bluuebunny/crossref_metadata_2025 huggingface dataset:
Distribution of Triclopyr and Picloram in Huisache (Acacia farnesiana)
Authors: Bovey R. W. , Ketchersid M. L. , Merkle M. G.
Published: May 2019

The triethylamine salt of triclopyr [(3,5,6-trichloro-2-pyridinyl)oxy] acetic acid and the potassium salt of picloram (4-amino-3,5,6-trichloropicolinic acid) were applied as soil, foliar, and soil-plus-foliar treatments to greenhouse-grown huisache [Acacia farnesiana(L.) Willd.]. At 1.12 kg/ha, picloram was more effective (97 to 100% defoliation) than triclopyr (51 to 83%) in defoliating huisache. Triclopyr was more effective at 2.24 kg/ha than at 1.12 kg/ha in defoliating huisache, except when applied to the soil. Soil or soil-plus-foliar treatments of triclopyr at 2.24 kg/ha were not significantly different from those of picloram at 1.12 kg/ha 15 weeks after treatment. Triclopyr and picloram content was determined in and on leaves, stems, and roots at 0, 3, 10, and 30 days after treatment. More picloram than triclopyr was found in the leaves 30 days after treatment with foliar sprays at equal rates. Soil, foliar, and soil-plus-foliar treatments resulted in greater accumulation of picloram than triclopyr in stem tissue. Herbicide concentrations in roots were usually low. Reasons for the greater herbicidal activity of picloram than of triclopyr in huisache are not clear; however, the greater accumulation of picloram than of triclopyr in leaf and stem tissue may partially explain the difference in herbicide activity.
Responses ofIpomoeaspp. andCassiaspp. to Preemergence Applied Herbicides
Authors: Crowley R. H. , Teem D. H. , Buchanan G. A. , Hoveland C. S.
Published: May 2019

Responses of six morningglories (Ipomoeaspp.) and twoCassiaspp. to 13 preemergence applied herbicides were determined at two locations in southern Alabama. Pitted (I. lacunosaL.), cypressvine (I.quamoclitL.), and willowleaf morningglories (I. wrightiiGray) were readily controlled with metribuzin [4-amino-6-tert-butyl-3-(methylthio)-as-triazin-5(4H)-one]; entireleaf [I. hederacea(L.) Jacq. var.integriusculaGray], tall [I. purpurea(L.) Roth.], and ivyleaf morningglories [I. hederacea(L.) Jacq.] were not controlled. Norflurazon [4-chloro-5-(methylamino)-2-(α,α,α-trifluoro-m-tolyl)-3(2H)-pyridazinone] controlled cypressvine morningglory, but did not adequately control the other morningglory species. Perfluidone {1,1,1-trifluoro-N-[2-methyl-4-(phenylsulfonyl)phenyl] methanesulfonamide} gave acceptable control of cypressvine and willowleaf morningglories, but gave poor control of other morningglory species. Sicklepod (C.obtusifoliaL.) was controlled better than coffee senna (C.occidentalisL.) with 2.2 kg/ha diuron [3-(3,4-dichlorophenyl)-1,1-dimethylurea] and 2.2 kg/ha cyanazine {2-[[4-chloro-6-(ethylamino)-s-triazin-2-yl]amino]-2-methylpropionitrile} controlled sicklepod better than coffee senna at one location each. Oxadiazon [2-tert-butyl-4-(2,4-dichloro-5-isopropoxyphenyl)-δ2-1,3,4-oxadiazolin-5-one] was more effective in controlling coffee senna than sicklepod. Induction of population shifts toward incidental species of these genera seems unlikely based on the herbicides included in these experiments. In most cases the incidental species were more readily controlled than the prominent weed species.
Dinitroaniline Herbicide Phytotoxicity as Influenced by Soil Moisture and Herbicide Vaporization
Authors: Jacques G. L. , Harvey R. G.
Published: May 2019

Effects of soil water and herbicide vapors on the phytotoxicity of eight dinitroaniline herbicides to oats (Avena sativaL. ‘Dal’) were studied. Oat primary root length was inhibited more by the herbicides than was shoot length or shoot fresh weight. All of the herbicides, except oryzalin (3,5-dinitro-N4,N4-dipropylsulfanilamide), inhibited primary root length through vapor activity. Vapors of dinitramine (N4,N4-diethyl-α,α,α-trifluoro-3,5-dinitrotoluene-2,4-diamine) were most inhibitory. Herbicide vapor inhibition increased with temperature. Soil water affected oryzalin activity more than it did that of the other herbicides. Oryzalin phytotoxicity to the oat primary root was reduced more at the low soil water than was that of the other herbicides. Its low vapor activity apparently reduced its effectiveness in dry soil. Difference in magnitude of herbicide phytotoxicity between two soil moisture levels generally was more pronounced at lower herbicide concentration.
The Effects of Shading on the Growth and Photosynthetic Capacity of Itchgrass (Rottboellia exaltata)
Authors: Patterson David T.
Published: May 2019

The effects of shade on the growth and photosynthetic capacity of the exotic noxious weed itchgrass (Rottboellia exaltataL. f.) were determined under controlled environment conditions. The plants were grown at day/night temperatures of 29/23 C under 100, 60, 25, and 2% sunlight in a climate-controlled greenhouse. Mathematical growth analysis techniques were used to evaluate the effects of shading on dry matter production and leaf area production. Infrared gas analysis and diffusion porometry techniques were used to evaluate the effects of shading on photosynthesis and stomatal resistance. Shading markedly reduced dry matter production. At 40 days after planting, plants grown in 2, 25, and 60% sunlight had 0.3, 16, and 55%, respectively, of the dry weight of the plants grown at 100% sunlight. Leaf area production was less severely retarded by shading; the plants grown at 2, 25, and 60% sunlight had, respectively, 1.7, 42, and 99% of the leaf area of the plants grown at 100% sunlight. Ambient photosynthetic rates of recently expanded, single, fully exposed leaves were 22.5, 51.6, and 65.5 mg CO2dm-2h-1in the 25, 60, and 100% sunlight treatments, respectively. Photosynthetic rates at saturating irradiance did not differ significantly in plants grown at 25, 60, or 100% sunlight and ranged from 76.4 to 78.0 mg CO2dm-2h-1. Stomatal resistances, ranging from 6.0 to 7.5 s cm-1, also did not differ significantly among these plants. In terms of dry matter production, itchgrass is a shade-intolerant plant. However, even when grown in shade, itchgrass maintains the capacity for high photosynthetic rates and high growth rates when subsequently exposed to high irradiance. These characteristics help explain its competitiveness with crop species.
Influence of Planting Date on the Growth of Johnsongrass (Sorghum halepense) from Seed
Authors: Keeley P. E. , Thullen R. J.
Published: May 2019

