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Aim How plants cope with increases in population density via root plasticity is not well documented, although abiotic environments and plant ontogeny may have important roles in determining root response to density. To investigate how plant root plasticity in response to density varies with soil conditions and growth stages, we conducted a field experiment with an annual herbaceous species (Abutilon theophrasti). Methods Plants were grown at low, medium, and high densities (13.4, 36.0, and 121.0 plants m−2, respectively), under fertile and infertile soil conditions, and a series of root traits were measured after 30, 50, and 70 days. Results Root allocation increased, decreased, or canalized in response to density, depending on soil conditions and stages of plant growth, indicating the complex effects of population density, including both competitive and facilitative effects. Main conclusions Root allocation was promoted by neighbor roots at early stages and in abundant resource availability, due to low‐to‐moderate belowground interactions among smaller plants, leading to facilitation. As plants grew, competition intensified and infertile soil aggravated belowground competition, leading to decreased root allocation in response to density. Root growth may be more likely restricted horizontally rather than vertically by the presence of neighbor, suggesting a spatial orientation effect in their responses to density. We emphasized the importance of considering effects of abiotic conditions and plant growth stages in elucidating the complexity of density effects on root traits., The research revealed the complexity of root response to density, which may increase, decrease, or canalize, depending on the strength of above‐ and belowground interactions, which varied with soil conditions or growth stage.

Cotton flea beetle, Podagrica puncticollis is the most destructive insect pest of cotton in north-western part of Ethiopia. This study was conducted to identify and determine the host range of cotton flea beetle in Metema area. The field survey was undertaken from June 27, 2015 to January 9, 2016 in ten kebele administrations of the district. At least three fields were prospected after every 15 days, in each kebele for host plants as well as to determine population density and percent leaf damage by adult cotton flea beetle, at different growth stages of cotton plant. The composition of plant species with damaged symptom or infested by flea beetle was analysed using quantitative means and identified by comparing specimens with description of identification manuals. A total of 11 host plant species of cotton flea beetle were identified in the cotton growing areas of Metema throughout a season. Indigofera longibarbata (Fabaceae), Hibiscus articulatus, H. cannabinus, H. vitifolius, Abutilon figarianum, Sida alba and S. urens (Malvaceae), Bidens pilosa and B. setigera (Asteraceae), Corchorus olitorius and C. trilocularis (Tiliaceae) found to be common host plants of cotton flea beetle. Thus, among the host plants, H. vitifolius, H. cannabinus, H. articulatus, C. olitorius and C. trilocularis were the most suitable hosts for adult cotton flea beetle in respect of the number of adults per plant and percent foliage damage they sustained. These findings could aid in developing longterm management strategies for this important insect pest existing in a hot dry tropical environment of north-western Ethiopia.

Velvetleaf is an economically important weed in popcorn production fields in Nebraska. Many PRE herbicides in popcorn have limited residual activity or provide partial velvetleaf control. There are a limited number of herbicides applied POST in popcorn compared with field corn, necessitating the evaluation of POST herbicides for control of velvetleaf. The objectives of this study were to (1) evaluate the efficacy and crop safety of labeled POST herbicides for controlling velvetleaf that survived S-metolachlor/atrazine applied PRE and (2) determine the effect of velvetleaf height on POST herbicide efficacy, popcorn injury, and yield. Field experiments were conducted in 2018 and 2019 near Clay Center, Nebraska. The experiments were arranged in a split-plot design with four replications. The main plot treatments were velvetleaf height (≤15 cm and ≤30 cm) and subplot treatments included a no-POST herbicide control, and 11 POST herbicide programs. Fluthiacet-methyl, fluthiacet-methyl/mesotrione, carfentrazone-ethyl, dicamba, and dicamba/diflufenzopyr provided greater than 96% velvetleaf control 28 d after treatment (DAT), reduced velvetleaf density to fewer than 7 plants m−2, achieved 99% to 100% biomass reduction, and had no effect on popcorn yield. Herbicide programs tested in this study provided greater than 98% control of velvetleaf 28 DAT in 2019. Most POST herbicide programs in this study provided greater than 90% control of up to 15 cm and up to 30 cm velvetleaf and no differences between velvetleaf heights in density, biomass reduction, or popcorn yield were observed, except with topramezone and nicosulfuron/mesotrione 28 DAT in 2018. On the basis of contrast analysis, herbicide programs with fluthiacet-methyl or dicamba provided better control than herbicide programs without them at 28 DAT in 2018. It is concluded that POST herbicides are available for control of velvetleaf up to 30-cm tall in popcorn production fields.

Natural fibre based composites are being used more frequently in the automotive industry because of their positive characteristics. Fibres currently used and mostly imported to Europe do not sufficiently meet all the demands for natural fibres. As a new fibre plant velvetleaf (Abutilon theophrasti) has been taken into consideration. However, there is no knowledge about the cultivation of velvetleaf in Europe. Four field trials in southwest Germany were set up to investigate the potential of fibre yield in a temperate climate. The factors crop density, nitrogen fertilization, accessions, and different harvesting dates were tested. Across all experiments fibre yield ranged from 0.4 to 1.5 t ha-1 dry matter. The highest yields were achieved with a crop density of 30 plants m-2, and with N fertilization of 100-150 kg N ha-1 for the accession ‘Herbiseed’. For highest fibre yield, the date of harvest should be at the beginning of maturity. This study provides first insights into possibility and variation of cultivating velvetleaf and suggests adequate fibre yield when cultivated in proper plant density and appropriate accession. However, before the plant can be implemented as a new crop, more research on fibre quality and breeding activity to improve agronomic factors is required.

summary We studied the effects of mycorrhizal infection by Glomus etunicatum Becker & Gerd. and P amendment (three levels) on growth and reproduction of Abutilon theophrasti Medic. Mycorrhizal infection increased total leaf area, but individual leaf size was more-affected than leaf number. Mycorrhizal infection decreased the time taken to initiate flowering, increased the total duration of flowering, and increased seed production by increasing the number of flowers produced, the proportion of flowers producing fruits, and the number of seeds per fruit. Seeds produced by mycorrhizal plants were also heavier and contained more N and P than those produced by non-mycorrhizal plants, P amendment generally had similar influences to mycorrhizal infection, but seed P content was far more plastic in response TO P amendment than to mycorrhizal infection. The various components of reproduction were not uniformly affected by either mycorrhizal infection or P amendment. The most phenotypically plastic reproductive components were fruit production and seed P content. The least plastic components were seed weight and seed N content.

