bluuebunny/crossref_metadata_2025 huggingface dataset:
Preharvest Effects of Applying Glyphosate to Soybeans (Glycine max)
Authors: Azlin W. R. , McWhorter C. G.
Published: May 2019

Over a 4-yr period, glyphosate [N-(phosphonomethyl)glycine] was applied over-the-top to soybeans [Glycine max(L.) Merr.] at five rates, from 0.56 to 3.36 kg/ha, at four periods of time prior to harvest, 23 to 29 days, 15 to 21 days, 7 to 12 days, and 1 to 4 days. Soybean yields were reduced when glyphosate was applied at 2.24 and 3.36 kg/ha 23 to 29 days before harvest. Soybean seed were discolored following all five rates of glyphosate applied 23 to 29 days before harvest, following glyphosate at 1.12 to 3.36 kg/ha applied 15 to 21 days before harvest, and following glyphosate at 3.36 kg/ha applied 7 to 12 days before harvest. Germination of soybean seed was reduced at 30 C only when glyphosate was applied at 2.24 and 3.36 kg/ha 23 to 29 days before harvest, or at 3.36 kg/ha applied 15 to 21 days before harvest. At alternating temperatures (10.6 C for 72 h followed by 30 C for 72 h), all treatments applied 23 to 29 days before harvest reduced soybean seed germination; glyphosate at 1.12, 1.68, and 3.36 kg/ha applied 15 to 21 days before harvest also reduced germination. Seed from plots treated with glyphosate 23 to 29 or 15 to 21 days before harvest produced atypical soybean plants. Glyphosate at 2.24 and 3.36 kg/ha applied 23 to 29 days before harvest reduced the oil content in soybean seed, but none of the treatments consistently affected the protein content.
Common Sunflower (Helianthus annuus) Interference in Onions (Allium cepa)
Authors: Menges Robert M. , Tamez Simon
Published: May 2019

Common sunflower (Helianthus annuusL.) interference in onions (Allium cepaL. ‘Yellow Granex PRR’) was studied at different weed densities and periods of interference. Onion yields were reduced when the highest density (360/m2) of common sunflower interference with onions from 6 weeks after emergence and when sunflower at densities of 50/m2and 5/m2interfered for 12 and 15 weeks after emergence, respectively. Yield was not reduced if the crop was kept weed-free for 2 to 12 weeks after emergence with the shortest weed-free periods of 2 and 6 weeks requiring high light irradiance and high soil temperature and intermediate soil moisture. Climatic factors were more useful than weed density in explaining differential interference of sunflower in onions. Onion yield was negatively linearly correlated (P<0.05) with sunflower fresh weight, but was not linearly correlated with sunflower height.
Interactions of Buthidazole with Clay Minerals and Soils
Authors: Li Song-Wu , Mortland Max M.
Published: May 2019

The newly developed herbicide buthidazole {3-[5-(1,1-dimethylethyl)-1,3,4-thiadizol-2-yl]-4-hydroxy-1-methyl-2-imidazolidinone} was studied with respect to its interaction with soils and homoionic clay minerals and its response to irradiation with ultraviolet light. Results showed that it could enter the interlamellar spaces of swelling clays such as smectite. Isothermic adsorption studies indicated that Cu+2-smectite adsorbed more buthidazole than Cu+2-kaolinite. The Cu+2-clay adsorption isotherm fitted the Langmuir model. The effect of exchangeable cations on adsorption was not significant in soils of high organic matter content. Bioassay studies indicated that buthidazole's phytotoxicity was not decreased in either clays or in organic soils. Infrared spectroscopic studies showed the coordination of buthidazole with Cu+2through C=O Cu interaction with buthidazole resulted in a ligand-to-metal ratio to 1:1. Protonation of buthidazole occurred in Al+3-and H+-smectite. The herbicide was labile to UV-light irradiation at 254 nm but not at 366 nm. The photoconversion indicated a first-order reaction. The photolytic product(s) included the –N=C=O structure. Copper(II) ions, which form complexes, retarded photolysis of buthidazole in UV-light, but the Ca+2ion, which is unable to form complexes, did not.
Competition between Potatoes (Solarium tuberosum) and Weeds
Authors: Nelson D. C. , Thoreson Myron C.
Published: May 2019

Mixtures of annual weeds emerging 1 week after and competing all season with potatoes (Solanum tuberosumL.) reduced tuber yields by an average of 54% compared to 16% in comparable treatments in which weeds emerged 3 weeks after potatoes. Weeds reduced tuber yields 19% 8 weeks after potatoes emerged and 25 to 45% 10 weeks after emergence. After full-season competition, for each additional 10% of the total dry biomass represented by weeds, there was a decrease of 12% in fresh tuber yield. This relationship was not valid if potatoes were harvested early, which reduced the deleterious effect of weeds on potato yields. Weed competition reduced both size and number of tubers, but had little effect on specific gravity of tubers. In some instances, the reduction in tuber size by weeds reduced the percentage of tubers that were marketable.
Effects of Low Concentrations of Herbicides on Submersed Aquatic Plants
Authors: Forney D. Raymond , Davis Donald E.
Published: May 2019

Laboratory studies were conducted to investigate the possibility that herbicide runoff from treated fields might be adversely affecting submersed aquatic plants in the Chesapeake Bay. In laboratory studies, I1 and I50 values (the concentrations inhibiting growth 1 and 50%, respectively) were calculated for three herbicides and several aquatic plants. Exposure periods varied from 3 to 6 weeks, with the 3-week exposure being most common. For atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine], I1 values were usually a few parts per billion (ppb), whereas I50 values varied from ca. 80 ppb for elodea (Elodea canadensis Michx) to ca. 1040 ppb for Eurasian watermilfoil (Myriophyllum spicatum L.). The toxicity of metribuzin [4-amino-6-tert-butyl-3-(methylthio)-as-triazin-5(4H)-one] was similar to that of atrazine. Glyphosate [N-(phosphonomethyl)glycine] was essentially non-toxic. Interactions between salinity and atrazine were studied using the brackish water species, vallisneria (Vallisneria americana Michx.). Increasing salinity did not affect atrazine toxicity. When atrazine was present in both the hydrosoil and water, the concentration in the water determined the toxicity. At concentrations below 1000 ppb, atrazine in the hydrosoil did not adversely affect the plants. Based on the results of these studies, and the known concentrations of herbicides in runoff water, these herbicides do not appear to pose any threat to the species tested.
Biology and Ecology of the Platte Thistle (Cirsium canescens)
Authors: Lamp William O. , McCarty M. K.
Published: May 2019

