bluuebunny/crossref_metadata_2025 huggingface dataset:
Growth, Reproduction and Chemical Composition of Horsenettle (Solanum carolinense)
Authors: Nichols Robert L. , Cardina John , Gaines T. Powell
Published: March 2018

Horsenettle was described quantitatively in two grazed bermudagrass pastures for two years. Six times from April through October, plants were counted, phenologically documented, and tops were harvested for estimation of above-ground phytomass. Roots were sampled for carbohydrate, N fraction, and macronutrient analyses. Top growth, flowering, fruiting, and chemical composition were similar between sites within years, but differed between years. Starch and total non-structural carbohydrates in roots increased following reproductive periods both years. Root concentrations of protein and non-protein N increased and concentrations of P decreased in August and September in one year only. Analysis of the relationship between seasonal trends in carbohydrate fluctuation and pasture management practices suggests that systemic herbicide application in mid-summer may lead to more effective control than application in spring.
Translocation of Glyphosate and Quizalofop and Metabolism of Quizalofop in Quackgrass Biotypes (Elytrigia repens)
Authors: Tardif François J. , Leroux Gilles D.
Published: March 2018

An experiment was conducted to evaluate the translocation pattern of14C-glyphosate and14C-quizalofop in five quackgrass biotypes at two stages of growth. Whole plant translocation differed between stages for each herbicide. The percentage of14C-glyphosate and14C-quizalofop in the leafwash and in the treated leaf did not differ among biotypes, but differences occurred for the translocation to the underground parts. The partitioning of the14C-glyphosate and14C-quizalofop in the treated crown, other crowns, propagating rhizomes, and other rhizomes differed among biotypes. On a disintegration per minute (DPM) mg-1basis, differences among biotypes were found with14C-glyphosate but much less with14C-quizalofop. Metabolism of14C-quizalofop in the treated leaf was similar in the two biotypes tested except for the percentage of polar metabolites 1 d after treatment. The percentage of14C-quizalofop available for translocation was the same in both biotypes.
Control of Downy Brome (Bromus tectorum) in Conservation Fallow Systems
Authors: Blackshaw Robert E.
Published: March 2018

Field studies were conducted to determine the most effective rate of several herbicides applied at various growth stages to control downy brome in conservation fallow programs. Downy brome growth stage affected the efficacy of all herbicides. All herbicides were less effective when application was delayed until the boot stage of downy brome. Fluazifop-P and sethoxydim must be applied prior to tillering to effectively control downy brome. Glyphosate, the commercial mixture of glyphosate plus 2,4-D, paraquat, and HOE-39866 consistently controlled downy brome up to the 3- to 5-tiller stage. Glyphosate at 180 to 200 g ha-1, paraquat at 250 to 300 g ha-1, and the commercial mixture of glyphosate plus 2,4-D at 600 to 660 g ha-1controlled downy brome 80 to 90%. The effective rates were lower than rates currently registered for downy brome control in western Canada, and thus there is potential for making conservation fallow programs more economical when downy brome is the predominant weed.
Timing of Nitrogen Application Affects Downy Brome (Bromus tectorum) Growth in Winter Wheat
Authors: Anderson Randy L.
Published: March 2018

Field studies were conducted to determine if varying the time N fertilizer was applied would affect downy brome interference in winter wheat. Five treatments were compared: four broadcast application times of NH4NO3at 56 kg N ha-1during the fallow-crop cycle: 1) during fallow; 2) at planting; 3) during crop dormancy; 4) before winter wheat jointing; and 5) a control where no N was applied. Downy brome was least responsive to N applied during fallow. All N applications during the growing season of winter wheat increased downy brome biomass and culms m-2. Downy brome interference prevented winter wheat from responding positively to N. For example, when crop season precipitation was only 70% of normal, applying N reduced grain yield of winter wheat infested with downy brome from 12 to 28%. This study indicates that N manipulation offers potential for reducing downy brome interference in winter wheat.
Integrated Weed Management: The Rationale and Approach
Authors: Swanton Clarence J. , Weise Stephan F.
Published: March 2018

A growing awareness of environmental issues in Canada has had a major influence on government policies. An initiative was launched by the government of Ontario to promote research toward the development of an integrated weed management (IWM) system. Research in IWM must take all aspects of the cropping system into consideration and evolve in a progressive manner. This approach must encompass the role of conservation tillage, knowledge of the critical period of weed interference, alternative methods of weed control, enhancement of crop competitiveness, modeling of crop-weed interference, influence of crop rotation and seed bank dynamics, and education and extension of the findings. The complexity involved in addressing these issues requires a multi-disciplinary approach.
Weed Succession under Conservation Tillage: A Hierarchical Framework for Research and Management
Authors: Swanton Clarence J. , Clements David R. , Derksen Douglas A.
Published: March 2018

The awareness and adoption of conservation tillage is one of the most important changes taking place in agriculture today. There are, however, concerns regarding weed species shifts under conservation tillage. Under conservation tillage, shifts toward grass, perennial, wind-disseminated weeds and volunteer crop plants have been observed. Shifts in weed species composition may either represent long-term ecological succession or temporary fluctuations in species composition; few long-term studies have examined the ecology of these shifts in detail. Further studies are needed to identify mechanisms driving these shifts to determine whether they are fluctuational or successional and to develop more sophisticated management strategies. In this paper, we present a research approach for studying ecological processes such as competition within a hierarchical framework of all possible causes, processes, and defining factors related to weed succession under conservation tillage. Succession management strategies can be developed to act at the causal level in the successional hierarchy. Three primary causes are site availability, colonization, and species performance. Site availability may be controlled through “designed disturbance”, while differential species availability may be regulated through “controlled colonization” and species performance may be regulated through “controlled species performance”. In general, the goals of succession management would involve reducing populations of the weed species most likely to proliferate under conservation tillage. Comprehensive ecological research, within the hierarchical framework outlined here, would identify potential problems and enable management strategies to account for the numerous factors that may be influencing fluctuations and succession of weeds under conservation tillage.
Broadleaf Weed Control in Soybean (Glycine max) with Chlorimuron plus Acifluorfen or Thifensulfuron Mixtures
Authors: Monks C. Dale , Wilcut John W. , Richburg John S.
Published: March 2018