Seed of johnsongrass [Sorghum halepense(L.) Pers.] were planted during 1976 and 1977 at monthly intervals from March through October to study the growth and reproductive habits of this weed at Shafter, California. Plants were grown for 12 weeks and harvested at 3-week intervals. Emergence and development of plants increased with temperature. April through August plantings yielded 10-to 20-fold as much total fresh weight as March and September plantings. After planting, rhizome production normally began in 3 to 6 weeks and seed production in 6 to 9 weeks. From the April through August plantings, rhizomes accounted for averages of 13, 25, and 40% of the total fresh weight of plants 6, 9, and 12 weeks after planting, respectively. This compared, respectively, with 16, 9, and 6% for roots and 70, 66, and 54% for shoots. Seedlings emerging in March produced rhizomes in early June and viable seed in late June. Seedlings emerging as late as September produced rhizomes and some viable seed before killing frosts in November.
Electronic Moisture Sensor for Maintaining Herbicide Solution on a Roller Applicator
Authors: Schepers J. S. , Burnside O. C.
Published: May 2019

Other research has shown that a roller applicator can selectively control weeds that protrude above the crop, conserve over 80% of the herbicide, eliminate spray drift and splash, and obviate recirculation of the spray solution. The carpet on the roller applicator must be moist enough to transfer ample herbicide to the weeds it contacts but dry enough to prevent dripping of herbicide solution from the carpet. An electronic moisture sensor and solenoid valve system was designed to permit operation of the roller applicator through various weed densities while automatically maintaining a proper level of herbicide solution in the carpet of the roller.
Soybean (Glycine max)Growth as Affected by Weed Removal, Cultivar, and Row Spacing
Authors: Burnside O. C.
Published: May 2019

The influence of weed removal, cultivar, and row spacing on soybean [Glycine max(L.) Merr.] yields was determined for 3 yr at the western edge of the soybean production area in the Great Plains in order to establish the critical weed-control periods. Early weed removal aided soybean stand establishment, and there was an inverse relationship between soybean stand and production of weed top-growth. Soybean seed weight and numbers per plant both increased as weed growth decreased. The soybean variety ‘Amsoy 71’ was more competitive than ‘Beeson’ to both early and late emerging weeds. Soybeans weeded at 2 through 4 weeks after planting did not show significantly reduced soybean yields from later emerging weeds. Thus, weed control the first month after planting is the most critical in obtaining high soybean yields.
Distribution, Competition, and Phenology of Hemp Dogbane (Apocynum cannabinum) in Nebraska
Authors: Schultz M. E. , Burnside O. C.
Published: May 2019

All land uses in eastern and southeastern Nebraska were infested to some extent with hemp dogbane (Apocynum cannabinumL.). The highest infestations were observed in oats (Avena sativaL.) and soybeans [Glycine max(L.) Merr.] and the lowest infestations were in alfalfa (Medicago sativaL.), pastures, and winter wheat (Triticum aestivumL.). Yield reductions from hemp dogbane infestations ranged from 0 to 10% in corn (Zea maysL.), 28 to 41% in soybeans, and 37 to 45% in sorghum [Sorghum bicolor(L.) Moench]. Emergence of hemp dogbane from crown roots occurred when the soil temperature was 17 to 19 C, during April in 1977 and 1978. Plants attained the bud stage within 4 to 7 weeks after emergence. Early flower, full bloom, and pod initiation occurred subsequently at about 1 week intervals. Seeds produced were first viable 10 weeks after full bloom. Root activity or regenerative capacity as measured by length and number of new shoots and roots produced at monthly intervals in the germinator showed a cyclic pattern. The highest activity occurred in the spring and late fall and lowest activity in summer and early fall. Protein levels in the roots ranged from 7 to 9% in the fall and spring to 4 to 5% during the summer. Percentage total nonstructural carbohydrates (TNC) ranged from 20 to 31% in lateral roots and 32 to 53% in crown roots, but there was not a consistent cyclic pattern of percentage TNC during the growing season.
Environmental and Edaphic Influences on the Selectivity of Alachlor on Snap Beans (Phaseolus vulgaris)
Authors: Putnam A. R. , Rice Robert P.
Published: May 2019

The influence of several environmental and edaphic factors on alachlor [2-chloro-2′,6′-diethyl-N-(methoxymethyl)acetanilide] selectivity in snap bean (Phaseolus vulgarisL.) was examined. Crop safety was consistently improved when alachlor was applied preplant incorporated as compared to surface preemergence treatment. Under field conditions, maximum injury occurred either when temperatures during germination were cool and rainfall was minimal, or when temperatures approached or exceeded 27 C and the soil was saturated. In the growth chamber, more damage occurred under low temperature regimes, although volatilization of alachlor from moist soil also produced injury under higher temperatures. Injury was less severe in soils high in organic matter content. Alachlor injury decreased after 5 cm of simulated rainfall were applied on a loamy sand.
Herbaceous Weed Control with Hexazinone in Loblolly Pine (Pinus taeda) Plantations
Authors: Fitzgerald C. H. , Fortson J. C.
Published: May 2019