Aspects of the life history and population dynamics of the Platte thistle (Cirsium canescensNutt.), a rangeland weed, were studied in the Nebraska Sandhills from 1977 through 1979. This thistle is a monocarpic perennial, reproducing only by seed production, which typically occurs in small, scattered groups of plants. Seedling mortality at four sites was 75% during the first year, mostly because of dry moisture conditions. In plots with good vegetative cover, thistle rosette plants had a lower mortality rate, but growth rate was slower than that of rosette plants in plots with sparse vegetative cover. Seed heads developed during May and June and gained more than one-half of their dry weight shortly before maturing. Plants averaged 72, 197, and 303 seeds at three sites. Within sites, plants produced seeds in proportion to the number of seed heads per plant. Although naturally occurring biological-control agents have little effect on the vegetative growth phase of the life cycle, they greatly reduce the production of seeds.
Napropamide Uptake, Transport, and Metabolism in Corn (Zea mays) and Tomato (Lycopersicon esculentum)
Authors: Barrett Michael , Ashton Floyd M.
Published: May 2019

Napropamide [2-(α-napthoxy)-N,N-diethylpropionamide] inhibited root and shoot growth in corn (Zea maysL. ‘NC+ 59’) and tomato (Lycopersicon esculentumMill. ‘Niagara VF315’) seedlings. Shoot growth was reduced less than root growth in both species. Corn roots were approximately 10 times more sensitive to napropamide than were tomato roots. Translocation of napropamide from the roots to the shoot of tomato occurred within 0.5 h and followed an apoplastic pattern. Little movement of napropamide from the roots to the shoots occurred in corn. Metabolism of napropamide was not evident in either species during an 8-h exposure. Absorption studies showed that total napropamide levels were 60% higher in corn root tissue than in tomato root tissue. The greater napropamide content in the corn roots was associated with a tightly bound fraction of the total napropamide influx.
Interactions of Diclofop-Methyl and 2,4-D in Cultivated Oats (Avena sativa)
Authors: Fletcher R. A. , Drexler D. M.
Published: May 2019

The chlorophyll levels and growth of oat (Avena sativaL. ‘Elgin’) seedlings were drastically reduced after foliar application of diclofop-methyl {methyl 2-[4-(2,4-dichlorophenoxy)phenoxy] propanoate}. The leaves were chlorotic and necrotic with the newly emerging leaves being most affected. Plants treated with 2,4-D [(2,4-dichlorophenoxy)acetic acid] were similar to the controls. When 2,4-D was applied to intact plants in combination with diclofop-methyl the toxicity symptoms produced by diclofop-methyl were reduced. Diclofop-methyl disrupted membrane integrity and inhibited chlorophyll formation in excised leaf segments. Addition of 2,4-D with diclofop-methyl did not change the effects produced by diclofop-methyl alone in excised leaf segments.
Goosegrass (Eleusine indica) Control in Bermudagrass (Cynodon dactylon) Turf
Authors: Johnson B. J.
Published: May 2019

Combinations of MSMA (Monosodium methanearsonate) with either methazole [2-(3,4-dichlorophenyl)-4-methyl-1,2,4-oxadiazolidine-3,5-dione] or metribuzin [4-amino-6-tert-butyl-3-(methylthio)-as-triazin-5(4H)-one] were applied at various rates for postemergence control of fully developed goosegrass [Eleusine indica(L.) Gaertn.], a major weed grass in bermudagrass [Cynodon dactylon(L.) Pers.] turf. Two applications of MSMA at 2.24 kg/ha applied in combination with either methazole or metribuzin at 0.14 kg/ha controlled 96 to 98% of the goosegrass and it was as effective as methazole (1.12 kg/ha) or metribuzin (0.56 kg/ha) applied alone. Two applications of methazole (1.12 kg/ha) or metribuzin (0.56 kg/ha) had lower quality ratings (28 and 39, respectively) on bermudagrass putting green at 2 weeks after treatment than combinations of MSMA (2.24 kg/ha) with either methazole (0.14 kg/ha) or metribuzin (0.14 kg/ha) (54 and 59, respectively). The initial injury from combination treatments was not severe and turf recovered within 3 to 4 weeks.
Effects of Glyphosate on Metabolism of Phenolic Compounds: VI. Effects of Glyphosine and Glyphosate Metabolites on Phenylalanine Ammonia-Lyase Activity, Growth, and Protein, Chlorophyll, and Anthocyanin Levels in Soybean (Glycine max) Seedlings
Authors: Hoagland Robert E.
Published: May 2019

