bluuebunny/crossref_metadata_2025 huggingface dataset:
Efficacy of Three Postemergence Grass Herbicides for Soybeans
Authors: Hartzler Robert G. , Foy Chester L.
Published: May 2019

The effects of herbicide concentration, adjuvants, and temperature on the phytotoxicity of CGA-82725 {2-propynyl 2-[4-[3,5-dichloro-2-pyridinyl)oxy] phenoxy] propionate}, RO 13-8895 {acetone-O-[D-2-[p-(α,α,α-trifluoro-p-tolyl)-oxy] phenoxy] propionyl] oxime}, and BAS 9052 OH {2-[1-(ethoxyimino)-butyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexene-1-one} to large crabgrass [Digitaria sanguinalis(L.) Scop. # DIGSA] were evaluated. The addition of adjuvants increased the toxicity of BAS 9052 OH at herbicide rates below 0.14 kg ai/ha, whereas the adjuvants had little effect on the activity of CGA-82725 or RO 13-8895. There were no differences among the adjuvants in enhancing grass control with any of the herbicides. Control of large crabgrass with CGA-82725 or BAS 9052 OH was not affected by temperature at the time of spraying; RO 13-8895 was slightly more toxic at 16 C than at 32 C. Soybean [Glycine max(L.) Merr.] had good tolerance to the three herbicides at rates 3 to 10 times those recommended; no differences in tolerance were observed among seven soybean cultivars. Stage of growth and the addition of an emulsifiable oil adjuvant did not affect soybean tolerance to BAS 9052 OH.
Effect of Growth Stage on Rice (Oryza sativa) Tolerance to Acifluorfen
Authors: Street Joe E. , Richard Edward P.
Published: May 2019

When applied at 0.1 or 0.3 kg/ha, acifluorfen {5-[2-chloro-4-(trifluoromethyl)phenoxy]-2-nitrobenzoic acid} did not reduce rough rice (Oryza sativaL. ‘Labelle’) yield, milling yield, seed weight, seed germination, or plant height, regardless of growth stage. Application of 0.6 kg/ha to rice in the boot, late boot, or panicle filling stage reduced yields, but had no effect on plant height, seed germination, or whole milling yield.
Toxicity, Absorption, and Translocation of Soil-Applied Chlorimuron in Yellow and Purple Nutsedge (Cyperus esculentusandC. rotundus)
Authors: Reddy Krishna N. , Bendixen Leo E.
Published: May 2019

The activity of soil-applied chlorimuron in yellow and purple nutsedge was studied in greenhouse and laboratory experiments. Soil-applied chlorimuron decreased tuber sprouting by 80% in yellow nutsedge and by 30% in purple nutsedge at 60 g ai/ha. Chlorimuron decreased shoot emergence by 53 to 83% and shoot growth by 85 to 99% in both species at rates as low as 10 g/ha. Previous exposure of tubers to chlorimuron-treated soil reduced tuber resprouting by 20 to 25% in herbicide-free soil at 60 g/ha in both species. There was no rate response in shoot emergence from tubers previously exposed to chlorimuron, but shoot dry weight decreased by 60 to 81% in both species at 60 g/ha. At 12 h after application, 47% of the total14C applied to the shoot in yellow nutsedge and 32% of that applied in purple nutsedge were absorbed. However, less than 1% of the total14C applied was translocated out of the shoot and into the roots and tuber in either species. In both species, 1.3% of the14C applied to the roots and tuber was absorbed and 0.1% was translocated out of the roots and tuber into the shoot at 12 h after application. The pattern of root- and tuber-absorbed14C distribution indicated that the14C absorbed by the tuber remained in the tuber and that absorbed by the roots was translocated to the shoots.
Absorption and Translocation of Picloram by Lindheimer Pricklypear (Opuntia lindheimeri)
Authors: Mayeux Herman S. , Johnson Hyrum B.
Published: May 2019

Removing the epicuticular wax from mature pads (cladophylls) of Lindheimer pricklypear increased picloram absorption by four- to sixfold in the laboratory, while the addition of surfactant had little effect on absorption. Absorption decreased with increasing pH of the picloram solution, indicating that picloram diffused through the cuticle as the undissociated molecule. Picloram entered detached pads at the areoles more readily than through the surrounding cuticle. In the glasshouse, whole plants consisting of an old, mature pad supporting a young, growing pad absorbed picloram very slowly whether picloam was applied as a spray to old or young pads or to the soil. About 90 and 80% of the applied picloram remained on the waxy surface of old and new pads, respectively, and about 2% of the applied picloram was recovered from within the epicuticular wax after 30 days. Picloram concentrations within pads treated in the glasshouse were greater when the herbicide was applied to new pads (4.6 μg/g) than old pads (1.9 μg/g) after 30 days. More picloram was translocated basipetally from treated new pads to untreated old pads than in the opposite direction, but concentrations in untreated pads were low (<1 μg/g). Little picloram was absorbed by roots, compared to pads, and little was translocated into or out of roots. These results conflict with the view that the effectiveness of picloram for pricklypear control is attributable to extensive root uptake and acropetal transport. However, observations of plants 6 months after treatment indicated that soil applications were more effective than sprays in the glasshouse.
Picloram Release from Leafy Spurge (Euphorbia esula) Roots in the Field
Authors: Hickman Michael V. , Messersmith Calvin G. , Lym Rodney G.
Published: May 2019