Hexazinone [3-cyclohexyl-6-(dimethylamino)-1-methyl-1,3,5-triazine-2,4 (1H, 3H)-dione] effectively controlled herbaceous weeds in a loblolly pine (Pinus taeda L.) plantation in 1975. Pine seedling height increased as a result of weed control following 1 to 3 kg/ha applications but phytotoxic symptoms were evident. A 1976 field study indicated activated charcoal root coatings may reduce phytotoxic action. Hexazinone at 3 and 4 kg/ha applied to either the foliage or the soil was toxic to potted pine seedlings in 1976. The addition of surfactant to hexazinone treatments at 2, 3, and 4 kg/ha increased pine phytotoxicity to unacceptable levels. When hexazinone was applied to soil at 2, 3, and 4 kg/ha, activated charcoal root coatings reduced pine mortality to acceptable levels on Norfolk sandy loam. Charcoal was less effective on Madison clay loam. Pine tolerance on both soils was acceptable at 2 kg/ha.
Asulam Controls Western Bracken (Pteridium aquilinum) on Forest Land in Western Oregon
Authors: Stewart R. E. , Cooley A. W. , Guardigli A.
Published: May 2019

Aerial sprays of asulam (methyl sulfanilylcarbamate) applied at 3.4 or 6.7 kg/ha to forest plantations in western Oregon effectively controlled western bracken [Pteridium aquilinum (L.) Kuhn var. pubescens Underw.] without damaging Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco] seedlings. Asulam also did not damage noble fir (Abies procera Rehd.) seedlings if applied without a surfactant. The half-life of asulam in forest soils ranged from less than 7 to 18 days and vertical movement in the soil profile was minimal. No herbicide residues were found in runoff water from treated areas up to 208 days after application.
Tanoak (Lithocarpus densiflorus) Leaf Surface Characteristics and Absorption of Triclopyr
Authors: King M. G. , Radosevich S. R.
Published: May 2019

Absorption of triclopyr {[(3,5,6-trichloro-2-pyridinyl)oxy] acetic acid} by tanoak [Lithocarpus densiflorus(Hook. & Am.) Rehd.] leaves was investigated. Greater amounts of14C-triclopyr were absorbed by immature leaves than mature leaves and by abaxial than adaxial surfaces. Both surfaces of immature and mature tanoak leaves were characterized. Stomata were present only on the abaxial surface and were more numerous on immature leaves than mature leaves. Immature leaves had less epicuticular wax and thinner, more permeable cuticular membranes than mature leaves. Stellate trichome densities were greater on abaxial surfaces than adaxial surfaces and on immature than mature leaves. Absorption of14C-triclopyr was influenced by each of the leaf surface features studied.
Evaluation ofAlternaria macrosporaas a Potential Biocontrol Agent for Spurred Anoda (Anoda cristata): Host Range Studies
Authors: Walker H. L. , Sciumbato G. L.
Published: May 2019

The host range of an isolate of the fungal pathogenAlternaria macrosporaZimmerman from infected spurred anoda [Anoda cristata(L.) Schlecht.] leaves was studied in the greenhouse and growth chamber. The fungus was inoculated to representative plants in the Malvaceae, Solanaceae, Leguminosae, and Gramineae families. Evidence of infection was limited to plants in the Malvaceae, with spurred anoda being the most susceptible species tested. Only negligible damage was incited on cotton (Gossypium hirsutumL. ‘Stoneville 213′) and long staple cotton (G. barbadenseL. ‘Pima S–5′), hollyhock [Althaea rosea(L.) Cav.], okra (Hibiscus esculentusL. ‘Clemson spineless’), prickly sida (Sida spinosaL.), velvetleaf (Abutilon theophrastiMedic.), and Venice mallow (Hibiscus trionumL.). Disease symptoms induced in cotton by the spurred anoda isolate ofA. macrosporawere much less severe than those reported for other isolates of the fungus. Therefore, the spurred anoda isolate may be a specialized form of the fungus.
American Germander (Teucrium canadense) Control in Corn (Zea mays)
Authors: Wyse D. L. , Strand O. E.
Published: May 2019

Experiments were conducted to develop systems for control of American germander [Teucrium canadenseL. var.virginicum(L.) Eat.] in corn (Zea maysL. ‘Trojan TXS 105A’). Soil-incorporated, preemergence, and postemergence herbicide treatments were evaluated in greenhouse studies. Soil incorporated applications of EPTC (S-ethyl dipropylthiocarbamate) + R-25788 (N,N-diallyl-2,2-dichloroacetamide), atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine] and alachlor [2-chloro-2′,6′-diethyl-N-(methoxymethyl)acetanilide] effectively reduced its growth. Preemergence applications of alachlor and atrazine did not control American germander. Postemergence applications of the dimethylamine salt of 2,4-D [(2,4-dichlorophenoxy)acetic acid] the butoxyethanol ester of 2,4-D and dicamba (3,6-dichoro-o-anisic acid) gave 20 to 41% control. Atrazine + crop oil gave 76 to 84% control. Soil-incorporated treatments of atrazine or EPTC + R-25788 controlled American germander better than alchlor when the rhizomes were planted at depths of 2.5 and 10 cm in greenhouse studies. In field trials American germander was a severe competitor in corn, especially when soil moisture was limited, and had the capability of substantially reducing corn yields when not controlled. EPTC + R-25788 and atrazine applied alone or in combinations as preplant incorporated treatments increased yield significantly and controlled 85 to 99% of the American germander 72 weeks after planting. Atrazine + oil was the only effective postemergence treatment.
Reactions ofEuglena gracilisto Fluometuron, MSMA, Metribuzin, and Glyphosate
Authors: Richardson J. T. , Frans R. E. , Talbert R. E.
Published: May 2019