The growth regulator, glyphosine [N,N-bis(phosphonomethyl)glycine], and other possible metabolites of glyphosine and glyphosate [N-(phosphonomethyl)glycine] [glycine, sarcosine, and aminomethylphosphonic acid (AMPA)] were tested individually (0.5 mM) or as a mixture (each at 0.5 mM) for their effects on growth, extractable phenylalanine ammonia-lyase (PAL) activity, hydroxyphenolic-compound production, chlorophyll and anthocyanin contents, and on soluble-protein levels in soybean [Glycine max(L.) Merr. ‘Hill’] seedlings. Most chemical treatments caused some inhibition of growth either on fresh weight accumulation or on root elongation in the light and dark over 72 h. Glyphosine was generally the most inhibitory and caused the greatest inhibition on axis dry-weight accumulation. Glyphosine significantly increased extractable PAL activity in axes of light- and dark-grown soybeans to a lesser extent than did glyphosate. AMPA had some inhibitory effects on extractable PAL activity whereas other compounds had little influence on the enzyme. These compounds had little effect on total soluble protein in axes or on soluble protein in PAL preparations from 12 to 72 h in light-or dark-grown seedlings. No in vitro effect of the chemicals on PAL activity was found at concentrations up to 0.5 mM. Hydroxyphenolic compound levels increased within 24 to 72 h (per gram fresh weight basis) in light- or dark-grown soybean axes treated with glyphosine, AMPA, or a metabolite mixture (AMPA, sarcosine, and glycine). Anthocyanin content was decreased by glyphosate and to a lesser extent by glyphosine, but was increased by AMPA and the mixture. Glyphosate significantly increased the chlorophylla/bratio and decreased total chlorophyll, but glyphosine decreased the chlorophyll content to a lesser degree.
Influence of Row Spacing on Competitiveness and Yield of Peanuts (Arachis hypogaea)
Authors: Buchanan G. A. , Hauser E. W.
Published: May 2019

Peanuts [Arachis hypogaea(L.) ‘Florunner’], infested with sicklepod (Cassia obtusifoliaL.) and Florida beggarweed [Desmodium tortuosum(Sw.) DC.] were grown in 20.3-, 40.6-, and 81.2-cm rows on Dothan sandy loam at Headland, Alabama, and on Greenville sandy clay loam at Plains, Georgia. In-row seeding rates were equal, regardless of row width. Peanuts were maintained free of sicklepod and Florida beggarweed for 0, 2, and 5 weeks after emergence or throughout the season. In either the absence or presence of weeds, peanut yields generally increased with decreasing row width. Quality of peanuts was not adversely affected; in fact, desirable attributes such as percent sound mature kernels (SMK's) were sometimes increased as the row width decreased. Weed growth with close rows was much less than with standard 81.2-cm rows. Although yields of peanuts were lower with increasing time of weed competition, the influence of row spacing on competitiveness of the peanut canopy remained relatively constant on both soil types. Generally, weeds from either seeded or natural stands produced equivalent competitive results.
Control of Six Morningglory (Ipomoea) Species in Soybeans (Glycine max)
Authors: Mathis W. D. , Oliver L. R.
Published: May 2019

A 4-yr field test was initiated in 1975 to determine susceptibility of a natural infestation of six morningglory species to herbicides which can be applied to the soil and foliage in soybeans [Glycine max(L.) Merr.]. The species studied were pitted morningglory (Ipomoea lacunosaL.), entireleaf morningglory [Ipomoea hederacea(L.) Jacq. var.integriuscula], ivyleaf morningglory [Ipomoea hederacea(L.) Jacq.], purple moonflower [Ipomoea muricata(L.) Jacq.], palmleaf morningglory [Ipomoea wrightii(Gray)], and small flower morningglory [Jacquemontia tamnifolia(L.) Griseb.]. Control with herbicides applied preplant incorporated and preemergence was dependent on morningglory species and on rainfall to allow plant uptake of the herbicide. Herbicides applied to the soil were not as effective as those applied postemergence. Oxadiazon [2-tert-butyl-4-(2,4-dichloro-5-isopropoxyphenyl)-δ2-1,3,4-oxadiazolin-5-one] gave the best and longest lasting preemergence control, averaging 79% control for all species. Preemergence control with metribuzin [4-amino-6-tert-butyl-3-(methylthio)-as-triazin-5(4H)-one] was dependent on species, with 84% control of small flower morningglory and only 26% for ivyleaf and 18% for entireleaf morningglory. At V2 (one trifoliolate) and V5 stages of soybean growth, acifluorfen {5-[2-chloro-4-(trifluoromethyl)phenoxy]-2-nitrobenzoic acid} at 0.56 kg/ha applied over-the-top and oxyfluorfen [2-chloro-1-(3-ethoxy-4-nitrophenoxy)-4-(trifluoromethyl)benzene] at 0.28 kg/ha applied post-directed gave 90 and 92% control of all species, respectively. Most effective were repeated post-directed applications at V5 and V7 stages of soybean growth. Metribuzin + 2,4-DB [4-(2,4-dichlorophenoxy)butyric acid] (99%), linuron [3-(3,4-dichlorophenyl)-1-methoxy-1-methylurea] + 2,4-DB (98%), 2,4-DB (95%), and paraquat (1,1′-dimethyl-4,4′-bipyridinium ion) + 2,4-DB (93%) provided excellent control regardless of the morningglory species.
Intraspecific Competition of Hydrilla verticillata
Authors: Sutton David L. , Littell R. C. , Langeland K. A.
Published: May 2019

Studies in outdoor, circular pools have shown that one shoot tip of hydrilla (Hydrilla verticillata Royle) produced as much plant dry weight during a 16-week period as 16 tips planted under the same conditions. Dry weight of plants 16 weeks after planting was as high as 1,561 times that of the shoot tips planted. Tubers were present within 8 weeks after planting the tips; higher numbers of these vegetative propagules were associated with the higher number of tips planted. Plants under a photoperiod of 11.5 h or less produced more tubers than those exposed to 12 h or more of light.
Pronamide Phytotoxicity in Ten Wisconsin Soils
Authors: Dutt T. E. , Harvey R. G.
Published: May 2019

Pronamide [3,5-dichloro-(N-1, 1-dimethyl-2-propynyl) benzamide] phytotoxicity was compared in 10 Wisconsin soils and the relationship of activity to soil physical and chemical properties appraised. Twelve soil properties were measured and correlated with pronamide I50(50% fresh weight inhibition) values using oats (Avena sativaL. ‘Portal’) as the indicator plant in bioassays conducted under greenhouse conditions. Organic matter was the soil variable most inversely correlated with pronamide phytotoxicity. Cation exchange capacity, field moisture capacity, and Mg content were also inversely correlated with pronamide phytotoxicity, but probably reflect changes in soil organic matter levels. Clay content did not significantly affect pronamide phytotoxicity.
Anatomy of Yellow Nutsedge (Cyperus esculentus)
Authors: Wills G. D. , Hoagland R. E. , Paul R. N.
Published: May 2019