Chlorimuron applied alone and in combination with acifluorfen or thifensulfuron was evaluated for POST control of common lambsquarters, common ragweed, common cocklebur, and a mixture of pitted, ivyleaf, entireleaf, and tall morningglory in soybean. Common cocklebur control was similar with thifensulfuron at 3 and 4 g ae ha−1and with chlorimuron at 7 and 9 g ae ha−1, Common ragweed and morningglory control was greater with chlorimuron while common lambsquarters control was greater with thifensulfuron. Control of all species was good with combinations of chlorimuron at 7 g ha−1plus thifensulfuron at 2 g ha−1or acifluorfen at 140 g ae ha−1and similar to or greater than the control with chlorimuron at 9 g ha−1. Soybean yields with all POST herbicide treatments were equivalent to that of the weed-free check.
Overcoming Antagonistic Effects of Na-Bentazon on Sethoxydim Absorption
Authors: Wanamarta Gunawan , Kells James J. , Penner Donald
Published: March 2018

The influence of adjuvants, inorganic salts, and herbicide formulations on the antagonistic effect of Na-bentazon on sethoxydim absorption was studied in quackgrass. Adjuvant BCH 815 00, at 2.4 L ha−1alone or at 1.2 L ha−1combined with 1.1 kg ha−1of ammonium sulfate, added to the sethoxydim and Na-bentazon spray mixture overcame the antagonism on14C-sethoxydim absorption in quackgrass. Crop oil concentrate at rates up to 9.6 L ha−1did not overcome the antagonism. Adding ammonium phosphate or ammonium nitrate to the spray solution was as effective as adding ammonium sulfate in overcoming the antagonism caused by reduced absorption of sethoxydim even from the combination of Na-bentazon plus Na-acifluorfen. Ammonium salts and NH4-bentazon overcame the antagonism of Na-bentazon by forming readily absorbed NH4-sethoxydim.
Imazaquin Absorption, Translocation, and Metabolism in Flue-Cured Tobacco
Authors: Walls Frank R. , Corbin Frederick T. , Collins William K. , Worsham A. Douglas , Bradley J. R.
Published: March 2018

Absorption of14C-imazaquin by leaves of field-grown flue-cured tobacco was similar when applied to young seedlings immediately after transplanting or to plants 3 wk after transplanting. The distribution of14C in treated leaves indicated that 40% was absorbed, 54% remained in water extracts of leaf surfaces, and 6% was found in the epicuticular wax layer 8 d after treatment. Translocation of the herbicide from treated leaves to roots was very low (4 to 5%). In contrast, soil applications of imazaquin and subsequent uptake by roots resulted in retention of 40 to 53% in roots and translocation of 47 to 60% to shoots after 8 d. Analyses of methanol-soluble extracts of14C indicated that more than 77% of the foliar-applied herbicide was metabolized in roots and upper shoots after 2 d. Similarly, 64% or more of the imazaquin was degraded in roots and shoots 2 d after root absorption.
Use of Tomato (Lycopersicon esculentum) Seedlings to Detect Bensulfuron and Quinclorac Residues in Water
Authors: De Barreda Diego Gomez , Lorenzo Elena , Carbonell Emilio A. , Cases Baltasar , Muñoz Niceto
Published: March 2018

During 1990, injury to tomatoes grown on the narrow land between the Albufera Lake (Spain) and the Mediterranean Sea was attributed to use of irrigation water coming from adjacent rice fields containing bensulfuron and quinclorac. A tomato root bioassay was developed to detect the herbicides in 10 ml of water. The assay was more sensitive to bensulfuron (0.5 ng ml−1) than quinclorac (100 ng ml−1). Only 30 ml of the affected water are necessary to conduct the test. Albufera water, sampled at three sites during 1991 and one during 1992 in the irrigation network canals caused different tomato main root length responses.
Development of a Biologically-Based System for Detection and Tracking of Airborne Herbicides
Authors: Al-Khatib Kassim , Mink Gaylord I. , Reisenauer Guy , Parker Robert , Westberg Halvor , Lamb Brian
Published: March 2018

This study was designed to develop a protocol for using a biologically-based system to detect and tract airborne herbicides. Common bean, lentil, and pea were selected for their quasi-diagnostic sensitivity to chlorsulfuron, thifensulfuron, metsulfuron, tribenuron, paraquat, glyphosate, bromoxynil, 2,4-D, and dicamba. Plants were grown in the greenhouse at Prosser, WA, and placed at 25 exposure sites at weekly intervals between Apr. 2 and Oct. 15, 1991. After 1 wk of field exposure plants were brought back and observed for herbicide symptoms over a 28-d period. Symptoms that developed were compared with symptoms caused by disease, insects, adverse weather conditions, and herbicides applied at different rates under controlled conditions on these species. In addition, if herbicide symptoms were observed, herbicide spray records and weather data in the area were used in a computer model to determine the source of potential herbicide drift. This study demonstrates that indicator plant species selected for high sensitivity to herbicides can be used to monitor the occurrence of herbicide movement.
Invert Emulsion Droplet Size and Mycoherbicidal Activity ofColletotrichum truncatum
Authors: Egley Grant H. , Hanks James E. , Boyette C. Douglas
Published: March 2018

