bluuebunny/crossref_metadata_2025 huggingface dataset:
Adjuvant Effects on Absorption, Translocation, and Metabolism of Haloxyfop-Methyl in Corn (Zea mays)
Authors: Harrison S. Kent , Wax Loyd M.
Published: May 2019

The effects of adjuvants and relative humidity (RH) on absorption, translocation, and metabolism of the methyl ester of14C-haloxyfop {2-[4-[[3-chloro-5-(trifluoromethyl)-2-pyridinyl]oxy]phenoxy] propanoic acid} in corn (Zea maysL. ‘B73 X Mo17’ hybrid) were evaluated. Addition of 1.0% (v/v) petroleum oil concentrate (POC) to the treatment solution resulted in greater foliar absorption and translocation of14C than addition of 1.0% (v/v) soybean oil concentrate (SBOC), 0.1% (v/v) oxysorbic (20 POE) (polyoxyethylene sorbitan monolaurate) (OXY), or no adjuvant (NONE). The least amount of14C absorption occurred in the treatment containing OXY. Absorption and translocation of radioactivity were significantly greater at 70% RH than at 30% RH. Thin-layer chromatography revealed that most of the14C recovered from treated plants was in haloxyfop-methyl 5 h after treatment (HAT). The remaining14C recovered was haloxyfop and an unidentified polar metabolite. The average percentage of14C-haloxyfop in the nonabsorbed fraction was 5, 39, 7, and 7% for treatments containing NONE, OXY, POC, and SBOC, respectively. The ratio of haloxyfop-methyl to haloxyfop and the percentage of polar metabolite in the absorbed14C fraction was not different among adjuvant treatments or between levels of RH.
Dormancy and Field Burial of Cowpea (Vigna unguiculata) Seed
Authors: Murphy Tim R. , Gossett Billy J. , Toler Joe E.
Published: May 2019

Seed dormancy and soil longevity characteristics of three weedy cowpea [Vigna unguiculata(L.) Walp.] cultivars were investigated. Seed germination was maximum at 40 C; however, ‘Clay’ had greater germination than ‘Black’ or ‘Red Ripper’ cowpea at temperatures ≥ 20 C. Concentrated sulfuric acid soaks, hot (70 C)-water soaks, and piercing the seed coat promoted germination. Seed with an initial water content of 12.3% were stored at relative humidities ranging from 0 to 60% at 25 C. After 4 weeks of storage at relative humidities of 0 to 50%, seed water content varied from 4.6 to 11.4%. Germination and hard seed content was 11% or more and 89% or less, respectively, for seed with water content ranging from 6.9 to 11.4%. Except for seed with an initial water content of 6.9%, cowpea seed water content increased after 3 weeks of storage in a 70% relative humidity environment. Rehydration increased germination for seed with initial water content of 9.2% or more, but not for seed with initial water content of 8.4% or less. In mid-November 1981 and 1982, Black, Clay, Red Ripper, and sicklepod (Cassia obtusifoliaL. # CASOB) seed were buried at soil depths of 2.5, 7.5, and 15 cm for 3, 6, and 9 months. Seed survival of Black and Red Ripper was similar to that of sicklepod; however, longevity of Clay seed was less than sicklepod. Survival was greater for seed buried in 1981 than in 1982 because of low seed water content of the 1981 seedlots.
Growth and Development of Field Horsetail (Equisetum arvenseL.)
Authors: Marshall George
Published: May 2019

The growth and development of field horsetail (Equisetum arvenseL. # EQUAR) was measured outdoors using potted plants grown from one-node rhizome fragments. Shoot growth rate increased slowly after planting in March, accelerating to a maximum during July with maximas for shoot height during August and shoot number in September. Rhizome system growth rates initially followed a similar pattern to that of the shoots achieving a maximum during July. Dry matter accumulated in the rhizomes until October and declined thereafter throughout the winter. Tubers initiated during August grew in size and number until November, well beyond the period of active shoot growth and onset of senescence. The characteristics of the growth and development of field horsetail are discussed in relation to achieving weed control via cultural and herbicide treatments.
Influence of Environment and Stage of Growth on Honey Mesquite (Prosopis glandulosa) Response to Herbicides
Authors: Meyer Robert E. , Bovey Rodney W.
Published: May 2019

Honey mesquite (Prosopis glandulosaTorr. # PRCJG) was treated with four herbicides at 1.1 kg ae/ha at 14 dates from April 30 through September 23 over a 2-yr period. Overall, clopyralid (3,6-dichloro-2-pyridinecarboxylic acid) was the most effective herbicide, killing 80% or more of the honey mesquite at most dates. Picloram (4-amino-3,5,6-trichloro-2-pyridinecarboxylic acid), triclopyr {[(3,5,6-trichloro-2-pyridinyl)oxy] acetic acid}, and 2,4,5-T [(2,4,5-trichlorophenoxy)acetic acid] were less effective than clopyralid. Honey mesquite control was correlated with Julian day of year sprayed, 15 plant, 11 environmental, and 8 herbicide concentration variables. Most effective control was negatively correlated with Julian day of year sprayed and new xylem ring thickness. Control was positively correlated with total daily apparent photosynthesis, upward methylene blue dye movement in the xylem, and herbicide concentration in the xylem 3 days after spraying. The only environmental variable of 11 measured that was significantly correlated with honey mesquite control was soil water and that was only with picloram. The concentration of herbicide in the stem was highest for clopyralid, followed by picloram, and then by 2,4,5-T and triclopyr, which were about equal. Variables most useful in regression equations for predicting control with herbicides were total daily apparent photosynthesis and rate of upward movement of methylene blue dye. Variables most incorporated into regression equations relating honey mesquite control with herbicide content were herbicide concentrations in the xylem 3 or 30 days after treatment.
Texas Panicum (Panicum texanum) Control in Peanuts (Arachis hypogaea) with Paraquat
Authors: Wehtje Glenn , McGuire John A. , Walker Robert H. , Patterson Michael G.
Published: May 2019

