bluuebunny/crossref_metadata_2025 huggingface dataset:
Future of Weed Science Research
Authors: Wyse Donald L.
Published: March 2018

The discipline of weed science is entering a critical period in its development. Decisions made in the next few years will determine if weed science will remain weed control technology oriented or develop into a broad-based scientific discipline. Over the last 30 yr the evolution of weed science has been based on the development of weed control methods. Currently, most crop production systems rely very heavily on one weed control technology, herbicides. Agriculture is now in a debate with society over how food and fiber should be produced. Society is asking weed science, because of food safety and water quality concerns, to develop new methods to control weeds. To do this, weed science must put more emphasis on principles-based research that can provide the basic knowledge required to develop new weed control technology. Weed scientists must join forces with private citizens and organizations concerned with the effect of current agricultural practices on the environment, to obtain, through the political process, new resources for weed science research. These resources are needed to develop the basic principles that will support the development of new weed control technologies with reduced environmental impact. Weed scientists must decide if they are going to lead the direction of weed science research or be led reluctantly by others.
Weed Demography and Population Dynamics: Implications for Threshold Management
Authors: Jordan Nicholas
Published: March 2018

Threshold weed management methods have recently been elaborated to consider effects of threshold management on weed population dynamics. Such economic optimum thresholds are calculated using population-dynamics models which require detailed information about weed demography, including seed production (as affected by events between germination and seed dispersal), seed dispersal, and seed survival and movement in soil. Factors affecting any of these aspects of demography appear likely to modulate the growth rate of a sub-threshold population and therefore to influence the economic optimum threshold value. To test this conjecture and evaluate weed threshold management, including associated risk, improved understanding is particularly needed of weed seed dispersal, seedbank processes, and unpredictable demographic variation.
A Comparison of Economic and Economic Optimum Thresholds for Two Annual Weeds in Soybeans
Authors: Bauer Troy A. , Mortensen David A.
Published: March 2018

Long term weed management programs for annual weeds should take into account seed production as well as yield losses from weeds. In this research economic optimum thresholds, determined with a simulation model, were compared to the economic thresholds derived from field studies with common sunflower and velvetleaf in soybean. An economic optimum threshold model, including a biological submodel and a submodel evaluating the financial benefit from controlling each weed species in soybean, was constructed to estimate the biological events and processes and economic costs of each weed. Long-term weed management programs were simulated in continuous soybean over a 15-yr period. The model optimized a POST treatment of bentazon by computing costs associated with weed interference and changes in estimated seedbank size. The economic optimum threshold populations were estimated to be 0.3 to 0.4 velvetleaf plants per 10 m2and 0.4 common sunflower plants per 10 m2. The economic thresholds calculated to be 2.6 velvetleaf plants per 10 m2and 1.5 common sunflower plants per 10 m2. The economic optimum threshold was calculated to be 7.5-fold and 3.6-fold lower than the economic thresholds for velvetleaf and common sunflower, respectively. The larger ratio for velvetleaf reflected the large quantity and longevity of seeds produced. The smaller ratio for common sunflower reflected the shorter persistence of the seeds and higher seed predation rates.
2,4-D and Salt Combinations Affect Glyphosate Phytotoxicity
Authors: Nalewaja John D. , Matysiak Robert
Published: March 2018

Experiments conducted in the greenhouse indicated that 2,4-D antagonism of glyphosate toxicity to wheat was sodium salt = butoxyethyl ester ≥ diethanolamine. Isopropylamine salt of 2,4-D generally was not antagonistic to glyphosate phytotoxicity. Isopropylamine salt of 2,4-D did not influence the antagonism of glyphosate by inorganic salts in the spray carrier. Antagonism of glyphosate toxicity to wheat by 2,4-D increased when sodium bicarbonate, calcium chloride, and ferric sulfate were in the spray carrier water. Isopropylamine alone as an adjuvant enhanced glyphosate toxicity to wheat, and overcame ferric sulfate and sodium bicarbonate antagonism of glyphosate. Diammonium sulfate adjuvant overcame antagonism to glyphosate phytotoxicity from 2,4-D, sodium bicarbonate, and calcium chloride each alone or the salts in combination with 2,4-D. Nonionic surfactants differed in enhancement of glyphosate but none overcame antagonism from salts or 2,4-D.
Effects of Harvest-Aid Herbicides on Soybean (Glycine max) Seed Yield and Quality
Authors: Ratnayake Sunil , Shaw David R.
Published: March 2018

Experiments were conducted in 1989 and 1990 to investigate the influence of 220 g ai ha–1AC 263,222, 840 g ai ha-4glufosinate, 560 g ai ha–1glyphosate, and 840 g ai ha–1paraquat applied at R5, R6, R7, and R8 soybean growth stages as harvest-aid treatments on soybean seed quality. Soybean yield was severely reduced by all herbicides applied at R5. Only paraquat and glufosinate reduced soybean yield when applied at R6, and none of the herbicides reduced yield when applied at R7 or R8. Paraquat and glufosinate reduced seed weight when applied at RS and R6. Glyphosate and AC 263,222 reduced seed germination when applied at RS, R6, and R7 growth stages, and normal seedling percentages were also reduced by glyphosate at these growth stages. Glufosinate and AC 263,222 affected normal seedlings only at R5 and R6. Soybean hypocotyl and primary root lengths were reduced by glyphosate and AC 263,222 applications at R5 and R6, whereas glufosinate and paraquat did not affect these variables. Glyphosate applied at R5 reduced shoot weight in 1-mo-old soybean plants. No effects were observed on soybean yield, seed germination or seedling development when herbicides were applied at R8.
Response of Alfalfa (Medicago Sativa) Grown for Seed Production to Glyphosate and SC-0224
Authors: Dawson Jean H.
Published: March 2018