When formulated and sprayed in an invert emulsion (IE), conidia of the mycoherbicide,Colletotrichum truncatum, controlled hemp sesbania in the absence of dew. To optimize hemp sesbania control, formulation droplet size influence upon the pathogen's germination and pathogenicity was investigated. Conidia germination in manually produced IE droplets decreased from 46% to 5% as droplet diameter decreased from 2700 to 900μm. Droplet size did not affect appressoria formation. On a per conidium basis, 900-μm droplets were more pathogenic to detached hemp sesbania leaves than were 2100-μm droplets. An air-assist spray system produced droplet spectra with volume median diameters of 421 and 104μm, respectively. The spectrum of smaller droplets covered the target better than did that of larger droplets. When applied to whole hemp sesbania plants in greenhouse trials, conidia in the smaller and larger droplet spectra gave 90 and 94% control, respectively. Sufficient conidia germinated in IE droplets of a variety of sizes to control hemp sesbania excellently.
Net Returns from Cheat (Bromus secalinus) Control in Winter Wheat (Triticum aestivum)
Authors: Justice Greg G. , Peeper Thomas F. , Solie John B. , Epplin Francis M.
Published: March 2018

In field experiments, wheat row spacing, seeding rate, and herbicide treatment affected cheat seed content of harvested wheat, wheat yield, and net returns. No individual practice or combination of practices consistently increased net returns from cheat-infested wheat. Net returns frequently were increased and never decreased by applying metribuzin at 420 g ha−1 or chlorsulfuron + metsulfuron at 21.9 + 4.4 g ha−1 or by increasing the seeding rate compared to baseline inputs. The data indicate that herbicide rates should not be reduced when row spacing is decreased and/or seeding rates increased.
Metalaxyl Toxicity to Citrus with or without Herbicides
Authors: Singh Megh , Mersie Wondimagegnehu
Published: March 2018

The response of potted ‘Cleopatra’ mandarin citrus seedlings to metalaxyl applied as a mixture with metolachlor, simazine, or bromacil, or as a sequential application after the herbicides was investigated under screen house conditions. The soils were drenched with herbicides at 2.5 ppmw (mg kg−1 soil dry wt basis) in tank-mixes with metalaxyl or metalaxyl was applied as a soil drench at 5, 50, and 250 ppmw 1, 2, 3, and 4 wk after herbicide application. Citrus seedling response to treatment was dependent on the presence or absence of herbicide, metalaxyl concentration, and the time following application. Fresh weights of citrus treated with 5 ppmw metalaxyl after herbicide application were no different from those treated with the mixture. Metalaxyl at 5 and 50 ppmw alone or with metolachlor did not affect citrus seedling fresh weight. However, delaying metalaxyl application at 50 ppmw by 3 or 4 wk after simazine and bromacil increased citrus seedling fresh weight as compared with the tank-mix. Separate applications of metalaxyl at 250 ppm reduced citrus seedling fresh weight less than the mixture for all the herbicides.
Serrated Tussock (Nassella trichotoma) in the United States
Authors: Westbrooks Randy G. , Cross Gene
Published: March 2018

Serrated tussock [(Nassella trichotoma (Nees) Hack. # STDTR] is a clump-forming, perennial, cool season grass. It is native to South America, where it occurs in Argentina, Brazil, Chile, Peru, and Uruguay. In the past century, it has been introduced to New Zealand, Australia and South Africa, and also occurs in small acreages in France, Italy, and the United Kingdom. Serrated tussock occurs in fields, wastelands, and pastures, but rarely in wet or shaded areas.
Crop Losses Due to Weeds in Canada
Authors: Swanton C. J. , Harker K. N. , Anderson R. L.
Published: March 2018

Concerns about the effect of pesticides on our environment has stimulated questions about the direction of future research in weed science. Knowledge of crop losses due to weeds would be helpful in guiding research objectives by identifying areas of greatest need. A survey was conducted in 1991 to estimate losses due to weeds in 58 commodities in Canada. Data generated included: percent loss in production, quantity loss in production, and loss of production value (monetary value) for each commodity in each province. The estimated average annual losses caused by weeds in the 58 commodities were $984 million, with losses of $372 million in Eastern Canada and $612 million in Western Canada. In Eastern Canada, approximately 50% of the total loss occurred in hay crops and 33% in field crops, whereas in Western Canada, 84% of the total loss occurred in field crops. Loss of potential production due to weeds for each commodity is shown by province.
Herbicides with Crop Competition Replace Endophytic Tall Fescue (Festuca arundinacea)
Authors: Bagegni Ali M. , Kerr Harold D. , Sleper David A.
Published: March 2018

Herbicides and interim summer crop treatments were studied in 1984 to 1987 to replace fungal endophyte-infected with endophyte-free tall fescue or red clover to improve forage quality. Foliar glyphosate or paraquat were applied in spring across interim crops with PRE herbicides. The interim crops, grain sorghum with atrazine, sorghum-sudangrass hybrid with metribuzin, or soybean with imazaquin, were each applied as confounded treatments across glyphosate or paraquat. Within an interim crop system, a follow-up glyphosate treatment was serially applied the next fall or spring. Then either red clover or endophyte-free tall fescue was spring drilled within the fall or spring glyphosate follow-up treatments. Glyphosate controlled old tall fescue better than paraquat, and improved the stand of the endophyte-free tall fescue. Control of tall fescue was 97% from 1.7 kg ai/ha glyphosate. Glyphosate reduced the endophyte from a 77% original infection level to 20% over all interim crops after drilling the endophyte-free tall fescue. Among interim crops, grain sorghum or the sorghum-sudangrass hybrid was more competitive than soybean with the uncontrolled tall fescue. Replacement with endophyte-free tall fescue was best in grain sorghum or sorghum-sudangrass hybrid stubble the next spring. Grain sorghum or sorghum-sudangrass hybrid following foliar glyphosate or paraquat treatment of endophyte-infected tall fescue reduced endophyte infection level in tall fescue to 28%. A follow-up fall treatment with glyphosate controlled tall fescue better than the spring retreatment and red clover and endophyte-free tall fescue were established better from fall retreated glyphosate. Red clover was easily established by drilling into the sod after treating endophyte-infected tall fescue with either glyphosate or paraquat.
Influence of Rye (Secale cereale) Plant Residues on Germination and Growth of Three Triazine-Resistant and Susceptible Weeds
Authors: Przepiorkowski T. , Gorski Stanley F.
Published: March 2018