Paraquat (1,1′-dimethyl-4,4′-bipyridinium ion) was applied to peanuts (Arachis hypogaeaL. ‘Florunner’) for Texas panicum (Panicum texanumBuckl. # PANTE) control at 0.07, 0.14, and 0.28 kg ai/ha under five application schedules; a single application at 0, 1, 3, or 5 weeks after ground cracking, or multiple applications at 1 + 5 weeks or 1 + 3 + 5 weeks after ground cracking. Peanuts were planted at two different times (normal and late). A herbicide application at the third week (normal planting), or the third or fifth week after ground cracking (late planting) provided acceptable Texas panicum control. Control generally increased with rate. However, increasing paraquat rates with single applications on late-planted peanuts or multiple applications to normal- and late-planted peanuts tended to reduce yield and grade. A single application of 0.07 or 0.14 kg/ha applied the third week after ground cracking consistently provided the best balance between Texas panicum control and crop safety.
Toxicity, Uptake, Translocation, and Metabolism of Norflurazon in Five Citrus Rootstocks
Authors: Achhireddy Nagi Reddy , Singh Megh
Published: May 2019

Five varieties of 3-month-old citrus rootstocks were grown for 1 month in nutrient solution containing 0, 10-3, 10-4, or 10-5M of norflurazon [4-chloro-5-(methylamino)-2-(3-(trifluoromethyl)phenyl)-3 (2H)-pyridazinone] to assess the effect of this herbicide on growth and chlorophyll levels. The uptake, translocation, and metabolism of root-applied14C-norflurazon was also examined in these rootstocks. Norflurazon treatment reduced chlorophyll level and lowered overall growth in sour orange (Citrus aurantium), Swingle (Poncirus trifoliata×C. paradisi), Milam (C. jambhiri), and Cleopatra mandarin (C. reshni) rootstocks. Herbicide treatments had little or no effect on chlorophyll levels or growth in Carrizo (C. sinensis×P. trifoliata). In Cleopatra, unlike in other rootstocks, leaf chlorosis was evident only along the midrib and major veins. Herbicide treatment reduced leaf flush (leaf production) in Swingle but not in other rootstocks. By the end of a 4-week treatment period, total absorption of14C-norflurazon was greater in Swingle than in the other rootstocks.14C-norflurazon detected in the roots (excluding taproot) of Swingle was greater than in the other rootstocks. The amount of14C-norflurazon translocation to the foliage was limited in all rootstocks. Stem and taproot also contained only a small amount of14C-norflurazon. Leaf extracts of all five rootstocks contained no parent compound, but up to 90% of recovered14C was identified as14C-norflurazon in root extracts. Differences in the uptake, translocation, and metabolism of norflurazon among citrus rootstocks were small and did not appear to explain their differential sensitivity to this herbicide.
Tolerance of Birdsfoot Trefoil (Lotus corniculatus) to 2,4-D
Authors: Davis Cynthia , Linscott Dean L.
Published: May 2019

Translocation and metabolism of14C-2,4-D [(2,4-dichlorophenoxy)acetic acid] and effects of 2,4-D on protein synthesis were compared in ‘T–68’ (2,4-D tolerant) and ‘Viking’ (susceptible) birdsfoot trefoil (Lotus corniculatusL.) in an attempt to elucidate some tolerance mechanisms. After14C-2,4-D was applied to upper trifoliate leaves, significantly less 2,4-D was found in stems, in leaves below the treated leaves, and in roots of T–68 compared to Viking. More 2,4-D was bound to alcohol-insoluble cellular constituents of T–68 leaves, stems, and roots. When alcohol-soluble components were fractionated, slightly more14C water-soluble compounds were found in T–68, indicating further inactivation by glycosylation. No amino acid-2,4-D conjugates were found. The rate of14CO2evolution from14C-2,4-D treated seedlings in T–68 was five times that in Viking. Protein synthesis appeared to be more rapid in T–68 but the relationship to 2,4-D was not clear. In part, 2,4-D resistance in T–68 may result from its ability to inactivate 2,4-D by differential binding and conjugation and by side chain breakdown as indicated by14CO2release.
Control of Broomrape (Orobanche ramosa) in Tobacco (Nicotiana tabaccum)
Authors: Lolas Petros C.
Published: May 2019

Ten herbicides were evaluated for broomrape (Orobanche ramosaL. # ORARA) control and their effect on growth, yield, and chemical composition of four tobacco (Nicotiana tabaccumL.) cultivars. Of the preplant-incorporated (PPI) herbicides, only pebulate (S-propyl butylethylcarbamothioate) at 7.2 kg ai/ha and metham (methylcarbamodithioic acid) at 66 kg ai/ha provided, although inconsistently, 30 to 50% broomrape control in oriental but not in burley tobacco. Single postemergence (POE) applications of glyphosate [N-(phosphonomethyl)glycine] at 0.2 kg ai/ha or MH (1,2-dihydro-3,6-pyridazinedione) at 0.7 kg ai/ha at 40 days after transplanting resulted in 60 to 80% broomrape control. Glyphosate or MH applications at 40 days after transplanting and again at 60 days resulted in 100% and 80 to 90% control, respectively. Very good (80 to 90%) control also occurred with pebulate (PPI) at 7.2 kg ai/ha followed by glyphosate (POE) at 0.2 kg ai/ha at 40 days after transplanting. Tobacco yield increased significantly, compared to that of untreated plots, where glyphosate or MH was used, but nicotine, total nitrogen, and reducing sugar contents were not significantly affected.
Tolerance of Tall Fescue and Kentucky Bluegrass to Chlorsulfuron Under Field Conditions
Authors: Maloy Brian M. , Christians Nick E.
Published: May 2019