Yellow nutsedge (Cyperus esculentusL.) develops as a series of shoots, bulbs, and tubers connected by rhizomes. The leaves contain parallel, collateral vascular bundles with the majority of the chlorophyll-containing cells concentrated in two sheathing girdles around each bundle. The upper leaf surface consists of a single layer of large epidermal cells covered by a thick cuticle. Stomates occur primarily in the lower surface. The vascular bundles are collateral in the leaves and amphivasal in the rhizome, changing their anatomical arrangement as they pass through the basal bulb. Newly developing rhizomes and tubers are white and fleshy with a parenchymatous epidermis and cortex. Mature rhizomes are brown and wiry with a deteriorated outer cortex and a lignified inner cortex and endodermis. Tubers and bulbs form similarly at the rhizome apices with the tubers accumulating starch. The rhizome vascular system remains intact throughout the growing season.
Weed Research at ICRISAT (International Crops Research Institute for the Semi-Arid Tropics)
Authors: Shetty S. V. R. , Krantz B. A.
Published: May 2019

The overall objective of research at ICRISAT (International Crops Research Institute for the Semi-Arid Tropics) is to develop effective, economically feasible, improved weed-management systems for major crops and cropping systems of the Semi-Arid Tropics (SAT). Initially, emphasis has been on surveys, ecological studies, weed management in crops, and herbicide screening. The aim was to identify possible cultural, mechanical, biological, and chemical inputs, and to determine their relative feasibility for small farmers. Systems research has involved manipulation of cropping systems to obtain better weed management and identification of the most effective techniques. Herbicide-related studies are designed to increase productivity rather than reduce the cost of hand weeding. Research on individual crops has been aimed at determining the extent of crop-weed competition in major crops. In collaboration with economists, operations research in farmers' fields was initiated to observe the success of farmers' weed-control methods. The primary program emphasis will be the evaluation of weed-management principles that may have wide applicability throughout the SAT. This paper outlines the approaches to weed-management research at ICRISAT and gives a conceptual framework of future research needs.
Integrated Weed Management Systems Technology for Pest Management
Authors: Shaw W. C.
Published: May 2019

The people of the world required from the dawn of time until 1830 to reach a population of 1 billion. By 1960, we reached 3 billion and by 1980 we had a population of about 4 billion. It is estimated that by the year 2000 there will be 7 billion people in the world. Just 30 yr from now the world's population will have doubled. This means that within the next 30 yr we must produce as much food as we have produced since the beginning of history. Can we feed this many people? Yes, but expanded research to develop improved technology will be required to meet the challenge.
Modeling the Biology of Weeds for Integrated Weed Management
Authors: Schreiber Marvin M.
Published: May 2019

In a special symposium on weed biology presented at the 1975 annual meeting of the Weed Science Society of America, Parka (37) reviewed the trend of published papers in WEED SCIENCE related to weed biology over the 20-yr period, 1952 to 1972. His data indicated a steady increase from 9.2 to 17.2% of published papers directly related to weed growth and development. My recent assessment of similarly classified papers in 1978, 1979, and 1980 showed a remarkable increase to 21.9, 24.3, and 27.2%, respectively. Further, the more recent papers on weed growth and development also include crop-effect data, i.e., the association of weed growth with crop competition.
Crop Manipulation in Integrated Weed Management Systems
Authors: Walker Robert H. , Buchanan Gale A.
Published: May 2019

Integrated weed management (IWM) became an accepted, and frequently used, term by weed scientists in the early 1970's. It has been argued by some that IWM is simply new terminology for a system that was previously called “weed control”. In any event, the acceptance of the “management concept” has assured the grower that chemicals for weed control are merely a component part of a total system for managing weeds in crops (9, 65).
Research Needs for Integrated Weed Management Systems
Authors: McWhorter C. G. , Shaw W. C.
Published: May 2019

Producers of food have always been troubled with weeds. Hand labor was the primary source of weed control for centuries, and selective weed control was not achieved until copper sulphate was used to control mustard (Brassicaspp.) in wheat (Triticum aestivumL.) in 1896 (4, 42). Adequate crop selectivity was usually difficult to obtain with herbicides during the first 40 yr of the 20th century and the cost of the early herbicides was high.
Selectivity Mechanisms for Foliar Applications of Diclofop-Methyl. I. Retention, Absorption, Translocation, and Volatility
Authors: Boldt P. F. , Putnam A. R.
Published: May 2019

Retention, absorption, translocation, and volatility of foliarly applied diclofop-methyl {methyl 2-[4-(2,4-dichlorophenoxy) phenoxy] propanoate} were compared in barnyardgrass [Echinochloa crus-galli(L.) Beauv.], a susceptible grass; proso millet (Panicum miliaceumL.), a moderately susceptible grass; longspine sandbur [Cenchrus longispinus(Hack.) Fern.], a tolerant grass; and soybean [Glycine max(L.) Merr. ‘Hark’] and cucumber (Cucumis sativusL. ‘Green Star’), both tolerant broadleaf plants. On a jug/plant basis, the order of diclofop-methyl spray retention was cucumber > soybean > proso millet > longspine sandbur = barnyardgrass. On a μg/mg dry weight basis, proso millet retained 3 to 10 times more diclofop-methyl than all other species. One day after treatment (DAT), absorption of14C-diclofopmethyl was 14 to 18% less in longspine sandbur than in the other species, 3 DAT absorption in cucumber was 8 to 14% greater than in the other species, and 5 DAT absorption in soybean was 3 to 12% less than in other species. Translocation of14C-diclofop-methyl did not differ among species, with 98% of the applied radioactivity located in the treated leaf. An average of 11% of radioactivity applied to the surface of intact, living plants and excised, dried leaves of cucumber, soybean, and barnyardgrass, as well as glass cover slips, was lost by evaporation. None of the parameters measured showed differences large enough to be implicated as primary selectivity mechanisms.
Adsorption of Buthidazole, VEL 3510, Tebuthiuron, and Fluridone by Organic Matter, Montmorillonite Clay, Exchange Resins, and a Sandy Loam Soil
Authors: Weber J. B.
Published: May 2019