How plants respond to density via modular plasticity is obscure, probably because relevant studies using covariance and allometry analyses rarely focus on multiple stages of plant growth, and also the two approaches are seldom used simultaneously in a same study. To address this issue, a field experiment was conducted by subjecting plants of Abutilon theophrasti to low, medium and high densities and measuring the mass of various plant modules, before covariance and allometry analyses at three stages of plant growth. Results showed inconsistent responses in allocation traits and allometric relationships at each growth stage. At 30 d, high density increased root:stem, root:leaf and stem:leaf ratios, but did not affect any allometric relationships. At 50 d, density altered most allocation traits, but not for allometric exponents. At 70 d, density altered allometric relationships, with no effects on allocation traits. The stage-dependent allometric relationships and inconsistent results of allometric and covariance analyses suggested one-stage allometric plasticity might be apparent plasticity. In response to the increase of density, plants first altered the strategy of biomass partitioning, then growth rate or developmental stage, indicating density effects intensified over time. For plasticity in a modular trait, size effects can be regarded as a component of (indirect) environmental effects, with the left variation after removal of size effects being the other component of plant (direct) active response. The insights into apparent plasticity of allometry and two components of plasticity should be of essential importance to investigating phenotypic plasticity and its implications in plants.

How plants cope with the increase of population density via root plasticity is not well documented. Abiotic environments and plant ontogeny may play an important role in determining plant response to density and thus contribute to understanding this issue. We aimed to investigate root plasticity in response to density under contrasting soil conditions at three stages of plant growth in an annual herbaceous species Abutilon theophrasti. We conducted a field experiment by subjecting plant individuals to low, medium and high densities (13.4, 36.0 and 121.0 plants m-2, respectively) under fertile and infertile soil conditions, and a series of root traits were measured at three harvests when they had grown for 30, 50 and 70 d. Results revealed the complexity of root response to density, which may increase, decrease or canalize, depending on the strength of above- and below-ground interactions, which varied with soil conditions or growth stage. The intensity of above- and/or below-ground interactions increased with decreased soil resources, but first increased then decreased with growth stage. Facilitation is more likely to occur at low to moderate below-ground interaction, when above-ground interaction is negligible, and resources are abundant and at early stage of plant growth. Plants may prefer to adjust biomass allocation to maintain total mass stable initially, before suffering decreased total mass, in response to intraspecific interactions.

Edamame [Glycine max(L.) Merr.] differs from grain-type soybean in several aspects, one being that edamame seeds are 65% to 100% larger than grain-type soybean seed. Crop seed size has implications for weed management in grain-type soybean; however, the extent to which this observation holds true for edamame is unknown. Because weed interference continues to be a barrier to domestic edamame production, the objective was to quantify the effect of edamame seed size on the crop’s ability to tolerate weed interference (CT) and the crop’s ability to suppress weeds (WSA). Five edamame cultivars plus one grain-type cultivar were each sorted to create “small” and “large” seed size classes. Seed lots were included in a split–split plot design, whereby an additional experimental factor was presence or absence of velvetleaf (Abutilon theophrastiMedik.). Crop and weed emergence and growth were monitored through 8 wk after emergence (WAE). Crop plants from large seed had higher tolerance toA. theophrastithan plants from small seed, as evidenced by crop height, area, and biomass. Edamame seed size had little effect on WSA; however, crop cultivars differentially reducedA. theophrastileaf area and biomass at 4 and 8 WAE. While both seed size and edamame cultivar influence early-season crop competitive ability, the magnitude of these factors on CT and WSA underscores the importance of considering them not as stand-alone tactics but rather as useful additions to a more comprehensive integrated weed management system.

Previous reports have underscored antagonism that may result from mixing glyphosate and glufosinate across a wide range of application rates and for various broadleaf and grass weed species, but no investigation has been conducted to characterize glyphosate absorption and translocation when combined with glufosinate. The objectives of this study were to evaluate herbicide efficacy and assess herbicide interaction and physiological response with combinations of glyphosate and glufosinate on common lambsquarters, velvetleaf, and giant foxtail. Greenhouse studies to determine interaction resulted in strong and persistent antagonism between glyphosate at 110 and 220 g ae ha-1 and glufosinate at 20 or 40 g ae ha-1 in giant foxtail, whereas only transient and reduced antagonism was noted for velvetleaf and common lambsquarters. Combining glyphosate and glufosinate increased the maximum absorption of glyphosate by 9% and 23% in velvetleaf and giant foxtail, respectively, compared with glyphosate alone. In velvetleaf, averaged over time, only 2.6% of the applied radioactivity translocated out of the treated leaf when glufosinate was mixed with glyphosate compared with 9.9% when glyphosate was applied alone. In giant foxtail, 21.6% of the [14C]glyphosate translocated out of the treated leaf when glufosinate was mixed with glyphosate compared with 52.4% when glyphosate was applied alone. Conversely, no change in the radioactive pattern of translocation was noted for common lambsquarters. These results suggest that reduced translocation of glyphosate is the physiological mechanism responsible for the antagonism observed between glyphosate and glufosinate in giant foxtail and, to a lesser extent, in velvetleaf.Nomenclature: Glufosinate; glyphosate; common lambsquarters, Chenopodium album L. CHEAL; giant foxtail, Setaria faberi Herrm. SETFA; velvetleaf, Abutilon theophrasti Medik. ABUTH.

Spent coffee grounds (SCG) represent a significant food waste residue. Value-added uses for this material would be beneficial. Gritty agricultural residues, such as corncob grit, can be employed as abrasive air-propelled agents for organically-compatible and selective shredding of weed seedlings within established crops. SCG were tested and compared with corncob grit for their ability to injure seedlings of two important weeds: waterhemp and velvetleaf. Waterhemp seedlings were controlled completely with as little as 0.5 g of SCG at an air pressure of 690 kPa. Velvetleaf seedlings were much larger than those of waterhemp at the time of grit application, better tolerated SCG abrasion, but still were damaged appreciably by 1 to 2 g of grit. SCG were at least as effective for abrading weed seedlings as corncob grit, whose value for this purpose in organic crops was demonstrated previously. Nomenclature: Tall waterhemp, Amaranthus tuberculatus (Moq.) Sauer; velvetleaf, Abutilon theophrasti Medik.

