bluuebunny/crossref_metadata_2025 huggingface dataset:
The Runaway Paul
Authors: Welborn Laurence L.
Published: May 2019

The little narrative of Paul's flight from Damascus in 2 Cor 11:32-33 holds a promise to the ear of the historian. In the first place, Aretas is the only figure of political history mentioned in an authentic letter of Paul. This fact alone indicates the importance of this text for the chronology of the apostle's life. Second, there is the remarkable parallel provided by the account in Acts 9:23–25. The extent of the agreement is impressive: it consists not only of the general course of events, but extends to the wording, which is partly identical and partly synonymous. The correspondence appears more extraordinary in light of the fact that Acts otherwise exhibits no verbal connections with the letters of Paul. Third, there is the vivid manner in which Paul relates the experience: the mention of a place and a particular person, the detailed description of the circumstances, and the concentrated account of the action, together create a living image of a dramatic event. The clarity and strength of representation suggest that the experience had a special significance. Perhaps, as Calvin postulated,haec persecutio fuit quasi primum tirocinium Pauli(“this persecution was, as it were, Paul's first military service”). The incident left a deep trace in the memory of the early church,9 one that time has not erased: the Damascenes still point to an opening in the wall as the window through which the apostle was let down.
“Beautiful as a wasp”: Angela of Foligno and Georges Bataille
Authors: Hollywood Amy
Published: May 2019

Georges Bataille (1897–1962) was a central figure within twentieth-century French avant-garde circles, yet the importance of his work for the study of religion is only beginning to be recognized. Between the First and Second World Wars, he not only edited journals(Documents, Acéphale)and engaged in literary and political movements, but also organized (together with Roger Caillois and Michel Leiris) the College of Sociology, which attempted to bring the sociological methods of Emile Durkheim and Marcel Mauss to bear on the study and pursuit of the sacred. Throughout his work of the 1930s, Bataille sought to reintroduce the sacred into modern industrial, secular societies, which, he argued, believed in God only insofar as they equated God with reason. For Bataille, the power of the sacred lies in its ambiguity and violence. Sacrifice and expenditure mark the antithesis of the instrumental rationality of modern bourgeois society; through sacrifice, then, new sovereign communities might be engendered. Religious questions, for Bataille, were irrevocably political. He thus attempted to theorize and to create a community without authority, one that might counter the authoritarian movements coming to dominate much of Europe in the 1930s.
Do parasites live in extreme environments? Constructing hostile niches and living in them
Authors: Combes C. , Morand S.
Published: May 2019

We develop the hypothesis that parasites do not invade extreme environments, i.e. hostile hosts, but rather ‘create’ them. We argue that parasites may have driven the evolution of the constitutive and adaptive immune system. This leads to several implications. First, parasites respond to ‘genes to kill’ by ‘genes to survive’ and this triggers an indefinite selection of measures and counter-measures. Second, these revolutionary arms races may lead to local adaptation, in which parasite populations perform better on local hosts. Third, the evolution of the immune system, whose responses are predictable, may allow parasites to specialize, to evade and even to manipulate. Finally we show that the correlations between the increase in the antibody repertoire, the expansion of MHC loci and parasite pressures support our hypothesis that both host complexity and parasite pressures can be invoked to explain the diversity of antibodies, T-receptors and MHC molecules.
Kyllinga brevifolia, K. squamulata, andK. pumilaseed germination as influenced by temperature, light, and nitrate
Authors: Lowe David B. , Whitwell Ted , McCarty Lambert B. , Bridges William C.
Published: May 2019

Kyllingaspecies are becoming more prevalent in turfgrass sites throughout North America. The effects of nitrate (50, 200, and 400 mg L−1), temperature (33/24, 25/17, 19/11 C day/night, respectively), and light on seed germination of threeKyllingaspecies were investigated in growth chambers. Nitrate concentrations did not stimulateKyllingaspecies seed germination compared with untreated seeds. AllKyllingaspecies seeds failed to germinate in darkness but resumed germination once they were placed in light. This is an important pest management strategy because a dense, uniform turfgrass stand with its minimum light penetration to the soil would minimizeKyllingaspecies seed germination. Higher temperatures increased seed germination rate and percentage of each species after 8 wk. Maximal (> 90%)K. brevifoliagermination occurred 2 to 4 wk after initiation in every seed study, whereasK. squamulataseeds germinated continuously. Minimal (< 10%)K. pumilaseeds germinated until alternating diurnal temperatures were imposed.
Effects ofEriochloa villosadensity and time of emergence on growth and seed production inZea mays
Authors: Mickelson James A. , Harvey R. Gordon
Published: May 2019

