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Crop yield loss–weed density relationships critically influence calculation of economic thresholds and the resulting management recommendations made by a bioeconomic model. To examine site-to-site and year-to-year variation in winter Triticum aestivum L. (winter wheat)–Aegilops cylindrica Host. (jointed goatgrass) interference relationships, the rectangular hyperbolic yield loss function was fit to data sets from multiyear field experiments conducted at Colorado, Idaho, Kansas, Montana, Nebraska, Utah, Washington, and Wyoming. The model was fit to three measures of A. cylindrica density: fall seedling, spring seedling, and reproductive tiller densities. Two parameters: i, the slope of the yield loss curve as A. cylindrica density approaches zero, and a, the maximum percentage yield loss as A. cylindrica density becomes very large, were estimated for each data set using nonlinear regression. Fit of the model to the data was better using spring seedling densities than fall seedling densities, but it was similar for spring seedling and reproductive tiller densities based on the residual mean square (RMS) values. Yield loss functions were less variable among years within a site than among sites for all measures of weed density. For the one site where year-to-year variation was observed (Archer, WY), parameter a varied significantly among years, but parameter i did not. Yield loss functions differed significantly among sites for 7 of 10 comparisons. Site-to-site statistical differences were generally due to variation in estimates of parameter i. Site-to-site and year-to-year variation in winter T. aestivum–A. cylindrica yield loss parameter estimates indicated that management recommendations made by a bioeconomic model cannot be based on a single yield loss function with the same parameter values for the winter T. aestivum-producing region. The predictive ability of a bioeconomic model is likely to be improved when yield loss functions incorporating time of emergence and crop density are built into the model's structure.

Field experiments designed to determine the efficacy and interaction of hexazinone [(3-cyclohexyl-6-(dimethylamino)-1-methyl-1,3,5-triazine-2,4(1H,3H)-dione] and nitrogen on weeds and lowbush blueberry [Vaccinium angustifolium (Ait.)] growth and yield were established at five locations in 1980 and 13 locations in 1981. Hexazinone was applied after pruning, preemergence with nitrogen, using a split-block design, with locations serving as replications. Grasses, goldenrod (Solidago spp.), and meadowsweet [Spiraea latifolia (Ait.) Borkh. # SPVLF] were reduced significantly as the rate of hexazinone was increased. Blueberry injury, plant stand, number of flower buds, and yield all increased with increases in hexazinone rate. Variations in blueberry yields occurred among locations due to differences in plant stand and productivity, as well as climatic and edaphic factors. Within each nitrogen rate, increases in the rate of hexazinone resulted in a quadratic increase in blueberry yield. Within the hexazinone treatments, increasing nitrogen had no effect on yield. Blueberry yield reached a maximum of 3926 kg/ha at a hexazinone rate of 1.83 kg/ha. Partial budgeting was used to evaluate the effect of combinations of hexazinone and nitrogen on net income. Response function analysis determined yield and profit-maximizing combinations of hexazinone and nitrogen. Partial budgeting indicated that hexazinone alone or combined with nitrogen increased net income, but nitrogen without hexazinone decreased net income. Response function analysis indicated that hexazinone at 1.79 kg/ha without nitrogen maximized profits.

Field trials were conducted in 1986 and 1987 to determine the effects of moisture on cinmethylin activity. The herbicide was applied preemergence at rates of 0.0, 0.3, 0.6, and 0.9 kg ai ha−1 to both dry and moist sandy loam soil, followed by varying irrigation regimes. Plant species used in the study included soybean, snap bean, cotton, peanut, and cucumber. Peanut was the most tolerant to cinmethylin, followed by cotton, soybean, snap bean, and cucumber. When cinmethylin was applied to a moist soil, less crop injury resulted than when it was applied to a dry soil. If 7.6 cm of water was applied shortly after cinmethylin application to a dry soil, severe crop injury occurred. When 2.5 cm of irrigation was applied within 8 h or at 5 days after cinmethylin application to a dry soil, crop injury was reduced when compared to applying 7.6 cm irrigation.