Greenhouse and laboratory studies were conducted to evaluate the effects of rye residues on germination and growth of three triazine-resistant weed species, barnyardgrass, willowherb, and horseweed. Soil containing rye roots was used to determine rye residue influence on seed germination. Willowherb and horseweed germination was inhibited up to 50% with the highest rate of rye, but there was no inhibition of barnyardgrass germination. Aqueous extracts of rye shoot tissue inhibited incubator germination of horseweed and willowherb, but did not significantly influence barnyardgrass germination. Although there were no germination differences between the susceptible and resistant biotypes, both were totally inhibited when a 5% w/v solution was used. Growth inhibition of the selected weeds was evaluated using rye root residues in soil. All combinations of biotypes, species, and rye seeding rates showed significant growth inhibition.
Leafy Spurge (Euphorbia esula) Control, Forage Production, and Economic Return with Fall-Applied Herbicides
Authors: Lym Rodney G. , Messersmith Calvin G.
Published: March 2018

Leafy spurge control and forage production after various fall-applied herbicide treatment rotations were evaluated in a bluegrass pasture and a mixed grass prairie. Dicamba at 2 kg ae/ha or picloram at 0.6 kg ae/ha alone or combined with 2,4-D at 1 kg ae/ha applied annually for 3 yr provided consistent leafy spurge control of 85% or better, but forage production was greater at the bluegrass pasture site than the mixed grass prairie site. Glyphosate plus 2,4-D at 0.4 plus 0.7 kg ae/ha applied annually or rotated with picloram plus 2,4-D or dicamba provided 90% or better leafy spurge control after 3 yr at the bluegrass pasture. Control was 50% or less at the mixed grass prairie site where forage production was severely reduced by glyphosate plus 2,4-D. All treatments on the bluegrass pasture provided a positive economic return averaging $227/ha after 3 yr. Picloram or picloram plus 2,4-D at the mixed grass prairie site provided net returns averaging $285/ha, but treatment rotations that included glyphosate plus 2,4-D one or more times in 3 yr averaged a net loss of $32/ha due to severe grass injury.
Economic Assessment of Tebuthiuron-Fire Systems for Brush Management
Authors: Scifres Charles J.
Published: March 2018

Economic performance of prescribed burning following aerial applications of tebuthiuron {N-[5-(1,1-dimethyiethyl)-1,3,4-thiadiazol-2-yl]-N,N′-dimethylurea} pellets was estimated for Texas whitebrush (Aloysia gratissima[Gillies & Hook.] Troncoso # ALYLY)-dominated rangeland and for post oak (Quercus stellataWangenh. # QUESL)-dominated mixed hardwood stands. Honey mesquite (Prosopis glandulosaTorr. # PRCJG) invasion largely negated differences in estimated beef production between treated and untreated pastures within 13 yr of controlling Texas whitebrush with tebuthiuron at 2 kg ai/ha. American beautyberry (Callicarpa americanaL.) and other shrubs increased such that the woody canopy cover was 87% of the original canopy 7 yr after applying tebuthiuron at 2.2 kg/ha to a heavy cover of oaks-mixed hardwoods. Burning at 2- to 4-yr intervals after tebuthiuron applications suppressed invading shrubs and increased projected internal rates of return by about 2% for each burning, compared to herbicide application only.
Applicators for a Weed Pathogen plus Acifluorfen in Soybean
Authors: Khodayari Khosro , Smith Roy J. , Walker Joel T. , Tebeest David O.
Published: March 2018

A low-volume (21.5 L/ha) spinning disc (controlled droplet applicator) and a high-volume (187 L/ha) boom-nozzle applicator were compared in applying tank mixtures of the weed pathogenColletotrichum gloeosporioides(Penz.) Sacc. f. sp.]aeschynomene(henceforth designated C.G.A.) and acifluorfen {5-[2-chloro-4-(trifluoromethyl)phenoxy]-2-nitrobenzoic acid} for control of northern jointvetch [Aeschynomene virginica(L.) B.S.P. # AESVI] and hemp sesbania [Sesbania exaltata(Raf.) Rydb. ex A.W. Hill # SEBEX] in soybean [Glycine max(L.) Merr. ‘Tracy M’]. Application with a spinning disc did not increase control of either weed species over the boom-nozzle applicator. C.G.A. controlled northern jointvetch in 2 of 3 yr. Northern jointvetch control with the spinning-disc was poorer at lower rates in years of unfavorable environment. Acifluorfen at 0.56 kg ai/ha and applied with either applicator controlled hemp sesbania satisfactorily.
Worldwide Distribution of Purple and Yellow Nutsedge (Cyperus rotundusandC. esculentus)
Authors: Bendixen Leo E. , Nandihalli U. B.
Published: March 2018