Field experiments were conducted in 1997 and in 1998 to determine the effects of density and time of emergence onEriochloa villosagrowth and seed production inZea mays. E. villosawas transplanted at four densities (3, 9, 27, and 81 plants m−2) to simulate emergence at four Z.maysgrowth stages (VE, V2, V5, and V10). Compared toE. villosaplants that emerged withZ. maysplants, total above-groundE. villosabiomass at maturity of plants grown at 3 plants m−2was reduced by 54, 97, and 99% when emergence was delayed until the V2, V5, and V10 stages ofZ. mays, respectively, in 1997. In 1998, total abovegroundE. villosabiomass at maturity was reduced by 70, 87, and 99% when emergence was delayed until the V2, V5, and V10 stages ofZ. mays, respectively.E. villosaaboveground vegetative biomass per plant at maturity was linearly related to seed production per plant in each year.E. villosaseed production m−2decreased nonlinearly as density decreased and time of emergence was delayed. Based on estimated model parameters, maximum seed production was 57,100 and 12,700 seeds m−2in 1997 and 1998, respectively. Within time of emergence,E. villosadensity did not affect seed mass per seed, however, seed mass of late-emerging cohorts was less than that of early-emerging cohorts. Time of weed emergence relative to the crop was a very important factor in determining biomass and seed production. Results suggest that late-emerging plants may not be very important to long-term management ofE. villosa.
Root morphology of youngGlycine max, Senna obtusifolia, andAmaranthus palmeri
Authors: Wright Shawn R. , Jennette Michael W. , Coble Harold D. , Rufty Thomas W.
Published: May 2019

Root development and the associated acquisition of water and nutrients are an important part of weed competitiveness. Characterization of root morphological development, however, is inherently problematic because of the complexities of soil–plant interactions. In this study, we used hydroponically grown plants and digital imaging to examine root characteristics ofGlycine maxand the competing weedsSenna obtusifoliaandAmaranthus palmeri. The purpose was to define inherent differences in root length and surface area that would contribute to growth responses during the establishment phase in the field. The methodology involved growing plants for 16 to 22 d, dissecting and staining root segments, mounting subsamples on slides, and imaging using a stereomicroscope and digital camera. Microscopy was required because of the small diameters of a significant proportion of the weed roots. With plants of similar root fresh weights (4.5 to 5.0 g), counting of individual roots revealed that 5.obtusifoliaandA. palmerihad 2 and 3.7 times more roots thanG. max(4,616 and 7,781 vs. 2,120, respectively). The imaging analyses indicated that roots ofS. obtusifoliaandA. palmerihad 2.9 and 5 times more length thanG. max(10,042 and 17,192 cm vs. 3,418 cm, respectively). Furthermore, the analysis of length in different root diameter classes indicated that weed roots were noticeably finer then those ofG. max. Approximately 84% ofS. obtusifoliaroot length was contributed by roots in the 0.1- to 0.25-mm range, whereas 45% of theG. maxroots were in the 0.1- to 0.25-mm range and 48% were in the 0.25- to 0.75-mm range. In contrast, 68% ofA. palmerilength was contributed by roots smaller than 0.1 mm in diameter with 26% in the 0.1- to 0.25-mm range. Based on the expression of root characteristics observed here, root systems of these weed species would have finer roots with much greater length that would occupy a much larger volume of soil than those ofG. max. Presumably, this would result in a competitive advantage in the acquisition of water and nutrients, especially when availability is limited.
Competitive attributes ofA. sativa, T. aestivum, andH. vulgareare conserved in no-till cropping systems
Authors: Légère Anne , Bai Yuguang
Published: May 2019

The robustness of competitive attributes of cereals such as rapid and uniform seedling emergence, tillering, early biomass accumulation and canopy closure, and height advantage over weeds have not yet been tested under environmental conditions typical of no-till (NT) cropping systems. Our objective was to evaluate the effects or NT practices on growth and productivity ofAvena sativa, Triticum aestivum, Hordeum vulgare, and associated weeds. The experiment was conducted on a Kamouraska clay at La Pocatière, QC, in 1994, 1995, and 1996.Avena sativa, T. aestivum, andH. vulgarewere grown under tilled and NT practices. Cereal growth parameters were measured six (1994) or seven (1995) times between planting and the 11th week after planting but only once in 1996. Grain yields and yield components were determined at crop maturity.Avena sativaandH. vulgarepopulations were little affected by tillage, whereasT. aestivumpopulations were reduced by 16 to 20% in NT systems. Growth in height in NT systems was either similar or greater than in tilled systems in all three cereals. Cereal leaf area index (LAI) and biomass accumulation was also comparable between tillage systems, except forT. aestivumLAI in 1994, which was greater in tilled plots on two sampling dates. Response of annual dicots to tillage was inconsistent in all crops. Annual monocots dominated in some but not all NT systems. Perennial dicots dominated in NT systems, whereas perennial monocots were more abundant in tilled systems in all three cereals.Avena sativaandT. aestivumyields in NT plots were comparable or greater than in tilled plots, in spite of having either lower test weights (A. sativa) or lower 1,000-grain weights (T. aestivum). NTT. aestivumproductivity was maintained in spite of reduced plant establishment.Hordeum vulgareyields were also similar across tillage systems, except in 1995, when yields in tilled plots were greater than in NT plots. The height advantage observed for NTH. vulgaredid not result in improved yields. All three cereals, and particularlyA. sativa, appeared well suited to NT systems, despite the pressure provided by different weed groups, compared to tilled systems. However, results suggest that NT production of cereals could benefit from improved attention to perennial dicot control and crop seedling establishment, particularly forT. aestivum.
Separating the effects of crop rotation from weed management on weed density and diversity
Authors: Doucet Colleen , Weaver Susan E. , Hamill Allan S. , Zhang Jianhua
Published: May 2019