A greenhouse study was conducted to determine the effectiveness of adjuvants on postemergence large crabgrass control with dithiopyr. Using barriers to isolate foliage or soil, the primary site of dithiopyr uptake was found to be via foliage. Laboratory and greenhouse studies elucidated the factors involved in enhancement of crabgrass control by dithiopyr with nine superior adjuvants. Two adjuvants increased dithiopyr absorption by 3.7 to 4.3% over the herbicide alone. However, none of the adjuvants increased dithiopyr translocation out of the treated leaf. Treatment of a single large crabgrass leaf indicated that enhancement of dithiopyr activity by adjuvants involved an effect on translocation, on spray retention, and on the external movement of the spray solution to the apical meristem, with the relative importance of any 1 factor depending on the particular adjuvant used. Because of the large losses of dithiopyr during absorption/translocation studies, a separate volatilization experiment determined that 70% of the applied dithiopyr volatilized within 24 h at 24 C. Dithiopyr absorption decreased and volatilization increased with each 10 C increase in temperature. Nonrecoverable dithiopyr ranged from 46 to 55% at 5 C to 92 to 95% at 35 C. Volatility losses of this magnitude may mitigate adjuvant enhancement of postemergence grass activity of dithiopyr.

Experiments were conducted from 1994 through 1996 to determine the response of the rice cultivars ‘Bengal,’ ‘Cypress,’ ‘Jodon,’ and ‘Kaybonnet’ to triclopyr at 0.42 (standard rate) and 0.84 kg ai/ha applied postemergence at the four-leaf and panicle initiation stages of growth. Applications at the four-leaf stage were made in close association with fertilization and flood establishment, which often increases the potential for triclopyr to injure rice. Visible injury from triclopyr was slightly higher for the cultivar Jodon than for the cultivars Bengal, Cypress, or Kaybonnet. Injury was 3% or less when triclopyr at 0.42 kg/ha was applied at panicle initiation regardless of the cultivar. Triclopyr at 0.42 and 0.84 kg/ha applied at the four-leaf growth stage injured rice 7% and 22%, respectively. Triclopyr at 0.84 kg/ha applied at the four-leaf stage of growth delayed days from seedling emergence to seed head emergence and rice grain yield, irrespective of cultivar.

Native Polyacrylamide gel electrophoresis (PAGE) and enzyme activity staining were used to identify possible progenitor species of velvetleaf (Abutilon theophrasti Medic. # ABUTH). Multiple forms of superoxide dismutase activity were observed in each of the plants surveyed. Three enzyme forms were common to all the species and bio types while one form was different in the velvetleaf biotypes compared to the other species. Multiple forms of peroxidase activity were also detected. The three velvetleaf biotypes possessed identical enzyme forms with minimal similarity to peroxidase forms found in the other species. Multiple forms of esterase activity separated as two nonoverlapping groups. A slowly migrating group was observed in all the velvetleaf biotypes and a more rapidly migrating group characterized the remaining Abutilon species. The results of this study indicated that the progenitors of velvetleaf were not among the species surveyed and suggested that the progenitors may no longer be extant.

Field trials were conducted in 1986 and 1987 to determine the effects of moisture on herbicidal activity of cinmethylin applied preemergence at 0.0, 0.3, 0.6, and 0.9 kg ai ha to both dry and moist sandy loam soil. Herbicide application was followed by varying amounts of irrigation. Weed species included velvetleaf, prickly sida, green foxtail, and barnyardgrass. When cinmethylin was applied to a moist soil or when 2.5 cm of irrigation was applied 5 days after cinmethylin application to a dry soil, overall weed control was reduced. Optimum weed control resulted from cinmethylin application to dry soil followed either by a 2.5-cm irrigation within 8 h or a 7.6-cm irrigation within 36 h.

Effects of repeated late-fall applications of the isopropylamine salt of glyphosate at 1.7 kg ae/ha plus 0.5% (v/v) surfactant on adventitious root buds, thickened propagative roots (> 1.3 mm diam), and shoot density of Canada thistle were studied in continuous hard red spring wheat over a 4-yr period. Glyphosate suppressed Canada thistle shoot density more quickly and to a greater extent than thickened root fresh weight or root bud number. A single fall application of glyphosate drastically decreased Canada thistle shoot density for 1 yr after treatment. However, shoot density was the same as the untreated control by 2 yr after a single fall treatment. Two consecutive late-fall applications of glyphosate in 2 yr decreased Canada thistle shoot density 94% in the fall 1 yr after the last treatment. Glyphosate reduced Canada thistle thickened root fresh weight 70% in the first fall 1 yr after a single fall treatment. However, 2 yr after a single fall application of glyphosate, root fresh weight equalled the controls. Two consecutive fall applications of glyphosate reduced thickened root fresh weight 77% 1 yr after the second treatment.