Picloram release by leafy spurge roots, as affected by picloram rate, plant growth stage, and time intervals after treatment, was quantified under field conditions. Picloram was pipe-wick applied to leafy spurge in the vegetative, flowering, and seed-filling growth stages. Percent leafy spurge control was evaluated and picloram residues were determined in soil samples from 0- to 13-, 13- to 26-, and 26- to 39-cm depths taken 1, 2, and 3 weeks after treatment. Leafy spurge was controlled (frequently >85%) by all picloram concentrations applied, although control tended to increase as solution concentration increased. Picloram release from roots was greater from plants treated in the flowering and seed-filling stages than from plants in the vegetative stage. Picloram release from roots generally was correlated with application rate, averaging 490, 820, and 1420 ppbw in soil for the 30, 60, and 120 g ae/L application rates, respectively. Picloram release from roots occurred rapidly with 86% of the picloram detected in the 0- to 13-cm soil depth present by 1 week after treatment. Picloram was detected at all soil depths sampled, but over 84% was in the upper 13 cm and 8% was in both the 13- to 26- and 26- to 39-cm depths. Leafy spurge shoots emerged through a 7.5- and 15-cm depth of picloram-treated soil at concentrations up to 1000 ppbw within 14 to 21 days after the untreated control. Picloram soil residue had little effect on leafy spurge root growth.
Absorption, Translocation, and Metabolism of Foliar-Applied Chlorimuron in Soybeans (Glycine max), Peanuts (Arachis hypogaea), and Selected Weeds
Authors: Wilcut John W. , Wehtje Glenn R. , Patterson Michael G. , Cole Tracy A. , Hicks T. Vint
Published: May 2019

Tolerance of species to foliar applications of the ethyl ester of chlorimuron as determined in greenhouse studies with 21-day-old seedlings was: soybean = peanut > prickly sida > sicklepod > Florida beggarweed > common cocklebur. Absorption of foliar-applied14C-chlorimuron 72 h after application was similar in soybean, peanut, sicklepod, common cocklebur, and prickly sida, but much less in Florida beggarweed. Slight symplasmic and apoplasmic translocation of the herbicide was evident in all species. Metabolism of chlorimuron 72 h after application was greatest in soybean and least in common cocklebur. Species tolerance to chlorimuron was directly correlated (r2= 0.93) to the amount of unmetabolized chlorimuron (dpm/g dry wt) in the plant. Peanut exhibited increased tolerance to chlorimuron with age; this result was attributed to reduced absorption and translocation and more extensive metabolism of the absorbed herbicide by older plants.
Environment and Spray Additive Effects on Picloram Absorption and Translocation in Leafy Spurge (Euphorbia esula)
Authors: Moxness Kevin D. , Lym Rodney G.
Published: May 2019

Relative humidity after application, spray additives, and solution pH affected both foliar absorption and translocation of14C-picloram to leafy spurge roots.14C-picloram absorption increased from 11 to 34% and translocation increased from 5 to 21% as time at posttreatment humidity increased from 0 to 48 h. Absorption and translocation were not different when pre- or posttreatment temperatures were 30/18 or 18/10 C (day/night).14C-picloram absorption and translocation to the roots were 18 and 6%, respectively, when applied alone, and increased to 46 and 12%, respectively, when applied with ammonium sulfate at 2.5 kg/ha. Absorption and translocation were unaffected by ammonium nitrate. Foliar absorption and translocation of14C-picloram in leafy spurge were unaffected by pH of unbuffered spray solution but increased at least 50% when applied in a solution buffered at pH 4.8 with trisodium citrate. Foliar absorption in detached leafy spurge leaves increased from 26 to 51% of applied14C as the citrate buffer concentration increased from 0.01 to 0.1 mM, respectively.
The Effects of Soybean (Glycine max) Interference on the Canopy Architecture of Common Cocklebur (Xanthium strumarium), Jimsonweed (Datura stramonium), and Velvetleaf (Abutilon theophrasti)
Authors: Regnier Emilie E. , Stoller Edward W.
Published: May 2019

Common cocklebur, jimsonweed, and velvetleaf were grown with soybeans in the field to determine how soybean interference affects weed canopy architecture. Common cocklebur had more leaves within the soybean canopy than jimsonweed or velvetleaf. At the end of the season, common cocklebur leaf area was distributed evenly below and above the top of the soybean canopy, while nearly all the jimsonweed and velvetleaf leaf area was above the soybean canopy. Common cocklebur exhibited more shade tolerance than jimsonweed or velvetleaf by also maintaining leaves in the shade within the soybean canopy. Differences among these weeds in leaf distribution within the soybean canopy were not related to differences in abscission of the lower leaves but to a differential response of lower axillary buds to soybean shading. Growth from lower axillary buds in jimsonweed and velvetleaf was strongly inhibited by soybean interference, but interference had little effect on lower axillary bud growth in common cocklebur. Axillary bud growth in the lower canopies of both common cocklebur and soybeans, and their similarity in height, caused these plants to compete for the same aboveground niche. However, common cocklebur had more extensive axillary growth along the lower stem than soybeans, which may allow it to compete for resources in this niche more aggressively than soybeans. Velvetleaf and jimsonweed did not share the same aboveground niche with soybeans due to the placement of their leaves above rather than within the soybean canopy. The lower branching characteristics and apparent shade tolerance of common cocklebur may be important factors in the superior competitive ability with soybeans compared to jimsonweed and velvetleaf.
Dispersal and Germination of Big Sagebrush (Artemisia tridentata) Seeds
Authors: Young James A. , Evans Raymond A.
Published: May 2019