Investigations were conducted onEuglena gracilisKlebs strain Z to determine the effects of fluometuron [1,2-dimethyl-3-(α,α,α-trifluoro-m-tolyl)urea], MSMA (monosodium methanearsonate), glyphosate [N-(phosphonomethyl)glycine], and metribuzin [4-amino-6-tert-butyl-3-(methylthio)-as-triazin-5(4H)-one] on cell number, chlorophyll content, and photosynthesis. Euglena cell number was reduced by 65% or more after 48 h with fluometuron levels above 4 X 10-5M. MSMA at 6 X 10-4M reduced cell number 42% after 144 h exposure. Chlorophyll content was reduced 33 to 80% by metribuzin levels of 2 X 10-6M or greater, and fluometuron inhibited chlorophyll content by 30% or more from 4 X 10-6M or greater concentrations. Chlorophyll was reduced 21 to 69% by treatment with glyphosate at 3 X 10-3M, but MSMA appeared to have little effect on chlorophyll except at the high level of 6 X 10-4M at 48 h. Photosynthesis was reduced 50% or more with metribuzin levels above 9 X 10-7M and with fluometuron above 9 X 10-5M. MSMA reduced photosynthesis by 20% at the 6 X 10-3M level, and glyphosate slightly reduced photosynthesis at levels below 1.2 X 10-4M but slightly stimulated it above that level. Chronic effects (Euglena exposed to herbicides 96 h prior to measurement) on photosynthesis indicated a more pronounced reduction from fluometuron than from short-term exposure, little change with glyphosate, but less reduction with metribuzin than from short-term exposure. Metribuzin caused increased respiration rates of 100 to 200% after 100 min of exposure. Respiration was stimulated 20% by glyphosate and relatively unaffected by the other compounds. Removal of Euglena from metribuzin- and fluometuron-treated media to non-treated media resulted in increased levels of chlorophyll to near that of the control. These results suggest that use of these herbicides is not detrimental to non-target algae if the exposure is not intensive.
Influence of Soil Moisture, Temperature, and Compaction on the Germination and Emergence of Downy Brome (Bromus tectorum)
Authors: Thill D. C. , Schirman R. D. , Appleby A. P.
Published: May 2019

The influence of soil moisture stress, temperature, and bulk density on the germination and seedling emergence of downy brome (Bromus tectorumL.) was investigated in the laboratory. Reductions in soil matric potential from -2 to -16 bars markedly reduced the percentage and rate of emergence. Seedling emergence was better at constant than at alternating temperatures. At high matric potentials, the rate of emergence was accelerated by warmer soil temperature (20 C), while at very low matric potentials, the percentage and rate of seedling emergence were least restricted at cooler temperatures (10 and 15 C). Soil matric potential did not influence the percentage or rate of emergence of seedlings grown from seed lots harvested during climatologically diverse years. Seedling emergence but not germination was inhibited by increased levels of soil compaction. Soil compaction times moisture interaction were not observed, as measured by final seedling emergence.
Effects of Simulated Field Temperatures and Chilling on Itchgrass (Rottboellia exaltata), Corn (Zea mays), and Soybean (Glycine max)
Authors: Patterson D. T. , Flint E. P.
Published: May 2019

Mathematical growth analysis techniques were used to study the effects of simulated field temperatures and chilling events on the growth of the exotic noxious weed itchgrass (Rottboellia exaltataL. f.) and adapted varieties of corn (Zea maysL. ‘DeKalb XL43’ and ‘DeKalb XL395′), and soybean [Glycine max(L.) Merr. ‘Corsoy’, ‘Williams', and ‘Tracy’] in climate-controlled greenhouses and growth chambers. Itchgrass grew vigorously and produced seed in temperature regimes simulating the warmest 4 months of the growing season in the Gulf Coast states (30/25 C, day/night), the central Midwest (27/21 C), and the northern Midwest (23/18 C). At 30/25 C day/night, itchgrass produced 707 g of dry matter and 1907 seed per plant after 119 days. Itchgrass produced 621 g dry matter and 1429 seed at 27/21 C and 499 g dry matter and 1160 seed at 23/18 C. Itchgrass and adapted varieties of corn and/or soybeans were grown in four additional temperature regimes simulating the first 5 weeks of the growing seasons for corn and soybean at Madison, Wisconsin (19/11 C day/night); for soybean at Carbondale, Illinois (24/20 C); for corn at Waycross, Georgia (20/14 C); and for soybean at Baton Rouge, Louisiana (27/23 C). After 24 days of growth, half the plants in each regime were exposed to 3 days of chilling (11/4 C for Madison, 17/10 C for Carbondale, 15/6 C for Waycross, and 24/18 C for Baton Rouge) and returned to the original growth regimes for recovery. The chilling treatments reduced dry matter production, net assimilation rate, and leaf area duration more in itchgrass than in corn or soybean. After recovery, the previously chilled itchgrass plants had greater reductions in height, leaf area, and dry weight, compared to unchilled controls, than did corn or soybean. Weed/crop ratios in height, leaf area, and dry weight for itchgrass/corn were significantly reduced by chilling. In the two cooler regimes, weed/crop ratios in leaf area and dry weight for itchgrass/soybean were significantly reduced by chilling. Because of its sensitivity to cool temperatures, itchgrass, is unlikely to be an important early-season competitor with corn or with soybean outside the South.
Comparisons of Dicamba, Picloram, and 2,4-D for Musk Thistle (Carduus nutans) Control
Authors: Roeth F. W.
Published: May 2019

Fall applications of 0.14 kg/ha of picloram (4-amino-3,5,6-trichloropicolinic acid) to musk thistle (Carduus nutansL.) rosettes controlled musk thistle stems better and more consistently than fall applications of 2.2 kg/ha of 2,4-D amine [(2,4-dichlorophenoxy)acetic acid], 0.6 kg/ha of dicamba (3,6-dichloro-o-anisic acid), or a mixture of 0.3 kg/ha dicamba + 1.1 kg/ha of 2,4-D. Dry conditions in 1975 and cool conditions in November, 1976, hampered control with all herbicides except picloram. In spring applications when growing conditions were favorable, herbicide differences were usually not significant. For all herbicides, treatment of bolted stems did not control musk thistle satisfactorily. Picloram was superior for reducing stems 12 to 18 months after application in 2 of 3 yr. Residual control resulted principally because the herbicide killed many seedlings and first-year rosettes at the time of application.
Persistence of Annual Applications of Herbicides in Winter-planted Safflower (Carthamus tinctorius)
Authors: Hamilton K. C.
Published: May 2019