The family Cyperaceae includes approximately 3000 species, of which about 220 species are identified as weeds (Table 1). Nearly 42% of these weeds are in the genusCyperus. An additional 43% are in three other genera,Eleocharis,Scirpus, andFimbristylis. The remaining 15% are found in six other genera,Scleria,Kyllinga,Rhynchospora,Bulbostylis,Fuira, andDichromena. Purple nutsedge (Cyperus rotundusL. # CYPRO) was identified as the world's worst weed based on the number of countries where it was reported as a serious, principal, or common weed. Competition with crops was the major factor in determining weediness. From the same report, yellow nutsedge (Cyperus esculentusL. # CYPES) ranked sixteenth. This contrasts with relative rankings of these two species in the United States where yellow nutsedge is more widespread than purple nutsedge.
Biology and Life Cycle of Purple and Yellow Nutsedges (Cyperus rotundusandC. esculentus)
Authors: Stoller E. W. , Sweet R. D.
Published: March 2018

Yellow and purple nutsedges (Cyperus esculentusL. # CYPES andC. rotundusL. # CYPRO) are herbaceous perennial weeds that are among the worst pests known. Holm et al. list purple nutsedge as the world's worst weed and yellow nutsedge as the sixteenth worst weed. Both weeds infest crop production areas in tropical and temperate climates, causing large losses in crop yields. While both species proliferate in the warm regions of the world, yellow nutsedge inhabits a wider range than purple nutsedge in the temperate areas, primarily because yellow nutsedge can tolerate colder temperatures. With such an extended range of habitation, many ecotypic variations of these species would be expected since they likely have adjusted to a multitude of local environments.
Interference and Interaction of Purple and Yellow Nutsedges (Cyperus rotundusandC. esculentus) with Crops
Authors: Keeley Paul E.
Published: March 2018

Ecological studies improve the understanding of crop losses caused by weeds and interactions among weeds and crops. Knowledge of weed-crop interactions can aid in developing more efficient weed management systems. Also, knowledge of the duration of weed interference and the length of the weed-free period required to prevent crop losses is essential for planning cost-effective control practices.
Cultural and Mechanical Manipulation ofCyperusSpp.
Authors: Glaze Norman C.
Published: March 2018

Cultural and mechanical methods are viable options for inclusion in any weed control program. Selection of weed control methods is determined by crop, cost, desired yield, weather, and labor availability. Yellow and purple nutsedge (Cyperus esculentusL. # CYPES and C.rotundusL. # CYPRO) have proliferated as production inputs have intensified. Nutsedge densities have increased largely due to reduced competition as better annual weed control and improved growing conditions have resulted.
Future Role of Weed Science in International Agriculture
Authors: Mercado Beatriz L.
Published: March 2018

Dr. Mercado is Professor, Department of Agronomy, University of the Philippines at Los Baños. Her undergraduate and Master's degrees are from the University of the Phillippines, and her Ph.D. from the University of Iowa. She has been active in weed science since the early 1970's and has trained some 27 M.S. and 8 Ph.D. students. In addition, she and her husband have raised a family of five children. Mercado is a well-recognized weed scientist in her part of the world, having lectured in Indonesia, Thailand, Korea, and Japan. Her weed science textbook, “Introduction to Weed Science,” is widely used in Asian countries. Among her many honors, perhaps those most prized would be three awards for outstanding achievement from her own University of the Philippines.
Selectivity of Diphenyl Ether Herbicides between Tomato (Lycopersicon esculentum) and Eastern Black Nightshade (Solanum ptycanthum)
Authors: Teasdale John R.
Published: March 2018

A non-linear dose-response model was used to analyze the response of tomato (Lycopersicon esculentumMill.) and eastern black nightshade (Solanum ptycanthumDun. #3SOLPT) to acifluorfen {5-[2-chloro-4-(trifluoromethyl)phenoxy]-2-nitrobenzoic acid}, fluoroglycofen {carboxymethyl 5-[2-chloro-4-(trifluoromethyl)phenoxy]-2-nitrobenzoate}, fomesafen {5-[2-chloro-4-(trifluoromethyl)phenoxy]-N-(methylsulfonyl)-2-nitrobenzamide}, and lactofen {(±)-2-ethoxy-1-methyl-2-oxoethyl 5-[2-chloro-4-(trifluoromethyl)phenoxy]-2-nitrobenzoate}. The relative potency of these herbicides to both species was lactofen > fluoroglycofen > fomesafen > acifluorfen. Tomato was significantly more resistant to acifluorfen, fluoroglycofen, and lactofen than was eastern black nightshade, but there was no significant difference between species in response to fomesafen. At the rate required to reduce tomato weight by 10%, eastern black nightshade weight was reduced 48, 32, 20, and 5% by acifluorfen, fluoroglycofen, lactofen, and fomesafen, respectively.
Training Weed Scientists for Teaching
Authors: Appleby Arnold P.
Published: March 2018

Although not all graduate students will teach in the classroom, all will use teaching skills in some aspects of their work. Graduate students can participate in activities that will prove useful in later teaching situations. They can prepare audio-visual materials or design and conduct experiments and demonstrations in the laboratory. Carefully selected and well-prepared graduate students can give lecture or laboratory presentations; however, care must be taken not to detract from the quality and continuity of the course from the standpoint of students who are enrolled for credit (and are paying for the course).
Effect of Herbicide and Weed Height on Johnsongrass (Sorghum halepense) Control and Cotton (Gossypium hirsutum) Yield
Authors: Bridges David C. , Chandler J. M.
Published: March 2018