Glyphosate and SC-0224, at rates that control dodder (75 to 150 g ae ba–1), injured flowers, caused flowers to abscise, and sometimes reduced seed yields when applied to alfalfa when buds or blooms were present. Glyphosate at 75 or 150 g ha–1did not injure flowers, impair seed set, or reduce yield or quality of seed when applied to alfalfa foliage before the bud stage.
Nutsedge (Cyperusspp.) Control in Peanuts (Arachis hypogaea) with Imazethapyr
Authors: Grichar W. James , Nester Paul R. , Colburn A. Ed
Published: March 2018

Experiments were conducted from 1988 through 1991 to evaluate the effectiveness of imazethapyr alone and in combination with metolachlor for control of yellow and purple nutsedge. Imazethapyr alone at 0.07 kg ha–1controlled yellow nutsedge irregularly while the addition of metolachlor greatly improved control. Metolachlor preplant incorporated (PPI) followed by imazethapyr at ground-crack (GC) or postemergence (POST) controlled 72 to 96% of yellow nutsedge, whereas a tank-mix of metolachlor plus imazethapyr PPI controlled 85 to 96%. The addition of metolachlor to imazethapyr did not result in any improvement in control of purple nutsedge. Metolachlor plus imazethapyr PPI controlled ≥ 85% of purple nutsedge PPI, whereas imazethapyr POST controlled ≥ 94%.
Influence of Droplet Size and Density on Phytotoxicity of Three Herbicides
Authors: Prasad Raj , Cadogan Beresford L.
Published: March 2018

The effects of droplet size and numerical deposit density on herbicide efficacy differed among investigations that relied on commercial nozzles to produce droplets strictly within small, medium, or large sizes. A droplet generator capable of producing uniform and homogeneous droplets was therefore used in a greenhouse experiment. Four droplet size classes (150, 350, 450, and 650 μm) using glyphosate, hexazinone, and triclopyr on red alder, aspen, and white birch were studied. Herbicides applied in small (150 to 450-μm) droplets were more phytotoxic than large (660-μm) ones because of their greater numerical coverage and translocation. Leaf age, weed species, herbicide type, and mixture of droplet sizes were not critical in modifying the effects of droplet behavior; however, the concentrations of herbicide used had a positive effect. When the herbicides were applied at high concentrations, the influence of droplet size was nullified. These findings may help reduce the cost of application and the chemical burden in a forest environment.
The Windgrasses(AperaAdans., Poaceae) in North America
Authors: Northam F. E. , Callihan R. H.
Published: March 2018

Two introduced windgrass species have become crop weeds in North America. Common windgrass is a major weed of winter cereals in Europe and was first documented in North America in the early 1800s. It is a weed of roadsides and waste areas in the northeastern United States and in winter grain fields of southern Ontario and Michigan. Interrupted windgrass was first reported in North America approximately 90 yr ago; it is adapted to more arid sites than common windgrass and is distributed predominantly in the northwestern U.S.A. During the past 10 to 15 yr, interrupted windgrass has adversely affected winter grain and grass seed producers in the Pacific Northwest due to additional control costs.
A Commentary on Agricultural Sciences and Federal Policy Development
Authors: Koppatschek Fritz K.
Published: March 2018

Agricultural scientists need to improve their communication with policy makers. Improving communication with federal policy makers will require new tactics by the research and extension community. A discussion on who is effectively communicating with policy makers, how agricultural policy is made, and what action is needed to improve communication is provided.
Application Rate and Timing of Acifluorfen, Bentazon, Chlorimuron, and Imazaquin
Authors: King Charles A. , Oliver Lawrence R.
Published: March 2018

Data from field studies at Fayetteville, AR, were used to predict the herbicide rate needed to provide 70, 80, or 90% control of a weed based upon weed age. Reduced herbicide rates generally needed to be applied within 6 to 12 d after emergence to control weeds 90%. Reduced rates (280 g ai ha–1or less) of acifluorfen controlled hemp sesbania, smooth pigweed, Palmer amaranth, and pitted and entireleaf morningglory 90%. Bentazon at 350 to 650 g ai ha–1controlled common cocklebur and prickly sida 90%. Common cocklebur, smooth pigweed, and pitted morningglory were controlled 90% with chlorimuron at 2 to 5 g ai ha–1and imazaquin at 20 to 80 g ai ha–1. Prickly sida and hemp sesbania were controlled 90% with imazaquin at 70 g ha–1and chlorimuron at 6 g ha–1, respectively. Barnyardgrass, large crabgrass, red rice, and sicklepod were not controlled with reduced herbicide rates.
Species Differ in Response to Adjuvants with Glyphosate
Authors: Nalewaja John D. , Matysiak Robert
Published: March 2018

Diammonium sulfate often is used as an adjuvant with glyphosate. Experiments were conducted in the greenhouse to determine the effectiveness of diammonium sulfate in overcoming calcium antagonism of glyphosate toxicity to wheat, sunflower, kochia, and soybean. Each species was a separate experiment and treatments varied with the experiment. Diammonium sulfate at 0.5% (w/v) in a spray carrier containing calcium chloride (500 ppm calcium) overcame calcium antagonism of glyphosate toxicity to wheat, overcame antagonism and enhanced toxicity to sunflower, but only partly overcame calcium antagonism of toxicity to kochia and soybean. With glyphosate at 100 g ae ha–1, diammonium sulfate at 2% (w/v) in a distilled water spray carrier enhanced toxicity to sunflower from a 11% to a 55% fresh weight reduction but was antagonistic to glyphosate toxicity to kochia and soybean.
Influence of Various Soil Properties on the Adsorption and Desorption of ICIA-0051 in Five Soils
Authors: Wilson John S. , Foy Chester L.
Published: March 2018