Kentucky bluegrass (Poa pratensisL. ‘Parade’, ‘Adelphi’, ‘Glade’, and ‘Rugby’ # POAPR) and tall fescue (Festuca arundinaceaSchreb. ‘Kentucky 31’ # FESAR) were treated in field experiments with chlorsulfuron {2-chloro-N-[[(4-methoxy-6-methyl-1,3,5-triazin-2-yl)amino] carbonyl] benzenesulfonamide}. The objectives of the two experiments were to determine if this herbicide has the potential to be used for selective control of tall fescue in Kentucky bluegrass turf. Chlorsulfuron treatments included single rates of 0, 18, 35, 71, 141, 212, and 282 g ai/ha and split rates, applied 14 days apart, of 18 + 18, 35 + 35, 71 + 71, 141 + 141, and 212 + 212 g/ha. Clipping weights and turfgrass quality ratings were taken in both experiments. Kentucky bluegrass showed a higher tolerance to the chemical, with no decrease in turf quality at the highest single and split application rates in both experiments. However, as the chlorsulfuron rate increased, clipping weight decreased. Tall fescue showed a low tolerance to the chemical and was controlled at single rates of 141 g/ha and split rates of 141 + 141 g/ha and greater. Although the tall fescue recovered from damage at single rates of 71 g/ha and split rates of 71 + 71 g/ha, severe growth inhibition and discoloration of aboveground tissue occurred at the lower rates. Twelve months after the first chlorsulfuron was applied in each experiment, glyphosate [isopropylamine salt ofN-(phosphonomethyl)glycine] was sprayed over the plots to kill all existing plant material, and Kentucky bluegrass was seeded into the plots 2 weeks later at the rate of 0.75 kg/100 m2. There was no inhibition of bluegrass seed germination at any of the rates of chlorsulfuron.
Corn (Zea mays) Yield in Relationship to Johnsongrass (Sorghum halepense) Population
Authors: Bendixen Leo E.
Published: May 2019

Corn (Zea maysL.) grain yield was measured in a 5-yr study at two locations in central Ohio in relationship to johnsongrass [Sorghum halepense(L.) Pers. # SORHA] populations infesting the plots. Herbicide treatments were EPTC + R-25788 (S-ethyl dipropyl carbamothioate) + (N,N-diallyl-2,2-dichloroacetamide) at 6.7 kg ai/ha to corn in a monoculture and in a 3-yr rotation of winter wheat (Triticum aestivumL.), corn, and soybeans [Glycine max(L.) Merr.], with each crop being grown each year. There were large increases in johnsongrass populations in the monocultures during the course of the 5-yr study, and corn grain yield fell to zero, even though ear formation was not greatly reduced. Conversely, johnsongrass populations in the rotation were low and maize grain yields and numbers of ears remained high. The differential in grain yields between the two treatments was apparently due chiefly to lack of pollination or kernel development, since ears were formed in approximately equal numbers, except for the last year.
Chlorsulfuron Dissociation and Adsorption on Selected Adsorbents and Soils
Authors: Shea Patrick J.
Published: May 2019

The dissociation constant for chlorsulfuron {2-chloro-N-[[(4-methoxy-6-methyl-1,3,5-triazin-2-yl)amino] carbonyl] benzenesulfonamide} in aqueous solution measured by spectrophotometric titration is 3.58 ± 0.05. Chlorsulfuron was more strongly adsorbed on IRA-400-Cl strong anion exchange resin than on IR-4B-OH weak anion exchange resin or Al2O3 anionotropic adsorbent. Hydrogen bonding was probably responsible for the adsorption observed on IR-120-Na(H) cation exchange resin. No chlorsulfuron was adsorbed on Al2O3 cationotropic absorbent, technical montmorillonite, illite, or kaolinite. Adsorption did occur on organic matter derived from a histosol. Chlorsulfuron was strongly adsorbed on activated charcoal but had little affinity for α-cellulose. Adsorption onto hydrophobic polymeric XAD-2 adsorbent at pH 5.2 was not significant for chlorsulfuron concentrations below 30 μM. No significant adsorption occurred on a variety of mineral soils low in organic matter. Adsorption on a Sharpsburg silty clay loam was inversely related to solution pH. Hydrogen bonding and charge transfer bonds were postulated as the major mechanisms responsible for chlorsulfuron adsorption in soil.
Floral Induction of Downy Brome (Bromus tectorum) as Influenced by Temperature and Photoperiod
Authors: Richardson Jesse M. , Morrow Larry A. , Gealy David R.
Published: May 2019

Seedling vernalization was more effective than seed vernalization in promoting flowering of downy brome (Bromus tectorumL. # BROTE). Vernalizing imbibed downy brome caryopses at 3 C for 0 to 30 days did not induce rapid flowering when the caryopses were planted. Downy brome seedlings were exposed for 30 days to six photoperiod/temperature treatments. After subsequent transfer to long days, plants from the short-day/3 C treatment flowered within 30 days. Flowering was delayed or was absent in treatments with higher temperatures or long days. The shoot apex increased in volume during the short-day/3 C vernalization period. Two days following vernalization, floral initiation had occurred. By day 5, lateral organs had proliferated. Rudimentary glumes and lemmas were visible by day 8.
Growth and Development of Dinitroaniline-Susceptible and -Resistant Goosegrass (Eleusine indica) Biotypes Under Noncompetitive Conditions
Authors: Murphy Tim R. , Gossett Billy J. , Toler Joe E.
Published: May 2019

A comparative study of the growth and development of several populations of dinitroaniline-susceptible (DS) and -resistant (DR) goosegrass [Eleusine indica(L.) Gaertn. # ELEIN] biotypes was conducted under noncompetitive field conditions. Plant height and width, number of tillers, aboveground dry weight, relative growth rate (RGR), number of inflorescences/plant, total inflorescence dry weight, individual inflorescence dry weight, number of spicate branches/inflorescence, and flag leaf length and width were recorded periodically during the growing season. There were no significant differences between biotypes in most characteristics with the exception of total inflorescence dry weight. The DS biotype produced more total inflorescence dry weight than the DR biotype at 8 and 13 weeks after transplanting. Significant variation among DS and DR populations occurred in 37 and 33 of 56 evaluations, respectively. When variation existed within a biotype, populations exhibited broad ranges of response for the various growth parameters. With the exception of total inflorescence dry weight, DS and DR biotypes generally exhibited similar ranges of variability.
Shade Development Effects on Pitted Morningglory (Ipomoea lacunosa) Interference with Soybeans (Glycine max)
Authors: Murdock Edward C. , Banks Philip A. , Toler Joe E.
Published: May 2019

