bluuebunny/crossref_metadata_2025 huggingface dataset:
Hormonal Control of Weed Seed Germination
Authors: Holm R. E. , Miller M. R.
Published: May 2019

Freshly-harvested seeds of several common weeds showed little or no promotion of germination by light. However, after burial for 6 months, germination becomes entirely dependent on exposure to light. Red light promoted the germination of the buried seeds, and this promotion was reversed by far-red light, indicating phytochrome involvement. Freshly-harvested seeds were made light-requiring by treatment with mannitol. The germination of these light-requiring seeds was promoted by red light, gibberellic acid (GA), acetylcholine (ACh), and adenosine 3′,5′-monophosphate (cyclic AMP). The phytochrome response may trigger ACh synthesis which causes the release of GA from a bound form and/or GA synthesis which enhances the production of cyclic AMP which initiates the germination response.
Effect of DCPA on Ultrastructure of Foxtail Millet Cells
Authors: Chang C. T. , Smith Don
Published: May 2019

Shoot apices of 7-day old foxtail millet(Setaria italica(L) Beauv.) seedlings treated with 2 and 20 mg/L of dimethyltetrachloroterephthalate (DCPA) were examined under the electron microscope. Cell division is interrupted. The nucleus and nucleolus do not disintegrate and chromosomes do not differentiate. Instead, giant nuclei and giant nucleoli occupy most of the cell volume in the meristematic regions. Several nucleolar caps form on the giant nucleolus; and in the advanced stages, they separate and are encircled by a nuclear membrane to form multiple nuclei. Other organelles are also affected. Cristae and thylakoid membranes of mitochondria and chloroplasts degenerate and multiple vacuoles form. Cell walls are markedly more osmophilic after DCPA treatment. Treated cells are less turgid than controls.
Fate of Fluorodifen in Susceptible Cucumber Seedlings
Authors: Eastin E. F.
Published: May 2019

Rapid absorption and acropetal translocation of14C fromp-nitrophenyl-α,α,α-trifluoro-2-nitro-p-tolyl ether (fluorodifen) labeled with14C at either the 1 position of thep-nitrophenyl ring (fluorodifen-1′-14C) or the trifluoromethyl carbon (fluorodifen-14CF3) were observed in cucumber(Cucumis sativusL. ‘Ashley’) seedlings after root treatment via nutrient solution. The major degradative products of fluorodifen-1′-14C werep-nitrophenol and Unknown I (possibly a conjugate ofp-nitrophenol). Somep-nitrophenyl-α,α,α-trifluoro-2-amino-p-tolyl ether (2-amino-fluorodifen),p-aminophenyl-α,α,α-trifluoro-2-amino-p-tolyl ether (p,2-diamino-fluorodifen),p-aminophenyl-α,α,α-trifluoro-2-nitro-p-tolyl ether (p-amino-fluorodifen), and several minor unknowns also were detected. The major degradative product of fluorodifen−14CF3was Unknown II (possibly a conjugate of 2-amino-4-trifluoromethylphenol). Also detected were some 2-amino-fluorodifen, 2-amino-4-trifluoromethylphenol,p-amino-fluorodifen,p2-diamino-fluorodifen, 2-nitro-4-trifluoromethylphenol, and several minor unknowns. The basic difference in susceptibility to fluorodifen of cucumber and peanut(Arachis hypogaeaL. ‘Starr’) appears to be due to the rate of acropetal translocation (cucumber translocates more than peanut) and the rate of degradation (peanut degrades fluorodifen much more rapidly than cucumber).
Weed Control Systems for Sunflowers
Authors: Johnson B. J.
Published: May 2019

The control of grasses and broadleaf weeds in sunflowers(Helianthus annuusL. ‘Peredovik’) generally was as good with one or two cultivations during the 3-year period as with chemicals applied alone or in sequence with cultivation. Plant injury was not evident from mechanical treatments or from α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine (trifluralin). However, plant injury occurred when plots were treated with 2-chloro-2′6-diethyl-N-(methoxymethyl) acetanilide (alachlor) plus 2,4-bis(isopropylamino)-6-(methylthio)-s-triazine (prometryne) as a preemergence application in 1 year and from postemergence applications of 2-tertiobutyl-4-(2,4-dichloro-5-isopropyloxyphenyl)-5-oxo-1,3,4-oxodiazoline (RP 17623) and 3-(3,4-dichlorophenyl)-1-methoxy-1-methylurea (linuron) in 2 years. Seed yields from plots cultivated once were as good as yields from plots that received multiple cultivation or herbicide treatments. Other agronomic characteristics were favorable from plots that received one cultivation.
Efficiency of a Tractor-Mounted Field Sprayer
Authors: Baur J. R. , Bovey R. W. , Meyer R. E. , Flynt T. O. , Riley T. E.
Published: May 2019

Samples of the spray pattern delivered by a tractormounted field sprayer were intercepted with 10 petri dishes divided between two heights in each of eight plots sprayed with 1.12 kg/ha of 4-amino-3,5,6-trichloropicolinic acid (picloram). The sprayer produced predictable residues on the intercept plates; no differences occurred between residues collected at ground level and 46 cm above the ground; and no differences occurred between replicate plots. Fractionation and analysis of specific plant parts, whose position relative to direction of spray and surrounding brush had been noted, revealed that the spray system delivered uniform coverage almost regardless of brush orientation.
An Oil Carrier for Increasing Purple Nutsedge Control
Authors: Burr R. J. , Warren G. F.
Published: May 2019