The soil organic matter and/or humic matter fraction was highly correlated with the adsorption of ICIA-0051 herbicide onto five soils; clay content and other soil factors were less correlated. The Freundlich equation was used to describe the adsorption of ICIA-0051 by the various soils. Based on the K constants, the general order for adsorption for each soil was Hyde silty clay loam > Frederick silt loam > Davidson clay = Bojac sandy loam > Appling loamy sand. Across all soils, 25 to 50% of the amount adsorbed was removed by two desorptions. Appling, Bojac, and Davidson soils retained less herbicide after two desorptions than did Frederick and Hyde.
Influence of Adjuvants on the Efficacy, Absorption, and Spray Retention of Primisulfuron
Authors: Hart Stephen E. , Kells James J. , Penner Donald
Published: March 2018

The effect of methylated seed oil (MSO), the organosilicone adjuvant DC-X2-5394, and ammonium sulfate on the efficacy, absorption, and spray retention of primisulfuron applied alone or with atrazine, dicamba, and bentazon to shattercane and giant foxtail was evaluated. Primisulfuron efficacy on both species was reduced by the three tank-mix combinations. Atrazine antagonism was not explained by decreases in foliar absorption and/or spray retention. Reductions in primisulfuron absorption and/or foliar spray retention appeared to cause bentazon antagonism on both weeds and dicamba antagonism on shattercane. MSO, DC-X2-5394, and ammonium sulfate completely reversed dicamba and bentazon antagonism on shattercane and partially reversed bentazon antagonism on giant foxtail by increasing foliar absorption and/or spray retention. Compared with non-ionic surfactant, MSO and DC-X2-5394 consistently increased giant foxtail control with primisulfuron by increasing foliar absorption and/or spray retention.
An Integrated Weed Management Procedure for the Control of Dodder (Cuscuta indecora) in Alfalfa (Medicago sativa)
Authors: Cudney D. W. , Orloff S. B. , Reints J. S.
Published: March 2018

Largeseed dodder is the most troublesome weed in alfalfa fields in the high desert of Southern California. Preemergence treatment with trifluralin controls dodder early in the season, but, as the season progresses, control declines. A method was needed to control attached dodder plants that escaped preemergence treatment. Flail mowing was compared to burning with a handheld propane-fueled weed burner. These methods were equally effective for controlling attached dodder, but flail mowing was more economical, and less injurious to alfalfa yield and stand density. Burning dodder patches at the end of the season reduced dodder seed viability by an average of 99%. Thus, we propose the use of a three tiered integrated approach consisting of PRE herbicide treatment followed by flail mowing in mid-season to control escaped dodder and burning at the end of the season to reduce dodder seed.
History of Identification of Herbicide-Resistant Weeds
Authors: Holt Jodie S.
Published: March 2018

At least 57 weed species, including both dicots and monocots, have been reported to have biotypes selected for resistance to the triazine herbicides. In addition, at least 47 species have been reported to have biotypes resistant to one or more of 14 other herbicides or herbicide families. These herbicides include the aryloxyphenoxypropionics, bipyridiliums, dinitroanilines, phenoxys, substituted areas, and sulfonylureas, with two or more resistant biotypes each, as well as several other herbicides in which resistance is less well documented. Although evolved resistance presents a serious problem for chemical weed control, it has also offered new potential for transferring herbicide resistance to crop species. Mechanisms of resistance that are due to single or a few genes have become the focus of biotechnology, as the probability of their successful transfer to crop species is high.
Technology Transfer for Herbicide-Tolerant Weeds and Herbicide-Tolerant Crops
Authors: Knake Ellery L.
Published: March 2018

Weed resistance has not generally been considered a serious problem where herbicide rotations and combinations are used. Herbicide-tolerant crops present new opportunities for decreasing risk of crop injury, decreasing carryover problems, broadening control spectrum, and for using herbicides that present less risk to the environment. However, herbicide-tolerant crops that allow intensified use of some herbicides may allow tolerant weed species to proliferate and herbicide carryover problems to increase for certain crops. Those responsible for the technology transfer process will need to keep well informed and objectively provide clientele with the basis for appropriate decisions as new weed control systems are designed as a result of these developments.
Site-Specific Pesticide Recommendations: The Final Step in Environmental Impact Prevention
Authors: Hornsby Arthur G.
Published: March 2018

A screening procedure to minimize adverse water quality impacts of pesticide application is presented that matches pesticide parameters to site-specific soil ratings. The pesticide parameters include a Relative Leaching Potential Index (RLPI), a Relative Runoff Potential Index (RRPI), the U.S. Environ. Prot. Agency (USEPA) lifetime health advisory level (HAL), and aquatic toxicity (LC50). Criteria used in developing soil ratings are described. Pesticide selection is accomplished by matching pesticide parameters values for the array of pesticides that control the pest of interest to soil ratings at the application site using selection criteria. A worksheet is presented to facilitate organization of information for the selection procedure and to serve as a record of the pesticide applicator's decision. The linking of an environmental fate model to a geographic information system (GIS) to create thematic maps of pesticide leaching potentials in terms of probability of exceeding the HAL in groundwater is described. A cost vs. groundwater hazard index frontier is described that suggests a method to assess the economic consequences of alternative pesticide selections.
The use of Runoff and Surface Water Transport and Fate Models in the Pesticide Registration Process
Authors: Zubkoff Paul L.
Published: March 2018

In support of the registration and reregistration processes under FIFRA ‘88, numerical models are used to estimate the dissolved runoff and soil erosion loadings of pesticides to surface waters and the subsequent fate and transport of pesticides in the receiving waters. Uses for simulations include:

1. Helping to determine whether additional studies on the fate and distribution of a candidate chemical in the environment and/or ecological effects may be needed when full chemical characterization is incomplete.

