nicosulfuron injury to sweet corn 2 WAT. Nicosulfuron applied postemergence directed (PDIR) caused less sweet corn injury than nicosulfuron applied broadcast POST. ‘Jubilee’ sweet corn was more sensitive to nicosulfuron and insecticide treatments than ‘Excellency’ or ‘Green Giant 40.’ Nicosulfuron reduced sweet corn vigor twice as much when terbufos was applied at planting compared to no insecticide at planting. Neither chlorpyrifos or chlorethoxyfos at planting increased sweet corn injury due to nicosulfuron compared to no insecticide. Excellency and Green Giant 40 yields were not reduced by any treatment. Yields were reduced only when nicosulfuron was applied to Jubilee treated with terbufos. Jubilee yield reduction from nicosulfuron and terbufos was prevented by applying nicosulfuron PDIR.
Herbicides Impregnated Onto Granular Fertilizer Carriers for Broadleaf Weed Control in Winter Wheat (Triticum aestivum)
Authors: Koscelny Jeffrey A. , Peeper Thomas F.
Published: March 2018

The efficacy of sulfonylurea herbicides impregnated on granular fertilizers applied PPI or POST was compared to broadcast spray applications for annual broadleaf weed control in winter wheat. Henbit and bushy wallflower were controlled by chlorsulfuron or triasulfuron impregnated onto diammonium phosphate granular fertilizer applied PPI. Efficacy of these herbicides for annual broadleaf weed control was reduced by applying them POST with granular urea fertilizer carrier instead of with water carrier.
Exploration of the Use of the “Bialaphos Genes” for Improving Bioherbicide Efficacy
Authors: Charudattan R. , Prange V. J. , Devalerio J. T.
Published: March 2018

We are studying the possibility of altering the virulence and host range of a phytopathogen by transferring and expressing certain genes from the soil-dwelling saprophyte,Streptomyces hygroscopicus, in a plant pathogen model,Xanthomonas campestrispv.campestris(XCC). The genes, referred to herein as the “bialaphos genes,” encode the production of bialaphos, a potent glutamine-synthetase-inhibiting herbicide. This cluster of genes was originally isolated from several biosynthetically blocked mutants ofS. hygroscopicusand constructed into a plasmid vector, pBG9. We have transferred a fragment of the gene cluster into pLAFR3, a plasmid that functions in bothEscherichia coliand XCC and contains a tetracycline resistance marker. The resulting plasmid, named pIL-1, was used to transformE. coliand was incorporated into XCC by conjugation. The transfer of the fragment was confirmed by Southern analysis. The genes were maintained in XCC for about 47 generations in the absence of selection for tetracycline, and no changes in cultural phenotypes were seen in the transformed XCC (XCC/pIL-1). The XCC/pIL-1 cells were pathogenic to their natural hosts cabbage and broccoli, but induced an altered hypersensitive response in the nonhosts bean, pepper, sunflower, and tobacco. The pathogenic host-reaction, induced by the parent XCC, XCC/pLAFR3, and XCC/pIL-1, was a typical black rot disease in inoculated leaves of the two hosts. The nonhost reaction on the nonhost leaves was necrotic hypersensitivity, induced by XCC and XCC/pLAFR3, or the inhibition of hypersensitivity accompanied by only chlorosis at sites inoculated with XCC/pIL-1. We hypothesize that the altered hypersensitivity phenotype may be due to the transformed XCC becoming more compatible with the nonhosts, a step toward acquiring nonhost-virulence, or due to disruption of the normal expression of the hypersensitivity and pathogenicity genes in the transformed XCC. More work is needed to confirm that the introduced genes are being expressed in XCC. With further understanding, this approach may provide a useful model to study host range, virulence, and strain improvement of plant pathogens for biological control of weeds.
Growth Stage and Broadleaf Herbicide Effects on CGA184927 Efficacy
Authors: Blackshaw Robert E. , Harker K. Neil
Published: March 2018