Purple nutsedge(Cyperus rotundusL.) control with (2,4-dichlorophenoxy)acetic acid (2,4-D) and 3-(3,4-dichlorophenyl)-1-methoxy-1-methylurea (linuron) was increased in greenhouse and growth chamber studies by application of these herbicides in an undiluted isoparaffinic oil carrier rather than water. Two applications of 2,4-D at 2.2 kg/ha in the oil carrier inhibited tuber and shoot production and reduced the number of viable tubers present, but two applications of linuron at 0.6 or 2.2 kg/ha in the oil inhibited only shoot production from repotted tubers. Studies with labeled 2,4-D showed an increase in both rate and quantity of penetration of this herbicide into purple nutsedge when applied in oil rather than water. Labeled linuron was applied to purple nutsedge and to beans(Phaseolus vulgarisL. ‘Improved Tendergreen’) and also showed an increase in penetration with the oil rather than water. Translocation out of treated leaves was not increased for either 2,4-D or linuron by application in the oil carrier.
Preemergence Herbicidal Activities of 3-Phenoxypyridazine Derivatives
Authors: Takematsu Tetsuo , Takeuchi Yasutomo , Tamura Saburo
Published: May 2019

Preemergence herbicidal activities of 27 3-phenoxypyridazine derivatives were evaluated in pots under upland and submerged conditions. Each of the compounds containing an alkyl or halogen at the ortho position of the benzene ring showed marked herbicidal effects. The activity of some disubstituted compounds carrying one of the substituents at the ortho position was the next. Among the compounds tested, 3-(2-methylphenoxy)-, 3-(2,3-dimethylphenoxy)-, 3-(2,4-dimethylphenoxy)-, and 3-(2,6-dimethylphenoxy)-pyridazines exhibited an excellent margin of selectivity for tomato (Lycopersicum esculentum Mill.), cotton (Gossypium hirsutum L.), soybean (Glycine max (L.) Merr.), and Azuki bean (Phaseolus angularis Wight). For transplanted rice (Oryza sativa L. ‘Norin No. 29′) under submerged conditions, 3-(2-isopropylphenoxy)-and 3-(2-n-butylphenoxy)-pyridazines showed a remarkable margin of selectivity, though the herbicidal activity of both compounds was slightly inferior to that of 3-(2-methylphenoxy)-pyridazine.
Sugars, Phosphorus, and Iron in Purple Nutsedge
Authors: Wills G. D.
Published: May 2019

Purple nutsedge(Cyperus rotundusL.) plants were analyzed for free reducing sugars, free glucose, free plus acid hydrolyzable fructose, phosphorus, and iron. The only sugars detected were sucrose, glucose, and fructose. Sucrose was the most concentrated sugar in the shoots with the greatest concentration in the younger leaves. Sucrose was also the most concentrated sugar in mature rhizomes. Glucose and fructose were the most concentrated sugars in the actively growing rhizomes and tubers. Phosphorus was concentrated in the actively growing leaves and rhizomes, while iron was most concentrated in older tissues including rachises with seedheads, mature shoots, tubers, and rhizomes.
Action of Trifluralin on Chromatin Activity in Corn and Soybean
Authors: Penner Donald , Early Roy W.
Published: May 2019

Trifluralin (α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine) at 10−5M applied to etiolated corn(Zea maysL. ‘Michigan 500′) seedlings 6 or 12 hr before the isolation of chromatin from the roots markedly reduced ribonucleic acid (RNA) synthesis supported by the chromatin. The addition ofEscherichia coliRNA polymerase failed to overcome the inhibition. Trifluralin increased the melting temperature of the chromatin. The presence of trifluralin during the isolation and reaction procedure inhibited RNA synthesis indicating possible trifluralin binding to the chromatin with subsequent reduction of template availability for transcription. Trifluralin did not inhibit chromatin activity in soybean [Glycine max(L.) Merr. ‘Hark’] seedlings.
Weed Science in Perspective
Authors: Klingman Dayton L.
Published: May 2019

The theme for our meetings this year is “A Positive Concern for Society.” It is in this context that I will talk about “Weed Science in Perspective.” In doing so, we need to consider where we are, where we have been, and where we are going.
The Role of Weed Science in Developing Countries
Authors: Parker C.
Published: May 2019

When the topic of this talk was first discussed, it was suggested that I might deal with developments in weed science outside the USA, but one had only to pause for a moment to realise that this was a hopelessly vast topic which could not usefully be dealt with in one presentation. I had, therefore, to choose between discussing the advances occurring in the more developed territories such as Europe and Japan and the advances or lack of advance in the less developed countries. It was natural enough for me to narrow my discussion to the developing countries, not only because of my personal experience in this sphere, but also because I believe there is a great deal to consider in this context which is of relevance to the theme for today, namely “a positive concern for society”.
Effects of DCPA on Tomato Hypocotyl Tissue
Authors: Anderson J. LaMar , Shaybany Bijan
Published: May 2019

Dimethyl tetrachloroterephthalate (DCPA) caused localized swelling of the hypocotyl of tomato(Lycopersicon esculentumMill. ‘VF-99′). DCPA caused phloem and xylem parenchyma cells to become multinucleate and to develop into masses undifferentiated tissue within the stele of the tomato hypocotyl. Xylem procambium differentiated earlier than that of controls and matured into shortened and often disconnected elements. Xylem formed prior to treatment was often disrupted due to pressure from the dividing xylem parenchyma. Xylem parenchyma tended to break down resulting in the formation of air cavities within the stele. Cells in the stele of treated hypocotyls tended to stain more intensely with safranin than did the cells in the steles of untreated tomato hypocotyls indicating a difference in cell wall composition. Treated tissue had a higher concentration of total oxalates than did untreated tissue.
Sources of CO2for Nuisance Blooms of Algae
Authors: Boyd Claude E.
Published: May 2019

Bacterial production of CO2from sucrose substrate increased growth of seven species of algae in CO2-limited laboratory cultures. Decomposition of organic matter in pond water also supplied enough CO2to support good algal growth in cultures deprived of other sources of CO2. Estimates of CO2production from decay of dissolved organic matter in six pond waters ranged from 0.32 to 3.53 mg/L per 24 hr. The carbonate-bicarbonate equilibrium system is a major source of CO2for algal photosynthesis. However, in waters of low or extremely high alkalinity, this system will not support high rates of photosynthesis. In such waters CO2from decomposition will stimulate photosynthesis. Decomposable organic compounds must be considered with nitrogen and phosphorus as factors responsible for accelerated eutrophication and nuisance algal blooms.
Adaptation of Johnsongrass
Authors: Burt Gordon W.
Published: May 2019