Adsorption isotherms were obtained for buthidazole {3-[5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl]-4-hydroxy-1-methyl-2-imidazolidinone}, VEL 3510 {1-β,β-dimethoxy-1-methyl-3-[5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl]urea}, tebuthiuron {N-[5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl]-N,N′-dimethylurea}, and fluridone {1-methyl-3-phenyl-5-[3-(trifluoromethyl)phenyl]-4 (1H)-pyridinone} on soil organic matter (H- and Ca-saturated), Ca-montmorillonite, and Cape Fear sandy loam soil. Prometryn [2,4-bis(isopropylamino)-6-(methylthio)-s-triazine] was included as a reference. The order of adsorption on all adsorbents was fluridone ≥ prometryn > > tebuthiuron ≥ VEL 3510 > buthidazole. Fluridone adsorption on the various adsorbents was: H-organic matter > Ca-montmorillonite > Ca-organic matter > > Cape Fear sandy loam. Tebuthiuron, VEL 3510, and buthidazole adsorption on the various adsorbents was in the order: H-organic matter > Ca-organic matter = Ca-montmorillonite > Cape Fear sandy loam. Adsorption of all herbicides increased with decreasing pH, suggesting that the adsorption mechanism was molecular under neutral pH conditions and ionic under acidic conditions. All of the herbicides were adsorbed in high amounts as protonated species on IR-120-H cation exchange resin and in low amounts as molecular species on IR-400-Cl anion exchange resin. Buthidazole and VEL 3510 were adsorbed in high amounts as anionic species by the IR-400-Cl exchange resin at high pH levels.
Control of Quackgrass (Agropyron repens) in Soybeans (Glycine max) with HOE 29152
Authors: Young F. L. , Wyse D. L.
Published: May 2019

In field studies, postemergence applications of HOE 29152 {2-[4-(trifluoromethyl phenoxy)phenoxy] propanoate} at rates of 1.68 to 3.36 kg/ha effectively controlled quackgrass [Agropyron repens(L.) Beauv.] when applied to plants in the one- to three-leaf stage. Control was still effective the following year. The addition of a surfactant to HOE 29152 did not increase quackgrass control, but it did increase soybean [Glycine max(L.) Merr.] injury. Cultivation 1 or 7 days after herbicide application increased the efficacy of HOE 29152 on quackgrass. Due to abundant moisture in 1977, untreated quackgrass-infested plots yielded as much as the weed-free plots. However, in 1976, a very dry year, the control of quackgrass with HOE 29152 resulted in greatly increased soybean yields. In greenhouse studies, postemergence applications of HOE 29152 at rates of 0.56 to 3.36 kg/ha effectively killed rhizome buds and reduced shoot dry weights of quackgrass. The phytotoxicity of HOE 29152 at 0.56 kg/ha was less at a postspray temperature of 36 C than at 17 or 27 C; however, the phytotoxicity of HOE 29152 at rates of 1.68 and 3.36 kg/ha was similar at all three temperatures. HOE 29152 can volatilize from soybean leaves, with volatility greater at 38 C than at 21 C. Postemergence applications injured soybeans similarly in field and growth chamber studies. Injury was observed only on leaves that were expanded at time of treatment, was short-term, and was most prevalent at 3.36 kg/ha.
Allelopathy in Dwarf Spikerush (Eleocharis coloradoensis)
Authors: Frank P. A. , Dechoretz N.
Published: May 2019

The production of new shoots of American pondweed (Potamogeton nodosusPoir.) and sago pondweed (P. pectinatusL.) was reduced significantly when winterbuds and tubers of these species were planted in dwarf spikerush [Eleocharis coloradoensis(Britt.) Gilly] sod. In most instances, the number of shoots produced was several times greater when winterbuds and tubers were planted in bare soil than when planted in spikerush sod. Similar results were obtained when the pondweeds were grown in separate aquaria, each aquarium being exposed to 500 ml of leachate per day from spikerush sod. The differences in reproduction of pondweeds could not be attributed to altered water quality nor to reduced levels of nutrients. No appreciable allelopathic response was elicited by the pondweed plants originating from planted tubers or winterbuds. The principal response appeared to be reduction in numbers of new shoots produced from the original propagules, although the reduction in biomass of the pondweeds exposed to the effects of spikerush was obvious. Of the two pondweeds investigated, sago pondweed was most sensitive to the influence of spikerush.
Effects of Temperature, Photoperiod, and Population Source on the Growth of Cogongrass (Imperata cylindrica)
Authors: Patterson D. T. , Flint E. P. , Dickens Ray
Published: May 2019

Responses of the vegetative growth of cogongrass [Imperata cylindrica(L.) Beauv.] to temperature and photoperiod were studied in plants grown from stem and rhizome propagules collected from plants originating at four locations in southern Alabama and Mississippi. The plants were grown in four controlled-environment chambers with day/night temperature regimes of 23/17 C and 29/23 C, photoperiods of 12 h and 16 h, and photosynthetic photon flux densities (PPFD) of 650 μE(einsteins)m−2s−1. After 87 days, heights, leaf areas, total dry weights, rhizome numbers, and rhizome dry weights were significantly greater in plants grown at 29/23 C than at 23/17 C. Total dry weights, rhizome numbers, and rhizome dry weights were greater at the 16-h photoperiod than at 12 h. Plants grown from propagules from the McNeil, Mississippi population, which originated from an introduction from the Philippines, were significantly smaller than plants grown from propagules collected from populations thought to have originated from an introduction of cogongrass from Japan. Mathematical analysis of the growth data showed that the observed differences in dry matter production were more closely related to differences in leaf area duration than to differences in net assimilation rate.
Stimulation of Common Cocklebur (Xanthium pensylvanicum) and Redroot Pigweed (Amaranthus retroflexus) Seed Germination by Injections of Ethylene into Soil
Authors: Egley G. H.
Published: May 2019