Crop rotation is thought to reduce weed density and maintain species diversity, thus preventing the domination of a few problem weeds. Because cropping sequence dictates other agricultural management practices, variations in weed populations between cropping systems may be the direct result of crop rotation, the result of different weed management practices associated with crop rotation, or both. Studies that fail to separate the effects of crop rotation from weed management may generate misleading results. A 10-yr crop rotation study was undertaken to study the dynamics of the standing weed vegetation inZea maysL.,Glycine maxL., andTriticum aestivumL. The present paper compared total weed density and diversity between monocultures and rotations under three levels of weed management. Weed management accounted for 37.9% of the variation in total weed density, whereas crop rotation accounted for only 5.5%. Weed density varied between monocultures and rotations in plots where herbicides were applied. The effectiveness of rotations in reducing weed density was dependent upon the crop. Margalef's species richness index (DMG), a measure of diversity, varied among weed management strategies, with 38.4% of the variance attributed to this factor. In the 10th year, when all plots were sown withZ. mays, few cumulative effects of crop rotation were apparent, with two exceptions. In weedy and herbicide-treated plots, weed density was higher on plots cropped withZ. maysthe previous year. Also, under these weed management treatments, including a cereal in the crop rotation reduced weed density. Crop rotation, when used in combination with herbicides, provides additional weed control and is therefore an effective tool in integrated weed management.
Euphorbia esula: perceptions by ranchers and land managers
Authors: Sell Randall S. , Bangsund Dean A. , Leistritz F. Larry
Published: May 2019

Euphorbia esula is an exotic perennial weed that is estimated to infest 650,000 ha in North and South Dakota, Montana, and Wyoming. The estimated annual economic effect of E. esula infestations in the four-state area is about $130 million. We present the results of a survey of ranchers, local decision makers, and public land managers of grazing and nongrazing property from a five-county area in North and South Dakota, Montana, and Wyoming. A total of 565 ranchers, local decision makers, and public land managers were surveyed, which resulted in 267 completed questionnaires. The main objective of the survey was to evaluate respondent's perspectives of managerial, institutional, and social factors that may affect the rate and extent of implementation of various E. esula control strategies. The reasons for not using the various E. esula controls generally fell into environmental, financial, and educational categories. In many cases, little can be done to remove environmental constraints; however, financial constraints may be addressed through cost-share programs either offered locally or through state agencies. The other main reason for not using some controls was a lack of knowledge to work with various controls (e.g., grazing and biological controls). These obstacles could be addressed with workshops, demonstrations, or educational bulletins. These educational tools could be provided by universities or governmental agencies, as respondents indicated this was their choice for information dissemination. Disagreements among the survey groups were not substantial, and many share similar concerns in controlling the weed.
Biorational approaches to managingDatura stramonium
Authors: Zhang Jianhua , Salas Maria L. , Jordan Nicholas R. , Weller Stephen C.
Published: May 2019

Field experiments were conducted from 1995 to 1997 to test approaches to managing atrazine-resistantDatura stramonium. Eight weed management programs in aZea maysandGlycine maxrotation were evaluated for their effects on the dynamics of atrazine-resistant and -susceptibleD. stramoniumpopulations. OverallD. stramoniumdensity and relative abundance of resistant (R) biotypes were greatly reduced in no-tillSecale cerealeL. (rye) cover crop management programs without triazine compared to conventional-tillage systems with the application of triazine herbicides. The negative effects of no-till onD. stramoniumwere greater under aG. max–Z. mays—G. max(SCS) rotation than under aZ. mays–G. max—Z. mays(CSC) rotation. A cropping system involving moreG. maxphases under no-till reduced both the resistant and susceptibleD. stramoniumpopulations. Results from this study support the use of soil management, crop rotation, and negative cross-resistant herbicides to manage atrazine-resistant biotypes.
Herbicides that inhibit cellulose biosynthesis
Authors: Sabba Robert P. , Vaughn Kevin C.
Published: May 2019

The cellulose-biosynthesis inhibitor (CBI) herbicides all selectively inhibit the synthesis of cellulose despite significant chemical differences. With the exception of quinclorac, they are most effective in inhibiting cellulose synthesis in dicot plants. Dichlobenil and isoxaben are the oldest and best studied of these herbicides, whereas flupoxam is a more recent introduction and acts in many ways similarly to isoxaben. Quinclorac is unusual in that it seems to act as a cellulose inhibitor in grasses but as an auxinic herbicide in dicots. These herbicides inhibit cell plate formation at one of two relatively late stages without affecting microtubule function. The effects of dichlobenil are different from other CBI herbicides; dichlobenil inhibits cellulose synthesis but promotes callose synthesis in its place. Suspension cells of bothLycopersicon esculentumandNicotiana tabacumcan become habituated to normally inhibitory concentrations of dichlobenil or isoxaben by replacing the normal cellulose network in their walls with pectin and extensin. Natural resistance to CBI herbicides is rare and has only been found in red algae species.Arabidopsislines produced by mutagenesis all share changes in active site rather than alterations in uptake, translocation, or metabolism of these herbicides. The lack of cross-resistance to different CBI herbicides of these mutants indicates that no fewer than three different sites in the cellulose biosynthesis pathway are affected by the different herbicides in this class.
Foxtail (Setariaspp.) seedling dynamics in spring wheat (Triticum aestivum) are influenced by seeding date and tillage regime
Authors: Spandl Eric , Durgan Beverly R. , Forcella Frank
Published: May 2019

