bluuebunny/crossref_metadata_2025 huggingface dataset:
Meeting of experts on committees or other bodies for the national implementation of international humanitarian law: Geneva, 23-25 October 1996
Authors: Dubois Olivier
Published: May 2019

In the past few years there has been a growing awareness of the need to strengthen implementation of international humanitarian law. States thus have to create the means enabling them to fulfil their obligation to respect and ensure respect for humanitarian law. This requires them to take action in peacetime and to adopt national measures to guarantee compliance with the law in all circumstances.
Chemical Weapons Convention enters into force
Authors: Herby Peter
Published: May 2019

The Convention on the prohibition of the development, production, stockpiling and use of chemical weapons and on their destruction, of 13 January 1993 (Chemical Weapons Convention - CWC) enters into force on 29 April 1997, following the deposit by Hungary on 31 October 1996 of the 65th instrument of ratification. This landmark Convention complements and reinforces the 1925 Geneva Protocol prohibiting the use of chemical and biological weapons by also banning the development, production and stockpiling of chemical weapons — as well as their use — and requiring the destruction of existing stockpiles. The 1925 Geneva Protocol was adopted following a dramatic appeal against chemical warfare by the ICRC at the end of the First World War. The Biological Weapons Convention, in force since 1975, has outlawed the development, production and stockpiling of these weapons.
Geneva Conventions for the protection of war victims of 12 August 1949 and Additional Protocols of 8 June 1977 Ratifications, accessions and successions as at 31 December 1996
Authors: Centre for Legal Documentation, ICRC
Published: May 2019

The names of countries given in the following list may differ from the official names of States.

The dates indicated are those on which the Swiss Federal Department of Foreign Affairs received the official instrument from the State that was ratifying, acceding to or succeeding to the Conventions or Protocols or accepting the competence of the Commission provided for under Article 90 of Protocol I. They thus represent neither the date on which ratification, accession, succession or acceptance of the Commission was decided upon nor that on which the corresponding instrument was sent.
Decapod Crustaceans from the Eocene Castle Hayne Formation, North Carolina: Paleoceanographic Implications
Authors: Feldmann Rodney M. , Bice Karen L. , Hopkins Carrie Schweitzer , Salva Eric W. , Pickford Katherine
Published: May 2019

Ten species of brachyuran decapod crustaceans, including four new species,Matutites miltonorum, Pororaria? granulosa, Eocarpilius blowi, andGlyphithyreus sturgeoni, are described from the Eocene Castle Hayne Formation in North Carolina. In addition, claw fragments suggest the presence of an additional four species. Analysis of the fauna within the formation, coupled with data from the enclosing rocks, suggests an environment of deposition in subtropical, clear water at shallow shelf depths. Wave and current energy were variable. Although no corpses were recognized and all the taxa were represented either by claw fragments or isolated carapaces, little abrasion or breakage was observed, which suggests that the material was deposited near the living site of the organisms. Many of the decapod taxa are congeneric with contemporaneous forms from Italy and with Miocene species in Hungary. Paleoceanographic modeling, using the Parallel Ocean Climate Model (POCM), forced by the GENESIS atmospheric circulation model, produces conditions of temperature, salinity, and ocean circulation that corroborate conclusions drawn from analysis of the Castle Hayne sediments and fauna and, additionally, yields similar conditions for the northern margin of the Tethyan region in the Mediterranean basin. Ocean circulation patterns demonstrate the feasibility of dispersal of subtropical organisms from the Mediterranean part of the Tethys across the Atlantic Ocean to the North American coastline.
Bicellular Trichomes of Johnsongrass (Sorghum halepense) Leaves: Morphology, Histochemistry, and Function
Authors: McWhorter Chester G. , Paul Rex N. , Ouzts J. Clark
Published: May 2019

Studies were conducted of one of the structural factors that influences microroughness on johnsongrass leaves. Bicellular trichomes, 47 ± 5 μm long, represented 4 to 5% of all epidermal cells. They secreted a mucilagenous material that covered 8 ± 4% of the leaf surface. Bicellular trichomes occurred in longitudinal rows, intermixed with intercostal cork-silica cells, between rows of stomata. Numbers of bicellular trichomes present per unit area were inversely related to numbers of intercostal cork-silica cells. The trichomes were the panicoid type that are reported not to secrete salts. Johnsongrass trichomes, however, could be induced to discharge salt in the mucilage-type secretions when plants were grown in a soil mixture that was high in lime. Not all secretory constituents were identified, but carbohydrates and callose were found in addition to possible low concentrations of protein. The apical or cap cell of the trichomes stained positively for lipid, protein, and polysaccharide and negatively for pectin, polyphenols, steroids, and alkaloids. The presence of trichomes increases leaf surface microroughness, but the secretion covers wax crystals, decreasing leaf microroughness and likely providing another barrier to herbicide entry through the cuticle. Bicellular trichomes on grain sorghum were similar to those on johnsongrass and also discharged secretions on the leaf surface.
Modeling the Population Dynamics and Economics of Velvetleaf (Abutilon theophrasti) Control in a Corn (Zea mays)-Soybean (Glycine max) Rotation
Authors: Lindquist John L. , Maxwell Bruce D. , Buhler Douglas D. , Gunsolus Jeffrey L.
Published: May 2019