‘Ransom’, ‘Govan’, and ‘Bragg’ soybeans [Glycine max(L.) Merr.] were seeded in 30-, 61-, and 91-cm row spacings to achieve a uniform population of 323 000 plants/ha. In 1979 and 1980, shade development within the row was similar for all row spacings, but 15 cm from the row the inflection point occurred earlier when soybeans were seeded at the 30-cm row spacing. In 1979, shading 30 cm from the row was similar with the 61- and 91-cm row spacings, but in 1980 the 61-cm row spacing provided earlier shading. Shading within the row and 15 and 30 cm from the row was similar for all cultivars in 1979, but Govan and Bragg shaded row middles earlier than Ransom at the 91-cm row spacing. In 1980, shade development in the row was similar for all cultivars, but delayed shading was observed between the rows with Ransom. In 1979, maximum soybean seed yields were produced with 2, 2, and 0 weed-free weeks at the 30-, 61-, and 91-cm row spacings, respectively. In 1980, 2 weed-free weeks prevented soybean seed yield reductions at all row spacings. In 1979, Ransom, Bragg, and Govan required 4, 2, and 0 weed-free weeks, respectively, for maximum seed yields. In 1980, all cultivars achieved maximum seed yields with 2 weed-free weeks.
Influence of Mulch, Tillage, and Diphenamid on Weed Control, Yield, and Quality in No-Till Flue-Cured Tobacco (Nicotiana tabacum)
Authors: Shilling Donn G. , Worsham A. Douglas , Danehower David A.
Published: May 2019

Field experiments were conducted to determine the effects of various densities of four fall-seeded small grain mulches and diphenamid (N,N-dimethyl-α-phenyl benzeneacetamide) on weed control, yield, and quality in no-till flue-cured tobacco (Nicotiana tabacumL. ‘McNair 944’). A greenhouse study investigated the effects of non-soil-incorporated mulch from the same small grains plus alfalfa (Medicago sativaL.) on various growth parameters of tobacco (‘Speight G-70’). None of the mulches used in the greenhouse study adversely affected growth of the tobacco. Mulch from rye (Secale cerealeL. ‘Abruzzi’) killed about 2 weeks before transplanting plus diphenamid provided better annual broadleaf weed control (85%) than wheat (Triticum aestivumL. ‘McNair’), barley (Hordeum vulgareL. ‘Keowee’), and no mulch. Oat (Avena sativaL. ‘Brooks’) mulch resulted in 80% broadleaf weed control. There were no differences in annual grass control (which was short lived) among mulches but control was lower in the no-mulch treatment. Rye mulch resulted in a 22% increase in the control of broadleaf weeds compared to no-mulch. Yield of the no-till tobacco did not differ among mulches and averaged 82% of that conventionally grown. The quality was not affected. The rye mulch did not affect the yield or quality of tobacco when compared to a nonmulch, noncultivated treatment. The 18% decrease in the no-till yield was apparently the result of the lack of tillage and increased weed interference and was not due to adverse effects from the rye.
Control of Jerusalem Artichoke (Helianthus tuberosus) in Barley (Hordeum vulgare)
Authors: Wall David A. , Kiehn Ferdinand A. , Friesen George H.
Published: May 2019

Field experiments were conducted over a 3-yr period to evaluate the efficacy of herbicides for the control of volunteer Jerusalem artichoke [Helianthus tuberosus (L.) # HELTU] in barley (Hordeum vulgare L.) and on summer fallow. In barley, Jerusalem artichoke was controlled with a single postemergence application of clopyralid (3,6-dichloro-2-pyridinecarboxylic acid) at 1 kg ae/ha, or at 0.5 kg/ha when combined with 2,4-D [(2,4-dichlorophenoxy)acetic acid] at 0.5 kg ae/ha. Dicamba (3,6-dichloro-2-methoxybenzoic acid) at 0.2 kg ae/ha plus 2,4-D at 0.4 kg/ha was also an effective combination. Split applications of 2,4-D at 0.4 kg/ha each were more effective than a single treatment at 0.8 kg/ha. On summer fallow, glyphosate [N-(phosphonomethyl)glycine] applied at 0.5 to 2 kg ai/ha, as a single or repeated treatment, provided only marginal control of Jerusalem artichoke during the season of treatment and, in one of three experiments, reduced regrowth in the year following treatment.
Factors Affecting Degradation of MSMA in Soil
Authors: Akkari Khalid H. , Frans Robert E. , Lavy Terry L.
Published: May 2019

The effects of herbicide concentration, soil water content, and temperature on the fate and degradation of the monosodium salt of methylarsonic acid (MSMA) were evaluated in four soils. Available arsenicals were extracted, purified, and separated using reversed-phase high-performance liquid chromatography (HPLC). Residual MSMA was determined with a graphite furnace atomic absorption spectrophotometer at 193.7 nm. Initial loss of MSMA was rapid, and degradation followed first-order kinetics. The rate of change of the rate constant was temperature dependent only at soil water contents less than field capacity. MSMA dissipation was significantly faster in finer textured soils with continuous flooding and under controlled laboratory conditions (<180 days) than under field (ca. 350 days) conditions. Also, in finer textured soils, degradation of MSMA resulted in significant increases in arsenate and cacodylic acid (dimethyl arsinic acid) over native levels under flooded conditions. However, MSMA treatments contributed only a small fraction to total soil arsenic which dissipated to original concentrations by 120 days. The results indicate that under present recommended use patterns it is highly unlikely that MSMA will accumulate in the environment or carry over from one growing season to the next.
Effects of CGA-92194 on the Chemical Reactivity of Metolachlor with Glutathione and Metabolism of Metolachlor in Grain Sorghum (Sorghum bicolor)
Authors: Zama Paul , Hatzios Kriton K.
Published: May 2019