Emergence patterns of foxtail in spring wheat following soybean were evaluated for three seeding dates and three tillage regimes. Cumulative foxtail emergence, as a percentage of total plants emerged in the growing season, was generally not influenced by tillage regime throughout most of the emergence period, but when differences occurred, emergence was lower with no-till than with moldboard plow. Foxtail seedling densities were greater in no-till and chisel plow than in moldboard plow. Weed biomass and wheat yields were not affected by tillage regime. Delaying wheat seeding reduced foxtail percent emergence and emerged seedling density. Differences in emergence patterns of foxtail were attributable to thermal accumulation after seeding. Wheat yield was not influenced by seeding date in 2 of 3 yr.
Influence of crop rotation, tillage, and management inputs on weed seed production
Authors: Kegode George O. , Forcella Frank , Clay Sharon
Published: May 2019

Approaches to crop production that successfully reduce weed seed production can benefit farming systems by reducing management inputs and costs. A 5-yr rotation study was conducted in order to determine the effects that interactions between crop rotation, tillage, and amount of herbicide and fertilizer (management inputs) have on annual grass and broad-leaved weed seed production and fecundity. There were 10 crop rotation and tillage system combinations and three levels of management inputs (high, medium, and low). Green and yellow foxtail were the major weed species, and together they yielded between 76 and 93% of collected weed seeds. From 1990 to 1994, average grass weed seed productions were 7.3 by 103, 3.7 by 1036.1 by 103and 5.7 by 103seeds m−-2, whereas average broad-leaved weed seed productions were 0.4 by 103, 0.4 by 103, 1.4 by 103, and 0.4 by 103seeds m−-2in crop rotations using conventional tillage (moldboard plow), conservation tillage, no tillage, and ridge tillage, respectively. Crop rotations using conventional or ridge tillage consistently produced more grass and broad-leaved weed seeds, especially in low-input plots. There was little difference in weed seed production among input levels for crop rotations using conservation tillage. Comparing rotations that began and ended with a corn crop revealed that by increasing crop diversity within a rotation while simultaneously reducing the amount of tillage, significantly fewer grass and broad-leaved weed seeds were produced. Among the rotations, grass and broad-leaved weed fecundity were highly variable, but fecundity declined from 1990 to 1994 within each rotation, with a concomitant increase in grass and broad-leaved weed density over the same period. Crop rotation in combination with reduced tillage is an effective way of limiting grass and broad-leaved weed seed production, regardless of the level of management input applied.
Stability of corn (Zea mays)-foxtail (Setariaspp.) interference relationships
Authors: Lindquist John L. , Mortensen David A. , Westra Philip , Lambert W. J. , Bauman Thomas T. , Fausey Jason C. , Kells James J. , Langton Steven J. , Harvey R. Gordon , Bussler Brett H. , Banken Kevin , Clay Sharon , Forcella Frank
Published: May 2019

Variation in interference relationships have been shown for a number of crop-weed associations and may have an important effect on the implementation of decision support systems for weed management. Multiyear field experiments were conducted at eight locations to determine the stability of corn-foxtail interference relationships across years and locations. Two coefficients (IandA) of a rectangular hyperbola equation were estimated for each data set using nonlinear regression procedures. TheIandAcoefficients represent percent corn yield loss as foxtail density approaches zero and maximum percent corn yield loss, respectively. The coefficientIwas stable across years at two locations and varied across years at four locations. Maximum yield loss (A) varied between years at one location. Both coefficients varied among locations. Although 3 to 4 foxtail plants m−-1row was a conservative estimate of the single-year economic threshold (Tc) of foxtail density, variation inIandAresulted in a large variation inTc. Therefore, the utility of using common coefficient estimates to predict future crop yield loss from foxtail interference between years or among locations within a region is limited.
Annual broadleaf crop frequency and residual weed populations in Saskatchewan Parkland
Authors: Stevenson F. Craig , Johnston Adrian M.
Published: May 2019

The development of problematic weed populations is a concern in western Canadian fields where canola and pea are grown in a 4-yr sequence with spring cereal grains. Weed densities were examined at a site near Melfort, Saskatchewan, Canada, from 1994 to 1997 in seven zero-till managed crop rotations. Four rotations that included canola, pea, or flax in at least 3 of 4 yr (HBF: high broadleaf–crop frequency) were compared with three rotations that included broadleaf crops grown in 2 of 4 yr (LBF: low broadleaf–crop frequency). Spring wheat and barley were the cereal crops in rotation. Residual (postherbicide application) weed density for each weed species in a given year was summed across all phases for each rotation to reflect the overall weed infestation. Four annual broadleaf weed species were most abundant in 1996 and a second group of three species, having a variety of reproductive strategies, became progressively less abundant as the study progressed. The difference between the HBF and LBF rotations for the density of these species varied and was most prominent in years when environmental conditions were conducive for their growth. More frequent applications of ethafluralin, with its residual weed control, best explained why wild oat and catchweed bedstraw generally were less abundant in the HBF rotations. Of particular interest was the 8 plants m−-2greater density of dandelion and perennial sowthistle in the HBF vs. LBF rotations in the last year of the study. It is thought that the limited herbicide options for the control of these species could present a future problem if they continued to develop in the HBF rotations. Differences in herbicide use between the HBF and LBF rotations were considered the primary factor controlling the rotation effects on weed density.
Effect of malathion on resistance to soil-applied herbicides in a population of rigid ryegrass (Lolium rigidum)
Authors: Tardif François J. , Powles Stephen B.
Published: May 2019