Abutilon theophrasti is a weed that is spreading worldwide and that has had to adapt to different combinations of environmental conditions. Wide interpopulation variability has been reported regarding dormancy and germination. This variability, controlled by the interaction of genetic diversity and maternal effect, could hinder the adoption of Integrated Weed Management (IWM) tools. A collaborative project was conducted to compare emergence dynamics of 12 European and North American populations under diverse environmental conditions. The main aim was to assess interpopulation variability and explain this according to environmental conditions in the seed collection sites. Seeds were sown at six experimental sites, and seedling emergence was monitored. The AlertInf model was tested to evaluate its ability to predict emergence dynamics of the different populations. A wide interpopulation variability was observed for emergence percentage and dynamics with consistent trends across sites and related to different seed dormancy levels. Populations from Catalonia, Iowa and Minnesota reached higher emergence percentage with earlier and concentrated emergence flushes probably due to low dormancy level, while populations from Croatia, Serbia and Hungary, given their low average emergence percentage, presented high dormancy levels. Good predictive accuracy of AlertInf model was obtained at the different sites, confirming the possibility of adopting it across a wide range of environmental conditions. Achieving a better knowledge of interpopulation variability can allow specific control strategies to be designed, facilitating the replacement of solely herbicide- based management with true IWM.

The supply of soil resources is critical for the establishment and long-term competitive success of a plant species. Although there is considerable research on the effects of water supply on crop growth and productivity, there is little published research on the comparative response of crops and weeds to limiting soil water supply. The objective of this research was to determine the growth and transpiration efficiency of corn and velvetleaf at three levels of water supply. One corn or velvetleaf plant was grown in a large pot lined with plastic bags. When seedlings reached 10 cm, bags were sealed around the base of the plant, so the only water loss was from transpiration. Daily transpiration was measured by weighing the pots at the same time each day. The experiment was conducted in the fall of 2007 and in the spring of 2008. Four replicates of each species–water treatment were harvested periodically to determine biomass accumulation and leaf area. The relationship between cumulative aboveground biomass and water transpired was described using a linear function in which the slope defined the transpiration efficiency (TE). Corn TE was greater than velvetleaf TE in all treatments during both trials. In the fall trial, corn TE was 6.3 g kg–1, 47% greater than that of velvetleaf TE. In the spring trial, TEs of both species were lower overall, and corn TE increased with declining water supply. Corn produced more biomass and leaf area than velvetleaf did at all water-supply levels. Velvetleaf partitioned more biomass to roots compared with shoots during early growth than corn did. The ability of corn to generate more leaf area and its investment in a greater proportion of biomass into root growth at all levels of water supply may enable it to more-effectively avoid velvetleaf interference under all levels of soil-water supply.

Agronomy Journa l • Volume 108 , I s sue 3 • 2016 Waterhemp is a diffi cult-to-control weed in maize, soybean [Glycine max (L.) Merr], and grain sorghum [Sorghum bicolor (L.) Moench] production, due to its competitive ability, outcrossing nature, high degree of genetic diversity, and resistance to multiple herbicide sites-ofaction (Horak and Loughlin, 2000; Hager et al., 2002; Steckel and Sprague, 2004; Steckel, 2007; Heap, 2015). Atrazine is still commonly used in maize and grain sorghum for PRE or POST control of waterhemp (Anderson et al., 1996) and other annual dicot weeds, in spite of hundreds of cases of triazine resistance occurring within Amaranthus spp. worldwide (Heap, 2014, 2015). Previous research reported that elevated rates of atrazine metabolism via GST activity contribute to atrazine POST resistance within two waterhemp populations (Ma et al., 2013). Th e MCR and ACR are both resistant to atrazine POST, and their responses have been compared with an herbicide-sensitive population, WCS (from Wayne County, Illinois) (Patzoldt et al., 2005; Hausman et al., 2011; Ma et al., 2013). Diff erences in PRE vs. POST activity of atrazine among several atrazine-resistant waterhemp populations identifi ed from Illinois were noted in previous studies (Patzoldt et al., 2003, 2005). In particular, an atrazine-resistant waterhemp population from Illinois (diff erent than MCR and ACR) was not resistant to atrazine PRE at a rate of 1.5 kg ha–1 (Patzoldt et al., 2003). Moreover, the ACR and MCR populations were not controlled but responded equally to atrazine POST at the rate of 560 g ha–1 (Hausman et al., 2011), and both populations demonstrated almost identical rates of atrazine metabolism (Ma et al., 2013) when 14C-atrazine was supplied using an excised-leaf assay (Ma et al., 2015). In addition to waterhemp, other dicot weed populations (most notably Abutilon theophrasti Medic.) have displayed non target-site resistance (NTSR) to atrazine POST (Anderson and Gronwald, 1987; Gronwald et al., 1989; Gray et al., 1996), and each has displayed enhanced rates of rapid metabolism via glutathione-atrazine conjugation (catalyzed by elevated GST activity) as the mechanism of resistance (Anderson and Gronwald, 1991; Gray et al., 1996). Th is is an important physiological factor to consider when studying NTSR mechanisms in weeds because GST enzymes are encoded by nuclear genes (Anderson and Gronwald, 1987; Patzoldt et al., 2003; Frova, 2006). In contrast, the target site for atrazine Differential Responses to Preemergence and Postemergence Atrazine in Two Atrazine-Resistant Waterhemp Populations

Field experiments were conducted in 2013 and 2014 to determine the influence of velvetleaf densities of 0, 0.125, 0.25, 0.5, 1, 2, 4, and 8 plants m−1of row on cotton growth and yield. The relationship between velvetleaf density and seed cotton yield was described by the hyperbolic decay regression model, which estimated that a density of 0.44 to 0.48 velvetleaf m−1of row would result in a seed cotton yield loss of 50%. Velvetleaf remained taller and thicker than cotton throughout the growing season. Both cotton height and stem diameter reduced with increasing velvetleaf density. Moreover, velvetleaf interference delayed cotton maturity, especially at velvetleaf densities of 1 to 8 plants m−1of row, and cotton boll number and weight, seed numbers per boll, and lint percentage were also reduced. Fiber quality was not influenced by weed density when analyzed over 2 yr; however, fiber length uniformity and micronaire were adversely affected in 2014. Velvetleaf intraspecific competition resulted in density-dependent effects on weed biomass, ranging from 97 to 204 g plant−1dry weight. Velvetleaf seed production per plant or per square meter was indicated by a logarithmic response. At a density of 1 plant m−1of cotton row, velvetleaf produced approximately 20,000 seeds m−2. The adverse impact of velvetleaf on cotton growth and development identified in this study have indicated the need for effective management of this species when the weed density is greater than 0.25 to 0.5 plant m−1of row and before the weed seed maturity.