2. Helping to more fully integrate data submissions of laboratory and field observations.

3. Estimating probable fate and distribution of an agrochemical after a severe runoff event.

4. Comparing alternative chemical application rates and methods for the same chemical/soil/crop/environmental combinations.

5. Comparing different soil/crop/environmental combinations representing different geographical areas with the same chemical.

6. Evaluating preliminary designs of proposed field studies.

7. Gaining insight into the environmental fate of modern chemicals that are applied at 1 to 2% of the rates of older chemicals when sampling designs and analytical methods are not available.

The Office of Pesticide Programs (OPP) commonly employs the SWRRB (45, 46) and PRZM (8, 9) models for runoff and EXAMS II (5), a fate and transport model, for surface waters. These three models are used in conjunction with appropriate databases for soils, chemical properties, and meteorological and other environmental parameters. Registrants are encouraged to clearly state assumptions, identify values for parameters by citation, report results of simulations with summary tables and graphics, and interpret their results in relation to current scientific disciplines.
Control of Annual Bluegrass (Poa annua) in Kentucky Bluegrass (Poa pratensis) Turf with Linuron
Authors: Hall J. Christopher , Carey C. Ken
Published: March 2018

Effects of linuron on annual bluegrass control and Kentucky bluegrass cultivar tolerance were studied in field and growth chamber experiments. In controlled environment experiments, linuron at 0.06, 0.12, 0.25, 0.50, and 0.75 kg ai ha-1 was applied to pure stands of annual bluegrass and eight Kentucky bluegrass cultivars. Linuron at the two highest rates controlled annual bluegrass, reducing the clipping dry weight by more than 85% 4 wk after treatment, and by 65 to 92% 6 wk after treatment. Growth of Kentucky bluegrass was reduced with the most severe reduction occurring 2 wk after linuron application. All cultivars exhibited normal growth 8 wk after treatment. In field experiments, linuron at rates from 1.5 to 2.0 kg ai ha-1 controlled annual bluegrass in old (> 5 yr) Kentucky bluegrass stands, and in 16 cultivars of 1-yr and 2-yr-old Kentucky bluegrass stands, with little or no damage. At rates of 1.5, 2.0, and 2.5 kg ai ha-1 linuron, damage to newly seeded cultivars was moderate to severe. However, 6 to 7 wk after linuron application to newly seeded cultivars, stand density and turf quality were equivalent to untreated checks.
Seed Germination, Physical and Chemical Control of Catclaw Mimosa (Mimosa pigravar.pigra)
Authors: Creager R. A.
Published: March 2018

Catclaw mimosa, an exotic member of the Leguminosae, occurs in three areas of Florida. Propagation is by seed only. Seeds collected from Florida were used for germination, growth, and herbicide evaluation studies. Seeds germinated at 75 to 94% but were not influenced by different environmental conditions under which they were stored. Greenhouse-grown plants cut or burned off at ground level failed to regrow. However, plants cut at 2 cm or more above ground level regrew from lateral shoots. Sixteen herbicides were evaluated to determine their effects on 6- to 8-wk-old plants grown in the greenhouse. Catclaw mimosa was killed by picloram, tebuthiuron, hexazinone and sulfometuron at 0.4, 0.07, 0.14, and 0.56 kg ha-1, respectively. Dicamba at 1.12, triclopyr at 1.12 (Garlon 3A and 4), linuron at 4.48, and glyphosate at 8.96 kg ha-1were also effective. Chlorsulfuron and metsulfuron killed 9 out of 10 plants at the highest rates tested. Four herbicides, imazapyr, thifensulfuron, DPX-L5300, and atrazine killed 50% or less of the plants at the highest rates of each compound tested. Fosamine did not kill catclaw mimosa at the rates tested.
Combined Postemergence Grass and Broadleaf Weed Control in Canola (Brassica napus)
Authors: Blackshaw Robert E. , Harker K. Neil
Published: March 2018

Field studies were conducted to study the interaction of sethoxydim or fluazifop-P with clopyralid and/or ethametsulfuron applied as tank mixtures to canola. Control of the indicator species barley, broadbean, and wild mustard with the tank mixtures was comparable to, or sometimes better than, that attained with each herbicide alone. Canola tolerated all herbicides applied individually and all tank mixtures of these herbicides except fluazifop-P and ethametsulfuron. Tank mixtures of fluazifop-P and ethametsulfuron, with or without clopyralid included in the mixture, suppressed early growth of canola in two of four tests and reduced seed yield in one. Sethoxydim, clopyralid, and ethametsulfuron combined in tank mixtures provide an effective POST alternative for selective control of grass and broadleaf weeds in canola.
Distinguishing Brush and Weeds on Rangelands Using Video Remote Sensing
Authors: Everitt James H. , Escobar David E. , Alaniz Mario A. , Villarreal Ricardo , Davis Michael R.
Published: March 2018