The effects of ethylene upon germination of common cocklebur (Xanthium pensylvanicumWallr.) and redroot pigweed (Amaranthus retroflexusL.) seeds were studied. In laboratory tests with seeds in sealed flasks in the dark, 10 μl/L ethylene increased germination of redroot pigweed seeds from 7% to 52% at 30 C, and increased germination of large and small common cocklebur seeds from 30% and 0% to 100% and 90% respectively, at 25 C. At least 12 h of exposure to ethylene was necessary for appreciable stimulation of germination. In growth chamber studies with known numbers of seeds in pots of soil, ethylene at 11 kg/ha was injected into the soil, and the pots were enclosed in plastic bags for 24 h. One such injection at 2 weeks after planting, and successive injections at 2, 3, and 4 weeks, significantly increased redroot pigweed seedling emergence, and significantly decreased the numbers of dormant, viable seeds remaining in the soil. When pots were not enclosed, injections did not significantly effect redroot pigweed seeds, but significantly increased common cocklebur seedling emergence and decreased the number of viable common cocklebur seeds remaining in the soil.
AChlamydomonasAlgal Bioassay for Detecting Growth Inhibitor Herbicides
Authors: Hess F. D.
Published: May 2019

The single-celled green algaChlamydomonas eugametoswas found to be well suited for detecting growth inhibitor activity of chemicals. Tests consisted of solubilizing technical grade compounds in 20-ml aliquots of a 1 × 105cells/ml zoospore culture. Commercially available growth inhibitor herbicides significantly inhibited synchronous cell population increases within 48 h at concentrations ranging from 1 × 10−4to 1 × 10−7M. Examples of compounds that inhibitedChlamydomonasmore than 50% were butylate (S-ethyl diisobutylthiocarbamate) and diallate [S-(2,3-dichloroallyl)diisopropylthiocarbamate] at 1 × 10−4M, CDEC [2 chloroallyl diethyldithiocarbamate] and propham (isopropyl carbanilate) at 1 × 10−5M, alachlor [2-chloro-2′,6′-diethyl-N-(methoxymethyl)acetanilide] and trifluralin [α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine] at 1 × 10−6M, and bifenox [methyl 5-(2,4-dichlorophenoxy)-2-nitrobenzoate] at 1 × 10−7M. Ethanol, dimethylsulfoxide (DMSO), or acetone can be used to solubilize herbicides in the aqueous medium. DMSO and ethanol are not detrimental to the cells if the concentration is kept at 1% v/v or less.
Phytotoxic Interaction between Phenylurea Herbicides in a Cotton (Gossypium hirsutum)-Soybean (Glycine max) Sequence
Authors: Chandler J. M. , Savage K. E.
Published: May 2019

Preliminary greenhouse studies indicated the presence of a synergistic interaction between low rates of fluometuron [1,1-dimethyl-3-(α,α,α-trifluoro-m-tolyl)urea] or diuron [3-(3,4-dichlorophenyl)-1,1-dimethylurea] in combination with linuron [3-(3,4-dichlorophenyl)-1-methoxy-1-methylurea] or chlorbromuron [3-(4-bromo-3-chlorophenyl)-1-methoxy-1-methylurea]. In a 3-yr field study, moderate injury of cotton (Gossypium hirsutumL. ‘Stoneville 213’) with no yield reduction was observed with fluometuron or diuron at 1.68 and 1.12 kg/ha, respectively, but higher rates (5.04 and 3.36 kg/ha, respectively) caused injury and yield reductions. Soybean [Glycine max(L.) Merr. ‘Hill’] injury ratings during the second year indicated a synergistic interaction between residue from fluometuron at 5.04 kg/ha combined with linuron at 2.48 kg/ha or chlorbromuron at 3.85 kg/ha, and from diuron at 3.36 kg/ha combined with linuron at 2.48 kg/ha. These interactions were not apparent in soybean yield data. Soybean injury the third year ranged from 30 to 60% with single or repeated applications of linuron or chlorbromuron, although yields were not affected. Residual fluometuron and diuron from 2 yr of application at 5.04 and 3.36 kg/ha, respectively, injured soybeans, but did not reduce yields. Significant synergistic interactions were observed through injury and yield measurements after two annual applications of fluometuron at 5.04 kg/ha combined with linuron or chlorbromuron. A synergistic interaction was detected in soybean yields with chlorbromuron at 3.85 kg/ha preceded by two annual applications of diuron at 3.36 kg/ha. Such interactions may occur under field conditions, but are unlikely to be economically significant. Chemical analysis indicated little evidence of accumulation, even with repeated application of fluometuron or diuron at 5.04 and 3.36 kg/ha, respectively.
Response of Selected Grass Weeds to Metriflufen
Authors: Rogers N. K. , Oliver L. R. , Talbert R. E.
Published: May 2019

Field evaluations for control of grass species were conducted with metriflufen, the methyl ester of {2-[4-(4-trifluoromethylphenoxy)phenoxy] propanoic acid}, applied as preemergence and postemergence treatments. The preemergence application of 0.28 kg/ha gave 84 to 100% control of all species except grain sorghum [Sorghum bicolor(L.) Moench], johnsongrass [Sorghum halepense(L.) Pers.], red rice (Oryza sativaL.), and green foxtail [Setaria viridis(L.) Beauv.]. These species required 0.84 kg/ha for at least 95% control. At the three-leaf stage, all species except cheat (Bromus secalinusL.) and red rice were highly susceptible to the herbicide at 0.56 and 0.84 kg/ha. At the six-leaf stage, 0.56 kg/ha of metriflufen gave 96% control of Texas panicum (Panicum texanumBuckl.) and goosegrass [Eleusine indica(L.) Gaertn.], but 0.84 kg/ha was necessary for 92% control of barnyardgrass [Echinochloa crus-galli(L.) Beauv.] and 85% control of large crabgrass [Digitaria sanguinalis(L.) Scop.]. Except for cheat, metriflufen gave less than 55% control if applied when grasses were heading. Little postemergence control was evident for red rice.
Redroot Pigweed (Amaranthus retroflexus) Seed Germination Responses to Afterripening, Temperature, Ethylene, and Some Other Environmental Factors
Authors: Schonbeck Mark W. , Egley Grant H.
Published: May 2019