ed from meteorological records of Iowa State University, Ames. In deriving 1% it was assumed that 50% of total incident shortwave radiation lies within the 400 to 700 nm waveband. Since it was impractical to monitor incident light interception continuously^ measurements were taken only at each of the four harvest dates, just prior to harvesting. A line quantum sensor^, oriented parallel to row direction, was used to measure the photosynthetic photon flux density (FFFD) at 0.01, 0.19, and 0.38 m to either side of each selected row section at the soil surface) one reading was taken directly above the canopy. The six FFFD values measured at the soil surface were averaged to obtain a mean value of FFFD below the canopy of each plot. FFFD was recorded automatically at 0.5 s intervals by a micrologger^ and averaged over a 25 s time period to obtain a better estimate of light interception. All FFFD measurements were taken at local solar noon i 1 h. The US was then calculated for each plot using these FFFD measurements. LUE was calculated in the following manner. A quadratic function was fitted to a plot of LIE over time (jDAP). Since LIE was not measured at emergence, an estimated value was used, based on typical expected LAI of soybean or velvetleaf at emergence. Daily lo and instantaneous daily values of LIE predicted from the equation of the line were then used to calculate J, the total amount of incident light (in energy terms) intercepted by canopies of the various species proportions, summed over each harvest interval from emergence to final harvest^ J S(LIE X lo). The LUE of each plot was then calculated for each harvest 4 Model LI-191SB. LiCor Inc., Lincoln, NE 68504. ^ Model 2iX. Campbell ScientiHc Inc., Logan, UT 84321.

This study was conducted to evaluate the effect of herbicidin, new natural herbicidal substances, derived from soil actinomycetes Streptomyces scopuliridis. Several weed species were subjected to examine the germination inhibition and herbicidal activity at the concentration from 100 to 2,000 ppm. There was no selectivity in germination inhibition and herbicidal activity against crops. Germination of Echinochloa oryzoides, Digitaria ciliaris, Abutilon theophrasti and Amaranthus retroflexus was inhibited completely when 7.81 ppm of extract was treated in petri dish. Pre-emergence application of herbicidin in soil condition showed low inhibition against weeds. However, post application of herbicidin in green house resulted in the necrosis of weeds at the concentration of 2,000 ppm. A. retroflexus was sensitive to herbicidin at the low concentration of 62.5 ppm, whereas E. oryzoides was tolerant to lower concentration of herbicidin until it became withered at the concentration of 2,000 ppm. In conclusion, herbicidal substances derived from S. scopuliridis herbicidin, which is consisted with herbicidin A and B, have dominant effect on germination and growth inhibition. On the other hand, herbicidin was insufficient to control gramineous weeds. In future, it will be needed to develop the combination of herbicidin with other herbicide or compounds to control gramineous weeds as well.

This study was conducted to investigate the ability for weed control of the shoot extract of sorghum (Sorghum bicolor (L.) Moench) and developing a sustainable weed management in organic farming. When the dried shoot powder was mixed with soil and treated with 2 ㎝ above the soil surface, the germination for Echinochloa crus-galli, Digitaria cilialis, Abutilon theophrasti and Amaranthus retroflexus was inhibited maxium 40%. The growth inhibition of germinated seedlings in the A. theophrasti and A. retroflexus was maxium 30% while it was less than 30% in the E. crus-galli and D. cilialis. Shoot extracts at rates above 25 ㎎ ml -1 was effective to inhibit germination of D. cilialis, A. theophrasti and A. retroflexus. The shoot extract concentration required for 50% of germination inhibition was 60 ㎎ ml -1 in the E. crus-galli, while it was less than 10 ㎎ ml -1 in the D. cilialis, A. theophrasti and A. retroflexus. For the foliar application, 11 adjuvants were tested at 0.5% and DOS70, TM15 and TDE7 were most effective adjuvants for the shoot extracts. DOS70 was most effective and provided up to 60% of weed control efficacy for the tested four weed species. Though herbicidal efficacy of sorghum shoot was not enough to give a proper weed control, it can be expected that long term use of sorghum shoots can provide gradual decrease in weed seeds and weed density.

Flaveria bidentis (L.) Kuntze, an invasive plant in China, has caused serious environmental and agricultural problems. A competition experiment with and without nitrogen fertilizer under field conditions was conducted to determine the competitive ability of the invasive plant species with two native species. The results showed that fertilization only increase relative growth rate of F. bidentis in the monoculture and the photosynthetic rates of the invasive species when it competed with Abutilon theophrasti. The growth of Leonurus heterophyllus was inhibited, while the growth of A. theophrasti was promoted by competition with F. bidentis. Nitrogen fertilizer addition significantly decreased the positive effect and increased the negative effect on A. theophrasti. The higher relative growth rate and net assimilation rate might give A. theophrasti a competitive advantage in comparison to L. heterophyllus in the competition with F. bidentis due to its greater ability to utilize available resources.

An alternative method to other technologies to clean up the soil, air and water pollution by heavy metals is phytoremediation. Therefore, a pot culture experiment was conducted at the College of Agriculture, Ferdowsi University of Mashhad, Mashhad, Iran, in 2014 to determine the potential absorption of cadmium by Portulaca oleracea (Common purslane), Solanum nigrum (Black nightshade), Abutilon theophrasti (Velvetleaf) and Taraxacum officinale (Dandelion). The type of experiment was completely randomized design with factorial arrangement and four replications. The soil in pot was treated with different rates of CdCl2.H2O (0 (control), 10, 20, 40, 60, and 80 mg Cd/kg soil) and the plants were sown. With increasing concentration levels, fresh weight and dry weight of shoots and roots of all plant species were reduced. The reduction severity was ranked according the following order, P. oleraceaA. theophrastiS. nigrumT. officinale. Bioconcentration factor (BCF), Translocation factor (TF) and Translocation efficiency (TE%) was ranked according the following order, T. officinaleS. nigrumA. theophrastiP. oleracea. The results of this study revealed that T. officinale and S. nigrum are effective species to phytoremediate Cd-contaminated soil.