Diuron [3-(3,4-dichlorophenyl)-1,1-dimethylurea], prometryn [2,4-bis(isopropylamino)-6-(methylthio)-s-triazine], and trifluralin (α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine) were applied pre-plant in safflower (Carthamus tinctoriusL. ‘AC-1′) for 6 yr at two locations. Diuron and prometryn reduced crop stands in 2 of 6 yr on the sandier soil at Mesa. Growth of sorghum [Sorghum bicolor(L.) Moench ‘Amak R-10′] in the greenhouse in soil collected 10 months after each herbicide application was reduced by 1.7 kg/ha of trifluralin in 3 of 6 yr in the Yuma silty clay loam and by both rates of trifluralin in 1 of 6 yr in the sandier soil at Mesa. Growth of barley (Hordeum vulgareL. ‘Arivat’) was not reduced in soil treated with any herbicide at either location. Herbicides did not accumulate in winter-planted safflower.
Persistence of Dinitroaniline Herbicides in Soil
Authors: Jacques G. L. , Harvey R. G.
Published: May 2019

An oat (Avena sativaL. ‘Dal’) primary root bioassay procedure was used to study the persistence of eight dinitroaniline herbicides in soil. Sensitivity of the bioassay to the herbicides depended on the length of time roots were exposed to the herbicide treatments. Root inhibition increased with time of exposure. Herbicide persistence was studied under growth chamber, greenhouse, and field conditions. The herbicides remained biologically active the longest under dry and cool soil conditions. At 5 C, little change in herbicide activity was observed over an 8-month period. Under greenhouse conditions, the herbicides in wet soil dissipated rapidly, as compared with those in dry soil. Soil samples taken from depths of 0 to 7.5 cm and from 7.5 to 15 cm in the field showed that the herbicides were retained primarily in the surface 7.5 cm. Small amounts were found from 7.5 to 15 cm only shortly after the herbicides were applied. Dinitramine (N4,N4-diethyl-α,α,α-trifluoro-3,5-dinitrotoluene-2,4-diamine) was the only herbicide tested of which soil residues from spring field applications were not detected the following fall.
The Effect of Surfactant and Environment on the Toxicity of Metriflufen to Soybeans (Glycine max) and Johnsongrass (Sorghum halepense)
Authors: McWhorter C. G.
Published: May 2019

Metriflufen {2-[4-(4-trifluoromethylphenoxy)phenoxy] propanoic acid} was applied as the methyl ester at 0.28 and 0.56 kg/ha over-the-top to johnsongrass [Sorghum halepense(L.) Pers.] growing from rhizomes and to soybeans [Glycine max(L.) Merr. ‘Lee 68′]. After herbicide treatment, plants were grown in the growth chamber for 14 days at 16, 24, or 32 C with relative humidity (RH) at 40 or 100% at each air temperature. Johnsongrass was not controlled at 16 C regardless of metriflufen rate, RH, or the addition of nonoxynol [α-(p-nonylphenyl)-ω-hydroxypoly (oxyethylene)] (with 9.5 moles of polyoxyethylene) surfactant at 0.25 (g/100 ml) to spray solutions. Johnsongrass control at 24 C varied from 5 to 98%, with significantly better control at 100% than at 40% RH. The presence of surfactant increased johnsongrass control at 24 C and 40% RH but not at 24 C and 100% RH. Johnsongrass control at 32 C varied from 48 to 98%, and it was not increased by the presence of the surfactant, regardless of metriflufen rate or RH level. At 16 C metriflufen was more injurious to soybeans than to johnsongrass, but at 24 and 32 C johnsongrass control was significantly greater than soybean injury. The presence of surfactant in spray solutions generally did not increase soybean injury, regardless of temperature or RH level. These results suggest that metriflufen is most selective in controlling johnsongrass in soybeans at 24 C, especially under high RH.
Effects of Wetting Agent, Stage of Growth, and Species on the Selectivity of Diclofop
Authors: Schreiber M. M. , Warren G. F. , Orwick P. L.
Published: May 2019

A 2-yr field study was conducted to determine whether the addition of wetting agents to diclofop {2-[4-(2,4-dichlorophenoxy) phenoxy] propanoic acid} could enhance its postemergence control of grass weeds without altering its crop tolerance. In each year, 12 species were treated at two stages of growth with at least two concentrations of diclofop. Regardless of the treatment, selectivity was not altered on wheat (Triticum aestivumL.), soybeans [Glycine max(L.) Merr.], cucumber (Cucumis sativusL.), or sorghum [Sorghum bicolor(L.) Moench]. The addition of wetting agent to diclofop was of no value on highly susceptible grass weed species such as barnyardgrass [Echinochloa crus-galli(L.) Beauv.] or on the more resistant species such as large crabgrass [Digitaria sanguinalis(L.) Scop.]. Only on an intermediately susceptible species such as giant foxtail (Setaria faberiHerrm.) could any significant differences in control be attributed to a wetting agent. The stage of growth of the grass weed species at time of treatment and the diclofop concentration were more important than the presence of a nonionic wetting agent.
Glyphosate Does Not Inhibit Photosynthetic Electron Transport and Phosphorylation in Pea (Pisum sativum) Chloroplasts
Authors: Richard E. P. , Goss J. R. , Arntzen C. J.
Published: May 2019