The effect of the organophosphate insecticide malathion on the response of resistant rigid ryegrass population SLR 31 to the herbicides trifluralin, pendimethalin, clomazone, and triallate was investigated. The insecticide and herbicides were soil-applied prior to emergence of plants grown under controlled conditions. In the absence of malathion, the resistant population exhibited significant resistance to the four herbicides compared with a susceptible population. Levels of resistance, as determined by comparison of herbicide rates required to inhibit growth by 50%, were 35, 11, 2.4, and 2.4 for pendimethalin, trifluralin, triallate, and clomazone, respectively. Malathion had a synergistic effect on pendimethalin in the resistant population but not in the susceptible population. Malathion had no synergistic effect on trifluralin, triallate and clomazone. Resistance to triallate and clomazone was found despite the fact that the resistant population had never before been selected with these herbicides. This resistance, selected by other herbicides, further indicates that the use of alternative herbicides to control multiple resistant weeds is unlikely to be a successful resistance management approach.
Weed suppression byMedicago sativain subsequent cereal crops: a comparative survey
Authors: Ominski P. D. , Entz M. H. , Kenkel N.
Published: May 2019

The ability ofMedicago sativato suppress weed growth may provide a viable alternative to chemical weed control and allow crop producers to reduce herbicide inputs. Quantitative information regarding the suppressive effect ofM. sativaon weed populations in current cropping systems is lacking. A survey was conducted in Manitoba, Canada, in 1993 and 1994 to investigate weed populations in commercial cereal fields that had been preceded by eitherM. sativahay or cereal grain crops. A total of 117 fields were surveyed; approximately half from each field type. Principle component analysis indicated that the inclusion ofM. sativain crop rotations resulted in weed communities different from those of continuous cereal fields. Naturally occurring populations ofAvena fatua, Cirsium arvense, Brassica kaber, andGalium aparinewere lower in cereal fields that had previously containedM. sativathan in cereal fields that had been preceded by a cereal crop. Lower field uniformity values forC. arvenseandAvena fatuaindicated that these weeds were also more patchy in theM. sativarotations. Population differences between field types were nonsignificant forAmaranthus retroflexus, Chenopodium album, andPolygonum convolvulus, and although populations ofTaraxacum officinaleandThlaspi arvensewere greater inM. sativa/cereal fields than in continuous cereal crops. No consistent effect of field type onSetaria viridispopulations was observed. These results show thatM. sativaeffectively suppressed some, but not all, of the weeds found in the study area. IncludingM. sativahay crops in crop rotations can be part of an integrated weed management strategy for weeds such asA. fatua, B. kaber, andC. arvense.
Prediction of corn (Zea mays) yield loss from early observations of the relative leaf area and the relative leaf cover of weeds
Authors: Ngouajio Mathieu , Lemieux Claudel , Leroux Gilles D.
Published: May 2019

The relative leaf area of weeds is a good predictor of the outcome of weed-crop competition. However, this variable has not been used in decision-making tools for integrated weed management because leaf area cannot be measured quickly. A powerful image analysis system for measuring leaf cover (the vertical projection of plant canopy on the ground) has been developed and validated. This research was conducted to compare the efficiency of weed relative leaf area and relative leaf cover in predicting corn yield loss. Field studies were conducted in 1996 and 1997 using varying densities of common lambsquarters, barnyardgrass, common lambsquarters plus barnyardgrass, and a natural weed community. Corn grain yield and biomass loss varied with weed infestation type and year. Values of the relative damage coefficient of weeds (q) were smaller in 1997 compared with 1996. For both years, the relative leaf area of weeds was an adequate predictor of corn yield loss (r2varied from 0.61 to 0.92). The precision of the predictions was not influenced by the leaf area sampling period (four- or eight-leaf stage of corn). In general, smaller values ofqandm(predicted maximum yield loss) were obtained as a consequence of using the relative leaf cover of weeds in model fitting. However, percentages of variation explained by the model (from 0.67 to 0.90) were similar to values obtained with the relative leaf area. On the basis of the residual mean squares, neither of the variables could be declared superior to the other in yield loss prediction. The development of weed control decision-making tools using the relative leaf cover of weeds may require improvements prior to being used in weed management systems. Such improvements would include use of appropriate sampling and image-processing techniques, development and validation of empirical models specific to individual situations, and proper identification of the crop growth stage at which leaf cover must be assessed.
Influence of weeds on insecticide deposition and soybean looper (Pseudoplusia includens) management
Authors: Grymes Charles F. , Griffin James L. , Leonard B. Rogers , Jordan David L. , Boethel David J.
Published: May 2019