Research was conducted from 1983 through 1985 in east central Texas to determine the effect of grass-specific herbicides, herbicide rates, and weed height on johnsongrass [Sorghum halepense(L.) Pers. #3SORHA] control and cotton (Gossypium hirsutumL. 'Stoneville 825’) yield. Seven herbicides were applied to johnsongrass less than 30 cm tall with 2 to 5 leaves approximately 4 weeks after cotton emergence. Good-to-excellent johnsongrass control was observed for each herbicide except cloproxydim {(E,E)-2-[l-[[(3-chloro-2-propenyl)oxy]imino] butyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexen-1-one} at 0.56 kg ai/ha and sethoxydim {2-[1-(ethoxyimino)butyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexen-1-one} at 0.28 kg ai/ha. Few significant differences were found in seed cotton yields even though johnsongrass control ranged from 43 to 99% 26 days after treatment (DAT). These data suggest that johnsongrass regrowth and/or reinfestation following initial control of 75% or higher during the first 4 to 6 weeks after cotton emergence has a minimum negative effect on cotton yield. Johnsongrass control was highest when either fluazifop-P {(R)-2-[4-[[5-(trifluoromethyl)-2-pyridinyl]oxy]phenoxy]propanoic acid} or haloxyfop {2-[4-[[3-chloro-5-(trifluoromethyl)-2-pyridinyl]oxy]phenoxy] propanoic acid} was applied to 15 to 30 cm tall johnsongrass.
Bermudagrass (Cynodon dactylon) and Johnsongrass (Sorghum halepense) Ecotype Response to Herbicides
Authors: Brown Steven M. , Chandler James M. , Bridges David C.
Published: March 2018

Common bermudagrass [Cynodon dactylon(L.) Pers. #3CYNDA] and johnsongrass [Sorghum halepense(L.) Pers. # SORHA] ecotypes were collected from seven locations in Texas. Ecotype responses to glyphosate [N-(phosphonomethyl)glycine], SC-0224 (trimethylsulfonium carboxymethylaminomethylphosphonate), sethoxydim {2-[l-(ethoxyimino)butyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexen-1-one}, fluazifop {(+)-2-[4-[[5-(trifluoromethyl)-2-pyridinyl] oxy] phenoxy] propanoic acid}, haloxyfop {2-[4-[[3-chloro-5-(trifluoromethyl)-2-pyridinyl] oxy] phenoxy] propanoic acid}, and quizalofop {(+)-2-[4-[(6-chloro-2-quinoxalinyl)oxy] phenoxy] propanoic acid} were evaluated in 1982, 1983, and 1984. Johnsongrass ecotype-by-herbicide interactions and ecotype differences were detected in only one of three years. Differences were observed consistently among the herbicide treatments. Numerous bermudagrass ecotype-by-herbicide interactions were detected each year with greater diversity occurring with less-than-optimum herbicide rates. The interactions were herbicide-by-ecotype specific and were not predictable with respect to geographic site of collection.
Response of Azalea (Rhododendron obtusum) Cultivars to Sethoxydim and Fluazifop-P
Authors: Derr Jeffrey F.
Published: March 2018

Experiments were conducted to evaluate varietal susceptibility of azalea [Rhododendron obtusum(Lindl.) Planch] to fluazifop-P {(R)-2-[4-[[5-(trifluoromethyl)-2-pyridinyl] oxy] phenoxy] propanoic acid } and sethoxydim {2-[l-(ethoxyimino)butyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexen-1-one}. Injury observed on ‘Delaware Valley White’, ‘Hinocrimson’, and ‘Poukhanense’, following broadcast applications of fluazifop-P at 1.12 kg ai/ha, ranged from 5 to 53% foliar damage. Injury symptoms observed were leaf burn, spotting, and distortion, especially in younger leaves. Sethoxydim at 2.24 kg ai/ha caused either slight or no foliar injury to the cultivars tested. Both sethoxydim and fluazifop-P caused temporary growth reduction in ‘Hershey Red’. Foliar injury or growth reduction resulting from these herbicides was temporary, with no damage evident 6 weeks after application. Although adding either crop oil concentration or a nonionic surfactant increased phytotoxicity of fluazifop-P to Hinocrimson and Poukhanense, these adjuvants were not phytotoxic to azalea cultivars when applied alone.
BromusControl in Winter Wheat (Triticum aestivum) with the Ethylthio Analog of Metribuzin
Authors: Ratliff Randall L. , Peeper Thomas F.
Published: March 2018

Twenty field experiments were conducted in Oklahoma from 1983 through 1986 to evaluate the ethylthio analog of metribuzin [4-amino-6-(1,1-dimethylethyl)-3-(ethylthio)-1,2,4-triazin-5(4H)-one] for selective control of cheat (Bromus secalinusL. #3BROSE), downy brome (Bromus tectorumL. # BROTE), and rescuegrass (Bromus catharticusVahl. # BROCA) in winter wheat (Triticum aestivumL.). The ethylthio analog of metribuzin applied postemergence at 1.1 kg ai/ha before the weeds tillered controlled 91 to 100% of theseBromusspp. in winter wheat. Control of tilleredBromusspp. was less consistent. AsBromusspp. control increased, wheat yields increased, and dockage decreased. The herbicide was selective on wheat over a wide range of soils, including sands. Adding surfactant to very early postemergence applications of 0.6 kg ai/ha increased cheat control but injured wheat slightly. Surfactant use had little or no effect on dockage reduction and yields.
Knapweed and Its Control in British Columbia
Authors: Dyck Peter D. Graham
Published: March 2018

In the last two decades the weed species, diffuse knapweed (Centaurea diffusa) and spotted knapweed (C. maculosa) have gained prominence in the British Columbia interior. These aggressive species have invaded over 40,000 hectares (100,000 acres) of British Columbia range and forest land and are spreading at a rate of about 10% per year. Knapweed can reduce the native forage by as much as 80 to 90% and thus destroy the food supply for cattle and wild animals such as elk and deer. If the weeds spread to their ecological limit over 1 million hectares in British Columbia could be affected, causing an estimated agricultural loss of $13 million annually (Cranston, R. 1985, B.C. Min. of Agric. 85–1). The potential extinction of native plant and animal species is a cost too great to be measured.
Germination of Two Foxtail (Setaria) Species
Authors: Manthey Diane R. , Nalewaja John D.
Published: March 2018