The activity of glyphosate [N-(phosphonomethyl)glycine], formulated as the isopropylamine salt, on in vitro photosynthesis was investigated. When pH 4.7 glyphosate solutions were titrated to a pH equal to that of the reaction media (pH 7.8), glyphosate additions had no effect on whole chain electron transport between coupled photosystem II (PS II) and photosystem I (PS I) in stroma-free chloroplast thylakoids from peas (Pisum sativumL. ‘Morse's Progress No. 9′). Inhibition did not occur even after a 2-h dark incubation of lamellae in a 5-mM solution of glyphosate. Fluorescence studies failed to detect an effect of glyphosate on PS-II mediated electron transport processes or upon light harvesting properties of PS II even after a 2-h glyphosate/chloroplast preincubation. Glyphosate had no effect on cyclic and noncyclic photophosphorylation even after a 100-min dark incubation of chloroplast membranes in a 5-mM solution of glyphosate. Based on these assays it is concluded that glyphosate has no direct effect on the photochemical reactions of photosynthesis when the pH of the active compound is adjusted to that of the reaction mixture prior to addition to a chloroplast suspension.
Injection Methodology for Evaluating Plant Growth Retardants
Authors: Sterrett J. P.
Published: May 2019

This study describes separate methods for injecting growth retardants into herbaceous and woody plants. Bean plants (Phaseolus vulgarisL. ‘Black Valentine’) were treated by injecting growth retardant solutions into the hypocotyl cavity with a syringe. The chemical was subsequently absorbed into the vascular system. Woody California privet (Ligustrum ovalifoliumHassk.) was injected by forcing chemical solution into the vascular system via a predrilled hole. Results with NAA (1-napthalene-acetic acid) and MH (1,2-dihydro-3,6-pyridazinedione) validated the methods by inhibiting growth, respectively. New growth regulators, mefluidide {N-[2,4-dimethyl-5-[[(trifluoromethyl) sulfonyl]amino]phenyl]acetamide} and dikegulac (sodium salt of 2,3: 4,6-bis-O-(1-methylethylidene-α-L-xylo-2-hexulofuranosonic acid], inhibited the growth of bean with concentrations of 60 mg/L and 480 mg/L, respectively. Sprout growth of privet was inhibited by 30 mg/L of mefluidide and by 188 mg/L dikegulac.
Fall and Spring Applications of Trifluralin and Metribuzin in Fababeans (Vicia faba)
Authors: Betts M. F. , Morrison I. N.
Published: May 2019

Field experiments were conducted to study the effect of fall and spring pre-plant incorporated applications of trifluralin (α,α,α-tri-fluoro-2,6-dinitro-N,N-dipropyl-p-toluidine) and metribuzin [4-amino-6-tert-butyl-3-(methylthio)-as-triazine-5(4H)-one] alone and in combinations on crop tolerance, seed yield, and weed control in fababeans (Vicia fabaL. ‘Diana’). Trifluralin applied either in the fall or the spring resulted in acceptable control of green foxtail [Setaria viridis(L.) Beauv.] and wild oat (Avena fatuaL.) while metribuzin resulted in excellent control of wild mustard [Brassica kaber(DC.) L.C. Wheeler var.pinnatifida(Stokes) L.C. Wheeler]. In 2 out of 3 yr, a tank-mixture of trifluralin plus metribuzin applied in the fall at 1.4 and 0.4 kg/ha, respectively, resulted in significantly larger seed yield than the same combination applied at 1.1 and 0.3 kg/ha in the spring. Although the fall treatments generally resulted in higher seed yields, there was no consistent difference in weed densities between fall and spring applications. In both field and growth room studies, trifluralin reduced the injury to fababeans from metribuzin. A postemergence application of metribuzin in the spring at 0.3 kg/ha following a fall-application of trifluralin resulted in good wild mustard control but caused considerable crop damage. Dinoseb (2-sec-butyl-4,6-dinitrophenol) and bentazon [3-isopropyl-1H-2,1,3-benzothiadiazin-4(3H)-one 2,2dioxide] controlled wild mustard effectively with no injury to the crop.
Chemical Mixtures for Control of Winged Elm
Authors: Stritzke J. F.
Published: May 2019

Various growth regulators, carrier systems, and ammonium thiocyanate (NH4SCN) additions in combination with herbicide mixtures were evaluated for their foliar phytotoxicity to winged elm (Ulmus alataMichx.). Silvex [2-(2,4,5-trichlorophenoxy)propionic acid] and 2,4,5-T [(2,4,5-trichlorophenoxy)acetic acid] were more effective than the dichlorophenoxy herbicides. Additions of NH4SCN to the ester of 2,4,5-T consistently increased control. Picloram (4-amino-3,5,6-trichloropicolinic acid) was the most effective herbicide for killing the trees, and in mixtures with the phenoxy herbicides consistently produced good tree kill. No increase in 2,4,5-T activity could be attributed to additions of growth regulators, concentrated nutrient solutions, or to type of carrier system used.
Inhibition of Nitrite Reduction with Photosynthetic Inhibitors
Authors: Klepper Lowell A.
Published: May 2019

Using a modified in vivo nitrate reductase assay, all photosynthetic inhibitors tested were shown to effectively block light-dependent nitrite reduction in green leaf tissue. Nitrate reduction continued so that nitrite accumulated. Nitrite, vacuum infiltrated into leaf tissue, disappeared linearly with time when incubated in the light. Nitrite, vacuum infiltrated with a photosynthetic inhibitor, did not disappear but accumulated to even higher levels. The degree of inhibition of nitrite reduction was a function of herbicide concentration and time of incubation.
Competition Between Purple Nutsedge and Vegetables
Authors: William R. D. , Warren G. F.
Published: May 2019