A number of studies have shown that under some conditions plants may fully or partially compensate for leaf tissue loss; however, the mechanisms underlying compensatory responses are not well understood. Previous work demonstrated that the annual herb Abutilon theophrasti fully compensated for 75% defoliation, but only when grown in the absence of stem competition. We examined potential mechanisms of compensatory response and how they are influenced by resource limitation (i.e., competition for light). Full compensation for these annual plants was defined as equal final reproductive output in defoliated and control plants. In the current study we observed substantial compensation in defoliated plants growing at low density, despite losing 75% of leaf area prior to the onset of flowering. Plant responses associated with compensation included (1) increased reproductive efficiency, which may in turn may have resulted from increased canopy light penetration and transient increases in leaf-level photosynthetic rates; (2) greater allocation to reproduction (RA); (3) changes in biomass allocation from roots to shoots; (4) lower leaf longevity, and (5) increased percent fruit set. Although some of these responses were also observed in defoliated plants grown at high density, the inability of high-density plants to compensate appeared to result from competition for light; these plants delayed reproduction and continued to produce new leaves late in the growing season after low-density, defoliated plants had shifted allocation of resources to reproduction.

Follak S., Aldrian U., Schwarz M. (2014): Spread dynamics of Abutilon theophrasti in Central Europe. Plant Protect. Sci., 50: 00–00. The spread pattern of Abutilon theophrasti (velvetleaf ) in Austria, the Czech Republic, and Slovakia was analysed based on an exhaustive distribution data set (389 records). Cumulative number of all records showed a continuous increase since its introduction in the 19 th century and > 1970 its spread gained momentum with an exponential increase > 2000. In fields, the species remained rare until 2000. Since then, A. theophrasti has invaded fields much more frequently (78% of all records in fields > 2000) and it was mainly found in sugar beet and maize. Approximately a total of 188 000 ha of the agricultural area are currently at risk of being invaded. Given the on-going spread into fields, the results provide evidence that A. theophrasti may cause serious impacts. Control measures should focus on the prevention of spreading seeds and the establishment of new foci.

Trap cropping is a useful tool in sustainable pest management. Trap crops usually target a single species or genus of insect pests. In this study, we assessed the potential of velvetleaf (Abutilon theophrasti) as a trap crop for two distant insect species, Bemisia tabaci and Sylepta derogata in Chinese cotton fields from 2006 to 2009. Under laboratory conditions, velvetleaf, a known trap plant of B. tabaci, was preferred over cotton by S. derogata for oviposition, and the subsequent offspring had greater survival and faster development on velvetleaf than cotton. Field-plot trials showed that population densities of S. derogata were 46–110 times greater on velvetleaf than on cotton, respectively. Commercial field trials indicated that S. derogata density and leaf damage were 79–90 % and 83–94 % lower in cotton fields inter-planted with sprayed velvetleaf strips than without them, respectively; whereas densities of B. tabaci were 21–51 % lower in fields with sprayed velvetleaf strips than in those without. At >10 m from velvetleaf strips, densities of B. tabaci and S. derogata in cotton gradually increased. Velvetleaf strips were an effective trap crop for simultaneous management of B. tabaci and S. derogata in cotton fields.

Summary Weed seeds in and on the soil are the primary cause of weed infestations in arable fields. Previous studies have documented reductions in weed seedbanks due to cropping system diversification through extended rotation sequences, but the impacts of different rotation systems on additions to and losses from weed seedbanks remain poorly understood. We conducted an experiment in Iowa, USA, to determine the fates of Setaria faberi and Abutilon theophrasti seeds in 2-, 3- and 4-year crop rotation systems when seed additions to the soil seedbank were restricted to a single pulse at the initiation of the study. Over the course of the experiment, seedlings were removed as they emerged and prevented from producing new seeds. After 41 months, seed population densities dropped >85% for S. faberi and >65% for A. theophrasti, but differences between rotation systems in the magnitude of seedbank reductions were not detected. Most of the reductions in seedbank densities took place from autumn through early spring in the first 5 months following seed deposition, before seedling emergence occurred, suggesting that seed predation and/or seed decay was important. For S. faberi, total cumulative seedling emergence and total seed mortality did not differ between rotation systems. In contrast, for A. theophrasti, seedling emergence was 71% lower and seed mortality was 83% greater in the 3- and 4-year rotation systems than in the 2-year system. Results of this study indicate that for certain weed species, such as A. theophrasti, crop rotation systems can strongly affect life-history processes associated with soil seedbanks.

Robinson, D. E., McNaughton, K. E. and Bilyea, D. 2013. Comparison of sequential preemergence-postemergence and postemergence-alone weed management strategies during critical period of red beet ( Beta vulgaris L.). Can. J. Plant Sci. 93: 863–870. Weed management during the first 4 wk after red beet emergence is critical to prevent yield loss. The purpose of this research was to compare weed control and red beet tolerance of postemergence (POST) treatments alone (full, split- and micro-rates of pyrazon plus triflusulfuron) with sequential preemergence (PRE) applications of s-metolachlor followed by these POST herbicide treatments. The experiment was carried out for 4 yr as a randomized complete block with four replications. Of the POST alone treatments examined, control of velvetleaf (Abutilon theophrasti Medik.), redroot pigweed (Amaranthus retroflexus L.), common lambsquarters (Chenopodium album L.) and green foxtail [Setaria viridis L. (Beauv.)] was 98, 86, 97 and 62%, respectively. Much more consistent control of all species (i.e., greater than 96%) was measured where the sequential treatment of s-metolachlor was applied PRE followed by POST split- or micro-rates in all study years. Red beet density and soluble solid levels were not different than the weed-free check in any of the POST or sequential treatments. However, red beet yield in the POST single and split-rate treatments alone ranged from 9500 to 12100 kg ha−1, and was significantly less than in the weed-free check (19400 kg ha−1). Yields in the sequential treatments were comparable to the weed-free check. The results of this study confirm that a sequential treatment of PRE s-metolachlor followed by POST split- and micro-rate applications of pyrazon plus triflusulfuron can be safely applied to red beet and control annual weed species.