Twelve different johnsongrass (Sorghum halepense L.) clones were selected from four different regions of the United States and were grown in the greenhouse. The johnsongrass clones grew differently depending upon the environment from which they were originally obtained, suggesting that geographical ecotypes of johnsongrass exist. The parameter of growth most closely correlated to the latitude from which the plants were obtained was the time required for floral initiation. Plants from a more northern latitude consistently flowered earlier than plants obtained from a more southern latitude. Differences in height, stem number, and the weight of rhizomes, shoots, and roots also supported the hypotheses that geographical ecotypes of johnsongrass exist. Susceptibility to dalapon (2,2-dichloropropionic acid) appeared not to be correlated to the latitude from which the plants were obtained.
Movement and Persistence of Bensulide and Trifluralin in Irrigated Soil
Authors: Menges R.M. , Tamez S.
Published: May 2019

Bensulide [0,0-diisopropyl phosphorodithioateS-ester withN-(2-mercaptoethyl)benzenesulfonamide] and trifluralin (α,α,α-trifluroro-2,6-dinitro-N,N-dipropyl-p-toluidine) were incorporated to a depth of 2.5 and 7.5 cm in sandy loam soil on the same plots in three annual applications to study the effect of incorporation depth on movement and persistence of the herbicides in furrow-irrigated soil. Bioassays and gas-liquid chromatographic assays indicated that, regardless of rainfall, both herbicides remained within the original soil zones of incorporation. Trifluralin persisted longer in soil as depth of incorporation was increased. Neither bensulide at 4.5 or 9.0 kg/ha nor trifluralin at 1.1 kg/ha persisted in appreciable amounts 12 months after treatment. At these rates, significant residues of bensulide and trifluralin were detected after 6 months only when tillage was restricted. Herbicide concentrations that persisted 6 months as determined in laboratory assays caused severe reduction in growth of field-grown sorghum [Sorghum bicolor(L.) Moench].
Metabolism of14C-Pebulate in Seedling Tobacco
Authors: Long John W. , Thompson Lafayette , Rieck C. E.
Published: May 2019

Extracts from the roots and shoots of tobacco (Nicotiana tabacumL. ‘Kentucky 14′) seedlings treated with14C-pebulate (S-propyl-1-14C butylethylthiocarbamate) were separated into various organic and aqueous phases to determine the distribution of14C. In the roots the organic acid-carbohydrate fraction became the most highly labeled fraction with time while in the shoots the fraction containing the sterol esters and oligoglycerides was the most highly labeled early in the treatment period but gradually lost radioactivity at later time intervals. Pebulate was not recovered in detectable amounts in either the leaves or roots.
Allelopathy of Leafy Spurge (Euphorbia esula)
Authors: Steenhagen D. A. , Zimdahl R. L.
Published: May 2019

The allelopathic potential of leafy spurge (Euphorbia esulaL.) was investigated in the field and greenhouse. Reductions in frequency and density of quackgrass [Agropyron repens(L.) Beauv.] and common ragweed (Ambrosia artemisiifoliaL.) were noted where leafy spurge had high densities in the field. Field soil samples taken from areas of moderate and high leafy spurge densities inhibited tomatoes (Lycopersicon esculentumMill.) in the greenhouse. Growth of seedlings was inhibited up to 60% when leafy spurge leaves, roots, or litter were incorporated into soil, but surface applied leafy spurge litter had no effect. Growth inhibition was demonstrated for crabgrass [Digitaria sanguinalis(L.) Scop.] and tomato when 0.1 to 1.0% (w/w) of leafy spurge leaves or roots were added to soil. Based on these studies we postulate that leafy spurge exhibits allelopathic characteristics which may result from the incorporation of dead or decaying plant material in soil.
Interaction of Selected Insecticide-Herbicide Combinations on Soybeans (Glycine max)
Authors: Hayes R. M. , Yeargan K. V. , Witt W. W. , Raney H. G.
Published: May 2019

Phorate {O,O-diethylS-[(ethylthio)methyl] phosphorodithioate}, disulfoton {O,O-diethylS-[2-(ethylthio)ethyl] phosphorodithioate}, linuron [3-(3,4-dichlorophenyl)-1-methoxy-1-methylurea], or metribuzin [4-amino-6-tert-butyl-3-(methylthio)-as-triazin-5(4H)-one] when used alone did not reduce soybean [Glycine max(L.) Merr. ‘Calland’] grain yield or plant population. However, combinations of metribuzin with either phorate or disulfoton interacted synergistically to reduce both soybean grain yield and plant population significantly even at recommended rates of both chemicals. Combinations of linuron with either phorate or disulfoton at recommended rates did not reduce soybean grain yield or plant population. Greenhouse studies further substantiated the synergistic interaction of phorate or disulfoton with metribuzin.
Evaluation of Allelopathic Cucumbers (Cucumis sativus) as an Aid to Weed Control
Authors: Lockerman R. H. , Putnam A. R.
Published: May 2019

Cucumber (Cucumis sativusL.) accessions which had demonstrated allelopathy under controlled environmental conditions were evaluated in the field. Plant introduction (PI) 169391 suppressed proso millet (Panicum miliaceumL.) fresh weight and population 58 and 84%, respectively. Total overseeded and volunteer weed population was reduced 54% when grown in association with PI 169391. Plant introduction 169391 was approximately twice as effective as PI 285605 in suppressing proso millet growth. Inhibition of weed species did not occur consistently in the field. The allelopathic effect of cucumbers was suppressed during periods of increased rainfall. However, these tests demonstrated that allelopathic activity could be obtained under certain edaphic and environmental conditions.
Light Requirement of the Diphenylether Herbicide Oxyfluorfen
Authors: Vanstone D. E. , Stobbe E. H.
Published: May 2019