A simulation model was developed to predict the population dynamics and economics of velvetleaf control in a corn-soybean rotation. Data compiled from the literature were used to parameterize the model for two situations, one in which velvetleaf was infected by aVerticilliumspp. wilt and one without infection.Verticilliumwas assumed to have no effect on corn or soybean yield. In the absence of control, simulated seedbank densities of aVerticillium-infected velvetleaf population were 5 to 50 times lower than for an uninfected velvetleaf population. The model was used to evaluate a threshold weed management strategy under the assumption that velvetleaf was the only weed and bentazon the only herbicide available for its control. In the absence ofVerticillium, an economic optimum threshold of 2.5 seedlings 100 m−2afforded the highest economic returns after 20 yr of simulation. Simulations in which velvetleaf was infected in 8 out of 20 randomly assigned years indicated a 6% increase in annualized net return and an 11 % reduction in the number of years that control was necessary. Sensitivity analysis indicated the parameter estimates having the greatest impact on economic optimum threshold were seedling emergence and survival, maximum seed production, and herbicide efficacy. Under an economic optimum threshold of 2.5 seedlings 100 m−2, management practices that manipulate the most sensitive demographic processes increased annualized net return by up to 13% and reduced long-term herbicide use by up to 26%. Results demonstrate that combining an economic optimum threshold with alternative weed management strategies may increase economic return and reduce herbicide use.
Characterizing the Sethoxydim-Bentazon Interaction with Proton Nuclear Magnetic Resonance Spectrometry
Authors: Thelen Kurt D. , Jackson Evelyn P. , Penner Donald
Published: May 2019

The antagonistic effect of Na-bentazon on sethoxydim absorption and herbicidal activity has been documented. The addition of ammonium sulfate (AMS) with a surfactant overcomes the observed loss of sethoxydim activity. Nuclear Magnetic Resonance (NMR) was used to study the chemical effects of commercially formulated Na-bentazon, NaCl, NaHCO3, Na-bentazon plus AMS, and NaHCO3plus AMS on commercially formulated sethoxydim. Technical grade Li-sethoxydim and sethoxydim were analyzed and1H-NMR spectra were used as comparative standards. Data indicate an association of Na+from Na-bentazon, NaHCO3, and NaCl with the sethoxydim molecule. NH4+from AMS appears to associate spatially with sethoxydim but does not exert the same electronic effect on the sethoxydim ring protons as observed with Na+or Li+. The addition of AMS to sethoxydim plus Na-bentazon or NaHCO3treatments prevents the complexation of Na+with the sethoxydim molecule. The data support the hypothesis that the observed Na-bentazon antagonism and ammonium sulfate reversal of antagonism are chemically based.
Soybean (Glycine max) Interference on Common Cocklebur (Xanthium strumarium) and Entireleaf Morningglory (Ipomoea hederaceavar.integriuscula)
Authors: Mosier Dwight G. , Oliver Lawrence R.
Published: May 2019

Field experiments were conducted to evaluate soybean interference on common cocklebur and entireleaf morningglory under irrigated and nonirrigated conditions. Interference from the mixture of soybean and entireleaf morningglory, and soybean alone reduced the total leaf area index (LAI), LAI within the common cocklebur canopy, and growth rate of common cocklebur more than did entireleaf morningglory; more reduction occurred without irrigation than with irrigation. Irrigated common cocklebur produced 687 burs per plant, while nonirrigated produced 359. Irrigated and nonirrigated soybeans and the mixture of soybeans and entireleaf morningglory reduced common cocklebur bur production 43 to 47%. Irrigated entireleaf morningglory reduced common cocklebur bur production 42%, while nonirrigated reduced bur production 28%. Interference from the mixture of irrigated soybeans and common cocklebur reduced the total leaf area index (LAI), LAI within the entireleaf morningglory canopy, and growth rate of entireleaf morningglory more than did soybean or common cocklebur alone. Irrigated entireleaf morningglory produced 542 and 1107 seeds per plant in 1982 and 1983, respectively. The mixture of irrigated soybeans and common cocklebur reduced entireleaf morningglory seed production 84 to 90%. Nonirrigated entireleaf morningglory was not competitive in any treatment combination either year due to lack of sufficient LAI.
Carryover Potential of Imazaquin to Cotton, Grain Sorghum, Wheat, Rice, and Corn
Authors: Johnson David H. , Talbert Ronald E. , Horton Diana R.
Published: May 2019

The duration of imazaquin soil activity on corn, grain sorghum, rice, and cotton was studied from 1988 to 1990. Imazaquin applied at 0.035, 0.07, 0.14 (1× rate), and 0.28 kg ai ha−1was incorporated into the soil, and rotational crops were planted at various times after application. Initial crop visual injury was directly related to imazaquin application rate. Cotton was most susceptible, followed by corn, grain sorghum, and rice. The carryover of imazaquin from soybeans to cotton, grain sorghum, and wheat was studied in separate experiments in Arkansas in 1987 to 1989. Wheat planted in the fall following soybean harvest was not affected by imazaquin residues. Grain sorghum planted the following spring was injured (16–35%), but there was no yield reduction. Cotton recovered from early injury (< 35%) in one year and did not recover from severe injury (> 50%) in the other, resulting in yield reduction.
Influence of Soil-Applied Herbicides on Ivyleaf Morningglory (Ipomoea hederacea) Growth and Development in Soybean (Glycine max)
Authors: Holloway James C. , Shaw David R.
Published: May 2019