Glycine maxfields withSesbania exaltataandSenna obtusifoliawere selected to evaluate weed effects on insecticide spray droplet deposition within the crop canopy and soybean looper (Pseudoplusia includens) mortality. Weedy and weed-free treatments with and without thiodicarb insecticide application were included. Soybean looper populations in plots withS. exaltataandS. obtusioliawere approximately half those found in weed-free plots. Thiodicarb reduced soybean looper larval survival in the absence of weeds or when weeds were present in three of four experiments. Dye-sensitive cards placed in the top, middle, and bottom thirds of theG. maxcanopy showed droplet coverage to be highest on cards placed in the top of the canopy. Weeds reduced insecticide coverage in the top of theG. maxcanopy 26 to 43%. Thiodicarb deposition within the middle and bottom levels of the canopy was not reduced by weeds. Leaflets from the top, middle, and bottom thirds of the crop canopy were collected immediately after insecticide application to bioassay for insecticide deposition. For both years, mortality of soybean looper larvae on leaflets collected from the middle or top of weedy and weed-freeG. maxtreated with thiodicarb was equivalent. Assuming that an economic return can be expected, soybean looper management may not need to be altered when moderate infestations ofS. exaltataandS. obtusifoliaare present inG. maxin late season.
Influence of tillage andTriticum aestivumcover crop on herbicide efficacy inOryza sativa
Authors: Jordan David L. , Bollich Patrick K. , Braverman Michael P. , Sanders Dearl E.
Published: May 2019

Field experiments were conducted from 1994 through 1996 in dry-seeded and water-seededOryza sativato compare weed control andO. sativayield in conventional tillage and reduced tillage (stale seedbed andTriticum aestivumcover crop) systems with no in-season herbicide, propanil applied early postemergence (EPOST), and propanil EPOST followed by propanil plus molinate (dry-seeded production) or granular molinate (water-seeded production). TheT. aestivumcover crop reducedEchinochloa crus-galli, Heteranthera limosa, Ammania coccinea, andCyperus esculentusinfestation and reduced the need for in-season herbicides in some but not all experiments.Oryza sativagrain yield was affected by both tillage systems and herbicide programs; however, these treatment factors influenced yield independently. Increasing the number of in-season herbicide applications increased weed control andO. sativayield in some but not all experiments.
Adaptation and evaluation of the WEEDSIM weed management model for Michigan
Authors: Renner Karen A. , Swinton Scott M. , Kells James J.
Published: May 2019

The WEEDSIM bioeconomic model was developed in Minnesota and was designed to support weed management decisions for both soil-applied and postemergence weed control programs inZea maysandGlycine max.In this research, we adapted the WEEDSIM weed management model to Michigan by modifying the crop yield loss functions and herbicide efficacy ratings. We then validated the components of the model and determined whether WEEDSIM led to more profitable weed management than recommendations from SOYHERB or CORNHERB, computer decision aids based solely on herbicide efficacy and cost. The crop year significantly influenced the weed-free yield inZ. maysandG. max, but the weed—crop interference function did not change each year. Total weed seed increased in the untreated compared with the weed-free control over the 3-yr period. Weed seed did not increase significantly in WEEDSIM preemergence/postemergence (PRE/POST), WEEDSIM postemergence, or CORNHERB or SOYHERB treatments compared with the weed-free control, although annual grass seedling density at the time of postemergence herbicide application had increased by 1995 in the WEEDSIM postemergence treatment inG. maxbecause of a 2,4-D amine application only inZ. maysin 1994. WEEDSIM PRE/POST and CORNHERB provided excellent weed control in all three years, and WEEDSIM PRE/POST resulted in gross margins over weed control costs equal to or greater than CORNHERB recommendations. InG. max, Chenopodium albumand annual grass control was excellent in all three years for WEEDSIM PRE/POST, WEEDSIM postemergence, and SOYHERB treatments. The highest average gross margin for the 3-yr study was from mechanical weed control in 76-cm-wide rows ofG. max($806 ha−1) and from SOYHERB in 38- and 19-cm-wide rows ofG. max($776 and $808 ha−1, respectively). WEEDSIM recommendations controlled weeds and maintained crop yield in bothZ. maysandG. max.
Flumetsulam mobility in two Mississippi soils as influenced by irrigation timing
Authors: Tingle Chris H. , Shaw David R. , Gerard Patrick D.
Published: May 2019

Laboratory studies were conducted to evaluate14C-flumetsulam mobility in two Mississippi soils of varied texture and organic matter content following delays in irrigation. Mobility was evaluated using packed soil columns, 25 cm deep, under unsaturated–saturated flow conditions. Irrigation timings included 0, 3, and 5 d after flumetsulam application. Flumetsulam mobility (defined as the amount collected in leachate) decreased from 45% to no more than 20% of the applied in the Prentiss sandy loam soil when irrigation was delayed 3 or 5 d. With the Okolona soil, flumetsulam recovery in the leachate was 21, 14, and 6%, respectively when irrigation occurred 0, 3, and 5 d after application. Flumetsulam proved to be mobile when irrigation immediately followed application, with 6 to 45% recovered in the leachate from all soils evaluated. The Prentiss soil retained 6% of the applied flumetsulam in the upper 5 cm and the Okolona soil retained 22% when irrigation immediately followed flumetsulam application. When the irrigation interval was delayed at least 3 d, the Okolona soil retained 40% in the upper 5 cm, whereas the Prentiss soil retained 10%. Flumetsulam mobility was dependent on irrigation timing and soil type.
Sorption, dissipation, and leaching of metsulfuron in Colorado soils
Authors: Cranmer Brian K. , Westra Philip , Zimdahl Robert L.
Published: May 2019