Germination responses of redroot pigweed (Amaranthus retroflexusL.) seeds to temperature, water potential, atmospheric ethylene and carbon dioxide concentrations, light, and nitrate ion were examined individually. Seeds kept in dry storage at −20 C and tested within 2 yr of harvest germinated at 35 C (12 to 25%) or 39.5 C (40 to 65%), but only 0 to 2% at 30 C and below. Germination at 35 C was prevented by water potentials below −4 bars. When seeds were kept in dry storage at 24 to 28 C, afterripening became evident within 2 months. After storage at this temperature for 4 yr, seeds showed 38% germination at 14 C, 40% at 35 C and −8 bars water potential, and over 90% under more favorable conditions. Ethylene (1 to 100 ppmv) or continuous light enhanced germination at 30 C regardless of degrees of afterripening, although the ethylene effect was most dramatic in nonafterripened seeds. Ethylene at 100 ppmv caused 40% germination in these seeds, compared to 1% for controls. Neither carbon dioxide (0.001 to 4.5% v/v) nor dissolved potassium nitrate (0.02 to 0.2% w/v) influenced germination. These results are discussed in relation to environmental factors influencing field emergence of redroot pigweed.
Determining Projected Leaf Area in Weed Control Research
Authors: Kraatz Gary W. , Andersen Robert N.
Published: May 2019

We developed a technique to measure the projected leaf area of plants any time during the day or night. “Projected leaf area” is the leaf area seen from directly above, and is the area most likely to intercept herbicide spray from an over-the-top application. The technique involves photographing a plant and a reference square of known area from directly overhead using a light-tight box containing a flash unit. Negative images thus obtained are reflected (by means of a slide projector and mirror) onto filter paper lying on a glass stage. The projected leaf area is determined by planimetry of the negative image of the leaves and the reference square. The projected leaf area can be compared to the actual total leaf area after one determines the latter with a conventional area meter.
Leaf Movements in Sicklepod (Cassia obtusifolia) in Relation to Herbicide Response
Authors: Kraatz Gary W. , Andersen Robert N.
Published: May 2019

Sicklepod (Cassia obtusifoliaL.) leaves and leaflets changed their orientation throughout 24-h periods. These endogenously controlled rhythmic movements resulted in dramatic changes in the percent projected leaf area (PPLA), the leaf area observed from directly above and expressed as a percentage of the total actual leaf area. The PPLA of sicklepod varied more than seven-fold throughout a 24-h period, being greatest during the day and least at night. Control of sicklepod with linuron [3-(3,4-dichlorophenyl)-1-methoxy-1-methylurea] applied postemergence at intervals throughout 24-h periods was greater from daytime applications than from late evening, night, and early morning applications. Percent control was highly correlated with PPLA, suggesting that rhythmic leaf movements and the resulting change in PPLA could be an important factor in determining the efficacy of postemergence herbicide applications on sicklepod by altering the area of the leaf surface most likely to intercept and retain herbicide spray from an over-the-top application. In addition to endogenously controlled leaf movements, we observed leaf movements caused by simulated cloud cover (80% shading). Shading increased the PPLA of sicklepod, suggesting that more leaf surface might be exposed to an over-the-top spray during cloudy periods than during sunny periods.
Influence of Time of Planting and Distance from the Cotton (Gossypium hirsutum) Row of Pitted Morningglory (Ipomoea lacunosa), Prickly Sida (Sida spinosa), and Redroot Pigweed (Amaranthus retroflexus) on Competitiveness with Cotton
Authors: Buchanan G. A. , Street J. E. , Crowley R. H.
Published: May 2019

Influence of time of planting and distance from the cotton row of pitted morningglory (Ipomoea lacunosaL.), prickly sida (Sida spinosaL.), and redroot pigweed (Amaranthus retroflexusL.) on yield of seed cotton (Gossypium hirsutumL. ‘Stoneville 213’) was determined on Decatur clay loam during 1975 through 1978. Weed growth was measured in 1977 and 1978. Seeds of the three weed species were planted 15, 30, or 45 cm from the cotton row at time of planting cotton or 4 weeks later. Weeds planted 4 weeks after planting cotton grew significantly less than did weeds planted at the same time as cotton. When planted with cotton, redroot pigweed produced over twice as much fresh weight as did prickly sida or pitted morningglory. The distance that weeds were planted from the cotton row did not affect weed growth in 1978, but did in 1977. The distance that weeds were planted from the cotton row did not affect their competitiveness in any year as measured by yield of cotton. However, in each year, yields of cotton were reduced to a greater extent by weeds planted with cotton than when planted 4 weeks later. In 3 of 4 yr, there were significant differences in competitiveness of each of the three weed species with cotton.
Physiological Interaction, Its Mathematical Expression
Authors: Drury Robert E.
Published: May 2019

The concept of interaction arises in the context of continuous functions. Verbally, it is the action of one independent variable on the action of another, and vice versa, on a dependent variable. Quantitatively, it is the second partial derivative of a function with respect to two independent variables. Misconceptions have arisen from attempts to understand action and interaction in discrete terms. The algebraic expressions for the actions of diuron and phorate on the fresh weight of oats and their interaction were determined from the regression polynomial and plotted in three-dimensional graphs. Three other mutually incompatible methods of assessing interaction, namely, the Colby (with its modification, regression estimate), the two-parameter, and the topographical methods were evaluated.
Susceptibility of Several Grasses to Glyphosate
Authors: Bingham S. W. , Segura J. , Foy C. L.
Published: May 2019