The purpose of this study was to investigate seed dispersal and germination of seeds in the soil as factors in establishment of big sagebrush seedlings. Seed dispersal began at seed maturity in December. Under the shrub canopy the dispersal of seeds was greater to the east. Between shrubs the dispersal of seeds tended to be uniform. For 6 months of each year there were no detectable germinable seeds in the litter and surface soil at the sites sampled. Germinable seeds in the soil increased rapidly during seed dispersal but were not detected by June of the next season. Enrichment of bioassay samples with GA3or KNO3did not enhance emergence of big sagebrush seedlings. Big sagebrush seedlings were found at very low densities in areas previously burned in wildfires. This suggests the presence of viable big sagebrush seeds in the soil at a very low density.
Impact of a Seed-Feeding Insect and Microorganisms on Velvetleaf (Abutilon theophrasti) Seed Viability
Authors: Kremer Robert J. , Spencer Neal R.
Published: May 2019

Field infestations of a seed-feeding insect developed from overwintered populations reduced viability of velvetleaf seed to 17.5 and 15.5% at two locations in central Missouri, compared to 95.5 and 87.5% at insect-free sites. Insect feeding enhanced the proportion of seedborne microorganisms in seed up to 98% compared to the average fungal infection of 8% for seed not exposed to the insect. There was a strong negative correlation between fungal infection associated with insect feeding and percent velvetleaf seed viability. The insect transmits microorganisms externally just as pollen is carried by various other insect species and not by ingestion and regurgitation. The effectiveness of the insect on reducing seed viability and seed production in central Missouri is mainly limited by the time required to build up populations capable of significantly affecting early-season velvetleaf seed production.
Effects of Tillage on the Efficacy and Persistence of Clomazone in Soybean (Glycine max)
Authors: Mills J. Anthony , Witt William W. , Barrett Michael
Published: May 2019

Experiments were conducted in 1985 to 1987 to evaluate the effects of conventional and no-tillage systems on the weed control provided by clomazone applied preemergence in soybeans. The persistence of clomazone in soil of the two tillage systems was also determined. Increasing the clomazone rate from 0.8 to 1.4 kg/ha did not increase weed control. Clomazone controlled 80% or more of jimsonweed, velvetleaf, and giant foxtail. Common cocklebur control ranged from about 50 to 70% in no-till and from 80 to 90% in conventional tillage. Generally, soybean pods/plant and yields were lower from clomazone treatments than from handweeded treatments due to inadequate common cocklebur control. Over 40% of the clomazone applied did not reach the soil surface; it was either intercepted by wheat straw, volatilized, or both. Clomazone persisted longer in conventional tillage than in no-tillage in. However, in 1986, clomazone was equally persistent in the two tillage systems. The half-life of clomazone was 34 and 6 days in 1985 in conventional and no-tillage, respectively, and in 1986, 18 and 16 days in conventional and no-tillage, respectively. Significant clomazone concentrations were not found below 10 cm in the soil profile. Corn planted without tillage (no-till) approximately 1 yr after clomazone application was not injured and yields were not reduced due to prior clomazone use.
Barnyardgrass (Echinochloa crus-galli) Control with Grass and Broadleaf Weed Herbicide Combinations
Authors: Minton Bradford W. , Kurtz Mark E. , Shaw David R.
Published: May 2019

Field experiments were established to investigate the effects of tank-mixing sethoxydim or quizalofop with imazaquin, chlorimuron, or lactofen for barnyardgrass control in soybeans. Sequential applications, where the grass herbicide was applied 24 h before or after the broadleaf weed herbicide, were also evaluated. There was an antagonistic decrease in barnyardgrass control when sethoxydim or quizalofop was tank mixed with any of the broadleaf weed herbicides. Antagonism was also observed when either grass herbicide was applied 24 h after imazaquin or lactofen, but not with chlorimuron. Control was not affected when the grass herbicide was applied 24 h before the broadleaf weed herbicide. In greenhouse experiments, the effects of tank-mixing sethoxydim, quizalofop, fluazifop-P, haloxyfop, fenoxaprop, or clethodim with imazaquin, lactofen, chlorimuron, acifluorfen, fomesafen, bentazon, or 2,4-DB were also evaluated for barnyardgrass control. Although acifluorfen provided 45% barnyardgrass control, tank-mixing it with fluazifop-P, haloxyfop, or fenoxaprop was antagonistic. Antagonism also occurred when chlorimuron was tank mixed with any of the grass herbicides except fenoxaprop. Barnyardgrass control by all of the grass herbicides applied in the field or greenhouse was most severely antagonized by tank mixes containing imazaquin.
Weed Management in Two Potato (Solatium tuberosum) Cultivars Using Tillage and Pendimethalin
Authors: Nelson Donald C. , Giles Joseph F.
Published: May 2019

Tillage and pendimethalin either alone or in combination were compared for weed management in two potato cultivars. The best weed management program consisted of a combination of pendimethalin and tillage. Pendimethalin alone did not adequately control weeds. Multiple cultivations gave better control than pendimethalin alone but not as good as pendimethalin and cultivation combined. The net returns using tillage, pendimethalin, and tillage plus pendimethalin for weed control averaged –$86, –$208, and $ 143/ha, respectively. Independent of their effect on weeds, cultivation had a significant negative effect and pendimethalin a significant positive effect on potato yields. Each cultivation reduced yields by 1.7% and pendimethalin increased yields by 4%. The cultivar ‘Red Pontiac’ was a better competitor with weeds than ‘Red Norland’.
Effect of Tillage Systems on the Efficacy and Phytotoxicity of Imazaquin and Imazethapyr in Soybean (Glycine max)
Authors: Mills J. Anthony , Witt William W.
Published: May 2019