This paper describes the application of a relatively new remote sensing tool, airborne video imagery, for distinguishing weed and brush species on rangelands. Plant species studied were false broomweed, spiny aster, and Chinese tamarisk. A multispectral video system that acquired color-infrared (CIR) composite imagery and its simultaneously synchronized three-band [near-infrared (NIR), red, and yellow-green] narrowband images was used for the false broomweed and spiny aster experiments. A conventional color camcorder video system was used to study Chinese tamarisk. False broomweed and spiny aster could be detected on CIR composite and NIR narrowband imagery, while Chinese tamarisk could be distinguished on conventional color imagery. Quantitative data obtained from digitized video images of the three species showed that their digital values were statistically different (P = 0.05) from those of associated vegetation and soil. Computer analyses of video images showed that populations of the three species could be quantified from associated vegetation. This technique permits area estimates of false broomweed, spiny aster, and Chinese tamarisk populations on rangeland and wildland areas.
Alfalfa (Medicago sativa) Response to Simulated Herbicide Spray Drift
Authors: Al-Khatib Kassim , Parker Robert , Fuerst E. Patrick
Published: March 2018

‘Vernal’ alfalfa response was evaluated when chlorsulfuron, thifensulfuron, 2,4-D, glyphosate, bromoxynil, and selected combinations of those herbicides were applied at rates simulating spray drift during the fourth trifoliolate leaf stage following the first cutting in 1990 and 1991. The order of phytotoxicity was 2,4-D > chlorsulfuron > thifensulfuron > glyphosate > bromoxynil. By the end of each growing season, alfalfa had recovered from injury caused by all herbicides except the highest rates of 2,4-D and 2,4-D plus glyphosate. The alfalfa stand was reduced only by 2,4-D and 2,4-D plus glyphosate. All herbicides caused characteristic symptoms, but some specific symptoms were similar among different herbicides or resembled symptoms caused by disease, mineral imbalance, and adverse weather conditions.
Effects of Harvest-Aid Herbicides on Sicklepod (Cassia obtusifolia) Seed Yield and Quality
Authors: Ratnayake Sunil , Shaw David R.
Published: March 2018

Experiments were conducted in 1989 and 1990 to study the effects of 220 g ai ha-1AC 263,222, 840 g ai ha-1glufosinate, 560 g ai ha-1glyphosate, and 840 g ai ha-1paraquat on sicklepod seed production and quality when applied at R5, R6, R7, and R8 growth stages of sicklepod. No seed were produced on plants treated at R5 with paraquat and glufosinate; glyphosate was the least effective herbicide at this growth stage. Although sicklepod seed germinated after AC 263,222 application at R5, no seedling emergence occurred. Normal seedlings, seedling emergence, and seedling radicle length were reduced by all herbicides applied to parent plants at R5, R6, and R7 growth stages. AC 263,222 applied at R7 reduced normal seedlings and seedling emergence more than any other herbicide. No effects were observed on any of the variables investigated when herbicides were applied at R8.
Herbicide Efficacy for Production of Container Ornamentals
Authors: Gallitano Lena B. , Skroch Walter A.
Published: March 2018

A study was conducted to evaluate efficacy of 17 PRE herbicides on seven weed species that are important competitors in container-grown ornamentals. Treatments included napropamide, metolachlor, acifluorfen, lactofen, oxyfluorfen, oryzalin, pendimethalin, prodiamine, trifluralin, isoxaben, oxadiazon, simazine and combination products. Control was evaluated by counting weed seedlings 42, 202, and 249 d after treatment. Some treatments provided nearly total control of less than 1.0 seedling per container at each rating over two years. Those treatments were: common groundsel—diphenyl ethers, isoxaben, oxadiazon, oxyfluorfen + oryzalin, and oxyfluorfen + pendimethalin; prostrate spurge—pendimethalin, prodiamine, prodiamine-ABD, trifluralin, oxadiazon, isoxaben + oryzalin, and methazole + prodiamine; common chickweed—isoxaben and isoxaben + oryzalin; hairy bittercress—oxyfluorfen, pendimethalin, prodiamine, prodiamine-ABE, oxadiazon, oxyfluorfen + oryzalin, oxyfluorfen + pendimethalin, and methazole + prodiamine; common ragweed—oxyfluorfen, prodiamine-ABD, methazole + prodiamine; Virginia pepperweed—lactofen, oxyfluorfen, oryzalin, pendimethalin, prodiamine, prodiamine-ABD, isoxaben, oxadiazon, oxyfluorfen + oryzalin, oryzalin + pendimethalin, isoxaben + oryzalin, and methazole + prodiamine; horseweed—oxyfluorfen, dinitroanilines, oxadiazon, oxyfluorfen + oryzalin, oxyfluorfen + pendimethalin, isoxaben + oryzalin, and methazole + prodiamine.
Soybean (Glycine max) Yield and Quality Responses Associated with Wild Poinsettia (Euphorbia heterophylla) Control Programs
Authors: Willard Teresa S. , Griffin James L.
Published: March 2018

In field studies conducted over 2 yr, POST applications of chlorimuron, imazaquin, fomesafen, or acifluorfen following PRE applications of clomazone, metribuzin, or metribuzin plus chlorimuron enhanced wild poinsettia control when compared with the PRE herbicides applied alone. Wild poinsettia control was highest for imazaquin compared with other PRE treatments and with the exception of fomesafen, applications of POST herbicides following imazaquin PRE did not improve weed control. With the addition of POST herbicides, soybean yields were generally not increased, but moisture content in one year and foreign material content both years were reduced. In other studies, early POST applications (2 to 8 cm) of fomesafen, imazaquin, acifluorfen, lactofen, and chlorimuron controlled wild poinsettia better than late POST applications (10 to 15 cm) in only one year. Soybean yields both years were generally similar regardless of herbicide application time.
Crop Responses to Hexazinone, Imazapyr, Tebuthiuron, and Triclopyr
Authors: Coffman C. Benjamin , Frank J. Ray , Potts William E.
Published: March 2018