Herbicidal activity of foliar-applied oxyfluorfen [2-chloro-1-(3-ethoxy-4-nitrophenoxy)-4-(trifluoromethyl)benzene] was light dependent in buckwheat (Fagopyrum esculentumMoench. ‘Tokyo’). Plants were not injured when placed in the dark for as long as 4 days after herbicide treatment. When these plants were brought to the light, injury occurred, albeit more slowly than when plants were placed in the light immediately after treatment. The rate of injury increased as light intensity increased. The most effective wave length was 565 to 615ηm, suggesting the involvement of a pigment with its absorption spectrum in this region. Chlorophyll content was not reduced by oxyfluorfen. Preliminary evidence suggests that photosynthesis was affected only after membrane integrity was disrupted.
Spot Spraying for Johnsongrass (Sorghum halepense) Control in Soybeans (Glycine max)
Authors: Mcwhorter C. G. , Barrentine W. L.
Published: May 2019

Dalapon (2,2-dichloropropionic acid), TCA ester [ethyleneglycol bis(trichloroacetate)], MSMA (monosodium methanearsonate), and glyphosate [N-(phosphonomethyl)glycine] were evaluated for their effectiveness as spot spray treatments to johnsongrass [Sorghum halepense(L.) Pers.] 30, 75, or 100 cm tall from rhizomes. Glyphosate was also applied as a spot spray to soybeans [Glycine max(L.) Merr. ‘Pickett 71′] to determine its effect on stand losses and subsequent soybean yields. Glyphosate at a concentration of 6 or 12 g/L of water was the most effective treatment regardless of johnsongrass height. A single application provided excellent-to-complete seasonal control within 2 weeks after application. Repeated applications of dalapon, MSMA, and TCA ester would be needed for season-long control. Glyphosate at a concentration of 6 g/L of water applied to 0.5 m long spots of soybeans in late August reduced soybean yields 9, 17, and 28% while the stand was reduced 5,10, and 20%, respectively.
Germination and Seedling Development of Canada Thistle (Cirsium arvense)
Authors: Wilson R. G.
Published: May 2019

Optimum germination of Canada thistle [Cirsium arvense(L.) Scop.] occurred at alternating temperatures of 20 to 30 C and 30 to 40 C and at a constant temperature of 30 C. Osmotic pressures of 7 bars and greater reduced germination, but 2% of the seeds germinated at 15 bars. Canada thistle seeds (14%) were able to germinate in NaCl concentrations of 20,000 ppmw. Light was important in seed germination, however, its effect could be overcome by adding GA3(gibberellic acid) to the germination medium. Optimum pH for germination was between 5.8 and 7.0. Depth of planting influenced emergence; the highest percentage of seedlings emerged from depths of 0.5 to 1.5 cm. Canada thistle seedlings tolerated average soil moisture tensions of 1.3 bars and continued to grow. Canada thistle seedlings 19 days old and with two true leaves were able to resprout after top-growth removal. Regrowth was evident on 8% of the clipped plants 4 days after initial top-growth removal.
Soil Persistence of Napropamide
Authors: Romanowski R. R. , Borowy A.
Published: May 2019

The persistence of napropamide [2-(α-naphthoxy)-N,N-diethylpropionamide] applied at 2.24- and 4.48-kg/ha was studied for 2 yr at two locations in the field. Wheat (Triticum aestivumL. ‘Arthur 71′) was severely injured when sown in the fall following a spring application of napropamide. A wheat root bioassay also showed that napropamide was persistent for more than 180 days. The yield of sweet corn (Zea maysL. var.rugosaBonaf. ‘Gold Cup’) was not significantly reduced when grown 1 yr after the initial application of napropamide.
Degradation of Benefin and DCPA in Thatch and Soil from a Kentucky Bluegrass (Poa pratensis) Turf
Authors: Hurto K. A. , Turgeon A. J. , Cole M. A.
Published: May 2019

The rates of degradation of14C-benefin (N-butyl-N-ethyl-α,α,α-trifluoro-2,6-dinitro-p-toluidine) and14C-DCPA (dimethyl tetrachloroterephthalate) were significantly faster in thatch than in soil from a Kentucky bluegrass (Poa pratensisL.) turf. These results suggest that herbicides applied preemergence in turf will persist for shorter periods of time because of the carbon-enriched medium (thatch) and that higher rates or more frequent applications may be required to maintain concentrations at effective levels.
Comparative Biocontrol of Purple Nutsedge (Cyperus rotundus)and Yellow Nutsedge (C. esculentus)withBactra verutanaunder Greenhouse Conditions
Authors: Frick K. E. , Williams R. D. , Quimby P. C. , Wilson R. F.
Published: May 2019

Purple nutsedge (Cyperus rotundusL.) and yellow nutsedge (C. esculentusL.) appeared to be equally acceptable for oviposition by cagedBactra verutanaZeller, but purple nutsedge was significantly more suitable as a host: 90% of the larvae survived to maturity on purple nutsedge compared with 65% on yellow nutsedge. Responses of the plant species to both larval feeding injury and plant density were similar but purple nutsedge tended to be injured more than yellow nutsedge. At a high shoot density (nine shoots per pot), production of tubers by purple nutsedge was more adversely affected by feeding of five larvae per shoot than was production by yellow nutsedge: tuber dry weights were reduced 93 and 80% and numbers of tubers per pot were reduced 77 and 62%, respectively. Production of inflorescences was greatly reduced in both species. The effect ofB. verutanaon inflorescences may be more important for yellow nutsedge, which is generally considered to reproduce freely by seeds. Both species of nutsedge probably would be about equally affected by augmentation ofB. verutanapopulations as a method of biological control.
Mechanism for the Suppression of pea (Pisum sativum) Root Rot by Dinitroaniline Herbicides
Authors: Teasdale J. R. , Harvey R. G. , Hagedorn D. J.
Published: May 2019