Metsulfuron sorption, dissipation, and leaching were studied in six Colorado soils. Sorption was studied in the laboratory by batch equilibration of soil horizons from the surface to 1 m deep found in each study area. Kdwas correlated to several soil parameters with pH (-0.773) and percent organic matter (OM) (0.666) the strongest, although low. Kdgenerally decreased with depth at each site and ranged from 0.10 to 0.83 among surface soils. The lowest Kdwas in the soil with the highest pH. Leaching and dissipation were studied by high-performance liquid chromatography/ultraviolet analysis of field samples collected 1 m deep. Bromide ion as conservative tracer was applied concurrently with metsulfuron at the four dryland and two irrigated sites. In most cases, metsulfuron was found only in upper horizons, and the half-life ranged from 11.8 to 27.7 d, the shortest being in the soil with highest percent OM and lowest pH. Very little leaching below the surface horizon was detected in any soil.
Weed control andZea maystolerance as affected by timing of RP-201772 application
Authors: Sprague Christy L. , Penner Donald , Kells James J.
Published: May 2019

Field studies were conducted in 1996 and 1997 to determine the effects of RP-201772 and RP-201772 tank mixtures applied to emergedZea mays.RP-201772 at 105 g ha−1and tank-mixed metolachlor/benoxacor or atrazine were applied preemergence and to spike, 2-leaf, and 4-leafZ. mays.Herbicide treatments over the four application timings provided greater than 90%Chenopodium album, Ambrosia artemisiifolia, Amaranthus retroflexus, andAbutilon theophrasticontrol. However,Setaria fabericontrol varied among years and application timings. SevereZ. maysinjury, 70% and 40%, was observed when RP-201772 tank-mixed with metolachlor/benoxacor was applied to 2-leaf and 4-leafZ. mays, respectively. Greenhouse studies confirmedZ. mayssensitivity from delayed applications of RP-201772 tank-mixed with metolachlor/benoxacor. Similarly, increasedZ. maysinjury was observed from postemergence applications of RP-201772 tank-mixed with acetochlor/MON-13900. Herbicide absorption, translocation, metabolism, and retention studies were conducted to determine the physiological basis for the observedZ. maysinjury from delayed applications of the RP-201772 tank mixture with metolachlor/benoxacor. Metolachlor/benoxacor increased radiolabeled RP-201772 absorption when applied to spike, 2-leaf, and 4-leafZ. mays.RP-201772 translocation and metabolism did not explain enhancedZ. maysinjury. However, RP-201772 retention increased fivefold when metolachlor/benoxacor was present in the spray solution and applied to 2-leaf and 4-leafZ. mays.Increased RP-201772 absorption and retention appeared to be the basis forZ. maysinjury when tank-mixed with metolachlor/benoxacor and applied to emergedZ. mays.
A serine-to-threonine mutation in linuron-resistantPortulaca oleracea
Authors: Masabni Joseph G. , Zandstra Bernard H.
Published: May 2019

We conducted several experiments on linuron-resistant and -susceptiblePortulaca oleraceaand on atrazine-resistant and -susceptibleChenopodium albumto determine their immediate and long-term responses to photosynthesis-inhibiting herbicides. Several photosynthesis-inhibiting herbicides were used, and O2evolution was measured with a Clark-type O2electrode. Resistance ratios (RRs) forP. oleracea, based on O2evolution inhibition, were 8 and > 6 for linuron and diuron, respectively; > 800 for atrazine; and > 20 for terbacil. Linuron-resistantP. oleraceawas negatively cross-resistant to bentazon and pyridate (RR = 0.5 and 0.75, respectively). Time-course measurements of fresh weight, photosynthetic CO2assimilation, and photochemical efficiency indicated that linuron and atrazine inhibited electron transport in susceptible (S)P. oleraceaandC. album, ultimately resulting in death. Measurements of photochemical efficiency and CO2assimilation of linuron-resistantP. oleraceatreated with linuron indicated a transient injury from which plants recovered within 14 d. Recovery of linuron-resistantP. oleraceafrom atrazine injury was more rapid than from linuron injury for all measured variables. Atrazine-resistantC. albumhad no cross-resistance to linuron. Sequence analysis of the D1 protein revealed that linuron-resistantP. oleraceahad a serine-to-threonine substitution at position 264.
Resistance to glyphosate inLolium rigidum.I. Bioevaluation
Authors: Pratley James , Urwin Nigel , Stanton Rex , Baines Peter , Broster John , Cullis Kerrie , Schafer David , Bohn Joseph , Krueger Roger
Published: May 2019