Field investigations were conducted for 2 yr to characterize the responses of wheat, kidney bean, field corn, squash, okra, potato, and banana to soil-applied hexazinone, imazapyr, tebuthiuron, and triclopyr at rates used for control of woody perennial plants. Test species were planted at seven selected intervals through the first and second years after herbicide applications to assess residual herbicide activity. Tebuthiuron treatments of 2.2 kg ai ha−1were not tolerated by any bioassay species planted 436 d after application (DAA). Only potato was tolerant of residual hexazinone 436 DAA. All species except banana generally tolerated residual imazapyr and triclopyr by the second growing season. Indigenous plants repopulated all herbicide-treated areas, except those treated with tebuthiuron, by the third growing season. Plots treated with tebuthiuron were 90% free of indigenous plants 40 mo after herbicide application.
Response of Cotton (Gossypium hirsutum) to Preplant-Applied Hormone-Type Herbicides
Authors: Baker Ralph S.
Published: March 2018

In a 3-yr field study on a Bosket silt loam, dicamba (0.3 and 0.6 kg ai ha−1) and 2,4-D amine (0.6, 1.1, and 2.2 kg ae ha−1) were applied at 3, 9, and 16 d before planting cotton. Most treatments applied 3 or 9 d before planting caused cotton injury and yield reduction. Replanting was necessary when 2,4-D at 2.2 kg ha−1was applied 9 d before planting, and all treatments except dicamba at 0.3 kg ha−1when applied 3 d before planting.
Effect of Dithiopyr Timing on Establishment of Three Cool-Season Turfgrass Species
Authors: Johnson B. Jack , Bundschuh Sarah H.
Published: March 2018

An experiment was conducted to determine the interval needed between dithiopyr formulation (EC and G) treatments and seeding of tall fescue, perennial ryegrass, and creeping bentgrass. The cover of tall fescue 10 wk after seeding was not reduced when the EC formulation was applied at ≤ 0.84 kg ha−1 ≥ 2 wk before seeding. Dithiopyr G at 0.56 kg ha−1 did not reduce tall fescue cover when applied at ≥ 8 wk before seeding; whereas, 0.84 kg ha−1 required a 12-wk interval between treatment and seeding in one of two years. Perennial ryegrass cover 10 wk after seeding was not reduced with dithiopyr at 0.56 kg ha−1 applied from 2 to 12 wk before seeding. When the dithiopyr G was applied at 0.56 kg ha−1, an 8-wk interval before seeding was needed to prevent a reduction in turf cover. When rates of EC and G dithiopyr were increased to 0.84 kg ha−1 an 8-wk interval was needed for the EC and a 12-wk interval was needed for the G formulation to prevent a reduction in cover in one of two years. Creeping bentgrass cover was not reduced when dithiopyr EC was applied at 0.56 kg ha−1 ≥ 8 wk before seeding. When the EC rate was increased to 0.84 kg ha−1 a 12-wk interval was needed between treatment and seeding in one of two years. When dithiopyr G was applied within 12 wk of seeding creeping bentgrass, the cover was reduced to an unacceptable level regardless of application rate.
Management of Field Violet (Viola arvensis) in Strawberries (Fragaria × anassa)
Authors: Doohan Douglas J. , Monaco Thomas J. , Sheets Thomas J.
Published: March 2018

Herbicides were evaluated for control of field violet in strawberries in North Carolina and in Nova Scotia, Canada. DCPA at 11.0 kg ai ha−1 and terbacil at 0.5 kg ai ha−1 PRE controlled field violet 80 to 95%. Control with simazine PRE at 1.0 kg ai ha−1 was 70 to 75%. Oxyfluorfen at 0.6 to 1.1 kg ai ha−1 controlled 95 to 100% of the established field violet in dormant strawberries following a mid-winter application. Control with acifluorfen and lactofen applied during mid-winter was 75 to 90%. Oxyfluorfen applied to dormant plantings at rates in excess of 0.60 kg ai ha−1 caused foliar damage; however, yield was not reduced at rates up to 4.5 kg ha−1. Oxyfluorfen at 0.25 kg ha−1 caused severe injury to newly-transplanted strawberries.
Clomazone as a Component in Cotton (Gossypium hirsutum) Herbicide Programs
Authors: Jordan David L. , York Alan C. , McClelland Marilyn R. , Frans Robert E.
Published: March 2018

Efficacy of herbicide programs containing clomazone PPI plus fluometuron PRE or clomazone plus pendimethalin PPI plus fluometuron PRE was compared with that of standard programs of pendimethalin PPI plus fluometuron PRE and norflurazon PPI plus norflurazon and fluometuron PRE. Cotton injury was less than 5% with all treatments when disulfoton or phorate was applied in the seed furrow. Control of fall panicum, goosegrass, large crabgrass, eclipta, entireleaf morningglory, ivyleaf morningglory, pitted morningglory, tall morningglory, prickly sida, redroot pigweed, smooth pigweed, hemp sesbania, spotted spurge, sicklepod, and velvetleaf and cotton yields with 0.8 kg ai ha−1 of clomazone plus fluometuron or 0.6 kg ha−1 of clomazone plus pendimethalin plus fluometuron equalled or exceeded that from the standard herbicide programs. POST-directed application of methazole at 0.8 kg ai ha−1 plus MSMA at 2.2 kg ae ha−1 increased sicklepod and morningglory control and cotton yield. Clomazone applied PRE at 0.6 kg ha−1 with fluometuron controlled broadleaf signalgrass, goosegrass, large crabgrass, prickly sida, and smooth pigweed equally with that of standard treatments of trifluralin or trifluralin plus norflurazon PPI and fluometuron PRE, whereas pitted morningglory control and cotton yield with clomazone plus fluometuron exceeded that with the standards.
Influence of Application Rate and Timing on Efficacy of DPX-PE350 Applied Postemergence
Authors: Jordan David L. , Frans Robert E. , McClelland Marilyn R.
Published: March 2018