Pea (Pisum sativumL. ‘Elf’) root rot suppression by dinitroaniline herbicides could not be explained by a direct effect on the host. Pre-incubation of pea roots with 0.1 ppmw of oryzalin (3,5-dinitro-N4,N4-dipropylsulfanilamide) or trifluralin (α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine) in solution culture did not alter their resistance to root rot. Furthermore, 0.1 ppmw of oryzalin or trifluralin did not alter the exudation of electrolytes or α-amino compounds from pea roots. Most of the dinitroaniline herbicides significantly inhibited mycelial radial growth of pathogen,Aphanomyces euteichesDrechs., at 1.0 ppmw and inhibited asexual spore production at 0.1 to 1.0 ppmw. Dinitramine (N4,N4-diethyl-α,α,α-trifluoro-3,5-dinitrotoluene-2,4-diamine), fluchloralin [N-(2-chloroethyl)-2,6-dinitro-N-propyl-4-(trifluoromethyl)aniline], and oryzalin inhibitedA. euteichesmycelial growth and asexual reproduction more effectively than the other dinitroaniline herbicides studied. The production of motile zoospores, the infecting propagule of the pathogen, was the most sensitive stage in the life cycle and was completely inhibited by 0.01 ppmw of all dinitroaniline herbicides tested. Since this concentration is below that estimated in the soil solution at registered rates of application, inhibition of motile zoospore production is sufficient to explain root rot suppression. Inhibition of pathogen motility resulted in a 2-week delay in the infection of pea roots. This delay allowed sufficient additional plant growth that the peas could better withstand the effects of subsequent disease development.
Interaction of Diclofop-Methyl and MCPA on Wild Oats (Avena fatua)
Authors: Qureshi F. A. , Vanden Born W. H.
Published: May 2019

Diclofop-methyl {methyl 2-[4-(2,4-dichlorophenoxy)phenoxy] propanoate} loses part of its activity on wild oats (Avena fatuaL.) when it is applied in combination with ester or amine formulations of MCPA {[4-chloro-o-tolyl)oxy] acetic acid.} Uptake of diclofop-methyl is reduced in the presence of commercial formulations of MCPA, particularly amine formulations, which are only partly compatible with the diclofop-methyl formulation. With added MCPA, regardless of formulation, hydrolysis of diclofop-methyl to the acid diclofop is slowed down, both in intact wild oat plants and in a crude leaf extract. At the same time, conversion of any acid formed to inactive conjugates is accelerated in the presence of MCPA. It is concluded that the loss of activity of diclofop-methyl by MCPA can be accounted for by the effects of MCPA on uptake and metabolic conversion of diclofop-methyl.
Control ofPoa annuaby Suppression of Seedheads with Growth Regulators
Authors: Watschke T. L. , Long F. W. , Duich J. M.
Published: May 2019

Field and greenhouse studies were conducted to determine the degree to which annual bluegrass (Poa annuaL.) could be controlled by inhibiting seedheads. The materials used were: MH (1,2-dihydro-3,6-pyridazinedione); chlorflurenol (methyl 2-chloro-9-hydroxyfluorene-9-carboxylate), plus methyl 9-hydroxyfluorene-9-carboxylate, and methyl 2,7-dichloro-9-hydroxyfluorene-9-carboxylate; and endothall [7-oxabicyclo (2.2.1) heptane-2,3-dicarboxylic acid]. The effects of these materials on pollen quality and the viability of seed produced by treated plants were also determined. For all chemicals used, multiple applications at low rates resulted in better seedhead inhibition than single treatments at higher rates and their effects lasted longer. However, treatments that inhibited seedheads by an amount predicted to reduce annual bluegrass (more than 75%) often caused objectionable foliar discoloration. Endothall, particularly the granular formulation, caused excessive injury at all rates. All growth regulators reduced the number of seed produced, which affected the number of seeds that germinated from soil that was taken from treated plots. The number of seed found in the soil was sufficient to allow the stand to be self-perpetuating. All treatments reduced the percentage of fertile pollen, however, this reduction was not significant because the germination of seed harvested from treated plants was not reduced significantly. Even though these treatments reduced seedheads significantly, the population of annual bluegrass the following year was not reduced.
Inhibition of Photosystem II andChlorellaGrowth by 1-(m-t-butylacetamidophenyl)-3-methyl-3-methoxy urea
Authors: Swader J. A. , Howe Celestia M.
Published: May 2019

The experimental herbicide R-24191 [1-(m-t-butylacetamidophenyl)-3-methyl-3-methoxy urea] inhibited growth ofChlorella sorokinianaShihira and Kraus, O2evolution during CO2fixation byChlorellaand isolated leaf cells of spinach (Spinacia oleraceaL. ‘Winter Bloomsdale 769′), the photoreduction of NADP by isolated chloroplasts using water or hydroxylamine as the electron donor, the photoreduction of 2,6-dichloroindophenol by isolated chloroplasts, and O2uptake by isolated chloroplasts using paraquat (1,1′-dimethyl-4,4′-bipyridinium ion) as the electron acceptor. The phenylurea herbicide had no effect on the last reaction when ascorbate plus 2,6-dichloroindophenol were used as the electron donor. The results indicate that the site of the phenylurea inhibition was in photosystem II between water-splitting and photosystem I.
Exchangeable Cations and Picloram Sorption by Soil and Model Adsorbents
Authors: Arnold J. S. , Farmer W. J.
Published: May 2019