Competition studies were conducted in Brazil during 1972 and 1973 between high populations (160 plants/0.1 m2at 5 to 7 weeks after planting) of purple nutsedge (Cyperus rotundusL.) and the following vegetable crops: garlic (Allium sativumL. ‘Mineiro’), okra (Hibiscus esculentusL. ‘UFV 1152’), carrot (Daucus carotaL. ‘Nantes’ and ‘Kuroda’), bush-type green bean (Phaseolus vulgarisL. ‘Topcrop’), cucumber (Cucumis sativusL. ‘Aldai’), transplanted cabbage (Brassica oleraceaL. var. capitata ‘Louco’) and transplanted tomato (Lycopersicon esculentumMill. ‘Santa Rita’). Purple nutsedge grew all year with irrigation, although growth was greater during the warm, wet season (October to March). Crop losses due to purple nutsedge competition during the entire cropping season were as follows: garlic 89%; okra 62%; two carrot cultivars, ‘Kuroda’ and ‘Nantes’ 39% and 50%, respectively; green bean 41%; cucumber 43%; cabbage 35%; and tomato 53%. Critical periods of purple nutsedge competition occurred between 3 and 13 weeks for garlic; 3 and 7 weeks for okra, cucumber and the carrot cultivar ‘Nantes’; 3 and 5 weeks for tomato and the carrot cultivar ‘Kuroda’; and at approximately 4 weeks for cabbage and green bean. Purple nutsedge competed for light in the slow-growing, non-competitive crops and for nutrients in all crops. Competition for water was reduced because the vegetables were irrigated regularly. The rate of leaf area development for a competitive crop, green bean, was similar to the rate for purple nutsedge, whereas the rate was much lower for the non-competitive okra.
Temperature Influences on Uptake, Translocation, and Metabolism of Alachlor in Snap Beans (Phaseolus vulgaris)
Authors: Rice Robert P. , Putnam A. R.
Published: May 2019

The uptake, translocation, and metabolism of14C-alachlor [2-chloro-2′,6′-diethyl-N-(methoxymethyl)acetanilide] by germinating and emerged snap bean (Phaseolus vulgarisL.) seedlings were monitored under 16-h daylength (21 klux) comparing 16 C night/21 C Day and 27 C night/32 C day temperature regimes. Total uptake of14C-alachlor by germinating snap beans was greater under the higher temperature, however, the compound was localized primarily in the roots where it was rapidly metabolized. At the lower temperature, the label was located in approximately equal amounts in all plant parts except cotyledons and significantly less of the alachlor was metabolized. Root uptake of14C-alachlor and translocation of labeled compounds to the shoots were significantly greater under the higher temperatures. Approximately 60% of14C-alachlor was shown to volatilize from a watchglass after 48 h at 27 C. After volatilization, uptake of14C-alachlor occurred in adjacent snap bean plants in a closed system.
Canopy and Chemistry of Pasture Weeds
Authors: Carlisle R. J. , Watson V. H. , Cole A. W.
Published: May 2019

Morphological and chemical characteristics of 11 warm season pasture weed species were defined. Goldenrod (Solidago altissima L.) was significantly taller and common ragweed (Ambrosia artemisiifolia L.) had the largest canopy diameter of the 11 species studied. Species ranged from 14 to 134 cm in height with canopy diameters of 25 to 70 cm. No direct correlation was found between individual leaf size and total leaf area. Macro- and micromineral content varied widely among species but all values obtained were considered high enough to meet the requirements of ruminant animals. Redroot pigweed (Amaranthus retroflexus L.) and horsenettle (Solanum carolinense L.) contained potentially toxic levels of nitrate. Five of the 11 species contained sufficient crude protein for ruminants and six of the 11 species were more than 50% digestible. Digestible energy values averaged 1.9 Mcal/kg for the 11 weeds evaluated.
Differential Atrazine Tolerance Within Cucumber (Cucumis sativus)
Authors: Werner G. M. , Putnam A. R.
Published: May 2019

The cucumber (Cucumis sativusL.) accession PI 390244 tolerated up to 0.56 kg/ha atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine] whereas most cultivars and accessions were killed by 0.14 kg/ha. The possible mechanisms for tolerance were investigated by comparing growth rates, effects on photosystem II in isolated chloroplasts, and differences in uptake and translocation of14C-atrazine between tolerant PI 390244 and the susceptible cultivar Marketmore 70. PI 390244 had significantly more leaf area than Marketmore 70, but less root biomass. Isolated chloroplast preparations from both cultivars were equally susceptible to the herbicide. Although PI 390244 absorbed more total14C-atrazine, it translocated less radioactivity from the roots. While the concentration of14C found in the PI 390244 roots was 10 to 30% greater than in Marketmore 70, the amount of radioactivity in the cotyledons, and first and second true leaves of Marketmore 70 were 53, 34, and 55% higher, respectively, after 48 h.
Effect of Lanolin or Lanolin + Starch Rings on Absorption and Translocation of 2,4-D or Glyphosate in Hemp Dogbane (Apocynum cannabinum)
Authors: Schultz M. E. , Burnside O. C.
Published: May 2019

Lanolin or lanolin + corn (Zea maysL.) starch rings are often used as barriers on leaves to prevent runoff of foliarly applied14C-herbicide treatments. A preliminary experiment showed that 64 and 90% of the applied 2,4-D [(2,4-dichlorophenoxy)acetic acid] and 57 and 87% of the applied glyphosate [N-(phosphonomethyl)glycine] was adsorbed to or absorbed into a lanolin and lanolin + starch ring, respectively, during 6 days on a glass slide. Absorption and translocation of 2,4-D in hemp dogbane (Apocynum cannabinumL.) was decreased from 26% down to 16 or 17% of the total applied when a lanolin or lanolin + starch ring was used. Glyphosate absorption and translocation increased with the lanolin ring but not with the lanolin + starch ring. Distribution of the translocated 2,4-D and glyphosate was also altered by use of the ring barriers. Results indicate that one should avoid use of the lanolin ring in14C-herbicide absorption studies to simulate field conditions.
Herbicides Applied Sequentially for Economical Control of Annual Weeds in Sugarbeets (Beta vulgaris)
Authors: Schweizer E. E.
Published: May 2019