Weed emergence models require biological parameters such as base temperature for germination, determination of which is costly and time-consuming. Transferability of these parameters across different populations may therefore represent one of the main constraints for the development and practical use of emergence models at a large scale. A collaborative project was undertaken to assess the interpopulation variability of base temperature for germination in different European populations of velvetleaf and jimsonweed and evaluate possible applicative consequences in terms of weed control. Seeds were collected in Italy, Portugal, and Spain, and each population was then sown in every country, obtaining nine seed batches named as experimental lots. Base temperature for germination was estimated for each experimental lot to calculate lot-specific accumulation of growing degree days (GDD) under three dissimilar climatic scenarios. Threshold date (TD50) was calculated as the date when GDD accumulation of a given experimental lot surpassed the values corresponding to 50% of cumulative field emergence of seedlings. GDD accumulation and TD50were then used as indicators to identify differences among experimental lots within each climatic scenario. No significant differences were detected among base temperatures estimated for velvetleaf experimental lots or among their patterns of accumulation of GDD and TD50values within climatic scenarios. Each value of base temperature determined for a single experimental lot could therefore be adopted to model germination for all the lots regardless of the population of origin or cultivation site. In contrast, the population of origin affected the base temperature for jimsonweed, with significantly higher values for experimental lots of the Portuguese population. From an applicative perspective, differences among patterns of accumulation of GDD and TD50of several experimental lots within each climatic scenario suggest the need to use population-specific values as base temperature for germination and emergence modeling of jimsonweed.

BACKGROUND Root-knot nematodes and soil-borne diseases constrain the rapid development of protected agriculture in China, especially while phasing out methyl bromide (MB). The fumigant sulfuryl fluoride (SF) is currently used as an alternative to MB for the disinfestation of buildings and post-harvest commodities. Our experiments aimed to evaluate a novel application of SF as a soil fumigant in greenhouses in China. RESULTS Dose–response experiments indicated that SF has good efficacy on root-knot nematodes (Meloidogyne spp.) and moderate activity against Fusarium spp. and weeds (Digitaria sanguinalis (L.) Scop. and Abutilon theophrasti Medicus). The field trials indicates that SF has good efficacy, between 80 and 94%, on Meloidogyne spp., and Fusarium spp. at the rates of 25–50 g m−2 in tomato and cucumber in Beijing and Shandong Province. Marketable yield and plant vigour was not significantly different in SF and MB treatments. SF has lower emissions than MB during the fumigation operation. It is simple to apply, can be used at low temperature, and has a short plant-back time. SF was found to be an economically feasible alternative to MB for nematode control in China. CONCLUSION SF can be used as a soil fumigant to control root-knot nematodes and to reduce the levels of key soil pathogens. © 2013 Society of Chemical Industry

Abutilon theophrasti and Barnyardgrass (Echinochloa crus-galli) are major weeds that affect cropping systems worldwide. Laboratory and greenhouse studies were conducted to determine the effects of temperature, pH, water and salinity stress, and planting depth on seed germination and seedling emergence of Velvetleaf and Barnyardgrass. For Velvetleaf, the base, optimum and ceiling germination temperatures were estimated as 5, 35 and 48 ºC, respectively. Seed germination was sensitive to drought stress and completely inhibited by a potential of -0.6 MPa, but it was tolerant to salinity. Salinity stress up to 45 mM had no effect on the germination of Velvetleaf, but germination decreased with increasing salt concentration. Drought and salinity levels for 50% inhibition of maximum germination were -0.3 MPa and 110 mM, respectively. Seed germination of Velvetleaf was tolerant to a wide range of pH levels. For Barnyardgrass, the base, optimum and ceiling germination temperatures were estimated as 5, 38 and 45 ºC, respectively. Seed germination was tolerant to drought stress and completely inhibited by a potential of -1.0 MPa. Salinity stress up to 250 mM had no effect on seed germination. Drought and salinity levels for 50% inhibition of maximum germination were -0.5 MPa and 307 mM, respectively. A high percentage of seed germination was observed at pH=5 and decreased to 61.5% at acidic medium (pH 4) and to 11% at alkaline medium (pH 9). Maximum seedling emergence of Velvetleaf and Barnyardgrass occurred when the seeds were placed on the surface of the soil or at a depth of 1 cm.

Velvetleaf ( Abutilon theophrasti Medik.) is an invasive alien species in many countries and one of the major weeds in summer row crops worldwide. Weed-management techniques that reduce weed production need to be investigated to provide new approaches. The first step in this process is the determination of weed productivity in different competitive conditions. Field experiments were conducted in 2006 and 2008 in an experimental field in Padinska Skela to quantify growth and seed production of velvetleaf in maize, as well as in a velvetleaf monoculture. A density of velvetleaf ranging from 1 to 8 plants m -1 was artificially created. In a mixture with maize, velvetleaf was sown in crop rows. The growth of velvetleaf was estimated based on plant height, fresh aboveground biomass and leaf area index (LAI). Velvetleaf fecundity was determined as seed mass plant -1 and seed mass m -2 . Differences between years in plant production were very prominent. In general, velvetleaf productivity in maize depended on its density. Intraspecific competition had a major influence on growth and seed production when velvetleaf density was from 4 to 8 plants m -1 in maize rows. This information indicates that environmental conditions and weed density can promote/reduce inter- and intraspecific competition and help in the construction of population dynamics models to predict population density, seed bank and competitiveness of weeds and reduce inputs for weed management. DOI: 10.2298/ABS160212092V Received: February 12, 2016; Revised: April 11, 2016; Accepted: April 19, 2016; Published online: October 4, 2016 How to cite this article: Vrbnicanin S, Onc-Jovanovic E, Božic D, Saric-Krsmanovic M, Pavlovic D, Malidža G, Jaric S. Velvetleaf (Abutilon theophrasti medik.) productivity in competitive conditions. Arch Biol Sci. 2017;69(1):157-66.