Soil-applied imazaquin or chlorimuron plus metribuzin reduced ivyleaf morningglory photosynthetic rate, leaf area, biomass, and seed production per plant compared to the nontreated control. Photosynthetic rate of ivyleaf morningglory was reduced a minimum of 53%, and total leaf area was reduced at least 67% with either herbicide, regardless of ivyleaf morningglory densities. Ivyleaf morningglory biomass and seed production were reduced at least 62% with either herbicide across all ivyleaf morningglory densities. Soybean leaf area, photosynthetic rate, and biomass were not affected by herbicide treatment or ivyleaf morningglory densities of 2, 4, 6, or 8 per m of row.
Sorption, Mobility and Degradation of Triclopyr and 2,4-D on Four Soils
Authors: Johnson William G. , Lavy Terry L. , Gbur Edward E.
Published: May 2019

Laboratory studies were conducted to determine the relative sorption, mobility, and degradation rates of triclopyr and 2,4-D on two surface soils and two subsoils from the rice-producing areas of Arkansas. Triclopyr sorption was slightly greater than 2,4-D sorption. However, mobility of the herbicides on a given soil did not differ. Sorption of both herbicides was greatest and mobility lowest on a subsoil with the lowest pH. Triclopyr degradation rates were lower than 2,4-D degradation rates in a dark incubator. The average half life was 138 d for triclopyr and 21 d for 2,4-D. High soil moisture content (0 versus 100 kPa water tension) increased the rate of 2,4-D degradation. Triclopyr degraded more rapidly at 30 C than at 15 C. The dissipation rates of both herbicides were lowest on the soil on which sorption was greatest.
Weeds in a Changing Climate
Authors: Patterson David T.
Published: May 2019

Current and projected increases in the concentrations of CO2and other radiatively-active gases in the Earth's atmosphere lead to concern over possible impacts on agricultural pests. All pests would be affected by the global warming and consequent changes in precipitation, wind patterns, and frequencies of extreme weather events which may accompany the “greenhouse effect.” However, only weeds are likely to respond directly to the increasing CO2concentration. Higher CO2will stimulate photosynthesis and growth in C3weeds and reduce stomatal aperture and increase water use efficiency in both C3and C4weeds. Respiration, and photosynthate composition, concentration, and translocation may be affected. Perennial weeds may become more difficult to control, if increased photosynthesis stimulates greater production of rhizomes and other storage organs. Changes in leaf surface characteristics and excess starch accumulation in the leaves of C3weeds may interfere with herbicidal control. Global warming and other climatic changes will affect the growth, phenology, and geographical distribution of weeds. Aggressive species of tropical and subtropical origins, currently restricted to the southern U.S., may expand northward. Any direct or indirect consequences of the CO2increase that differentially affect the growth or fitness of weeds and crops will alter weed-crop competitive interactions, sometimes to the detriment of the crop and sometimes to its benefit.
The competitive ability of wheat (Triticum aestivum) compared to rigid ryegrass (Lolium rigidum) and cowcockle (Vaccaria hispanica)
Authors: Tanji Abbes , Zimdahl Robert L. , Westra Philip
Published: May 2019

Greenhouse and field experiments were conducted to study competition between wheat and rigid ryegrass or between wheat and cowcockle using additive series and growth analysis. Wheat was the dominant competitor with either weed. One wheat plant was as competitive as 1 1 or 19 rigid ryegrass plants in greenhouse and field experiments, respectively. One wheat plant was as competitive as three to 24 cowcockle plants, depending on environmental conditions. Dry weight of roots, leaves, stems, and spikes or capsules responded similarly to the effects of competition between wheat and rigid ryegrass or cowcockle. Shoot dry weight was the easiest, fastest, and least expensive component to measure competition. Growth analyses of individual plants showed that wheat had a greater leaf area, shoot and root dry weight, and absolute growth rate than rigid ryegrass or cowcockle, particularly early in the season. A range of 120 to 240 wheat plants m−2can minimize rigid ryegrass or cowcockle competition and achieve an acceptable grain yield in semiarid areas in Morocco.
Relative time of redroot pigweed (Amaranthus retroflexusL.) emergence is critical in pigweed-sorghum [Sorghum bicolor(L.) Moench] competition
Authors: Knezevic Stevan Z. , Horak Michael J. , Vanderlip Richard L.
Published: May 2019

Redroot pigweed is a common weed in sorghum fields throughout the southcentral United States including Kansas. In 1994 and 1995, field studies were conducted at two sites near Manhattan, KS, to determine the influence of redroot pigweed densities and times of emergence on sorghum yield and yield components. Redroot pigweed was sown at densities of 0.5, 1, 2, 4, and 12 plants meter−1of row within a 25-cm band over the sorghum row at planting and at the three- to four-leaf stage of sorghum. A rectangular hyperbola was used to describe the relationship between crop yield loss and weed density. Because of the instability of both coefficientsI(percentage yield loss at low weed density) andA(percentage yield loss at high weed density), our results do not support the use of a model based exclusively on weed number to estimate sorghum yield loss across all locations within a region. A quadratic polynomial equation that accounts for the time of weed emergence relative to the crop growth stage is suggested as an alternative method to estimate sorghum yield loss. At the densities studied, the time of pigweed emergence relative to the sorghum leaf stage was critical for the outcome of sorghum-pigweed competition. Significant sorghum yield losses occurred only when pigweed emerged before the 5.5-leaf stage of sorghum. An examination of yield components suggested that the yield loss was a result of a reduction in number of seeds per head.
Prediction of flowering in common crupina (Crupina vulgaris)
Authors: Roché Cindy Talbott , Thill Donald C. , Shafii Bahman
Published: May 2019