The susceptibility of 2- and 4-month-old perennial ryegrass (Lolium perenneL.), orchardgrass (Dactylis glomerataL.), Kentucky bluegrass (Poa pratensisL.), red fescue (Festuca rubraL.) and highland bentgrass (Agrostis tenuisSibth.) to glyphosate [N-(phosphonomethyl)glycine] was studied in the greenhouse. All 2-month-old grasses were killed by 0.28 kg/ha and higher rates of glyphosate. At 0.14 kg/ha, red fescue was moderately resistant, and bluegrass, orchardgrass, and perennial ryegrass were moderately susceptible. Bent-grass was very susceptible. When 4-month-old grasses were treated, bluegrass was as tolerant to 0.28 kg/ha of glyphosate as was red fescue. At this same rate, orchardgrass and perennial ryegrass were moderately susceptible, whereas bentgrass remained the most susceptible. Dosages lower than 0.28 kg/ha had little effect; whereas higher doages injured all five species.14C-glyphosate was absorbed and translocated via both apoplast and symplast in 1-month-old red fescue, orchardgrass and perennial ryegrass seedlings. Comparatively, less radioactivity was transported to the untreated areas in red fescue than in orchardgrass and perennial ryegrass. Thus, the differential tolerances of these species to low rates of glyphosate may be explained, in part, by differential translocation of glyphosate.
Herbicide and Cultural Practices in Smutgrass (Sporobolus poiretii) Control
Authors: Mislevy P. , Curry W. L. , Brecke B. J.
Published: May 2019

Dalapon (2,2-dichloropropionic acid) was applied at 3.3 kg/ha during late May or early June to a well-established grass sward consisting of smutgrass [Sporobolus poiretii (R.&S.) Hitchc], pangolagrass (Digitaria decumbens Stent.), and bahiagrass (Paspalum notatum Flugge. ‘Pensacola’). Two cultural treatments, mowing or roller chopping, and two fertilizer treatments, 0 or N-P-K at 112-25-93 kg/ha were superimposed on the dalapon treatments at four different time intervals in a split plot design. Chopping or mowing 2 weeks after the dalapon treatment resulted in the highest bahiagrass ground cover and smutgrass control with a minimum amount of bare soil. Chopping tended to favor pangolagrass recovery, and mowing favored bahiagrass recovery. Fertilizer application increased pangolagrass ground cover 90-days after treatment, and smutgrass control after 1 yr. Fertilizer application 6 weeks after dalapon treatment generally increased pangolagrass ground cover and smutgrass control. Pangolagrass responded to fertilizer regardless of chopping or mowing. Mowing controlled more smutgrass than did chopping on the non-fertilized plots.
Effects of Herbicides on in vitro Growth of Mycorrhizae of Pine (Pinus spp.)
Authors: Kelley W. D. , South D. B.
Published: May 2019

Effects of various herbicides on growth of ectotropic mycorrhizal fungi were determined over a 3-week period on modified Melin-Norcrans agar amended with the herbicides at rates of 0, 1, 3, 5, 10, 40, 80, 100, and 500 μg active ingredients/ml. Considerable variation in effect was observed among the herbicides for certain fungi and among the fungi for certain herbicides. All of the test fungi grew in the presence of each of the test herbicides at a rate of 80 μg/ml, and some growth was observed at the 500 μdg/ml rate in a majority of the herbicide-fungus combinations. Significant decreases (P = 0.05) in growth were observed for specific herbicide-fungus combinations at herbicide rates of 1 and 3 μg/ml; however, 50% or greater decreases in fungal colony areas were observed in only 12 of 112 of the combinations at such low rates. The herbicides, in decreasing order of activity against the fungi, were: diphenylethers > dinitroanilines > s-triazines > substituted amides > perfluidone [1,1,1-trifluoro-N-[2-methyl-4-(phenylsulfonyl)phenyl] methanesulfonamide]. With few exceptions, the herbicide concentrations necessary to affect fungal growth significantly were considerably higher than would be expected to occur in soil treated with the test herbicides at recommended application rates.
Selective Weed Control from EPTC Applied with Seed of Alfalfa (Medicago sativa)
Authors: Dawson J. H.
Published: May 2019

In field and greenhouse experiments, liquid or granular formulations of EPTC (S-ethyl dipropylthiocarbamate) applied by hand directly in the row with seed of alfalfa (Medicago sativa L. ‘Vernal’), controlled grass seedlings in bands, usually 5 to 8 cm wide, without injuring alfalfa significantly. Grass was similarly controlled selectively when a mixture of alfalfa seed and clay granules, similar in size to alfalfa seed and containing 10% EPTC, was seeded mechanically.
Picloram Dissipation in a Small Southwestern Stream
Authors: Johnsen Thomas N. , Warskow William L.
Published: May 2019

Picloram (4-amino-3,5,6-trichloropicolinic acid) injected directly into a small, central-Arizona stream was lost by normal stream flow actions, such as the mixing of fast- and slow-moving water, and the interchange of surface and subsurface water in gravel and sand beds along the stream. Picloram was injected at a concentration of 6.26 ppmw; the maximum amount detected was 2.362 ppmw at 0.4 km downstream, 0.943 ppmw at 0.8 km, 0.316 ppmw at 1.6 km, 0.014 ppmw at 3.2 km, 0.001 ppmw at 6.4 km, and none further downstream. Picloram was detected near the limits of detection (0.001 to 0.004 ppmw) 2 days after injection at the 0.4-, 0.8-, and 1.6-km sites. In photodegradation tests, sunlight decomposed 57% of the picloram in containers after 8.8 h of exposure.
Weed Science, a Changing Technology
Authors: Hay J. R.
Published: May 2019

Slow advances were made in weed technology over 10,000 yr as agriculture progressed from hand weeding to the use of hand tools, animal power, cultural practices, mechanical power, biological controls, and most recently to chemical control.