Velvetleaf (Abutilon theophrasti Medik.) is an annual broad-leaf weed species from the family Malvaceae (Mallow family). It is an erect summer annual, up to 2 m tall, with yellow flowers and large, velvety, heart-shaped leaves. This plant originated in India and China, from where it was introduced into North America in the mid-1700s, as a potential fiber crop plant. Today it has spread over many countries of the world, including southeastern Europe, and has been categorized as an alien invasive weed species. It is an important weed of many crops in Serbia and is especially problematic where corn, soybean, sunflower and sugar beet are major crops. Velvetleaf reproduces by seeds (dimensions: 2.75-3.25 x 1.5-1.75 mm). The majority of seeds fall near the parent plant, but some are also dispersed over greater distances by water, mud, soil movement and especially agricultural activities. Seed production can be high, up to 50000+ seeds per plant. Seeds can survive for 50 years or more in the soil. The seedlings are tipically vigorous and mostly emerge from the soil depth of about 1-7 cm (no more than 10-13 cm). A. theophrasti competes with the abovementioned crops for light and nutrients. This weed species can produce relatively large quantities of biomass late in the season, which may increase the competition for light in many crops. Once established, velevetleaf is difficult to control due to its long-lived seeds and sporadic germination pattern. Preemergernce and postemergence control measures, such as: crop rotation, cultural control (preplant tillage, cultivation after crop planting, manual removal of individual plants), physical and chemical (preem and postem herbicide application) control, are essential for effective control of velvetleaf.

A class of phenolic compounds, ortho-dihydroxyphenols (hereafter “o-DHP”), has been implicated with seed survival. Based on expectations of the growth-differentiation balance hypothesis, we predicted that seed o-DHP concentration exhibits a curvilinear response to increasing resource availability in the maternal environment, with maximum o-DHP occurring at moderate resource levels. To test this hypothesis, Abutilon theophrasti seeds were produced under field conditions at two locations. Each location included twelve maternal environments established through factorial combinations of soil compost (+/-), species assemblage (A. theophrasti with and without maize), and soil nitrogen fertilizer (0, 0.5× or 1× local recommendations for maize). Resource availability with respect to A. theophrasti growth was summarized by above-ground biomass at seed harvest (maternal biomass). Results indicated that seed o-DHP concentrations increased then decreased in response to increasing maternal biomass. This relationship was modeled with a unimodal function specific to location (Location 1, y = 1.18 + 0.03xe-0.02x, pseudo-R2 = 0.59, p = 0.003; Location 2, y = 1.40 + 0.006xe-0.005x; pseudo-R2 = 0.34, p = 0.05). Seed protein concentrations remained constant across maternal biomass levels. Because inherent vulnerability to predation and decay is considered a consequence of chemical protection relative to nutritional offering, our results suggest that A. theophrasti seed susceptibility to lethal attack is influenced by resource levels in the maternal environment. More broadly, our results suggest that the growth-differentiation balance hypothesis can be extended to maternal effects on seed phenolics.

Summary Soyabean (Glycine max) was grown at ambient and projected levels of atmospheric carbon dioxide (+250 μmol mol−1 above ambient) over two field seasons with and without the presence of a weed, Abutilon theophrasti, to quantify the potential effect of rising atmospheric carbon dioxide concentration on weed–crop interactions and potential yield loss in soyabean. Under weed-free conditions, elevated CO2 resulted in stimulations in soyabean seed yield and associated components, including pod number. At an approximate density of 6 plants m−2, A. theophrasti competition resulted in a significant reduction (−40%) in soyabean seed yield. Although differences in seed yield reduction by A. theophrasti were observed as a function of year, the relative decrease in seed yield with A. theophrasti biomass did not differ in response to CO2. Although careful weed management will be necessary if CO2-induced increases in seed yield for soyabean are to be achieved, these data suggest that soyabean seed yield may be more resilient in competition with A. theophrasti as a function of rising atmospheric levels of carbon dioxide.

The potential as natural herbicide of d-limonene natural agent was conducted on several weeds in a greenhouse and Sciyos angulatus in field condition. Herbicidal activity of foliar application at a concentration of 100 and 200 kg ai of d-limonene on seven weed species was completely killed in a greenhouse condition. Also, d-limonene at a concentration of 50 kg ai was completely killing on Abutilon theophrasti, Aeschynomene indica, Echinochloa crus-galli and Digitaria ciliaris 3 days after treatment. While pre-emergence treatment of d-limonene concentration of 12.5 to 200 kg ai showed not significant visible damages. Phytotoxic symptoms of d-limonene by foliar treatment were characterized by wilting and burn-down of leaves and stems followed by discoloration, finally, plant death. Crop selectivity at d-limonene concentration of 100 kg ai over to five main crops including Zea mays by foliar application was not at all. Field trial of foliar treatment with d-limonene 70 to 140 kg ai have effectively controled over 5~20 leaf stages of S. angulatus at the natural habitats. And herbicidal efficacy of foliar application on S. angulatus with carrier volume in field condition was increased with dose dependent manners. These results suggest that d-limonene is considered possible as herbicide, and may be further optimized for natural agent for environmental friendly natural herbicide.

Time of day has been observed to affect flaming efficacy. The basis for the differential plant response is not well understood; however, daily variation in leaf relative water content (RWC) is thought to contribute to the response. Leaf RWC is the ratio of the amount of water in the leaf tissue compared to when fully turgid. To determine the influence of leaf RWC in plant response to propane flaming, greenhouse experiments were conducted during April and repeated in September of 2009. Two crops [4-leaf maize ( Zea mays ) and second trifoliate soybean ( Glycine max )] and two weed species [5-leaf velvetleaf ( Abutilon theophrasti ) and 6-leaf green foxtail ( Setaria viridis )] were flamed with four propane doses of 0, 29, 43 and 87 kg ha −1 at 0, 4, 8 and 12 h after sunrise-HAS. Leaf RWC was measured before treatment application. Flaming treatment was conducted utilizing a hand flamer with one VT 2–23 C vapor phase burner positioned 20 cm above soil surface and angled horizontally at 30°. The propane pressure was 120 kPa and the application speeds were 1.6, 3.2 and 4.8 km h −1 . The plant responses evaluated were plant injury and fresh weight at 7 days after treatment (DAT). All plant species were more susceptible to flaming during the afternoon when they had lower leaf RWC at 8 HAS; however, the response of these plants did not differ with the plants flamed at 12 HAS. Green foxtail flamed at 87 kg ha −1 at 0, 8 and 12 HAS had injury of 62, 76 and 82%, respectively. The same response was observed in velvetleaf which had 80% injury when flamed with 87 kg ha −1 at 0 HAS and 93% injury when flamed at 12 HAS with the same propane dose at 7 DAT. Similar trends occurred for maize and soybean suggesting that leaf RWC could be one of the factors affecting plant response to flaming. Practical implication is that flaming operation should be conducted in the afternoon in order to improve efficacy of weed control and reduce propane consumption rate.