Exotic annual weeds on western U.S. rangelands owe at least part of their invasion success to prolific seed production. Reproductive output is determined largely by timing of flowering in relation to soil moisture, light, and competing vegetation. This study investigated the influence of temperature (including vernalization), photoperiod, and intraspecific competition on reproductive phenology in three populations (two varieties,typicaandbracbypappa) of common crupina. Monthly plantings at four densities were grown in field plots through two consecutive cycles, and the date each plant reached bud and flowering stage was recorded. Development of greenhouse-grown plants from the same populations was compared with those grown outside for 4, 6, 8, and 10 wk of cold induction. Reproductive development in common crupina was influenced by all factors investigated: temperature, photoperiod, density, and vernalization. Conditions fostering the shortest thermal time from emergence to floral induction were a period of cold temperatures/short photoperiod as seedlings followed by warming temperatures and lengthening photoperiod. Both varieties of common crupina responded quantitatively to vernalization, but lack of vernalization caused a greater delay of flowering in var.brachypappathan in var.typica.Vernalization contributed to convergence of spring flowering among the August to December plantings, but earlier emergence and lower plant density greatly increased final plant size and fecundity. Lack of vernalization, high temperatures, and shortening day length delayed flowering of spring/summer emergents, increasing the probability of succumbing to drought before producing seed.
Estimation of base and optimum temperatures for seed germination in common crupina (Crupina vulgaris)
Authors: Roché Cindy Talbott , Thill Donald C. , Shafii Bahman
Published: May 2019

Thermal time models for predicting phenological development require an estimate of base temperature, an attribute not previously defined for common crupina, a Mediterranean winter annual introduced in western North America. The stage of seed germination was selected for estimating base temperature, because facilities were available for experiments over a range of constant temperatures and base temperature is relatively constant throughout the life cycle in other species. Achenes from three populations of common crupina, including two varieties,typicaandbrachypappa, were produced under uniform conditions. Cumulative germination was recorded at 12 h intervals for achenes in darkness and optimum moisture at 23 constant temperatures from 4 to 17 C. The time course of germination was best described by a logistic growth curve from which time to 50% germination was estimated. A parabolic model provided the best fit in a regression of germination rate (reciprocal of time to 50%) against the temperature gradient, yielding base and optimum temperatures of 1 and 10.5 C, respectively. Bootstrap confidence intervals indicated no significant difference in base and optimum temperatures in germination between the two varieties nor between two populations of var.typicaof common crupina introduced in the northwestern United States.
Green kyllinga (Kyllinga brevifolia): germination and herbicidal control
Authors: Molin William T. , Khan Rehana A. , Barinbaum Robert B. , Kopec David M.
Published: May 2019

Green kyllinga is a relatively new weed species in well-irrigated turfs in the southwest US. To understand the germination requirements of green kyllinga, the effects of planting depth, temperature, pH, and osmotic potential were determined. Green kyllinga emergence was sensitive to planting depth. At 21 days after planting (DAP), emergence of green kyllinga was 60% when planted at the soil surface but only 20% at 0.5 cm and less than 5% at 1 cm. Germination occurred at temperatures between 17 and 30 C but was notably better between 20 and 24 C. Germination was uniform from pH 5.5 to 9.5. Germination decreased between the water potentials −0.1 to −0.6 MPa, although germination was high at water potentials found in irrigated turf. The environmental conditions found in nonstressed turf areas in Arizona will likely support the establishment of green kyllinga. The efficacy of herbicides for the control of green kyllinga was also determined. Control of kyllinga (95% or greater) was obtained with preemergence applications of oxadiazon, dithiopyr, and metolachlor, and with postemergence applications of DSMA, halosulfuron-methyl, and imazaquin.
Field persistence of bioavailable flumetsulam
Authors: Shaw David R. , Murphy Glen P.
Published: May 2019

Field research was conducted in 1994 and 1995 to monitor the dissipation of flumetsulam in five Mississippi soils for a period of 16 wk. These soils allowed evaluation of flumetsulam persistence across three soil series with a relatively constant soil pH of 6.0, as well as across three soils of varied pH from 6.0 to 7.6 within a constant soil series. Bioavailability was determined with a rice root length bioassay. Predicted half-lives ranged from 20 to 26 d in 1994 and from 23 to 46 d in 1995. Persistence decreased with increasing cumulative rainfall and decreasing organic matter content (within a range of 1.2 to 3.5%). Soil pH had no measurable effect on flumetsulam persistence.
Variation in vetch (Vicia spp.) response to Orobanche aegyptiaca
Authors: Goldwasser Yaakov , Kleifeld Yeshayahu , Plakhine Dina , Rubin Baruch
Published: May 2019