In laboratory experiments, the safener CGA-92194 {α-[(1,3-dioxolan-2-yl-methoxy)imino] benzeneacetonitrile} increased the in vitro chemical reactivity of the herbicide metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide] for glutathione (GSH) when tested at 1, 50, and 100μM. Pretreatment of sorghum [Sorghum bicolor(L.) Moench. cv. ‘G623’] seeds with the safener CGA-92194 (1.25 g ai/kg of seeds) enhanced significantly the amount of14C-metolachlor absorbed by the roots and translocated to the shoots and leaves of grain sorghum seedlings grown hydroponically in a nutrient solution. Thin-layer chromatographic analysis of methanol-soluble extracts from roots or shoots and leaves of sorghum seedlings treated with14C-metolachlor revealed the detection of 8 to 10 metabolites of this herbicide. One of the major metabolites detected was tentatively identified as the conjugate of metolachlor with GSH. A safener-induced stimulation of metolachlor metabolism via conjugation to GSH was observed in sorghum seedlings grown from seeds pretreated with CGA-92194. Addition of tridiphane [2-(3,5-dichlorophenyl)-2-(2,2,2-trichloroethyl)oxirane], a potent inhibitor of plant GSH-S-transferase enzymes, to the nutrient solution of hydroponically grown sorghum seedlings reduced the formation of GS-metolachlor in both control and safener-treated seedlings and minimized the stimulatory effect of the safener CGA-92194 on the conjugation of metolachlor to GSH. It is suggested that the safener CGA-92194 may protect grain sorghum against injury from the herbicide metolachlor by stimulating the spontaneous and enzymatic conjugation of this herbicide with GSH.
Variation Within Pure Lines of Wild Oats (Avena fatua) in Relation to Degree of Primary Dormancy
Authors: Adkins Stephen W. , Loewen Mary , Symons Stephen J.
Published: May 2019

The germination of caryopses on water or GA3solutions was used to characterize the degree of primary dormancy present in the seed progeny of 10 genetically pure lines of wild oats (Avena fatuaL. # AVEFA). These 10 lines represented a range of types from lines exhibiting no dormancy to those with a high degree of dormancy. Repeated propagation of these pure lines under constant environmental conditions identified several genetically inherited characters that were associated with the inherited differences in degree of primary dormancy. Correlation of the seed development period, number of primary caryopses produced, and caryopsis moisture content to the degree of primary dormancy shows: a) Lines characterized by low degrees of primary dormancy were, in general, those that had a short seed development time and produced few heavy seed low in percent water; and b) lines characterized by high degrees of primary dormancy were, in general, those that had a long seed development time and produced many light seed high in percent water. The adaptive advantage of the coupling of physiological and morphological characters with degree of dormancy is discussed and the possibility that some characters are determined by others is indicated.
Integrated Control of Rush Skeletonweed (Chondrilla juncea) in the Western U.S.
Authors: Lee Gary A.
Published: May 2019

Rush skeletonweed (Chondrilla junceaL. CHOJU) infestations occur along the eastern seaboard and in several western states of the United States. This Eurasian species was inadvertently introduced prior to 1870, with established stands first reported in Maryland and West Virginia (16). These infestations (16) were assessed as lacking aggressive characteristics and posed little threat as a problem weed. Although rush skeletonweed was discovered in the Pacific Northwest as early as 1938, the species was not recognized as a potential weed problem until nearly three decades later (27). Subsequent surveys revealed that infestations occupied over 2.3 million ha in California, Idaho, Oregon, and Washington (6). Attempts to generate support for an organized control program in Idaho were met with little enthusiasm during the 1960's.
Integrated Control of Waterhyacinth (Eichhornia crassipes) with a Pathogen, Insects, and Herbicides
Authors: Charudattan R.
Published: May 2019

Although the problems with waterhyacinth (Eichhornia crassipes[Mart.] Solms; # EICCR) have diminished in the United States over the last decade, the weed continues to be troublesome and requires constant management on a maintenance basis (29, 30). Chemical herbicides are currently the principal means of control when an immediate solution to a waterhyacinth problem is needed. Preventive maintenance programs also rely on chemicals to keep the weed populations at acceptable levels and to prevent weed migration into unwanted areas. However, when control is not urgently required or is economically unfeasible due to the location of the weed, a combination of biological control agents is used. The latter may have been the important factor that contributed to the lessening of the weed problem in this country over the past decade (43).
Nematode Control of Silverleaf Nightshade (Solanum elaeagnifolium); a Biological Control Pilot Project
Authors: Parker Paul E.
Published: May 2019

The use of nematodes as biological control agents has been met with skepticism, partly due to the newness of the approach and also to the potential difficulties of using a parasitic worm as a control organism. Most of the attention directed towards nematodes as biological control agents has been focused on several species that act as insect parasites. Considerable headway has been achieved with several of these parasites, especially with those parasitic on wood-boring insect larvae. The insect gallery of wood-boring larvae provides an optimum microclimate for the nematode to survive and seek out its larval insect host. A system where this strategy has proved successful involves the use of the insect parasitic nematodeNeoaplectana carpocapsaeWeiser as a biological control agent for carpenterworms (Prionoxystus robinaePeck) in fig (Ficus cariaL.) orchards in California (6). Similar systems are being developed both here and abroad with the same nematode or a closely related genus or species. Many of these systems show promise (5).
Mycoherbicide Research at the University of Arkansas–Past, Present, and Future
Authors: Templeton George E.
Published: May 2019

Biological weed control research at Arkansas has been with indigenous fungal pathogens applied as inundative inoculum to weed populations (9, 19, 22, 32, 34, 39). We term this concept the mycoherbicide approach to biological weed control (35). Our experience with this concept began in 1969 with the discovery by R. J. Smith, Jr., of a previously undescribed fungal pathogen on northern jointvetch, [Aeschynomene virginica(L.) B.S.P. # AESVI] (20, 22, 29). It was ultimately commercialized as COLLEGO™in 1982 by the Upjohn Co. for use by Arkansas rice (Oryza sativaL.) and soybean [Glycine max(L.) Merr.] farmers. Nothing has been found nor can be foreseen from the experience during discovery, development, and deployment of COLLEGO™that would preclude extension of the mycoherbicide concept to controlling other weeds in annual crops or noncrop areas (29). Nevertheless, the concept does have limitations. An overview of the COLLEGO™effort plus a statement of some research interests engendered by it will be useful for assessment of the practical potential of this new approach to biological weed control.
Effects of Photoperiod and Temperature on Root Bud Development and Assimilate Translocation in Canada Thistle (Cirsium arvense)
Authors: McAllister Ray S. , Haderlie Lloyd C.
Published: May 2019