The adsorption of picloram (4-amino-3,5,6-trichloropicolinic acid) was determined on an Aiken silt loam, on three cation exchange resins and on a single anion exchange resin. Adsorption data were evaluated using parameters in the Freundlich equation and their dependance upon cationic composition of the exchange complex, the ionic composition of the equilibrium solution, and the equilibrium solution pH. For the Aiken soil saturated with metallic cations the order of decreasing picloram adsorptive capacity was Fe+3= Cu+2> Al+3> Zn+2> Ca+2> native soil. Increases in adsorption compared to the native Aiken soil could be explained on the basis of decreases in the equilibrium solution pH except for Fe+3, Zn+2, and especially the Cu+2treatments. The adsorptive capacity of the Aiken soil was altered by the addition of several salts simulating addition of fertilizer salts. The Cu+2and Zn+2salts were the only treatments showing increased adsorption which could not be explained readily by pH changes. KH2PO4and NH2CONH2(urea) reduced picloram adsorption. Dowex 50-1 × 4, a strongly acidic cation exchange resin, showed increased picloram adsorptive capacity in the order Cu+2> Al+3> Ca+2> Zn+2= H+. Cellex CM, a weakly acidic cellulose exchanger had increased adsorptive capacities in the order of Cu+2> Ca+2> Al+3> Na+> Fe+3> Zn+2. Picloram adsorption by an anion exchange resin at pH 6.1 was nearly 100%. These results suggest that complex formation of picloram with polyvalent cations on the exchange complex is likely especially for Cu+2and to a lesser extent Fe+3and Zn+2. In soils such complex reactions would most probably involve organic matter, polyvalent cations, and picloram. The formation of chelate ring species is proposed.
Soybeans (Glycine max) as a Rescue Crop Following Cyanazine and Procyazine Application
Authors: Brewer P. E. , Slife F. W.
Published: May 2019

Field studies were conducted in 1975 and 1976 at Urbana, Illinois, to evaluate soybeans [Glycine max(L.) Merr. ‘Amsoy 71′] as a potential rescue crop following the use of cyanazine{2-[[4-chloro-6-(ethylamino)-s-triazin-2-yl] amino]-2-methylpropionitrile} and procyazine {2-[[4-chloro-6-(cyclopropylamino)-1,3,5-triazine-2-yl] amino]-2-methylpropanenitrile} with corn (Zea maysL.). Preplant incorporated and preemergence applications of each herbicide were made at the recommended broadcast rates to Dana and Flanagan silt loams. Corn was removed and soybeans were planted 7, 13, and 21 days (1975) or 10, 15, and 23 days (1976) following herbicide application. Visual injury ratings, stands, and yields for soybeans were determined. In spite of varying degrees of visible injury and stand reductions, yields were not reduced significantly when soybeans were planted 3 weeks after cyanazine or procyazine application.
EPTC Induced Modification of Gibberellin Biosynthesis
Authors: Wilkinson R. E. , Ashley D.
Published: May 2019

Wheat (Triticum aestivumL. ‘Holley’) was grown for 14 days in 0.5 strength Hoagland and Arnon's complete mineral nutrient solution containing 0. 15.6, 31.25, 62.5, 125.0, or 250.0 ppbw EPTC (S-ethyl dipropylthiocarbamate). Gibberellic acid (GA) content, as measured by gas-liquid chromatography, was decreased 96.4% by 125.0 ppbw EPTC. When 0.05 μCi mevalonic acid-2-14C-(MVA-2-14C) (DBED salt) (0.15 mCi/mg MVA) was added to the nutrient solution, incorporation of MVA-2-14C into total kaurenoids was decreased 90% by 250 ppbw EPTC. Metabolism of kaurene was reduced by 250 ppbw EPTC with resultant 3-fold accumulations of kaurene.
Movement of Chlorpropham after Application to Soil for Control of Dodder (Cuscutaspp.)
Authors: Dawson J. H.
Published: May 2019

When clay granules containing chlorpropham (isopropylm-chlorocarbanilate) were applied to the surface of moist soil, the herbicide gradually moved to the atmosphere as a vapor and little entered the soil. Chlorpropham killed seedlings of field dodder (Cuascuta campestrisYunck.) and largeseed dodder (C. indecoraChoisy) effectively whether it contacted them in the soil or in the air above the soil.
Control of Field Bindweed (Convolvulus arvensis) in Winter Wheat (Triticum aestivum) with Foliar and Subsurface Layered Herbicides
Authors: Banks P. A. , Hill L. V. , Santelmann P. W.
Published: May 2019

Field bindweed (Convolvulus arvensisL.) was controlled most effectively when glyphosate [N-(phosphonomethyl)glycine] was applied as a foliar spray to blooming field bindweed. This control resulted in significant yield increases of winter wheat (Triticum aestivumL.). Earlier growth stage treatments were less effective. Dicamba (3,6-dichloro-o-anisic acid), used similarly, controlled field bindweed but caused injury to the following wheat crop. Preharvest treatments of glyphosate in wheat aided harvesting operations and controlled the perennial field bindweed through the summer. Several dinitroaniline herbicides applied as a subsurface layer (SSL), controlled field bindweed for more than 8 months after treatment. However, these treatments caused visible injury and affected the yield of the first crop of wheat but had little effect on a second crop. Dicamba applied SSL at lower rates resulted in excellent field bindweed control.
Bahiagrass (Paspalum notatum) and Common Lespedeza (Lespedeza striata) Control with Herbicides in Centipedegrass(Eremochloa ophiuroides)
Authors: Johnson B. J.
Published: May 2019

Multiple applications of atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine] during the winter, spring, and summer were evaluated for bahiagrass (Paspalum notatumF.) control in centipedegrass [Eremochloa ophiuroides(Munro) Hack.]. Single and repeated atrazine, metribuzin [4-amino-6-tert-butyl-3-(methylthio)-as-triazine-5(4H)-one], and methazole [2-(3,4-dichlorophenyl)-4-methyl-1,2,4-oxadiazolidine-3,5-dione] treatments were applied in the spring for common lespedeza [Lespedeza striata(Thunb.) H. & A. ‘Kobe’] control in centipedegrass. Atrazine at 2.2 kg/ha in two (July + August) or three (January + April + May, April + May + July, or May + July + August) applications controlled bahiagrass without injuring centipedegrass turf. In most instances repeated treatments were needed a second year for consistent control of 98 to 100%. A single treatment of atrazine at 2.2 kg/ha, metribuzin at 0.6 kg/ha, or methazole at 1.1 kg/ha satisfactorily controlled emerged common lespedeza in centipedegrass turf. None of the treatments injured centipedegrass. When atrazine was applied to actively growing centipedegrass, the turf had a darker green color than untreated turf. This usually occurred within a month after treatment and lasted for 3 to 4 weeks.
Seed Coat Impermeability and Germination of Showy Crotalaria (Crotalaria spectabilis) Seeds
Authors: Egley G. H.
Published: May 2019