Glyphosate is the world's most widely used herbicide. It is nonselective and has been used to control a broad range of weed species for the past 20 yr, without the appearance of resistant weed biotypes. However, a biotype ofLolium rigidumfrom a field in Northern Victoria, Australia, in which glyphosate had been used for the past 15 yr, failed to be controlled by label recommended rates. Based on LD50values from pot dose-response experiments, this biotype exhibited resistance to glyphosate and was nearly 10-fold more resistant compared to the susceptible biotypes tested. The biotype was resistant to three different salts of glyphosate. The biotype was also nearly threefold more resistant to diclofop-methyl but was susceptible to other commonly used selective and broad-spectrum herbicides. Between the two-leaf and tillering stages of development, a susceptible biotype exhibited a small but significant decrease in tolerance to glyphosate, whereas tolerance of the resistant biotype remained unchanged with age. The resistant phenotype was verified in experiments in which seed was germinated in the presence of glyphosate. Observations on shoot and root growth of seedlings in these experiments suggested that the resistance mechanism might be associated more with the shoot than with the root.
Weed population responses to weed control practices. I. Seed bank, weed populations, and crop yields
Authors: Buhler Douglas D.
Published: May 2019

Weed control practices affected the weed seed content of the soil, weed seedling populations, and corn and soybean yields in two 4-yr field experiments. When the initial weed seed density was high, giant foxtail seed numbers in soil declined rapidly under weed-free conditions. Changes in seed densities when initial densities were low varied over years. Mechanical and chemical control treatments had variable effects on weed seed numbers over the course of the experiment. Weed seed numbers and weed densities were sometimes greater if herbicides were banded, but crop yields were similar to full-rate herbicides in both experiments in all years. When the initial density was low, giant foxtail seed numbers in soil increased over the course of the experiment regardless of the weed control treatment. Seed densities of broadleaf species decreased under the same conditions. Also, when initial weed densities were low, weed control and crop yields were less sensitive to weed control practices than at high weed densities. Weather factors that influenced treatment efficacy had a major affect on weed populations and crop yield responses to the weed control treatments over years. The interactions of weed control practices, weed populations, and crop yields were complex. Initial weed density and species composition interacted with weed control treatments and weather patterns to generate the results observed.
Role of mature leaves in inhibition of root bud growth inEuphorbia esulaL.
Authors: Horvath David P.
Published: May 2019

Earlier studies on the source of signals controlling correlative inhibition of root buds (underground adventitious buds located on the lateral roots) inEuphorbia esulaindicated that either growing meristems (apical or axillary buds) or fully expanded leaves could prevent root buds from breaking quiescence. An investigation of the production and transport requirements of the leaf-derived signal is described. As few as three leaves remaining on budless stems greatly reduced the growth of (but not the number of growing) root buds. Also, light and CO2fixation were necessary for the leaf effects on root bud growth, but not necessary for correlative inhibition imposed by growing axillary buds. Treatment of plants with Ametryn induced root bud growth on budless plants but not on plants with intact axillary buds. The polar auxin transport inhibitor N-1-naphthylphthalamic acid prevented transmission or the signal from growing axillary buds, but it had only a minor effect on the transmission of the leaf-derived signal. Treatment of plants with gibberellic acid (GA) induced growth of root buds under otherwise noninducing conditions to some extent in all plants. However, the greatest effects of GA were on plants with intact leaves (meristemless/budless and meristemless). GA had no significant effect on root bud quiescence under conditions that induced root bud growth.
Effect of tillage on timing ofSetariaspp. emergence and growth
Authors: Stahl Lizabeth A. B. , Johnson Gregg A. , Wyse Ronald L. , Buhler Douglas D. , Gunsolus Jeffrey L.
Published: May 2019

Weed management can be a significant challenge in cropping systems, partly because the effects of tillage systems on weed seedbank and seedling population dynamics are not well understood. Field research was conducted from 1994 to 1996 in established tillage plots consisting of moldboard plow (MP), chisel plow (CP), and no-tillage (NT). The objectives were to determine the effects of long-term tillage systems on the timing and duration ofSetariaspp. emergence and percentage cumulative emergence from the soil seedbank and to investigate the effect of tillage onSetariaspp. density and seed production following glyphosate application atSetariaspp. heights of 5, 10, and 15 cm. NT contained a greater number ofSetariaspp. seed in the 0- to 1-, 1- to 3-, and 3- to 6-cm depths than MP or CP systems. There was little difference between the three tillage systems at depths greater than 6 cm.Setariaspp. emergence was greater in NT than in MP or CP in 1994 and 1996 and greater than in MP in 1995. There was a substantial increase inSetariaspp. emergence in NT between 3 and 4 weeks after planting (WAP) in 1994 and between 5 and 6 WAP in 1995 and 1996. Significant emergence did not occur past 5 to 6 WAP in 1994 and 1995 but continued over a longer period of time in 1996.Setariaspp. plants consistently reached targeted herbicide application heights 4 to 9 d earlier in NT than in CP and MP. In 1994, finalSetariaspp. density was greater in NT compared to CP and MP at the 5- and 10-cm herbicide application timings. When glyphosate was applied to 15-cm-tallSetaria, very few weeds were present following application across all tillage systems. In 1995, NT resulted in greaterSetariaspp. density than MP or CP across all application timings. There was no difference in finalSetariaspp. density between MP and CP across all glyphosate timings in 1994 and 1995. Seed production was negligible in MP and CP, regardless of glyphosate timing. In NT, however, significant seed production occurred, especially with early application. Results indicate that the effectiveness of nonresidual herbicides forSetaria faberiHerrm. control is influenced by tillage system and the timing of application.