Adventitious root bud development and assimilate translocation were studied in Canada thistle [Cirsium arvense(L.) Scop. ♯ CIRAR] grown in nutrient solution in controlled environments using combinations of two photoperiods (PP) (13 and 15 h), three day/night shoot temperatures (ST) (15/5, 25/15, and 30/22 C), and three root temperatures (RT) (10, 20, and 30 C). Total root bud elongation increased with RT and length of PP and was greatest (65 cm/plant) at 25/15 C ST, 15-h PP, and 30 C RT. The number of root buds produced was greatest at 20 C RT (7.3 to 10.3 buds/plant), whereas variations in PP and ST had little effect. Total dry-matter production was greatest (7.2 g/plant) at 15-h PP, 30/22 C ST, and 20 C RT. To study phloem translocation, photoassimilates were labeled in Canada thistle plants by exposing mature leaves to14CO2. Net assimilate translocation from a source leaf following 24-h temperature acclimation was affected little by RT and ST, but was greater under the 13-h PP than under the 15-h PP. After 7 days of temperature preconditioning, net translocation of14C-assimilates increased with both RT and ST, but no effects due to PP were noted. With 24-h temperature acclimation, net assimilate accumulation in roots was enhanced by 13-h PP and low ST (15/5 C), whereas RT itself had no effect. In temperature-preconditioned plants, 10 C RT enhanced assimilate accumulation in roots, but ST and PP had no effect.
Translocation of14C-Glyphosate and14CO2-Labeled Photoassimilates in Canada Thistle (Cirsium arvense)
Authors: McAllister Ray S. , Haderlie Lloyd C.
Published: May 2019

Translocation of14CO2-labeled photoassimilates was compared to movement of14C-glyphosate [N-(phosphonomethyl)glycine] in Canada thistle [Cirsium arvense(L.) Scop. ♯ CIRAR] under field and controlled-environment conditions. Field-grown Canada thistle plants were treated on mature upper leaves at the midflower stage in mid-June and harvested 8 days later. No differences were found in glyphosate and assimilate distribution, and movement was primarily basipetal. Of the glyphosate and photoassimilates translocated from the treated leaves, 25 and 31%, respectively, were recovered from the roots, while 59 and 58%, respectively, were found in the shoot tissue below the treated leaf. Concentration of labeled glyphosate in the roots as much as 95 cm from the treated shoot was as high as at the base of the treated shoot. Photoperiods that induce flowering (15 h) or maintain vegetative growth (13 h) did not differentially affect the distribution of photoassimilates or glyphosate in 7-week-old Canada thistle plants in the growth chamber. In growth chamber-grown plants equivalent amounts of glyphosate and assimilates were translocated out of treated leaves; however, relatively more glyphosate than photoassimilates accumulated in the roots.
The Effects of Temperature and Rainfall on Emergence and Growth of Eight Weeds
Authors: Nussbaum Emily S. , Wiese Allen F. , Crutchfield Donald E. , Chenault Ellis W. , Lavake Dwane
Published: May 2019

From 1976 to 1981, emergence date, height, and dry weight per plant were taken for eight weed species grown at Bushland, TX, at two stand densities. Height and dry weight per plant were related to precipitation and degree-days for air and soil temperatures using base temperatures of 10, 15.5, or 21 C. Kochia [Kochia scoparia(L.) Schrad. ♯ KCHSC] emerged early in March and was followed by poison suckleya [Suckleya suckleyana(Torr.) Rydb. ♯ SUKSU], sunflower (Helianthus annuusL. ♯ HELAN), and common cocklebur (Xanthium pensylvanicumWallr. ♯ XANPE) in early April. Buffalobu(Solanum rostratumDunal. ♯ SOLCU), puncturevine (Tribulus terrestrisL. ♯ TRBTE), lanceleaf sage (Salvia reflexaHornem. ♯SALRE), and barnyardgrass (Echinochloa crus-galliL. Beauv. ♯ECHCG) emerged in late April. The weeds began to increase in height during May but plants did not start increasing in weight until June. Kochia, common cocklebur, and sunflower grew tallest, produced most dry matter, made most efficient use of water, and weighed most per plant. Heat unit accumulations were strongly correlated with plant height.
Metribuzin Degradation Kinetics in Organically Amended Soil
Authors: Pettygrove Dennis R. , Naylor Denny V.
Published: May 2019

The rates of degradation of metribuzin [4-amino-6-tert-butyl-3-(methylthio)-as-triazin-5(4H)-one] were determined in an untreated Portneuf silt loam, in soil with added organic amendments, and in soil previously treated with metribuzin. While first-order rate kinetics generally described the degradation of the metribuzin in the soil, a quadratic expression was superior. Organic amendments were found to inhibit or accelerate the rate of breakdown of metribuzin depending upon the kind of amendment. Neither a lag phase nor an enrichment was observed from prior treatment with metribuzin.
Growth and Morphological Characteristics of Red Rice (Oryza sativa) Biotypes
Authors: Diarra Amadou , Smith Roy J. , Talbert Ronald E.
Published: May 2019