Showy crotalaria (Crotalaria spectabilisRoth) seed dormancy was due to seed coat impermeability to water. The seed coats became impermeable during later stages of maturation on the plant. When incubated immediately after harvest, 9% of the mature, black seeds (11% water content) imbibed water and germinated. The remaining 91% had impermeable coats and did not germinate. After dry storage for 3 months at 23 C, 24% of the seeds imbibed water and germinated. Seeds of another seed lot, which contained seeds of different maturity stages, attained 47% imbibition and germination after storage for 1 yr. The dry, less mature green seeds had a higher percentage (51%) of permeable seeds than did the black seeds (31%) from the same lot. Several seed coat treatments induced imbibition of water and germination of previously impermeable seeds. Effective treatments included piercing of seed coats, scarification with sandpaper, soaking in 70 C water, and simply applying pressure on the strophiole area. Covering the pressed strophiole with petroleum jelly significantly blocked imbibition and indicated that water entered the seeds at only the pressed area. However, studies indicated natural loss of impermeability in showy crotalaria seeds may occur at other sites as well.
Degradation of Phenoxyalkylcarboxylic Acids by White Clover (Trifolium repens) Cell Suspensions
Authors: Smith A. E. , Oswald T. H.
Published: May 2019

Cell suspension cultures of white clover (Trifolium repensL. ‘Regal Ladino’) were treated with 2,4-D [(2,4-dichlorophenoxy)acetic acid], 2,4-DB [4-(2,4-dichlorophenoxy)butyric acid], 2,4,5-T [(2,4,5-trichlorophenoxy)acetic acid], 2,4,5-TP [2-(2,4,5-trichlorophenoxy) propionic acid], and 2,4,5-TB [4-(2,4,5-trichlorophenoxy)butyric acid]. Cell population densities were monitored throughout the treatment period and herbicide remaining in the cells and culture medium was extracted and quantified at the termination of the treatment. Herbicide tolerance increased in cell populations which were conditioned by pretreatment with 2,4-DB and 2,4,5-T. However, 2,4-DB was rapidly degraded by all cell populations regardless of pretreatment. White clover cell suspension cultures treated with 2,4-D, 2,4-DB, 2,4,5-T, 2,4,5-TP and 2,4,5-TB metabolized the homologs, according to the following sequence: butyric acidåpropionic acidåacetic acid homologs. There was no difference in the rate of degradation of similar homologs of the 2,4-dichloro- and 2,4,5-trichloro- analogs.
Metabolism of 2,4-DB by White Clover (Trifolium repens) Cell Suspension Cultures
Authors: Smith A. E.
Published: May 2019

The metabolism of 2,4-DB [4-(2,4-dichlorophenoxy)butyric acid] in cell suspension cultures of white clover (Trifolium repensL. ‘Regal Ladino’) was investigated using (ring)-14C 2,4-DB. The herbicide and its14C-labeled metabolites were isolated from treated cells and medium after 48 h by partition and thin layer chromatography (TLC). The major portion of the radiolabel was in the glycoside fraction (47%) and incorporated into the cell structural material (34%). The remainder of the14C remained either as the parent herbicide (8%) or an amino acid conjugate of 2,4-DB (10%).
Methodology and Terminology for the Measurement of Light in Weed Studies—A Review
Authors: Patterson David T.
Published: May 2019

Definitions and properties of light, the effects of light on plant growth and physiological processes, and methodology and terminology for the measurement and reporting of light are reviewed. Alternatives to photometric methods now generally used in studies of the effects of light on plants in weed research are proposed. For studies of leaf energy budgets and plant water relations, the irradiance may be appropriately measured with radiometric methods and the data reported as W [watts] m-2. For studies of photosynthesis, the photosynthetic photon flux density may be measured and the data reported as μE [einsteins] m-2s-1or μmol [μmoles of photons] m-2s-1. Different types of instruments are described and sources for these instruments are provided.
Comparison of Four Cropping Systems for Yellow Nutsedge (Cyperus esculentus) Control
Authors: Keeley P. E. , Thullen R. J. , Miller J. H. , Carter C. H.
Published: May 2019

Four cropping systems were evaluated from 1975 to 1977 for the control of yellow nutsedge (Cyperus esculentusL.). Crops grown in 1975 and 1976 included alfalfa (Medicago sativaL. ‘Elcamino WL-600′), barley(Hordeum vulgareL. ‘CM-67′), corn (Zea maysL. ‘Dekalb T214′), and cotton (Gossypium hirsutumL. ‘Acala SJ-2′). Herbicides used included butylate (S-ethyl diisobutylthiocarbamate) in corn, EPTC (S-ethyl dipropylthiocarbamate) in alfalfa, glyphosate [N-(phosphonomethyl)glycine] in fallow plots, and MSMA (monosodium methanearsonate) in cotton. Cotton, which was grown continuously as one of the four cropping systems, was the only crop grown in 1977. Based on weed counts, crop yields, and the consistent decline in the number of tubers, all cropping systems provided substantial control of yellow nutsedge each year. Two years of either alfalfa treated with EPTC or double cropping barley with corn treated with butylate preceeding cotton reduced the number of viable yellow nutsedge tubers by 96%. Two years of chemically fallowing plots with glyphosate following barley and preceeding cotton was 98% effective in reducing viable tubers. Treating continuous cotton with MSMA, although somewhat inferior to the above systems, reduced the number of viable nutsedge tubers by 91% in 3 yr.
Factors Affecting the Suppression of Pea(Pisum sativum)Root Rot(Aphanomyces euteiches)by Dinitroaniline Herbicides
Authors: Teasdale J. R. , Harvey R. G. , Hagedorn D. J.
Published: May 2019