Orobanche aegyptiaca is a chlorophyll-lacking holoparasite that subsists on the roots of plants, inflicting severe damage to legumes and other crops in the Mediterranean region. Common vetch and purple vetch are important legume forage crops in Israel and the Middle East. Experiments in pots containing soil inoculated with O. aegyptiaca seeds have shown that common vetch genotypes ‘Yovel’ and ‘473-A’ are susceptible to the parasite, whereas purple vetch genotypes ‘Popany’ and ‘Sadot’ are resistant. When grown in association with O. aegyptiaca in polyethene bags, purple vetch genotypes stimulated a significantly higher rate of parasite seed germination than that stimulated by common vetch genotypes. However, the number of successful Orobanche attachments developed on the host root was lower on resistant genotypes compared to susceptible ones. This differential response between purple and common vetch genotypes was evident at diverse temperature regimes (17/12, 22/17, and 27/22 C day/night). Microscopic observations revealed that resistant genotypes rapidly developed necrotic lesions surrounding the contact point of the parasite radicle (germ tube) with the host root, hence preventing further development of the parasite. In the sensitive genotypes, attachments developed without necrotic lesions. These data may indicate involvement of host defense mechanisms induced by the parasite attachment.
Giant foxtail (Setaria faberi) control in sethoxydim-resistant corn (Zea mays)
Authors: Young Bryan G. , Hart Stephen E.
Published: May 2019

Field studies were conducted at Dekalb and Urbana, IL, in 1995 and 1996 to evaluate the effectiveness of sethoxydim for giant foxtail control in sethoxydim-resistant (SR) corn. Experiments studied sequential and total postemergence applications of grass herbicide standards compared to sethoxydim. Additional studies evaluated the compatibility of sethoxydim with postemergence broadleaf herbicides. Metolachlor plus atrazine and metolachlor followed by dicamba plus atrazine gave at least 88% control of giant foxtail at both locations in both years. Metolachlor plus flumetsulam plus clopyralid provided 90% or greater grass control over all experiments, with the exception of only 75% control at Dekalb in 1995 due to a heavy giant foxtail infestation. In comparison, flumetsulam plus clopyralid followed by postemergence applications of sethoxydim or nicosulfuron provided the same level of grass control as preemergence metolachlor, except at Dekalb in 1995 where control was 72% for both sethoxydim and nicosulfuron. Sequential applications of sethoxydim increased control of giant foxtail compared to a single sethoxydim application in 1995. Sethoxydim applied alone controlled giant foxtail 8% better than nicosulfuron at Urbana in 1996. Postemergence sethoxydim applied alone provided 87% or better control of giant foxtail. Sethoxydim performance was consistent when applied with flumetsulam plus clopyralid plus 2,4-D (NAF-73), halosulfuron plus dicamba, and bromoxynil. The efficacy of sethoxydim was reduced in combination with dicamba plus atrazine in three of the four trials, and bentazon plus atrazine as well as primisulfuron plus prosulfuron in all trials. Sethoxydim outperformed nicosulfuron in combinations with bromoxynil at Urbana. These studies indicate sethoxydim has excellent potential to be used in corn for postemergence control of giant foxtail.
Effect of soil water content and temperature on dormancy breaking and germination of three weeds
Authors: Martinez-Ghersa Maria A. , Satorre Emilio H. , Ghersa Claudio M.
Published: May 2019

In laboratory experiments, we studied barnyardgrass, common lambsquarters, and redroot pigweed seed dormancy release by alternating temperatures under different soil water regimes, to determine whether that response serves as a mechanism for assuring seedling establishment. Alternating temperatures were important in breaking seed dormancy in the three weeds, but the species' response to alternating temperatures differed with soil water content. For redroot pigweed and newly dispersed seeds of barnyardgrass, dormancy breaking by alternating temperatures occurred only when soil water content was high enough for germination. Moreover, adverse incubation conditions (constant temperature and low water content) induced secondary dormancy in these seeds. Seventy percent of seeds incubated in open boxes emerged before the soil reached wilting point, when seeds were incubated at temperatures high enough for a high germination rate. A dormancy breaking mechanism that triggers a high rate of germination may be important in assuring success of seedling establishment where rainfall patterns result in wetting and drying cycles of the soil, especially in soil types that lose water rapidly from the surface layers.
Variation in photoperiod response of different isogenic lines of wild oats (Avena fatua)
Authors: Armstrong Leisa J. , Adkins Stephen W.
Published: May 2019

For wild oats, persistence characters such as seed production and seed dormancy may be affected by genetic variation and several environmental factors during the development of the parental plant. However, the effect of varying photoperiods on such characters is unclear. Previous studies have concentrated on natural populations and have not studied the genetic variability within the population. Consequently, a study was conducted to examine how photoperiod (10, 12, 14, 16, and 18 h at 20 C) influenced the persistence of different members of a synthetic population of wild oats. This synthetic population consisted of several isogenic lines with differing degrees of seed dormancy that originated from one region in North America. All lines were photoperiod sensitive, quantitative long day plants, with an increase in time to maturity for all lines (about 78 to 213 d) when photoperiod was reduced from 18 to 10 h. The lines within this synthetic population (with the exception of one, M73) showed a similar degree of photoperiod sensitivity. This may be expected, as the lines are from one region with the same photoperiod environment. It could be concluded that such a photoperiod sensitivity is a beneficial character that has allowed persistence of these lines in this region. When photoperiod was reduced from 18 to 10 h, plants produced fewer seeds (about 141 to 61 primary seeds per plant) with a higher degree of seed dormancy (about 88 to 54% germination in 10−4M gibberellic acid; GA3). The reduced seed production under the shortest photoperiod (10 h) was due to poor panicle exsertion, which resulted in poor development of basal florets. There was no consistent relationship between photoperiod and other plant characters such as tiller production, caryopsis weight, and water content. However, significant relationships were found between seed dormancy characters and other plant characters such as maturity time, caryopsis weight, and water content under certain photoperiod treatments.
Tillage and seed depth effects on velvetleaf (Abutilon theophrasti) emergence
Authors: Webster Theodore M. , Cardina John , Norquay Heather M.
Published: May 2019