Broadleaf weed control with DPX-PE350 at 56, 84, 110, 140, and 170 g ae ha−1applied postemergence was evaluated. DPX-PE350 was less effective and higher rates were required when applied to three- to six-leaf weeds compared to one- to two-leaf weeds. Listed in order of increasing susceptibility are sicklepod, tall morningglory, pitted morningglory = palmleaf morningglory, and entireleaf morningglory = hemp sesbania = velvetleaf.
Barnyardgrass (Echinochloa crus-galli) Interference in Soybeans (Glycine max)
Authors: Vail Gordon D. , Oliver Lawrence R.
Published: March 2018

A 2-yr field experiment was conducted at Fayetteville and Stuttgart, AR, to predict soybean yield loss as a function of barnyardgrass density and total dry weight. Predicted soybean yield reductions were 0 to 78% for original densities of 1 to 500 barnyardgrass plants per m of row. Soybean yield reductions were linear from 0 to 150 barnyardgrass plants per m of row with an average yield reduction of 0.25% for each plant per m of row. Soybean yield was reduced 10, 25, and 50% from original barnyardgrass densities of 42, 110, and 250 plants m of row. Predictions of soybean yield reduction from barnyardgrass dry weight and original density were similar. traspecific interference of barnyardgrass occurred for all variables tested, with individual barnyardgrass plants becoming less competitive as density increased.
Use of Ground Water Monitoring Data for Pesticide Regulation
Authors: Barrett Michael R. , Williams W. Martin , Wells David
Published: March 2018

Growing public concern for pesticide residues in drinking water has resulted in tighter federal and state regulations to prevent ground-water contamination. There are many uncertainties in estimating human exposure risk, yet standards are being set to protect human health. In the last several years, drinking water health standards have been developed for a number of pesticides, often at levels of a few μg L−1 or less. Ground-water monitoring studies, first required by the U.S. Environmental Protection Agency in 1984, have now become an integral requirement to support registration of pesticides shown to have leaching potential. Regulators are now faced with deciding the extent to which pesticides can still be used while continuing to meet legal requirements to protect the public and preserve ground-water resources. The implications are that pesticide use may be severely limited in regions with ground-water resources considered especially vulnerable to contamination, dramatically affecting the type of agricultural practices and crops grown in these regions.
SELOMA: Expert System for Weed Management in Herbicide-Intensive Crops
Authors: Stigliani Lucia , Resina Cosimo
Published: March 2018

A practical expert system is needed to handle POST weed control in herbicide-intensive crops such as wheat, barley, oat, rye, sugarbeet, corn, and sorghum. SELOMA is an expert system having a step-by-step problem-solving procedure closely resembling what a weed management expert would follow. It is based on field surveys of weed density, and crop and weed growth stage and height. SELOMA evaluates weed competitiveness and provides weed management advice. It suggests whether or not to intervene, chemical and mechanical weed control treatments, and selects the best herbicides, including commercial formulations, costs, and optimal dosages.
Interactions of DPX-PE350 with Fluazifop-P, Sethoxydim, Clethodim, and Quizalofop-P
Authors: Jordan David L. , Frans Robert E. , McClelland Marilyn R.
Published: March 2018

Interactions of fluazifop-P, sethoxydim, clethodim, and quizalofop-P with DPX-PE350 were evaluated. DPX-PE350 at 110 g ae ha−1reduced control of large crabgrass when mixed with all graminicides and control of broadleaf signalgrass when mixed with fluazifop-P or quizalofop-P. Increasing the rate of graminicide reduced or eliminated antagonism. Applying sethoxydim and DPX-PE350 sequentially eliminated antagonism on large crabgrass. Control of seedling johnsongrass by the graminicides was not reduced by DPX-PE350. DPX-PE350 reduced control of rhizomatous johnsongrass by sethoxydim. Graminicides had no effect on entireleaf morningglory control with DPX-PE350.
Effect of Prior Year's Weed Control on Herbicide Effectiveness in Corn (Zea mays)
Authors: Hartzler Robert G. , Roth Greg W.
Published: March 2018

Three levels of weed control (0, 70, and 100%) were maintained in 1989 during corn production at two sites. Weed control in 1990 with a premix formulation of metolachlor and atrazine was directly related to 1989 control levels. Herbicides generally were more effective in conventional tillage than in no-tillage. In no-tillage, giant foxtail control in 1990 averaged 59% following 100% control in 1989 compared to 15% following 0% weed control. At one location, tillage minimized the impact of the prior year's weed control with herbicides providing greater than 85% control in conventional tillage regardless of prior history. In no-tillage, weed control of 85% or better was obtained only following 100% control the previous year.
Influence of Tillage Systems on Weed Abundance in Southwestern Ontario
Authors: Thomas A. Gordon , Frick Brenda L.
Published: March 2018

Weed data were collected over three tillage systems and two years in southwestern Ontario, in fields of corn, soybean, and winter wheat. Tillage systems involved soil inversion by moldboard plow, soil disturbance without inversion, and no tillage. The data were subjected to multivariate ordination techniques to determine if weed communities were associated with the different crops, tillage systems, or years. Crop, year, and tillage system all had significant effects on the weed community. Weed communities in corn and winter wheat were least similar; those in soybean were intermediate. Several grass weeds were more abundant in the drier of the two years. Some variation was related to tillage system but the effect of tillage was less than that of either crop or year.
Spray Droplet Size for Water and Paraffinic Oil Applied at Ultralow Volume
Authors: Hanks James E. , McWhorter Chester G.
Published: March 2018