Field and greenhouse studies have shown that dinitroaniline herbicides suppress root rot of peas (Pisum sativumL.) caused by the fungusAphanomyces euteichesDrechs. This investigation was conducted to identify factors which could enhance root rot suppression. In a temperature-soil moisture growth chamber study, dinitroaniline herbicides significantly reduced disease severity symptoms at all temperature and soil moisture regimes except 32 C and 0.75 field capacity. Dinitroaniline herbicides increased pea fresh weight significantly only under those conditions which favored severe disease development. Maximum root rot suppression occurred at 24 C and 1.25 field capacity. In a greenhouse study of the interaction of root rot suppression with pea varieties, dinitroaniline herbicides significantly increased growth of all 12 pea varieties tested including a root rot tolerant wild type of pea. A series of experiments explored the effect of uniformity, time, and depth of dinitroaniline herbicide incorporation on root rot suppression. In greenhouse studies, non-uniform incorporation significantly reduced root rot suppression indicating the need for thorough incorporation to achieve maximum root rot suppression. The combination of trifluralin (α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine) + oryzalin (3,5-dinitro-N4,N4dipropylsulfanilamide) was more effective than either trifluralin or oryzalin alone under non-uniform incorporation conditions but not under uniform incorporation conditions. Field studies showed that herbicide incorporation 2 weeks prior to planting may improve pea yield by 1.12 kg/ha of trifluralin or 0.56 + 0.56 kg/ha of trifluralin + oryzalin but not by 0.56 kg/ha of trifluralin. Herbicide incorporation to 15.2 cm rather than the normal 7.6 cm, increased pea yield at the 1.12 kg/ha rate of trifluralin or oryzalin or at 0.56 + 0.56 kg/ha of trifluralin + oryzalin. At the 0.56 kg/ha rate of trifluralin or oryzalin, herbicide dilution offset any benefit from deeper soil incorporation.
Herbicide-Crop Rotation for Johnsongrass (Sorghum halepense) Control
Authors: Dale J. E. , Chandler J. M.
Published: May 2019

The feasibility of herbicide and crop rotation for the control of johnsongrass [Sorghum halepense(L.) Pers.] in corn (Zea maysL.) was studied in field experiments. Light infestations of johnsongrass were initially present, but it became the predominant weed after 4 yr of continuous corn treated with atrazine [2-chloro-4-(ethylamino)-6-(isopropylamine)-s-triazine], cyanazine {2-[[4-chloro-6-(ethylamino)-s-triazin-2-yl]amino]-2-methylpropionitrile}, and linuron [3-(3,4-dichlorophenyl)-1-methoxy-1-methylurea], alone and in combinations at rates of 2.24, 2.24, and 0.84 kg/ha, respectively. The infestation of johnsongrass was effectively controlled by growing corn in rotation with cotton (Gossypium hirsutumL.) in a cropping sequence of corn-cotton-cotton-corn, in which trifluralin (α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine), fluometuron [1,1-dimethyl-3-(α,α,α-trifluoro-m-tolyl)urea] and MSMA (monosodium methanearsonate) at 0.56, 2.24, and 2.24 kg/ha respectively, were used for weed control in cotton. In the corn-cotton-cotton-corn cropping sequence, the herbicide treatments also prevented increases in the populations of other indigeneous weeds including prickly sida (Sida spinosaL.), prostrate spurge (Euphorbia supinaRaf.), spotted spurge (Euphorbia maculataL.), common purslane (Portulaca oleraceaL.), tall morningglory [Ipomoea purpurea(L.) Roth], common cocklebur (Xanthium pensylvanicumWallr.), spurred anoda[Anoda cristata(L.) Schlecht.], hemp sesbania [Sesbania exaltata(Raf.) Cory], redroot pigweed (Amaranthus retroflexusL.), goosegrass [Eleusine indica(L.) Gaertn.], junglerice [Echinochloa colonum(L.) Link], large crabgrass [Digitaria sanguinalis(L.) Scop.], and purple nutsedge (Cyperus rotundusL.).
Seed Production and Germination inCyperus esculentusandC. rotundus
Authors: Thullen R. J. , Keeley P. E.
Published: May 2019

Yellow nutsedge (Cyperus esculentusL.) produced an average of 1227 and 6685 flowers per inflorescence from eight California fields sampled during 1974, 1975, and 1976. Up to 17% of the flowers produced seeds and up to 78% of the seed germinated. There was a linear relationship between seed weight and germination percentage. Purple nutsedge (C.rotundusL.) averaged between 186 and 1354 flowers per inflorescence from three California fields sampled in 1974 and 1976. Only 43 purple nutsedge seed were collected and none germinated. Yellow nutsedge produced viable seed about 2 weeks after anthesis. A day/night temperature of 38/32 C was best for seed germination, especially when accompanied by a light period. Yellow nutsedge has potential to reproduce by seed, but probability of purple nutsedge reproducing by seed is low.
Antagonistic Effects of Desmedipham on Diclofop Activity
Authors: Dortenzio W. A. , Norris R. F.
Published: May 2019

The methyl ester of diclofop [2-(4-(2,4-dichlorophenoxy) phenoxy) propionic acid] was used in all of a series of experiments. When it was applied postemergence, it selectively controlled barnyardgrass [Echinochloa crus-galli(L.) Beauv.] in sugarbeets (Beta vulgarisL. ‘USH 9′). Tank-mixing diclofop with desmedipham [ethylm-hydroxycarbanilate carbanilate (ester)] resulted in decreased control of barnyardgrass under greenhouse and field conditions. Losses in activity ranged from 10 to 80%. Delaying application of desmedipham following application of diclofop by 4 days in the greenhouse or in the field resulted in no reduction in barnyardgrass control. Increased rates of diclofop offset the antagonistic effect of desmedipham. Similar losses in activity occurred when Hoe-29152 {methyl-2-[4-(4-trifluoromethylphenoxy)phenoxy] propanoate} was tank-mixed with desmedipham.