Twelve sequential herbicide treatments were compared to cycloate (S-ethylN-ethylthiocyclohexanecarbamate), a standard treatment, for control of annual weeds in sugarbeets (Beta vulgarisL.) in three field experiments conducted from 1971 through 1977. At harvest, seven sequential treatments had less than 10 annual broadleaf weeds per 30 m of row, whereas there were 40 broadleaf weeds per 30 m of row for the cycloate treatment. Four of these sequential treatments had significantly higher root yields and net returns than the cycloate treatment. Dependent on the sequential treatment and year, tonnage was increased 7.3 to 20.3 t/ha, and net returns $150 to $515/ha above those with cycloate. The most effective sequential treatment for control of weeds was a preplanting mixture of 2.2 kg/ha of ethofumesate [(±)-2-ethoxy-2,3-dihydro-3,3-dimethyl-5-benzofuranyl methanesulfonate] plus 1.7 kg/ha of diclofop {2-[4-(2,4-dichlorophenoxy)phenoxy] propanoic acid} followed by a postemergence mixture of 0,6 kg/ha each of desmedipham [ethylm-hydroxycarbanilate carbanilate (ester)] plus phenmedipham (methylm-hydroxycarbanilatem-methylcarbanilate). This sequential herbicide treatment increased root yields by an average of 20.3 t/ha and net returns by $515/ha above those with cycloate.
Yellow Foxtail (Setaria lutescens) Biotype Studies: Dormancy and Germination
Authors: Norris R. F. , Schoner C. A.
Published: May 2019

Seeds of five yellow foxtail [Setaria lutescens(Weigel) Hubb.] biotypes, collected from Connecticut, Iowa, Massachusetts, Pennsylvania and California, were tested for dormancy and germination characteristics. Seeds of the California biotypes, while dormant at time of dispersal, germinated readily following a 4-month after-ripening period in dry storage. California biotype seeds did not require stratification. The eastern biotypes also showed high initial dormancy. Prolonged dry storage (16 months) or stratification overcame this dormancy to varying degrees. All five biotypes germinated over the range of 15 to 35 C, but the California biotype exhibited much higher germination at 35 C than any eastern biotype. The California biotype germinated more rapidly, by 1 to 3 days, at any given temperature than the eastern biotypes. These differences in dormancy and germination requirements between the five biotypes are considered as evidence to support a hypothesis of genetically controlled, physiological differences between geographically separated biotypes.
Chemical Control of Dandelion (Taraxacum officinale) and Perennial Sowthistle (Sonchus arvensis) in Alfalfa (Medicago sativa) Grown for Seed
Authors: Waddington J.
Published: May 2019

Applications of 2,4-D [(2,4-dichlorophenoxy)acetic acid] at 1.1 kg/ha at the start of each growing season severely damaged established alfalfa (Medicago sativaL. ‘Beaver’) and reduced seed yield 32% over a 4-yr period. Dandelion (Taraxacum officinaleWeber) populations were reduced but perennial sowthistle (Sonchus arvensisL.) increased in frequency. Dichlobenil (2,6-dichlorobenzonitrile) applied at 2.1 kg/ha controlled both dandelion and perennial sowthistle. Alfalfa was damaged initially but rapid recovery resulted in an increase in seed yield in 2 yr out of 4. Terbacil (3-tert-butyl-5-chloro-6-methyluracil) applied at 1.1 kg/ha also controlled dandelion and perennial sowthistle. No alfalfa damage was evident and seed yields were increased 34% over a 3-yr period. Seed yield increased 30% where asulam (methyl sulfanilylcarbamate) was applied at 4.5 kg/ha, but there was no visible effect on the growth of either alfalfa or weeds. Simazine [2-chloro-4,6-bis (ethylamino)-s-triazine], propham (isopropyl carbanilate) + PCMC (p-chlorophenyl-N-methyl carbamate), pronamide [3,5-dichloro(N-1,1-dimethyl-2-propynyl)benzamide], and diuron [3-(3,4-dichlorophenyl)-1,1-dimethylurea], did not affect alfalfa seed production significantly, although simazine and diuron did reduce dandelion populations.
Environmental Influences on the Selectivity of Diphenamid in Seeded Tomato (Lycopersicon esculentum)
Authors: Rice Robert P. , Putnam Alan R.
Published: May 2019

Several environmental and edaphic factors were monitored to determine their association with tolerance of seeded tomatoes (Lycopersicon esculentumMill.) to diphenamid (N,N-dimethyl-2,2-diphenylacetamide). Injury increased with increasing soil pH and reduced temperature within 7 days of seeding in both field and growth chamber tests. The application of soluble fertilizer and diphenamid at planting acted synergistically to increase tomato injury. Prior to emergence of the tomato seedlings,14C-diphenamid uptake was slight but increased with higher temperatures, while growth was inhibited at both low and high temperatures. Uptake and metabolism of14C-diphenamid by plants in the cotyledon stage was not greatly affected by temperature or pH; however, translocation from the root to the shoot was reduced under low temperatures and high pH. These differences in translocation paralleled reported differences between tolerant and susceptible species, and may account for the increased diphenamid injury to tomatoes grown under stress conditions.
Reduced Transpiration and Increased Water Efficiency by Diuron in Corn (Zea mays)
Authors: Ahmed Shabir , Fletcher R. A.
Published: May 2019

Of several herbicides tested on both monocotyledon and dicotyledon species, diuron [3-(3,4-dichlorophenyl)-1,1-dimethylurea] was found to be the most effective in reducing transpiration in corn (Zea maysL.) plants; a reduction of 40% occurred. It was established that diuron was the active component in reducing transpiration, and not the additives in the commercial formulation (Karmex) used in this study. Foliar applications of low concentrations (0.035 to 0.56 kg/ha) of diuron effectively reduced transpiration in both cultivars (Pioneer 3780A and Pride 1108) of corn plants, at all stages of growth tested (from 3- to 10-leaf stage). This effect of diuron on reduced transpiration occurred when the supply of water or nutrients to the corn plants was either limiting or non-limiting. The reduction of transpiration of corn plants after treatment also prevented the leaves from wilting and becoming senescent. This effect was persistent over 16 days. Diuron treatment increased the water efficiency of the plants and this effect was more pronounced when water was limiting. Compared to the control, the treated plants used up to 68% less water for each gram of shoot dry weight produced. The increase in water efficiency indicates that transpiration was reduced more than photosynthesis.