Field experiments were conducted to determine the effect of CGA184927 rate, weed growth stage, and tank mixes with various broadleaf herbicides on the control of green foxtail and wild oat in spring wheat. CGA 184927 controlled green foxtail and wild oat equally well when applied at the 2- to 3- or 4- to 5-leaf stages. Green foxtail and wild oat were controlled at similar rates of CGA 184927 but the application rate giving > 90% control ranged from 22 to 90 g/ha over locations and years, indicating that CGA 184927 efficacy is sensitive to environmental conditions. CGA 184927 in tank mixtures was compatible with bromoxynil, clopyralid, and 2,4-D ester. However, tank mixing with metsulfuron or dicamba reduced activity on green foxtail and wild oat. Broadleaf herbicide activity on kochia and redroot pigweed was not reduced when such herbicides were tank-mixed with CGA 184927. Spring wheat tolerated 120 g/ha of CGA 184927. CGA 184927 provides growers with another herbicide option to control green foxtail and wild oat in wheat.
Emergence Pattern of Five Weeds in the Central Great Plains
Authors: Anderson R. L. , Nielsen D. C.
Published: March 2018

Seedling emergence was characterized for five weeds that infest summer annual crops in the central Great Plains as affected by crop canopy or tillage. The study was established in winter wheat stubble between 1987 and 1990, with seedling emergence recorded weekly between April 1 and November 1. Kochia emerged primarily from early April to late June, whereas green foxtail, wild-proso millet, and redroot pigweed began emerging in late May and continued until August. Volunteer wheat emerged throughout the growing season. Tillage did not affect the emergence pattern of any species, but the numbers of kochia, volunteer wheat, and green foxtail seedlings were increased in no-till. Conversely, wild-proso millet emergence was greater with tillage. Only volunteer wheat's emergence was affected by crop canopy, as fall emergence of volunteer wheat was more than three times greater in corn than in proso millet.
Downy Brome (Bromus tectorum) Emergence Variability in a Semiarid Region
Authors: Anderson R. L.
Published: March 2018

This study characterized seedling emergence of downy brome from August to early December over a 6-yr period. Seedlings were counted weekly in quadrats established in winter wheat stubble at Akron, CO. Seedling emergence varied among years, which was caused by erratic seasonal precipitation. Producers delay planting of winter wheat to reduce downy brome density in the crop, but in only 1 yr out of 6 would producers have benefited from this control strategy. Furthermore, delayed planting has negative crop consequences: less grain yield and more susceptibility to plant diseases and wind erosion because of less fall plant growth. Because fall precipitation is erratic in the semiarid Great Plains, other control strategies, such as nitrogen placement and increased seeding rates of winter wheat, would be more effective for downy brome management, yet not detrimental to winter wheat production.
Weed Hosts forRhizoctonia solani, Causal Agent for Rhizoctonia Foliar Blight of Soybean (Glycine max)
Authors: Black B. David , Griffin James L. , Russin John S. , Snow Johnnie P.
Published: March 2018

Greenhouse studies were conducted to determine host status of weed species forRhizoctonia solaniAG-1, which causes Rhizoctonia foliar blight of soybean. Weed species were barnyardgrass, broadleaf signalgrass, common cocklebur, entireleaf morningglory, hemp sesbania, itchgrass, johnsongrass, large crabgrass, northern jointvetch, prickly sida, purple nutsedge, redweed, sicklepod, and smooth pigweed. Seedling weeds were inoculated with suspensions containing intraspecific group IA and IB isolates of the fungus. In the first study, sclerotia of IA were recovered from tissue of all weeds except smooth pigweed, and mycelia of IA were recovered from all except smooth pigweed and redweed. In that study, neither microsclerotia nor mycelia of IB were recovered from sicklepod, barnyardgrass, or large crabgrass, and only microsclerotia were recovered from itchgrass and purple nutsedge. In the second study, sclerotia of IA, microsclerotia of IB, and mycelia of each isolate were recovered from all weed species. In other studies,R. solanispread from at least six of seven weed species to a noninfected soybean plant growing in close proximity. These studies emphasize the importance of weed control, not only for reducing plant competition and increasing yield, but also for the potential impact on development of RFB.