Field experiments were conducted to evaluate the interactions of tillage systems with imazaquin and imazethapyr on weed control and soybean injury and yield. Control of jimsonweed, common cocklebur, ivyleaf morningglory, velvetleaf, and giant foxtail from imazaquin and imazethapyr in conventional tillage was generally equal to or greater than control in no-tillage. However, under limited rainfall, weed control in no-tillage was generally equal to or greater than control in conventional tillage. Reductions in soybean heights due to herbicide treatment were evident in both tillage systems in 1985 and 1986 but not in. Soybean yields were reduced in 1985 from imazaquin at 140, 210, and 250 g/ha and imazethapyr at 105 and 140 g/ha. Yields were not reduced in 1986 and. Imazaquin and imazethapyr appear to provide adequate control of jimsonweed, common cocklebur, ivyleaf morningglory, velvetleaf, and giant foxtail in conventional and no-till systems.
Sago Pondweed (Potamogeton pectinatus) Tuber Size Influences Its Response to Fluridone Treatment
Authors: Spencer David F. , Ksander Gregory G. , Whiteand Linda C.
Published: May 2019

In greenhouse experiments, sago pondweed plants were grown from three different size classes of tubers and treated with four levels of fluridone. Results indicate that although fluridone significantly reduced mean plant weight, the extent of the reduction in weight depended on the size of tuber from which the plant was grown. Mean plant weight was greater for plants exposed to fluridone (up to 0.5 mg/L) for 7 days, if the plants were initially from larger tubers (51 to 60 or 101 to 200 vs. 11 to 20 mg fresh weight). Mean plant length and the number of ramets/plant were affected in a similar manner. The results underscore the importance of specifying the size of tubers used in growth studies and contribute to understanding of the roles that biological factors play in regulating aquatic plant response to herbicide treatment.
Activity of Imazaquin in Soil Solution as Affected by Incorporated Wheat (Triticum aestivum) Straw
Authors: Wolt Jeff D. , Rhodes G. Neil , Graveel John G. , Glosauer Eva M. , Amin Mohammad K. , Church Patty L.
Published: May 2019

The effect of wheat straw incorporation on imazaquin concentration and biological activity in soil solution was determined as a function of herbicide rate and time of incubation. Etowah silt loam, amended with wheat straw (2 g/kg) or unamended, received imazaquin (0, 31, 62, or 124 μg ai/kg oven-dry soil). Soils incubated at 25 C were subsampled 0, 12, 24, 48, and 96 h after treatment and soil solutions were analyzed for imazaquin, pH, and electrical conductivity. Wheat straw amendment, imazaquin rate, and time of incubation influenced the concentration of imazaquin in the soil solution. Imazaquin concentration in soil solution exhibited gradual linear declines with time. Relative length of sunflower radicles declined with increased imazaquin rate. Regression of relative radicle length on activity of imazaquin anion in soil solution indicated differential response in the presence of wheat straw-amended versus unamended soil.
Availability and Persistence of Imazaquin, Imazethapyr, and Clomazone in Soil
Authors: Loux Mark M. , Liebl Rex A. , Slife Fred W.
Published: May 2019

The availability and persistence of imazaquin, imazethapyr, and clomazone were studied in a Cisne silt loam (1.3% organic matter) and a Drummer silty clay loam (5.8% organic matter). Availability of all three herbicides to bioassay species was greater in the Cisne soil than in the Drummer soil. Corn root growth was more sensitive to imazaquin and imazethapyr than corn shoot growth. Shoot and root growth of wheat was inhbited by similar clomazone concentrations. In field experiments conducted in 1984, 1985, and 1986, all three herbicides were more persistent in the Drummer silty clay loam than in the Cisne silt loam. Clomazone and imazethapyr were detected by liquid or gas chromatographic analysis in the Drummer soil 3 yr following application. Crop injury occurred 5 months after application of imazaquin and clomazone to the Drummer soil. In the Cisne soil, only imazethapyr caused crop injury 5 months after application. Herbicide residues found below 7.5 cm were greater in the Drummer soil than in the Cisne soil.
A Comparison of Methods for Measuring Effects of Density and Proportion in Plant Competition Experiments
Authors: Roush Mary Lynn , Radosevich Steven R. , Wagner Robert G. , Maxwell Bruce D. , Petersen Terry D.
Published: May 2019

Three approaches to data analysis were compared to describe competitive interactions between wheat and Italian ryegrass. Replacement series were performed using the two species at total densities of 100, 200, and 400 plants/ m2, and separate monoculture experiments for each species at densities from 33 to 800 plants/m2. Approaches to data analysis included: 1) conventional analysis of replacement series experiments, 2) development of synthetic no-interaction responses from monoculture experiments for comparison with results from mixtures, and 3) responses of the reciprocal yield of individual plants to variation in densities of the two species. Wheat was the superior competitor to ryegrass; however, the three approaches varied in ability to quantify this competitive relationship. The conventional replacement series analysis was least sensitive in describing the influences of either density or proportion on the plant association. The synthetic no-interaction approach provided the most detailed analysis of the influence of proportion on the species interaction. The reciprocal yield approach provided the simplest and most sensitive analysis of the joint influences of density and proportion. The latter approach also provided the most quantitative analysis of the influence of density on the species interaction. Plant density and species proportion are important variables for interpreting the process of plant competition.
Weed-Crop Competition: Experimental Designs and Models for Data Analysis
Authors: Rejmánek Marcel , Robinson George R. , Rejmánková Eliska
Published: May 2019