Green and yellow foxtail [Setaria viridis(L.) Beauv. #3SETVI andS. glauca(L.) Beauv. #SETLU] seed germination after 14 days were similar at 15, 20, and 25 C. However, at 10, 30, and 35 C, green foxtail seed germination was higher than that of yellow foxtail, indicating that temperature extremes influenced green foxtail seed germination less than that of yellow foxtail. Seed germination of both species was initiated at about the same time; however, green foxtail seed germinated 1 to 2 days faster than yellow foxtail at all temperatures. After 72 h in −4 bars osmotic potential solution at 25 C, green foxtail seed germination was 70% compared to 12% for yellow foxtail, suggesting that green foxtail seed may germinate more rapidly than yellow foxtail seed in soils with limited moisture.
Field-Scale Tebuthiuron Application on Brush-Infested Rangeland
Authors: Gibbens Robert P. , Herbel Carlton H. , Lenz James M.
Published: March 2018

The objective of this study was to determine the effectiveness of tebuthiuron {N-[5-(1,1-dimethylethyl)- 1,3,4-thiadiazol-2-yl]-N,N′-dimethylurea} to treat brush-infested arid rangeland under field-scale conditions. A 130-ha tract in southern New Mexico dominated by creosotebush [Larrea tridentata(Sesse & Moc. ex DC.) Coville #3LARTR) was treated with pelleted tebuthiuron at 0.4 kg ai/ha. After the fourth season following treatment, control of creosotebush, honey mesquite (Prosopis glandulosaTorr. #PRCJG), and tarbush (Flourensia cernuaDC. # FLOCE) was 87, 48, and 100%, respectively. Total shrub density was reduced from 4440 plants/ha to 570 plants/ha. Grass basal area increased from 1.1 to 3.4%. The treatment did not affect forbs greatly. Total herbaceous above-ground biomass production in the fourth season after treatment was 860 kg/ha compared to 140 kg/ha on an adjacent untreated area. Perennial grass production was nearly 11-fold greater on the treated area than on the untreated area.
Accelerated Degradation Potential of Selected Herbicides in the Southeastern United States
Authors: Dowler Clyde C. , Marti Luz R. , Kvien Craig S. , Skipper Horace D. , Gooden Dewitt T. , Zublena Joe P.
Published: March 2018

The influence of previous herbicide applications on the degradation rate of butylate [S-ethyl bis (2-methylpropyl)carbamothioate], EPTC (S-ethyl dipropyl carbamothioate), alachlor [2-chloro-N-(2,6-diethyl-phenyl)-N-(methoxymethyl)acetamide], and metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide] was measured. Degradation studies were conducted on soils with zero to eight previous applications of butylate, zero and six consecutive annual applications of alachlor, and zero to seven previous applications of metolachlor. Previous applications of alachlor or of metolachlor did not affect the rate of degradation when the same herbicide was reapplied. Soils with previous butylate-use history had more rapid degradation of butylate or EPTC than soils with no previous butylate applications. Because soil sterilization reduced14CO2evolution to a low level, soil microorganisms could be the primary mechanism of butylate degradation. There was no difference between butylate or EPTC degradation rate in soils treated previously with butylate. Butylate could not be detected 28 days after treatment in soils previously treated with butylate, whereas soils not previously treated with butylate still contained biologically active butylate. Dietholate (O,O-diethylO-phenyl phosphorothioate) added to butylate generally reduced the rate of butylate degradation in soils previously treated with butylate, but the butylate concentration always was lower in soils treated previously with butylate than in soils without previous butylate applications. Weed control in the field showed rapid loss of butylate and EPTC in soils with previous butylate treatment and that dietholate reduced the rate of butylate and EPTC degradation.
Glyphosate and Sc-0224 for Bermudagrass (CynodonSpp.) Cultivar Control
Authors: Johnson Billy J.
Published: March 2018

An undesirable bermudagrass [Cynodon dacytlon(L.) Pers. # CYNDA] often must be removed before converting to an improved bermudagrass turf or to a different turfgrass species. Because bermudagrass control with glyphosate [N-(phosphonomethyl)glycine] has been inconsistent, an experiment was initiated to determine the necessary application rates and frequency for glyphosate and SC-0224 (trimethylsulfonium carboxymethylaminomethylphosphonate) to control bermudagrass. Both glyphosate and SC-0224 applied in three applications (May, June, and August) had controlled three bermudagrass hybrids [Cynodon transvaalensisBurtt-Davy # CYNTR x C.dactylon(L.) Pers. Tifway’, Tifgreen’, and ‘Tifdwarf’] and ‘Ormond’ bermudagrasses when evaluated the next June. None of the cultivars were controlled effectively with either herbicide applied in one (May) or two (May and June) applications regardless of rate. Control with glyphosate and SC-0224 was similar.
Efficacy Comparisons of Alachlor and Metolachlor Formulations in the Field
Authors: Wilson Henry P. , Hines Thomas E. , Hatzios Kriton K. , Doub J. Peyton
Published: March 2018

In field studies conducted in 1984, 1985, and 1986, annual grass control by a microencapsulated (ME) formulation of alachlor [2-chloro-N-(2,6-diethylphenyl)-N-(methoxymethyl)acetamide] generally was greater than that by the emulsifiable concentrate (EC) in no-till and was comparable to EC-alachlor in conventionally tilled corn (Zea maysL.) and soybeans [Glycine max(L.) Merr.]. In 1986, ME-metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide] controlled annual grass similar to EC-metolachlor. In greenhouse studies, shoot height and fresh weight of barnyardgrass [Echinochloa crus-galli(L.) Beauv. # ECHCG] sown in pots and treated with ME-alachlor was significantly greater than that treated with EC-alachlor. Soybean straw on the soil surface did not affect the differences between alachlor formulations in the greenhouse.
Soybean (Glycine max) Competition Helps Herbicides Control Johnsongrass (Sorghum halepense)
Authors: Bendixen Leo E.
Published: March 2018