Pot experiments were conducted in the field at Stuttgart, AR, during 1982 and 1983 to evaluate growth and morphological differences between strawhull and blackhull red rice (Oryza sativaL. ♯ ORYSA) biotypes collected from Arkansas, Louisiana, and Texas. All red rice biotypes were compared with rice (Oryza sativaL.) cultivars ‘Lebonnet’ and ‘Nortai’. Growth and morphological differences were greatest between cultivars and red rice biotypes, less between blackhull and strawhull types, and least among collections within blackhull or strawhull. Cultivars emerged slower, were shorter, tillered less, produced less straw and fewer panicles/plant, had a lower leaf area index, and had less grain shattering than most of the red rice biotypes. Blackhull red rice biotypes tillered 27% more, produced 18% more straw, and had later maturity than strawhull. Blackhull red rice from Arkansas emerged earlier, tillered 6 to 38% more, and produced 8 to 38% more panicles per plant than other red rice biotypes, whereas blackhull red rice from Texas was 11 to 26% taller at maturity than other biotypes.
Comparing a Strain of Illinois Sorghum to Tennessee Johnsongrass (Sorghum halepense)
Authors: Chernicky Jon P. , Slife Fred W.
Published: May 2019

Uncertainty exists among extension agents and growers in northern Illinois whether a particular sorghum (Sorghumsp.) strain should be identified as johnsongrass [Sorghum halepense(L.) Pers. ♯ SORHA] or sorghum-almum (Sorghum almumParodi. ♯ SORAL). To reduce confusion over its identity, field studies were conducted at Urbana, IL, in 1982 and 1983 to determine if phenotypic differences existed between a johnsongrass strain from Tennessee and the northern Illinois sorghum strain. Three planting dates (May 20, June 3, June 17) were used to determine if time of establishment would affect growth habits and phenotypic expression. Averaged over planting dates, the Illinois sorghum was taller (200 cm vs. 161 cm), produced more seed per panicle (2215 vs. 741), and had a larger shoot to rhizome plus root ratio (2:1 vs. 1:1) and a wider leaf blade (4.6 cm vs. 2.9 cm) than johnsongrass. In contrast, the johnsongrass produced more rhizomes per plant (51 vs. 10) with almost eight times the cumulative rhizome length per plant (778 cm vs. 117 cm). These results were consistent across planting dates. Comparison of chromosome counts from pollen mother cells and root tips showed both johnsongrass and the Illinois sorghum had 2n = 40; thus observed differences between the sorghum strains could not be explained by differences in chromosome number. The northern Illinois sorghum strain more closely resembled sorghum-almum morphologically than the Tennessee johnsongrass.
Herbicide Mixtures for Control of Honey Mesquite (Prosopis glandulosa)
Authors: Bovey Rodney W. , Meyer Robert E.
Published: May 2019

Clopyralid (3,6-dichloro-2-pyridinecarboxylic acid) was superior to 2,4,5-T [(2,4,5-trichlorophenoxy)acetic acid], dicamba (3,6-dichloro-o-anisic acid), picloram (4-amino-3,5,6-trichloropicolinic acid), and triclopyr {[(3,5,6-trichloro-2-pyridinyl)oxy] acetic acid} for control of honey mesquite (Prosopis glandulosaTorr. ♯ PRCJG) in the field. However, equal ratio mixtures of clopyralid + picloram or triclopyr (0.28 + 0.28 or 0.56 + 0.56 kg ae/ha) were as effective for honey mesquite control as clopyralid at rates of 0.56 and 1.12 kg/ha. Equal mixtures of picloram + 2,4,5-T, picloram + triclopyr, picloram + dicamba, triclopyr + 2,4,5-T, or triclopyr + dicamba were less effective in controlling honey mesquite than clopyralid alone or clopyralid + picloram or triclopyr in 1:1 mixtures. In the greenhouse, mixtures of clopyralid + 2,4,5-T, picloram, or triclopyr were highly effective for the control of honey mesquite. Mixtures of 2,4,5-T + picloram, 2,4,5-T + triclopyr, or triclopyr + picloram were also effective when applied at 0.28 + 0.28 kg/ha.
Long-Term Effects on Vegetation of Herbicide Treatments in Chaparral
Authors: Holt Jodie S. , Radosevich Steven R. , Graves Walter L.
Published: May 2019

Field studies were established in 1974 and 1975 at various locations in San Diego County, CA, to evaluate several herbicides for the control of chamise (Adenostoma fasciculatumH.&A.) and redshank chamise (Adenostoma sparsifoliumTorr.). Herbicide effects on vegetation were reevaluated in 1982. Plots originally treated with 2.2 or 4.5 kg ae/ha of glyphosate [N-(phosphonomethyl)glycine] had virtually no chamise regrowth 8 yr after treatment. The herbicides 2,4-D [(2,4-dichlorophenoxy)acetic acid], combinations of 2,4-D with 2,4,5-T [(2,4,5-trichlorophenoxy)acetic acid] or dichlorprop [2-(2,4-dichlorophenoxy) propionic acid], fosamine [ethyl hydrogen (aminocarbonyl)phosphonate], triclopyr {[(3,5,6-trichloro-2-pyridinyl)oxy] acetic acid}, tebuthiuron {N-[5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl]-N,N′-dimethylurea}, and picloram (4-amino-3,5,6-trichloropicolinic acid) had no long-term effects on chamise. Soil collected in 1982 from glyphosate-treated plots contained similar numbers of chamise seeds but fewer seeds of other species compared to untreated plots. Canopy cover of redshank chamise was similar in treated and untreated plots after 8 yr. These results document the effectiveness of glyphosate in killing the underground root-crown of chamise, which prevented sprouting, but not redshank chamise.
Efficacy and Economics of Leafy Spurge (Euphorbia esula) Control in Pasture
Authors: Gylling Steven R. , Arnold W. Eugene
Published: May 2019

Herbicide treatments containing the butoxyethanol ester of 2,4-D [(2,4-dichlorophenoxy)acetic acid], the dimethylamine salt of dicamba (3,6-dichloro-o-anisic acid), the potassium salt of picloram (4-amino-3,5,6-trichloropicolinic acid), and the isopropylamine salt of glyphosate [N-(phosphonomethyl)glycine] were applied for 6 yr to a pasture in east-central South Dakota containing leafy spurge (Euphorbia esulaL. ♯ EPHES). Several treatments resulted in leafy spurge control exceeding 90%. Mean herbage dry-weight yield in treated plots was 2340 kg/ha, a 67% increase over untreated plots. Forage yields did not significantly differ among treatments controlling 90% or more leafy spurge. Marginal net return over marginal cost from herbicide treatments ranged from $35 to –$63/ha. Treatments providing satisfactory leafy spurge control with minimum economic risk were annual spring applications of 2,4-D at 1.7 kg ae/ha or dicamba + 2,4-D at 0.6 + 1.1 kg ae/ha and the biannual application of 2,4-D at 0.8 kg ae/ha.
Rainfall Effects on Desmedipham and Phenmedipham Performance
Authors: Anderson Monte D. , Arnold W. Eugene
Published: May 2019