Field studies conducted in 1991 to 1993 evaluated the efficacy of clomazone applied at various timings for weed control in soybean. Clomazone applied 45, 30, 15, or 0 days prior to planting (DPP) provided season-long control of velvetleaf and giant foxtail. In 1991 and 1992 clomazone alone 30 and 45 DPP failed to control redroot pigweed. Clomazone alone 45 DPP failed to control common lambsquarters. In 1991 and 1992 clomazone at 0.84 kg/ha plus metribuzin applied 45 DPP failed to control redroot pigweed. The addition of metribuzin plus chlorimuron to the above clomazone treatments resolved these weed control deficiencies. Weed control in 1993 was nearly complete across all clomazone treatments. In 1993 clomazone treatments which included metribuzin or metribuzin plus chlorimuron applied PPI or PRE reduced yield. Herbicide injury is the likely cause of this reduction because most treatments in 1993 provided 99% control of all weed species.

The spread of noxious weeds on rangeland and forests in the United States has been described as a raging biological wildfire. This analogy applies to aspects of spread, impact, and control of weeds. Patterns and means of spread are similar. Noxious weeds and wildfires can dramatically change natural plant communities, alter distribution and species composition of wildlife populations, damage watersheds and increase soil erosion, and adversely affect recreation and aesthetic values. Wildfire management involves prevention, early detection, timely control, and site rehabilitation; elements which are also the foundation of sound weed management. Principles and practices associated with wildfire suppression can be used to illustrate many weed science fundamentals, and to improve weed management programs. Federal land management agencies are directed to train employees in effective weed management and to increase public awareness about noxious weeds. Most agency employees are familiar with wildfire management; knowledge which could be useful in teaching weed management principles. Fire prevention could serve as a model to promote greater public awareness of the impact of noxious weeds and the need for weed prevention and early detection.

A root washer was constructed which rapidly separated Canada thistle [Cirsium arvense (L.) Scop. # CIRAR] roots larger than 1.3-mm diam with 96% or greater efficiency from cohesive clay soil. The washer removed 93 ± 15% of 43 200 cm clay soil from Canada thistle roots in 2 h. Small residual soil clods and organic debris were removed by hand after washing. The washing action did not damage the root system. From 4 to 6 h were required to wash the large Canada thistle roots from an equivalent volume of clay soil by hand, without using the washer. Rhizomes, seeds, and tubers also may be separated from soil with the washer. The tank and frame of this washer are durable, and moving parts such as bearings can be replaced easily.

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 (I and A) of a rectangular hyperbola equation were estimated for each data set using nonlinear regression procedures. The I and A coefficients represent percent corn yield loss as foxtail density approaches zero and maximum percent corn yield loss, respectively. The coefficient I was 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−-1 row was a conservative estimate of the single-year economic threshold (Tc ) of foxtail density, variation in I and A resulted in a large variation in Tc . 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.

Concern over the development of herbicide-resistant weeds has led to interest in integrated weed management systems that reduce selection pressure by utilizing mechanical and cultural weed control practices in addition to herbicides. Increasing crop seeding rate increases crop competitive ability and thus can enhance herbicide efficacy. However, it is unknown how increasing the seeding rate affects an herbicide’s efficacy. The objective of this study was to examine the interaction between increasing seeding rate and herbicide dose to control weeds. To meet this objective, the herbicide fluthiacet-methyl was applied to field-grown lentil, with Indian mustard, a proxy for wild mustard, used as a model weed. The experiment was a factorial design with four lentil seeding rates and seven herbicide rates. Overall the herbicide dose response was altered by changing lentil seeding rate. Increasing lentil seeding rate decreased the weed biomass production when herbicides were not applied. In two of the four site-years, increasing lentil seeding rate lowered the herbicide ED50, the dose required to result in a 50% reduction in weed biomass. Increasing the crop seeding rate altered the dose response to provide greater weed control at lower herbicide rates compared with normal crop seeding rates. Increased seeding rates also resulted in higher and more stable crop seed yields across a wider range of herbicide dosages. These results suggest that dose–response models can be used to evaluate the efficacy of other weed management practices that can interact with herbicide performance.