Substitutive (replacement) and partial additive experimental designs, with their underlying models, remain the two most popular techniques in weed-crop competition studies, despite considerable criticism of these approaches in the recent literature. We review standard designs for two-species competition experiments and demonstrate the advantages of a reciprocal yield model applied to data from an additive series experiment, using mixtures of Japanese millet and tomato. A traditional replacement series analysis failed to provide a general model of competition among these two species over several total plant densities, while an application of a reciprocal yield (inverse linear) model to the same data was successful. This technique allows evaluation of the influences of both weed on crop and crop on weed, as well as the partitioning of net competition effects into intra- and interspecific components. One Japanese millet plant was competitively equivalent to 3.7 tomato plants, as measured by effects on tomato biomass, while one tomato plant was equivalent to 0.14 Japanese millet plants, as measured by effects on millet biomass. Skewness of per plant biomass distribution is shown to be a result but not an unambiguous measure of competition. Expansion of a reciprocal yield model to mixtures of more than two species is illustrated using three species of duckweed. While some caution is recommended, the reciprocal yield analysis applied to data from appropriately designed experiments is a substantial improvement over more traditional methods.
Differential Imazaquin Tolerance and Behavior in Selected Corn (Zea mays) Hybrids
Authors: Sander Kip W. , Barrett Michael
Published: May 2019

‘Cargill 921′, ‘Great Lakes 422′, ‘Northrup King 9410′, ‘Pioneer 3901′, ‘Pioneer 3737′, and ‘Stauffer 5650’ corn hybrids were tested in the greenhouse for imazaquin tolerance. Imazaquin rates that reduced shoot growth 50%, when compared to the untreated hybrid check, ranged from 17 to 50 g/ha. When averaged together, the three most tolerant hybrids (Cargill 921, Pioneer 3901, and Great Lakes 422) were approximately one-half as sensitive to imazaquin as the three least tolerant hybrids (Northrup King 9410, Pioneer 3737, and Stauffer 5650). Studies were conducted to determine if the observed differential tolerance was caused by differences in acetolactate synthase (ALS, EC 4.1.3.18) levels and sensitivity of ALS to imazaquin. Differential imazaquin uptake, translocation, and/or metabolism were also studied as a basis for the tolerance range as was seed size and seedling growth. There were differences among hybrids in the physiological and growth parameters studied; however, these differences did not correlate with imazaquin tolerance. None of the factors studied could alone account for the differences in imazaquin tolerance.
Protection of Corn (Zea mays) and Sorghum (Sorghum bicolor) from Imazethapyr Toxicity with Antidotes
Authors: Barrett Michael
Published: May 2019

Antidotes were evaluated under greenhouse conditions for their ability to prevent injury to corn and sorghum from imazethapyr. Corn was more tolerant to imazethapyr and more effectively protected from imazethapyr toxicity than sorghum. Naphthalic anhydride (NA)3, CGA 92194, or flurazole treatment of corn seed reduced plant injury from preemergence applications of imazethapyr. Corn injury from postemergence applications of imazethapyr was decreased by seed treatment with NA or CGA 92194. Sorghum injury from preemergence applications of imazethapyr was not reduced by seed treatment with the antidotes. NA treatment of sorghum seed was the most effective antidote treatment for decreasing injury from postemergence applications of imazethapyr but the level of sorghum protection was much less than that achieved with corn. Corn seedlings grown from NA-treated and untreated seed absorbed equal amounts of14C into the roots from nutrient solution containing14C-imazethapyr. The NA-treated corn plants translocated less of the absorbed14C to the shoots than the untreated plants. NA treatment of corn seeds increased the rate of imazethapyr conversion to soluble metabolites 2-and 10-fold in the corn seedling roots and shoots, respectively. The increased rate of imazethapyr metabolism in corn following NA seed treatment may be responsible for the protection from imazethapyr toxicity.
Common Cocklebur (Xanthium strumarium) Root and Shoot Interference in Soybeans (Glycine max)
Authors: Regnier Emilie E. , Stoller Edward W. , Nafziger Emerson D.
Published: May 2019

Common cocklebur root and shoot interferences were investigated as factors causing soybean yield reductions in the field. Significant decreases in soybean yield resulted from common cocklebur shoot interference when the two were grown together with the common cocklebur roots confined in plastic bags. Soybean yield decreased further when common cocklebur roots were not confined, but this decrease resulted, in part, from increased common cocklebur shoot growth. Wire mesh cylinders of varying diameters, placed in gaps in the soybean rows and designed to spatially restrict soybean shoot growth, reduced yield more than did gaps alone. When similar cylinders lined with black plastic were placed next to the soybean rows to restrict both within-canopy light and space for soybean shoot growth, soybean yield was reduced most (44%) with concomitant changes in stem height, stem diameter, lodging, and branches, nodes, and pods/plant. Interference of common cocklebur with soybeans resulted primarily from shoot interference, and competition for light within the soybean canopy implicated as the major factor causing the soybean yield reduction.
Effect of Watering Frequency, Drought, and Glyphosate on Growth of Field Bindweed (Convolvulus arvensis)
Authors: Dall'Armellina Armando A. , Zimdahl Robert L.
Published: May 2019