Understanding patterns of weed seedling emergence within a growing season and over years is important to develop models to predict optimum timing of weed management practices. A study was conducted in a field with no previous velvetleaf infestations to describe emergence patterns following seed burial at three depths in two tillage systems. Freshly harvested velvetleaf seeds were planted 0, 2, and 6 cm deep in moldboard plowed (MP) and no-tillage (NT) corn stubble in October 1990. Velvetleaf seedling emergence was monitored over the following 4 yr in continuous corn. Emergence was higher in NT than in MP plots throughout 4 yr of observation. The first growing season following seeding, emerged seedlings represented 9.3 to 15.8% of the seeds sown in NT, compared with 0.1 to 0.8% of seeds sown in MP. After four growing seasons, emerged seedlings were 12.5 to 25% of seeds sown in NT but only 6 to 7.4 % of seeds sown in MP. Emergence was consistently higher from the 0-cm depth than from the 6-cm depth in NT, but seeding depth did not influence emergence in MP due to mixing of the soil during tillage. Velvetleaf emergence was related to growing degree days (base 7.5 C), with greater consistency in NT than in MP. Averaged over years and planting depths, 50% velvetleaf emergence occurred within 8 and 13 d of the predicted date in NT and MP systems, respectively.
Influence of planting date on common cocklebur (Xanthium strumarium) interference in early-maturing soybean (Glycine max)
Authors: Rushing G. Scott , Oliver Lawrence R.
Published: May 2019

Field studies were conducted to determine the effect of common cocklebur interference in early-maturing (maturity group IV) soybean planted in April, May, and July. Common cocklebur density and length of interference did not affect soybean height, canopy width, or node number at any planting date. Removal of common cocklebur 4 weeks after emergence (WAE) prevented reduction of soybean leaf area, stem dry weight, dry leaf weight, dry pod weight, and seed yield. Aboveground biomass for common cocklebur emerging in July was less than biomass of April or May plantings. Common cocklebur planted into soybean 2, 4, or 8 wk after soybean emergence did not reduce soybean yield. Under parameters of this study, planting date was not a significant factor in yield reduction. Interference from one common cocklebur plant per 1.8, 0.9, and 0.3 m of soybean row for 8 wk reduced yields 7, 14, and 30%, and full-season interference reduced yields 16, 33, and 65%, respectively. The Arkansas Weed Management Computer program closely predicted actual yield loss for early-maturing soybean.
Prevention of fungal diseases in transgenic, bialaphos- and glufosinate-resistant creeping bentgrass (Agrostis palustris)
Authors: Liu Chien-An , Zhong Heng , Vargas Joseph , Penner Donald , Sticklen Mariam
Published: May 2019

The antifungal activity of the herbicides bialaphos and glufosinate, the active moiety of bialaphos, was assessed. Bialaphos showed a higher level of in vitro antifungal activity againstRhizoctonia solani, Sclerotinia homoeocarpa, andPythium aphanidermatumthan glufosinate. Glufosinate suppressed the mycelial growth ofR. solaniandS. homoeocarpa, but it had no inhibitory effect onP. aphanidermatumup to the highest concentration in our testing regimes. Various concentrations of bialaphos solutions were applied to transgenic, bialaphos- and glufosinate-resistant creeping bentgrass inoculated with fungal pathogens. Bialaphos applications were able to significantly reduce symptomatic infection byR. solaniandS. homoeocarpaon transgenic plants. Bialaphos significantly inhibitedP. aphanidermatum, but not to the same degree thatR. solaniandS. homoeocarpawere inhibited. These results indicate that bialaphos may provide a means for the simultaneous control of weeds and fungal pathogens in turf areas with transgenic, bialaphos-resistant creeping bentgrass.
Altered acetolactate synthase activity in ALS-inhibitor resistant prickly lettuce (Lactuca serriola)
Authors: Eberlein Charlotte V. , Guttieri Mary J. , Mallory-Smith Carol A. , Thill Donn C. , Baerg Roger J.
Published: May 2019

The effect of target site mutation for acetolactate synthase (ALS)-inhibitor resistance on ALS activity was evaluated in a sulfonylurea-resistant (R) biotype of prickly lettuce with a proline173to histidine substitution in Domain A of the ALS enzyme. I50values for ALS inhibition by several ALS-inhibitor herbicides were determined for R and susceptible (S) biotypes. Results from both a standard ALS assay and a chloroplast assay for ALS activity showed that the R biotype also was cross-resistant to representatives of the imidazolinone (imazethapyr) and triazolopyrimidine (flumetsulam) families, but was not cross-resistant to the pyrimidinyl oxybenzoate (4,6-dimethoxypyrimidin-2-y 1-oxy-2-benzoic acid) tested. TheKm(pyruvate) was similar for ALS extracted from the R and S biotypes, suggesting that mutation for resistance did not alter pyruvate binding on the enzyme. However, specific activity of ALS from the R biotype was 57% less than specific activity of ALS from the S biotype, suggesting that the resistance mutation may affect enzyme function, expression, or stability. ALS from the R biotype was less sensitive to inhibition by the branched chain amino acids, valine, leucine, and isoleucine, than ALS from the S biotype. Reduced sensitivity to feedback inhibition was correlated with 70, 40, and 9% higher concentrations of valine, leucine, and isoleucine, respectively, on a per seed basis in R vs. S seed.
Influence of barnyardgrass (Echinochloa crus-galli) time of emergence and density on corn (Zea mays)
Authors: Bosnic Aca C. , Swanton Clarence J.
Published: May 2019