Spray droplet size of water and paraffinic oil was affected by air pressure, nozzle type, and liquid flow rate when applied with an ultralow volume (ULV), air-assist sprayer. Volume median diameters of water were generally larger than oil at constant air pressure and liquid flow rate. Droplet size decreased as air pressure increased, but increased as liquid flow rate increased. Volume median diameters of water droplets ranged from 41 to 838μm and from 16 to 457μm with oil when atomized at air pressures ranging from 14 to 84 kPa. Relative spans ranged from 1.2 to 18.0 and 2.0 to 7.2 for water and oil, respectively.
Silverleaf Nightshade (Solanum elaeagnifolium) Control with Foliar Herbicides
Authors: Eleftherohorinos Ilias G. , Bell Carl E. , Kotoula-Syka Eleni
Published: March 2018

Four experiments (three in Macedonia, Greece and one in Holtville, CA) were conducted in 1988 and 1989 to evaluate foliar applications of picloram, glyphosate alone and with adjuvant, and triclopyr for the control of established silverleaf nightshade. Silverleaf nightshade control was determined by comparing stem population at the time of herbicide application to stem population 6 to 11 mo after application. Picloram, averaged over rate and location, controlled silverleaf nightshade consistently, restricting regrowth to less than 5%. Silverleaf nightshade control with glyphosate alone or with adjuvant varied with location, regrowth ranged from 0 to 69%. Regrowth of silverleaf nightshade treated with triclopyr approached that of the untreated control.
Reduced-Herbicide Weed Management Systems for No-Tillage Corn (Zea mays) in a Hairy Vetch (Vicia villosa) Cover Crop
Authors: Teasdale John R.
Published: March 2018

Weed management treatments with various degrees of herbicide inputs were applied with or without a hairy vetch cover crop to no-tillage corn in four field experiments at Beltsville, MD. A hairy vetch living mulch in the no-treatment control or a dead mulch in the mowed treatment improved weed control during the first 6 wk of the season but weed control deteriorated in these treatments thereafter. Competition from weeds and/or uncontrolled vetch in these treatments without herbicides reduced corn yield in three of four years by an average of 46% compared with a standard PRE herbicide treatment of 0.6 kg ai/ha of paraquat plus 1.1 kg ai/ha of atrazine plus 2.2 kg ai/ha of metolachlor. Reducing atrazine and metolachlor to one-fourth the rate of the standard treatment in the absence of cover crop reduced weed control in three of four years and corn yield in two of four years compared with the standard treatment. Hairy vetch had little influence on weed control or corn yield with any herbicide treatments.
Triazine-Resistant Common Lambsquarters (Chenopodium albumL.) Control in Field Corn (Zea maysL.)
Authors: Myers Mark G. , Harvey R. Gordon
Published: March 2018

Field studies were conducted near Beechwood, WI in 1986 and Sturgeon Bay, WI in 1987 and 1988 to evaluate herbicide treatments for control of triazine-resistant common lambsquarters (TR-CHEAL) in corn. AH PRE and many early postemergence (EP) and POST treatments were less effective in 1988 than in 1986 or 1987 due to drought. Atrazine, cyanazine, and metolachlor PRE controlled less than 15% TR-CHEAL late-season over the three years. Dicamba or pendimethalin applied PRE controlled 88 to 99% late-season TR-CHEAL in 1986 and 1987. Late-season TR-CHEAL control in 1986 and 1987 from acetochlor plus atrazine, alachlor plus atrazine, and metolachlor plus linuron applied PRE ranged from 58 to 86%. Pendimethalin plus cyanazine or atrazine applied EP controlled TR-CHEAL 97% or more late-season in 1986 and 1987, while pendimethalin plus dicamba plus atrazine applied EP controlled TR-CHEAL 97% or more each year. Late-season TR-CHEAL control from tridiphane plus cyanazine or atrazine EP was less than 58%. Late-season TR-CHEAL control from dicamba, 2,4-D amine, pyridate, and thifensulfuron applied POST was 87 to 99% each year, and was 94 to 99% in 1986 and 1987 from bromoxynil or bentazon applied POST. Dicamba, thifensulfuron, pendimethalin, pyridate, and 2,4-D amine were most effective in controlling TR-CHEAL in corn.
Influence of Residual Herbicides on Rate of Paraquat and Glyphosate in Stale Seedbed Soybean (Glycine max)
Authors: Lanie Andrew J. , Griffin James L. , Reynolds Daniel B. , Vidrine P. Roy
Published: March 2018

Field studies were conducted to evaluate weed control with paraquat and glyphosate applied at various rates alone and in combination with residual herbicides. Morningglory, prickly sida, and hemp sesbania control 28 d after treatment was similar regardless of herbicide treatment. In contrast, barnyardgrass control when paraquat was tank mixed with pendimethalin plus imazaquin was equal to that of paraquat alone but less than that for tank mixtures with metolachlor plus metribuzin plus chlorimuron or metolachlor plus metribuzin. Barnyardgrass control and soybean yield when paraquat was applied at 1050 g ai/ha in combination with metolachlor plus metribuzin plus chlorimuron or metolachlor plus metribuzin was greater than when the same residual herbicide treatments were applied with paraquat at 350 g/ha. Yield following glyphosate at 840 and 1120 g ai/ha in combination with residual herbicides was no greater than when glyphosate was applied alone, which was reflective of barnyardgrass control. Tank mixtures of glyphosate at 1680 g/ha with metolachlor plus metribuzin plus chlorimuron or metolachlor plus metribuzin resulted in soybean yield higher than for glyphosate alone. Regardless of the glyphosate and residual herbicide combination, soybean yield was no greater than when paraquat was applied at 350 g/ha in combination with metolachlor plus metribuzin plus chlorimuron.