Nuclear energy holds the promise to provide vast amounts of reliable baseline electricity at commercially competitive costs with modest environmental impact. However, the future of nuclear energy lies beyond the current generation of light water reactors. Future reactors will be expected to provide additional improvements in safety, maintain high reliability, use uranium resources more efficiently, and produce lower volumes of less toxic solid wastes. Several advanced reactor concepts are under development to meet these demands. In most cases, these designs translate into higher operating temperatures and longer lifetimes, more corrosive environments, and higher radiation fields in which materials must reliably perform. This issue focuses on the materials challenges that will determine the feasibility of these advanced concepts and define the long-term future of nuclear power.

High conflict and low warmth in families may contribute to immune cells developing a tendency to respond to threats with exaggerated inflammation that is insensitive to inhibitory signaling. We tested associations between family environments and expression of genes bearing response elements for transcription factors that regulate inflammation: nuclear factor kappa B (NF-κB) and glucocorticoid receptor. The overall sample (47 families) completed interviews, questionnaires, and 8-week daily diary assessments of conflict and warmth, which were used to create composite family conflict and warmth scores. The diaries assessed upper respiratory infection (URI) symptoms, and URI episodes were clinically verified. Leukocyte RNA was extracted from whole blood samples provided by a subsample of 42 children (8–13 years of age) and 73 parents. In children, higher conflict and lower warmth were related to greater expression of genes bearing response elements for the proinflammatory transcription factor NF-κB, and more severe URI symptoms. In parents, higher conflict and lower warmth were also related to greater NF-κB–associated gene expression. Monocytes and dendritic cells were implicated as primary cellular sources of differential gene expression in the sample. Consistent with existing conceptual frameworks, stressful family environments were related to a proinflammatory phenotype at the level of the circulating leukocyte transcriptome.

In order to empirically investigate the economic development process in rural areas, factors that are associated with the level and changes in employment must be conceptualized, operationalized and measured accurately. This symposium was organized to discuss the conceptualization, operationalization and measurement of these factors.

We present results from a multiwavelength study of the blazar PKS 1954–388 at radio, UV, X-ray, and gamma-ray energies. A RadioAstron observation at 1.66 GHz in June 2012 resulted in the detection of interferometric fringes on baselines of 6.2 Earth-diameters. This suggests a source frame brightness temperature of greater than 2 × 1012 K, well in excess of both equipartition and inverse Compton limits and implying the existence of Doppler boosting in the core. An 8.4-GHz TANAMI VLBI image, made less than a month after the RadioAstron observations, is consistent with a previously reported superluminal motion for a jet component. Flux density monitoring with the Australia Telescope Compact Array confirms previous evidence for long-term variability that increases with observing frequency. A search for more rapid variability revealed no evidence for significant day-scale flux density variation. The ATCA light-curve reveals a strong radio flare beginning in late 2013, which peaks higher, and earlier, at higher frequencies. Comparison with the Fermi gamma-ray light-curve indicates this followed ~ 9 months after the start of a prolonged gamma-ray high-state—a radio lag comparable to that seen in other blazars. The multiwavelength data are combined to derive a Spectral Energy Distribution, which is fitted by a one-zone synchrotron-self-Compton (SSC) model with the addition of external Compton (EC) emission.

How firms’ dynamic capabilities lead to their competitive advantage and improved firm performance has been a core issue and full of debates. In this research, we theorize that dynamic capabilities, which could be defined by three distinct dimensions (sensing capability, integration capability, and reconfiguration capability), facilitate different types of innovation that in turn improve firm performance. Based on a sample of 204 Chinese firms, results from partial least squares structural equation modeling analyses generally support our arguments despite some nuanced differences existing among different dimensions of dynamic capabilities. This study contributes to dynamic capabilities literature by reducing the scarcity of empirical research and by uncovering the mechanisms through which dynamic capabilities influence firm performance.