Greenhouse experiments were conducted to determine effects of watering frequency, drought stress, and a combination of watering frequency and glyphosate on growth of field bindweed. Watering daily, twice weekly, or weekly to field capacity affected field bindweed grown from seed differently than plants grown from root runner segments. Shoot and root dry matter of plants grown from seed increased when plants were watered frequently but dry matter allocated to root runners did not change when plants were watered less frequently. Plants grown from root runner segments increased their shoot and root runner dry matter when watered frequently, but root dry matter was not affected by watering frequency. Plants grown from seed had highest regrowth when watered weekly and plants grown from root runner segments had higher regrowth when watered daily. Drought reduced survival rate and dry matter of surviving plants. Frequency of watering and whether plants began from seeds or root runner segments influenced glyphosate action on field bindweed. No regrowth was observed 6 months after 1.5 kg ai/ha of glyphosate was applied to plants that had been grown for 8 weeks under three different watering frequencies.
Reciprocal Common Garden Studies of the Germination of Seeds of Big Sagebrush (Artemisia tridentata)
Authors: Young James A. , Evans Raymond A.
Published: May 2019

Experiments were conducted to compare the influence of production site and seed source on the germination of big sagebrush seeds in relation to incubation temperatures. Seeds of big sagebrush were collected from five plant communities located on the margin of the Carson Desert in western Nevada. Seedlings were grown from the seeds and transplanted back to the sites of collection in reciprocal gardens. Seeds from 1-yr-old gardens were tested for germination at a constant 15 C for three consecutive years. The greater quantity of seeds produced by 2- and 3-yr-old gardens were tested at 55 constant or alternating temperature regimes. Seeds of big sagebrush produced in reciprocal gardens had lower germination than seeds collected from native stands at the same locations. The reduced germination disappeared as the reciprocally transplanted plants grew older and larger, but seeds from these plants did not reach the same levels of germination as those collected from native stands at the same location. Moisture stress and/or freezing temperature conditions during flowering may have directly influenced the quality of seeds produced or interacted with the inherent genotypes of big sagebrush to trigger seed production of variable quality in relation to germination characteristics.
Growth and Competition of Black Nightshade (Solanum nigrum) and Palmer Amaranth (Amaranthus palmeri) with Cotton (Gossypium hirsutum)
Authors: Keeley Paul E. , Thullen Robert J.
Published: May 2019

Black nightshade plants were controlled by hoeing in the same cotton plots each year (1982 to 1986) for 3 to 15 weeks after crop emergence to evaluate the influence of several black nightshade-free periods on cotton yield, reproduction of black nightshade, and longevity of weed seeds in soil. Similar information, although limited, was also collected for Palmer amaranth that escaped the initial herbicidal treatment each year. Except for 1982, black nightshade competing with cotton for the duration of the growing season in nonhoed plots severely reduced yields (60 to 100%), with greatest yield reductions (82 to 100%) occurring in 1983 and 1984 when 0.5 to 0.7 cm of rain fell within 10 days after cotton planting. When combined with cultivation, a 3-week nightshade-free period at cotton planting was of sufficient duration to protect cotton yields. Weed seed production for all hoed treatments was less than 1% of the nonhoed treatment, and after five consecutive cotton crops (1982 to 1986), the amount of both black nightshade and Palmer amaranth seeds in soil was similar for all hoed treatments. These populations were 60 to 80% and 95 to 97% less than beginning populations of black nightshade and Palmer amaranth in 1982, respectively. After 5 yr of continuous treatments, cotton was grown in 1987, with standard cultivation as the only method of weed control, to evaluate how the weed-free periods in 1982 to 1986 influenced weed seed populations in the soil and the resultant effect on weed competition and cotton yields. Reduction of cotton yields in 1987, in the absence of weed-free periods, indicated that black nightshade seed survival in soil appears to be sufficiently long for ample establishment of this weed to compete with cotton. Thus, fields will have to be kept weed free for greater than 5 yr to reduce black nightshade populations to a level that will not reduce cotton yields.
Increased Phytochrome Responsiveness and a High-Temperature Transition in Barnyardgrass (Echinochloa crus-galli) Seed Dormancy
Authors: Taylorson R. B. , Dinola L.
Published: May 2019

Dormant barnyardgrass seeds imbibed in darkness for 8 days at 38 C displayed a very low fluence response to phytochrome, and very little germination occurred in darkness. However, if seeds were imbibed at temperatures >42 C or exposed to 46 C for only 0.5 h, considerable germination was evoked in the absence of a light stimulus. It is proposed that the high temperatures caused a transition in dormancy from a light-requiring to a light-independent state. The finding may have relevance to field behavior of barnyardgrass seeds where burial could prevent reception of the required light stimulus.
Growth and Interaction of Johnsongrass (Sorghum halepense) with Cotton (Gossypium hirsutum)
Authors: Keeley Paul E. , Thullen Robert J.
Published: May 2019

Several weed-free and johnsongrass competition periods were established and maintained in cotton to evaluate their influence on cotton yield and reproduction of johnsongrass. When johnsongrass was sprayed with fluazifop in field plots 3, 6, 9, or 12 weeks after cotton emergence, only plots sprayed at 3 weeks yielded as much cotton as weed-free plots. Johnsongrass permitted to compete for 6, 9, 12, and 25 weeks reduced cotton yields 20, 60, 80, and 90%, respectively. When johnsongrass was transplanted into weed-free plots 3, 6, 9, and 12 weeks after cotton emergence, a weed-free period of 9 weeks was required to prevent significant cotton yield reduction. Cotton in plots weed free for 3 and 6 weeks yielded 81 and 89% as much seed cotton, respectively, as weed-free controls. Johnsongrass competing with cotton for 9 to 12 weeks produced 20 and 40% as many seeds and rhizomes, respectively, as weedy control plots. Some seeds and rhizomes were produced (1% of weedy check plots) in plots weed free for 9 to 12 weeks. Cotton grades were reduced in plots weed free for 3 and 6 weeks, and in plots where johnsongrass competed for 9 to 25 weeks.
Application Timing and Corn (Zea mays) Residue Effects on Weed Control from Metribuzin plus Metolachlor
Authors: Koppatschek Fritz K. , Liebl Rex A. , Slife Fred W.
Published: May 2019