Barnyardgrass is a serious weed problem in cornfields in Ontario. Field experiments were conducted at two locations in 1994 and 1995 to determine the influence of emergence time and barnyardgrass density on corn yield loss, leaf area at 50% silking, and barnyardgrass seed production. Selected barnyardgrass densities up to 200 plants m−1were established within 12.5 cm on either side of the corn row. Barnyardgrass seeds were planted concurrently with corn and at the 3- to 5- or 1- to 2-leaf stage of corn growth in 1994 and 1995, respectively. Barnyardgrass density and seedling emergence relative to corn influenced the magnitude of corn yield loss. Maximum corn grain yield loss ranged from 26 to 35% for early emerging barnyardgrass, and less than 6% yield loss occurred from barnyardgrass seedlings emerging later than the 4-leaf stage of corn growth. Changes in corn leaf area index at 50% silking reflected the level of barnyardgrass competition in corn. Maximum leaf area reduction ranged from 21 to 23%. Barnyardgrass seed production varied with time of seedling emergence and density. Ten barnyardgrass plants emerging up to the 3-leaf stage of corn growth produced 14,400 to 34,600 seeds m−2compared to only 1,200 to 2,800 seeds m−2from plants emerging after the 4-leaf corn stage. The results of this study are essential in the development of an integrated weed management strategy for corn.
Reduced herbicide rates for large crabgrass (Digitaria sanguinalis) and goosegrass (Eleusine indica) control in bermudagrass (Cynodon dactylon)
Authors: Johnson B. Jack
Published: May 2019

Five PRE herbicides were applied at below maximum registered use rates to the same bermudagrass turf plots for three consecutive years for large crabgrass and goosegrass control. In most instances, full labeled herbicide rates were needed for acceptable large crabgrass and goosegrass control during the 1st year of treatment. All herbicides controlled large crabgrass but not goosegrass during the 1st year. Weed management programs that utilized the lowest herbicide rates while maintaining ≥ 80% control during the 2nd and 3rd years varied with herbicides. The programs for large crabgrass were prodiamine at 0.8 kg ha−1the 1st year followed by 0.2 kg ha−1the 2nd and 3rd years; oryzalin at 2.2 kg ha−1the 1st year followed by 0.6 kg ha−1the 2nd and 3rd years; dithiopyr at 0.3 kg ha−1the 1st year followed by 0.1 kg ha−1the 2nd and 3rd years; pendimethalin at 1.7 kg ha−1the 1st year followed by 0.8 kg ha−1the 2nd and 3rd years; and oxadiazon at 3.4 kg hha−1the 1st year followed by 2.5 kg ha−1the 2nd year and 1.7 kg ha−1the 3rd year. The programs for goosegrass were prodiamine at 0.8 kg ha−1followed by 0.6 kg ha−1the 2nd and 0.4 kg ha−1the 3rd year; dithiopyr at 0.8 kg ha−1the 1st year followed by 0.4 kg ha−1the 2nd and 3rd years; pendimethalin at 3.4 kg ha−1the 1st year followed by 1.7 kg ha−1the 2nd year and 0.8 kg ha−1the 3rd year; and oxadiazon at 3.4 kg ha−1followed by 0.8 kg ha−1the 2nd and 3rd years. Because goosegrass control with oryzalin at reduced rates was unacceptable during the 1st and 2nd years, this herbicide should not be used in a reduced rate program. The quality of common bermudagrass was not affected by reduced herbicide rates.
Weed biology: importance to weed management
Authors: Bhowmik Prasanta C.
Published: May 2019

Knowledge of weed biology is essential for development of both economically and environmentally acceptable weed management systems. Weed biology relates to plant attributes such as morphology, seed dormancy and germination, physiology of growth, competitive ability, and reproductive biology. Concepts of population biology such as seedbank dynamics for annuals and root reserves, dormancy, and longevity of vegetative propagules for perennials can be used to predict weed infestations better and to evaluate sustainable management strategies. Integrated approaches that give priority to depletion of root reserves or seedbanks through interfering with dormancy or germination requirements have great potential to enhance weed management strategies in the future.
Weed diversity and weed management
Authors: Dekker Jack
Published: May 2019