Six postemergence herbicides were applied two consecutive years in single and split applications to compare johnsongrass [Sorghum halepense(L.) Pers. # SORHA] control in soybeans [Glycine max(L.) Merr.] planted in 25- and 76-cm inter-row spacings. Significantly less johnsongrass existed at harvest in the 25-cm spacings than in the 76-cm spacings with split applications of fenoxaprop {(±)-2-[4-[(6-chloro-2-benzoxazolyl)oxy] phenoxy] propanoic acid} at 100 g ae/ha, fluazifop {(±)-2-[4-[[5-(trifluoromethyl)-2-pyridinyl] oxy] phenoxy] propanoic acid} at 100 g ae/ha, sethoxydim {2-[1-(ethoxyimino)butyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexen-1-one} at 200 g ai/ha, and SC-1084 {3-hydroxy-4-[4-[[5-(trifluoromethyl)-2-pyridinyl] oxy] phenoxy] pentanoic acid} at 250 g ae/ha. Quizalofop {(±)-2-[4-[(6-chloro-2-quinoxalinyl)oxy] phenoxy] propanoic acid} at 70 g ae/ha and haloxyfop {2-[4-[[3-chloro-5-(trifluoromethyl)-2-pyridinyl] oxy] phenoxy] propanoic acid} at 100 g ae/ha controlled johnsongrass so well that differences between the two row spacings were not significant.
Metribuzin Tolerance Within the GenusVigna
Authors: Harrison Howard F.
Published: March 2018

A simple, labor-efficient screening procedure was developed for identifying metribuzin [4-amino-6-(1,1-dimethylethyl)-3-(methylthio)-1,2,4-triazin-5(4H)-one] tolerant southernpea [Vigna unguiculata(L.) Walp.] germplasm in the greenhouse. Of 1241 southernpea plant introduction (PI) accessions screened, two (PI 293569 and PI 427221) tolerated metribuzin. In additional greenhouse experiments, the two selected southernpea accessions were slightly more tolerant than the susceptible cultivar ‘Lady’ or the moderately tolerant cultivar ‘Big Boy’. However, several accessions from relatedVignaspecies tolerated 1.5 ppmw metribuzin, twice the concentration that killed the southernpea selections.
Electrostatic Ground-Rig Spraying: An Overview
Authors: Hislop Eric C.
Published: March 2018

Contact, induction, and corona electrostatic charging systems for pesticide spraying are reviewed and are compared with uncharged spraying systems. When uncharged sprays are poorly intercepted by plants, charging significantly increases deposition, drawing from the reservoir normally deposited on the soil. Post-emergent herbicide spraying is the one area where the benefits of electrostatic charging are identified least easily. For insecticides and fungicides where the young crop is the ‘general’ target, increased capture of charged spray may permit reducing doses with economic and environmental benefits. While charging may not increase total capture where uncharged spray interception is good, it does alter spray distribution throughout the crop canopy. The biological consequences of modifying spray distribution depend upon the ‘real’ pesticide target. In situations where the crop acts as an electrical shield limiting spray penetraton, air assistance is necessary to augment charged spray deposition within the crop canopy. Drift of charged spray clouds should be related to drop spectra, velocities and trajectories and requires further study as do protocols for spray charge measurement and definition. In addition to biological performance, the transfer of electrostatic technology to farms is limited because of financial, legal, and practical factors. Identifying specific major crop/pest problems will help to introduce electrostatic spraying, which will complement, rather than replace, traditional spray systems.
Potential Biocontrol of Multiflora Rose, Rosa multiflora
Authors: Hindal Dale F. , Wong Sek Man
Published: March 2018

Multiflora rose is a serious weed pest in West Virginia. There are cultural and chemical means for control, but expense and environmental consequences often preclude their use. Limited information is available concerning biotic agents with potential for multiflora rose biocontrol. A literature search, contacts with scientists in Asia where multiflora rose originated and apparently is not a pest, and disease and insect surveys in West Virginia indicate this plant is healthy and, generally, pest free. However, three insects in West Virginia and one disease occurring in the midwestern United States were of special interest. The rose hip borer, Grapolita packerdi Zeller, which consumes the hypanthium tissues of the hips; the rose seed chalcid, Megastigmus aculeatus var. nigroflavus Hoffmeyer, which destroys the seeds within the achenes; and the raspberry cane borer, Oberea bimaculata Oliv., which kills canes, were found in West Virginia. The disease, rose rosette, not found in West Virginia, is killing multiflora rose in Arkansas, Indiana, Kansas, and Missouri. There is little information on the biology and/or host ranges of these insects or the disease. However, finding three insects in West Virginia adversely affecting growth and/or reproduction of multiflora rose and learning of a disease that kills this plant suggest there are biotic agents that might help manage multiflora rose.
Annual Grass Control in Flax (Linum usitatissimum) with Quizalofop
Authors: Friesen George H.
Published: March 2018

In field experiments over a 3-yr period, quizalofop {(±)-2-[4-[(6-chloro-2-quinoxalinyl)oxy)phenoxy] propanoic acid} at 100 to 150 g ae/ha effectively controlled several annual grass weeds and volunteer barley (Hordeum vulgareL. # HORVX) in flax (Linum usitatissimumL. ‘Linott’). Quizalofop applied when flax was 10 cm tall generally was more effective on wild oats (Avena fatuaL. # AVEFA) and green foxtail [Setaria viridis(L.) Beauv. # SETVI] than when flax was 4 cm tall. Volunteer barley was controlled at both stages of flax growth. Weed interference in untreated plots adversely affected flax quality factors such as seed size, seed weight, percent oil, and iodine value of the oil but not in quizalofop-treated plots.