Field and laboratory studies were conducted in 1985 and 1986 to determine the effect of herbicide application timing and level of corn residue on metribuzin plus metolachlor for weed control in soybean. Herbicides were applied early preplant (35 days before planting), sequentially (early preplant and preemergence), or preemergence. Giant foxtail control was better with sequential application than early preplant herbicide application in both years. Control of velvetleaf, smooth pigweed, and jimsonweed was independent of application timing, except in 1986, when jimsonweed control was less from herbicides applied early preplant compared to sequentially. Metribuzin reaching the soil was less when applied to high levels of corn residue compared to low residue levels. However, corn residue level had no effect on weed control.
Efficacy, Phytotoxicity, and Persistence of Imazaquin, Imazethapyr, and Clomazone in No-Till Double-Crop Soybeans (Glycine max)
Authors: Mills J. Anthony , Witt William W.
Published: May 2019

Experiments were conducted in 1985 and 1986 to determine and compare the efficacy, phytotoxicity, and soil persistence of imazquin, imazethapyr, and clomazone in no-till double-crop soybeans. All herbicides controlled 93% or greater jimsonweed, velvetleaf, and giant foxtail. Imazaquin and imazethapyr controlled more common cocklebur and ivyleaf morningglory than clomazone. Soybeans were injured from imazaquin and imazethapyr applications in 1986 but yields were not reduced. First-order kinetics described the dissipation of each herbicide. Imazaquin and imazethapyr were more persistent in the soil than clomazone. Averaged over both years, half-lives of 10, 43, and 60 days were calculated for clomazone, imazaquin, and imazethapyr, respectively. Clomazone was not detected 10 to 20 cm in the soil profile. More imazethapyr was detected 10 to 20 cm in the soil profile than imazaquin in 1985. Slight corn injury (≤10%) was observed in 1987 following previous year applications of imazaquin to no-till double-crop soybeans but corn yields were not reduced.
Control of Selected Perennial Weeds with Glyphosate
Authors: Yonce Mark H. , Skroch Walter A.
Published: May 2019

The efficacy of glyphosate as affected by rate, time of application, and addition of surfactant3was evaluated on blackberry, Japanese honeysuckle, poison ivy, sericea lespedeza, and trumpetcreeper. The addition of surfactant (0.5% v/v) to glyphosate had no effect on the control of the weeds studied. Glyphosate applied in mid-June to September at 1.1 or 2.2 kg/ha controlled blackberry. Mid-August glyphosate applications of 2.2 kg/ha controlled 83% of actively growing Japanese honeysuckle; there was less than 75% at one site due to moisture stress. Use of 2.2 kg/ha of glyphosate from mid-June through mid-August controlled 87% of poison ivy. Consistent commercially acceptable control of sericea lespedeza was obtained when glyphosate was applied at 1.1 or 2.2 kg/ha at the time of flowering. Applying glyphosate at 1.1 or 2.2 kg/ha from late July through early October controlled 50% or more of the trumpetcreeper.
Weed Control in Soybeans (Glycine max) with Reduced Rates of Postemergence Herbicides
Authors: Defelice Michael S. , Brown William B. , Aldrich Richard J. , Sims Barry D. , Judy Dan T. , Guethle David R.
Published: May 2019

Field studies were conducted at three sites in Missouri in 1986 and 1987 to evaluate the performance of below-label rates of bentazon, acifluorfen, and chlorimuron tank mixed with sethoxydim and applied to soybeans 7 and 14 days after planting to evaluate broadleaf and grass weed control and weed seed production. Sequential applications of 0.25X-labeled rates of all three broadleaf herbicides tank mixed with 0.5X sethoxydim rates controlled giant foxtail, velvetleaf, and common cocklebur equivalent to one application of standard-labeled rates of the same tank mixes. Single applications of below-labeled rates of the postemergence herbicides did not control weeds, and soybean yields were not equal to sequential 0.25X or single full-rate treatments. A preemergence treatment of clomazone plus imazaquin applied at labeled rates controlled weeds, and soybean yields were equal to a handweeded check in both years at all test locations. Weeds survived and produced seed to reinfest the plots the following year unless nearly 100% control was achieved.
Herbicides for Postemergence Control of Annual Grass Weeds in Seedling Forage Grasses
Authors: Peters Thomas J. , Moomaw Russell S. , Martin Alex R.
Published: May 2019

The control of three summer annual grass weeds with herbicides during establishment of forage grasses was studied near Concord and Mead, NE, in 1984, 1985, and 1986. Three cool-season forage grasses, intermediate wheatgrass, tall fescue, and smooth bromegrass, and two warm-season grasses, big bluestem and switchgrass, were included. The control of three major summer annual grasses, green foxtail, barnyardgrass, and large crabgrass, was excellent with fenoxaprop at 0.22 kg ai/ha. Slight to moderate injury to cool-season forage grasses and severe injury to warm-season grasses were evident. Sethoxydim at 0.22 kg ai/ha and haloxyfop at 0.11 kg ai/ha controlled green foxtail and large crabgrass, but not barnyardgrass. Sulfometuron-treated big bluestem and switchgrass plots had the best forage stand frequencies and yields and, at the rate used, sulfometuron satisfactorily controlled green foxtail but only marginally controlled barnyardgrass and large crabgrass.
Influence of 2,4-D and MCPA Formulations and Oil on Diclofop Phytotoxicity
Authors: Gillespie Greg R. , Nalewaja John D.
Published: May 2019