The story of agriculture is the story of weed interference. After millennia of weed control we still have weeds. This situation has led many growers to observe that “the weeds always win.” One of the most important reasons weeds are so successful is their biodiversity. Biodiversity is an inevitable consequence of the struggle an individual weed species undergoes in the presence of neighbors, and by occupying a physical space in an agroecosystem. Weeds have evolved in response to cropping system practices by adapting and occupying niches left available in agroecosystems. Forces created by our cropping practices over evolutionary time have led to the weed diversity we observe today. Diversity underlies weed management in several important ways. A plant experiences diversity among its neighbors in at least five different ways. Weeds have adapted to selection in agroecosystems in several ways: (1) genetic variants within a species; (2) somatic polymorphism of plant parts; (3) success in diverse habitat microsites; (4) temporal adaptations within the community; and (5) floristic diversity of a community at higher levels than the species. Herein, weed diversity is discussed in this broader context, in terms of population behaviors that emerge as a consequence of the activities of individual components at lower levels of organization. Diversity is also discussed in terms of its implications for weed management. The potential exists to develop management strategies based on differences in weed and crop diversity. These strategies might be developed by characterization of weedy genetic and phenotypic diversity; enhancement of crop, cropping system, and agroecosystem diversity; and characterization of the spatial distribution of weed populations.
Soil water thresholds for photoinduction of redroot pigweed germination
Authors: Gallagher Robert S. , Cardina John
Published: May 2019

Perception of light by phytochrome is a mechanism that triggers weed seed germination in response to soil disturbance. Photoconversion of phytochrome from the red light absorbing form to the active far-red absorbing form depends on hydration of phytochrome. This research was conducted to determine the soil water threshold for the photoinduction of germination by the brief exposure of light that occurs during soil disturbance, and to determine how this threshold is affected by the fluence of the light stimulus and fluence sensitivity of the seed population. Redroot pigweed seedling emergence and germination response to red light (R) was studied for a range of water potentials. Water potential gradients were established by incubating seeds in soils wetted to various water contents, or in polyethylene glycol 8000 (PEG) solutions. After imposing the light treatments, seeds were returned to a fully hydrated state. Seedling emergence in response to R increased as the volumetric water content (θv) of soils increased. At volumetric water contents of 4.0%, R-induced seedling emergence was inhibited 50% compared to photoinduced seedling emergence at the highest soil water contents tested. Attenuation of photoinduction was more pronounced at low vs. high R fluences in freshly imbibed seeds, but was unaffected in seeds that exhibited enhanced fluence sensitivity. In ecosystems where seasonal soil moisture extremes are prevalent, the photoinduction of seed germination may be limited in dry microsites such as surface crusts or under extreme drought conditions.
Response of peanut to low rates of MSMA
Authors: Johnson W. Carroll , Wauchope R. Donald , Mullinix Benjamin G.
Published: May 2019

The response of peanut to low rates of MSMA under weed-free conditions was studied in 1992 and 1994 near Tifton, GA. MSMA was applied 40, 70, 100, or 130 days after emergence (DAE). At each application timing, MSMA was applied at 0, 90, 168, and 336 g ai ha−1. MSMA application timing did not affect peanut yield. Increasing rates of MSMA caused minor reduction in peanut yield. Analysis using atomic absorption spectroscopy showed elemental arsenic accumulation of ≤ 0.7 ppm in peanut kernels from MSMA applied 70 and 100 DAE. This approximates the time interval of peanut pod and kernel formation. MSMA applied 40 and 130 DAE resulted in little detectable arsenic in kernels. Low rates of MSMA, originating as drift from aerial applications to cotton or illegal and unsound applications to peanut for Florida beggarweed control, are not likely to reduce peanut yields. The greatest hazard from peanut exposure to MSMA is accumulation of arsenic in kernels, which would adversely affect peanut marketability and consumer demand.
A regional framework for analyzing weed species and assemblage distributions using a geographic information system
Authors: Burkart Michael R. , Buhler Douglas D.
Published: May 2019

This paper presents a framework in which the spatial and temporal domain of weed populations can be analyzed using geographically referenced information. The regional framework for analysis is based on the premise that the domain of a weed species or an assemblage of species can be described in terms of the space and time in which they survive. Published maps of the spatial distribution of individual weed species were converted to digital records defining their geographic domain. Digital records were imported into a geographically referenced data system. Assemblage maps were produced by intersecting domains of individual species. The assemblage maps show areas with similar intensity of the occurrence of species selected for analysis. The most intense occurrence of summer annual species, for example, exists in a relatively small area of the Midwest. The framework presented in this paper is a concept for a tool to evaluate, manage, and manipulate weed distribution data at the regional scale. Analysis at the regional scale is a perspective substantially different from the plot or field-scale analysis traditionally used to study and manage weed populations. Regional analysis has application to weed science by increasing the understanding of regional patterns of weed infestation and the factors that regulate them. This information will be useful to the herbicide industry, plant ecologists, resource managers, and agricultural policy makers.
A comparison of clinical and linguistic indices of deviance in the verbal discourse of schizophrenics
Authors: Sanders Lynne M. , Adams Jane , Tager-Flusberg Helen , Shenton Martha E. , Coleman Michael
Published: May 2019

The goal of this study was to compare clinical and psycholinguistic approaches to the measurement of verbal behavior according to their ability to discriminate schizophrenic (n = 11) from manic-depressive (n = 11) and normal control (n = 11) subjects. Language samples were obtained during Rorschach testing and analyzed using a clinical measure, the Thought Disorder Index (TDI), and a battery of linguistic measures. Five linguistic categories were examined: productivity, repetition, dysfluency, cohesiveness, and syntactic complexity. On the clinical measure, schizophrenic subjects had high thought disorder scores. On the linguistic measures, the speech of schizophrenics differed significantly from the other two groups in productivity and in the number of clearly referenced elements, a measure of cohesion. This measure of cohesion was positively correlated with TDI scores. The findings are discussed in terms of the benefits of using more objective and quantitative measurements in research on thought disorganization in schizophrenia.