The effect of rainfall on the performance of a tank mixture of desmedipham [ethylm-hydroxycarbanilate carbanilate(ester)] and phenmedipham (methylm-hydroxycarbanilatem-methylcarbanilate) applied postemergence to redroot pigweed (Amaranthus retroflexusL. ♯ AMARE), wild mustard (Sinapsis arvensisL. ♯ SINAR) and sunflower (Helianthus annuusL.) was evaluated in field studies. The occurrence of 1 mm of rain immediately after herbicide application significantly decreased the control of redroot pigweed and wild mustard. A rainfall quantity of 1 mm also reduced injury symptoms on sunflower. Simulating a 12.7-mm rain less than 18 h after desmedipham and phenmedipham application effectively reduced toxicity to redroot pigweed and sunflower. Toxicity to these two species increased at a lesser rate than for wild mustard as the time interval prior to rain was increased. A rain-free period of 6 h was predicted for near-maximum control of wild mustard with these herbicides.
Photosynthesis and Stomatal-Conductance Responses of Johnsongrass (Sorghum halepense) to Water Stress
Authors: Stuart Bryan L. , Krieg Daniel R. , Abernathy John R.
Published: May 2019

The influence of water stress on johnsongrass [Sorghum halepense(L.) Pers. ♯ SORHA] physiology was evaluated in a semiarid environment. Stomatal conductance of johnsongrass responded to more negative leaf water potential and increasing leaf temperature. The sensitivity of the leaf temperature effect was dependent on the soil water content. At low soil water content, conductance was limited by low water potential, and increasing leaf temperature had little effect. Conductance of CO2was related to net photosynthesis in a curvilinear manner, with conductance levels greater than 0.3 mol·m-2· s-1being in excess of that necessary for maximum photosynthesis. At both high conductance levels and low levels associated with increased water stress, intercellular CO2concentration increased, indicating nonstomatal limitations to photosynthesis. Decreased osmotic potential provided the highest correlation with the linear decline of photosynthetic rate as stress intensified. The expression of osmotic adjustment in johnsongrass is reported during grain filling. Plants in the milkdough stage of grain filling had approximately 0.3 MPa lower osmotic potential at any relative water content than those at anthesis.
Responses of Intact and Scarified Curly Dock (Rumex crispus) Seeds to Physical and Chemical Stimuli
Authors: Hemmat Minou , Zeng Guang-Wen , Khan Anwar A.
Published: May 2019

The influence of acid scarification on the responsiveness of curly dock (Rumex crispusL. ♯ RUMCR) seeds to physical and chemical factors was studied. Scarification made the seeds responsive to GA4+7(a mixture of gibberellin A4+ A7) and markedly improved the responsiveness to light, moist-chilling, and a 1-h 40-C temperature shift. Scarification reduced the mechanical restraint of the seedcoat by 0.4 to 0.8 MPa. Removal of the entire pericarp induced 69% germination in the dark. Moist-chilling treatment of seeds reduced the soaking period needed for maximum response to the high-temperature shift from 24 to 6 h. The embryo growth potential generated by moist-chilling was less in magnitude than that by the reduction in seed coat restraint by scarification. Induction of secondary dormancy was prevented to a marked degree in scarified (chilled or unchilled) seeds during polyethylene glycol-6000 (PEG) treatment in light or in the presence of GA4+7while intact seeds rapidly became secondarily dormant in light. The ability of scarified seeds to remain germinable or nondormant for a longer period than the intact seed in low water potential imbibing medium may be due to a net reduction (by 0.4 to 0.8 MPa) in the impact on the embryo of germination-preventing forces (low water potential plus mechanical restraint of the seed coat).
Johnsongrass (Sorghum halepense) Control in Soybeans (Glycine max) with Postemergence Grass Herbicides Applied Alone and in Mixtures
Authors: Whitwell Ted , Wehtje Glenn , Walker Robert H. , McGuire John A.
Published: May 2019

Sethoxydim {2-[1-(ethoxyimino)butyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexen-1-one}, CGA-82725 {2-propynyl 2-[4-[(3,5-dichloro-2-pyridinyl)oxy]phenoxy]propanoate}, RO 13-8895 {acetone-O-[D-2-[p-(α,α,α-trifluoro-p-tolyl)oxy]phenoxy]propionyl oxime}, and difenopenten {4-[4-[4-(trifluoromethyl)phenoxy]phenoxy]-2-pentenoic acid} were evaluated as single and/or split applications for postemergence control of johnsongrass [Sorghum halepense(L.) Pers. ♯ SORHA] grown from rhizomes in soybeans [Glycine max(L.) Merr.]. Good to excellent control, crop safety, and yield enhancement were achieved with all herbicides evaluated. Antagonism between postemergence grass and broadleaf herbicides was evaluated by applying sethoxydim, CGA-82725, RO 13-8895, and difenopenten alone to soybeans infested with johnsongrass grown from seed, and applying these herbicides as mixtures with acifluorfen {5-[2-chloro-4-(trifluoromethyl)phenoxy]-2-nitrobenzoic acid}, bentazon [3-isopropyl-1H-2,1,3-benzothiadiazin-4(3H)-one 2,2-dioxide], or benazolin (4-chloro-2-oxobenzothiazolin-3-ylacetic acid). Acifluorfen was most antagonistic to the activity of postemergence grass herbicides, with difenopenten and sethoxydim the most susceptible to antagonism. Reductons in johnsongrass control were attributed to antagonism by broadleaf herbicides, which caused soybean yield reductions of up to 67%.