Field experiments were conducted during 1984 and 1985 to determine the influence of 2,4-D and MCPA amine and ester formulations on control of foxtail millet with diclofop. Foxtail millet control increased as the diclofop rate increased from 0.6 to 1.7 kg ai/ha whether diclofop was applied alone or with 2,4-D or MCPA amine and ester formulations; however, foxtail millet control was lower when diclofop was applied with 2,4-D or MCPA amine and ester formulations compared to diclofop applied alone. MCPA ester, MCPA amine, 2,4-D ester, or 2,4-D amine at 0.14 kg ai/ha added to a diclofop spray mixture reduced foxtail millet control 8, 15, 20, and 30% compared to diclofop applied alone, averaged over diclofop rates of 0.6, 0.8, 1.1, 1.4, and 1.7 kg/ha. Adding a petroleum oil to diclofop increased foxtail millet control with diclofop at 0.6 kg/ha but not at 0.8 kg/ha. The petroleum oil additive did not overcome the antagonism of foxtail millet control when diclofop at 0.6 kg/ha was applied with 2,4-D or MCPA amine and ester formulations. The amount of14C-diclofop absorbed by oats was greater when diclofop was applied with the ester formulations of 2,4-D or MCPA compared to the amine formulations. Either once-refined sunflower oil or sunflower oil methyl ester applied with14C-diclofop increased the amount of14C absorbed and translocated in oat plants compared to14C-diclofop applied alone.
Postemergence Weed Control Systems Without Dinoseb for Peanuts (Arachis hypogaea)
Authors: Wilcut John W. , Wehtje Glenn R. , Cole Tracy A. , Hicks T. Vint , McGuire John A.
Published: May 2019

Postemergence treatments utilizing various combinations of fluazifop-P, paraquat, and 2,4-DB were compared to a preplant-incorporated (PPI) application of benefin followed by a ground-cracking application of alachlor and dinoseb plus naptalam and a postemergence application of 2,4-DB for weed control, peanut yield, and net economic return to land, overhead, and management. The greatest peanut yields (3-yr average of 4510 kg/ha) and net returns (3-yr average of $521/ha) were provided by a postemergence system that utilized one ground-cracking and one postemergence application of paraquat and one postemergence application of fluazifop-P and 2,4-DB. Seven postemergence systems provided equivalent or greater yield and net returns than the PPI and dinoseb plus naptalam system. Fresh weight reductions of Texas panicum, sicklepod, Florida beggarweed, and pitted morningglory from postemergence weed control systems were equivalent to reductions obtained from the PPI and dinoseb plus naptalam system. The addition of paraquat and 2,4-DB to the PPI and dinoseb plus naptalam system improved the 3-yr average peanut yield and net economic return by 510 kg/ha and $136/ha, respectively, compared to the same system without paraquat and 2,4-DB.
Weed Control from Imazaquin and Metolachlor in No-till Soybeans (Glycine max)
Authors: Buhler Douglas D. , Werling Virginia L.
Published: May 2019

In 1985, when weed densities were low (169 plants/m2in untreated control), imazaquin applied at 0.07 kg ai/ha early preplant controlled over 90% of all weeds before no-till planting of soybeans. In 1986 and 1987 when weed densities were higher (589 plants/m2in untreated control), addition of 1.1 kg ai/ha or more of metolachlor to imazaquin (0.07 kg/ha) before soybean planting controlled 95% or more of the grass weeds and 83% or more of the broadleaf weeds. Imazaquin plus metolachlor applied less than 1 day after soybean planting controlled less than 70% of the emerged weeds in 1986 and 1987; common lambsquarters was most tolerant. Early preplant treatments controlled more weeds throughout the growing season than treatments applied after planting. Splitting herbicide treatments among application times generally did not increase weed control compared to single applications. Early preplant applications resulted in higher soybean densities and taller soybeans 30 days after planting in 1986 and 1987 than treatments applied after planting. Soybean yields increased as weed control increased. Weed control and soybean yields were greater with early preplant treatments than paraquat plus alachlor plus metribuzin applied preemergence in 1986 and 1987. No carryover of imazaquin residue was detected through corn bioassay in the field.
The Basis of Bentazon Antagonism on Sethoxydim Absorption and Activity
Authors: Wanamarta Gunawan , Penner Donald , Kells James J.
Published: May 2019

The antagonistic effect of bentazon on sethoxydim adsorption and activity was studied in quackgrass. The diffusion of14C-sethoxydim into and through an isolated tomato fruit cuticle was inhibited in the presence of the sodium salt of bentazon. Bentazon also increased the partitioning of14C-sethoxydim into CH2Cl2and water; however, it decreased partitioning into ethyl acetate. Removal of epicuticular wax from quackgrass leaf surfaces did not prevent the antagonism. Addition of sodium acetate or sodium bicarbonate to the sethoxydim spray solution at 10 mM reduced uptake of14C-sethoxydim by quackgrass similar to the effect of bentazon. Sodium ions in the bentazon formulation appeared responsible for the antagonism by exchanging with the H+of the sethoxydim hydroxyl group to form a more polar sodium salt of sethoxydim. The addition of Li+, K+, Cs+, Ca++, and Mg++cations associated with a weak acid also reduced14C-sethoxydim absorption. Addition of organic acids to the spray solution overcame the antagonism by preventing the formation of sodium salt of sethoxydim. In the field, the addition of a 3000 ppm sodium acetate solution delivering 0.56 kg/ha produced the same antagonism as bentazon on quackgrass control with sethoxydim.