This study was carried out to establish an improved bioassay system on the side of practicality, pre-emergence bioassay which is more effective in developing soil application natural herbicides. A miniaturized method which have a 50 cm2 of soil surface area and was efficient by 7 times compared to the existing soil application assay ( of soil surface area) was established, in which four weed species (Echinochloa crus-galli, Digitaria sanguinalis, Aeschynomene indica, and Abutilon theophrasti) were planted and grown in greenhouse. This would be applicable when the amount of screening compound is much more than 50 mg. The initial application rate was desirable at . On the other hand, the 6 well plate assay which has 4 weed species in each well containing upland soil and could be conducted in growth chamber, was established. This assay was resulted in minimizing in level of 1/14 test volume and 1/14 amounts of test compound to the conventional method that has been used for screening of synthetic compounds in KRICT, and applicable for the small amount of test compound (less than 10 mg). Therefore, the improved bioassays established in this study would be helpful for a rapid and efficient development of soil application natural herbicides.

Crop seedlings detect the presence of neighboring competitors by means of the red to far-red ratio (R/FR) of light reflected from the leaf surfaces of adjacent seedlings. Although previous studies have suggested that shifts in the R/FR initiate crop– weed competition, no studies have documented the R/FR of light reflected from weeds or explored how weed management practices may affect the R/FR. Experiments were conducted to test the following hypotheses: (1) the duration of R/FR signals reflected from the leaf surface of weed seedlings will vary among herbicides following treatment and will decline faster as the dose of a given herbicide increases, (2) the R/FR of reflected light will differ among weed species, and (3) the R/FR of reflected light will decrease as weed seedling leaf area and stage of development increases. Velvetleaf was used as a model weed species to examine herbicide chemistry and dose, and six weed species including Powell amaranth, velvetleaf, Eastern black nightshade, barnyardgrass, proso millet, and green foxtail were evaluated in order to characterize the R/FR of light reflected from their leaf surfaces. Results of this study confirm that the R/FR reflected from the leaf surface of weeds is affected by: herbicide chemistry, herbicide dose, weed species, stage of weed development, and distance of the weed from the crop. The relative decline in the R/FR (as a percent of the untreated control) was most rapid following treatment with paraquat, followed by glufosinate and then glyphosate. As glyphosate dose decreased, so did the reduction in the relative R/ FR. Based on reflected R/FR, weed species tended to be grouped into monocots and dicots, with the latter reflecting a lower R/FR per unit leaf area than the former. This disparity was attributed to the compact leaf arrangement and orientation of dicot weed canopies, which may contribute to the greater competitiveness of dicot weeds. Nomenclature: Glyphosate; glufosinate; paraquat; barnyardgrass, Echinochloa crus-galli L. Beauv. ECHCG; Eastern black nightshade, Solanum ptycanthum Dunal. SOLPT; green foxtail, Setaria viridis L. (Beauv.) SETVI; proso millet, Panicum milliaceum L. PANMI; Powell amaranth, Amaranthus powellii S. Wats. AMPO; velvetleaf, Abutilon theophrasti Medik. ABUTH.

SUMMARYThe presence of velvetleaf (Abutilon theophrasti) in crops is increasing in arid and semi-arid environments. Field experiments were conducted in Greece in 2009 and 2010 to determine the influence of velvetleaf emergence time and maize (Zea mays) hybrids with different growth rates on maize yield and velvetleaf growth and fecundity. Velvetleaf was uniformly seeded in order to emerge at the 1, 3, 5 and 7-leaf stage of maize (V1, V3, V5 and V7 growth stages, respectively). Velvetleaf biomass, canopy area and seed production were significantly affected by the date of velvetleaf emergence. Velvetleaf plants emerging just after maize (V1) produced 7–17 times lower seed number, compared with the V5 growth stage. Maximum maize grain yield loss ranged from 26 to 37% for early emerging velvetleaf, and less than 6% yield loss occurred from velvetleaf seedlings emerging at V7 growth stage. Maize hybrids with high initial growth rate seem to be more competitive than the other hybrids. The results of this study are essential in the development of an integrated weed management strategy for maize in semi-arid environments, since they highlight the importance of the careful selection of a competitive maize hybrid and avoidance of early velvetleaf emergence.

The average mealy bug (Phenacoccus solenopsis Tinsley) population was maximum (2.69, 2.40 and 1.73 adults/plant) on Parthenium hysterophorus at wasteland, in or near field and weeds present near stacks at Muktsar. At Ferozepur, the mean mealy bug population was 1.10 adults/plant on cotton. On the weeds, near or in the field, the maximum population (5.94 adult/plant) was recorded on P. hysterophorus followed by Digeria arvensis (3.74 adults/plant). The population was 2.69, 2.66 and 2.86 adults/plant on Sida acuta, Abutilon theophrasti and Achryanthus aspera, respectively. On wasteland weeds, similar trend was observed, i.e. maximum population was on P. hysterophorus (7.31 adults/plant), while minimum (3.00 adults/plant) on S. acuta, during 2008. Similar trend was followed in 2009 in Muktsar and Ferozepur but the population was lower than the previous year. Among the weeds, P. hysterophorus was the most preferred host for multiplication. During carry-over studies all the stages and ovisac was maximum, follo...

Weed-suppressive soils contain naturally occurring microorganisms that suppress a weed by inhibiting its growth, development, and reproductive potential. Increased knowledge of microbe–weed interactions in such soils could lead to the identification of management practices that create or enhance soil suppressiveness to weeds. Velvetleaf death and growth suppression was observed in a research field (fieldA) that was planted with high populations of velvetleaf, which may have developed via microbial mediated plant–soil feedback. Greenhouse studies were conducted with soil collected fromfieldA(soilA) to determine if it was biologically suppressive to velvetleaf. In one study, mortality of velvetleaf grown for 8 wk insoilAwas greatest (86%) and biomass was smallest (0.3 g plant−1) in comparison to soils collected from surrounding fields with similar structure and nutrient content, indicating that suppressiveness ofsoilAwas not likely caused by physical or chemical factors. WhensoilAwas autoclaved in another study, mortality of velvetleaf plants in the heat-treated soil was reduced to 4% compared to 55% for the untreated soil, thus suggesting that suppressiveness ofsoilAis biological in nature. A third set of experiments showed that suppressiveness to velvetleaf could be transferred to an autoclaved soil by amending the autoclaved soil with untreatedsoilA; this provided additional evidence for a biological basis for the effects ofsoilA.The suppressive condition in these greenhouse experiments was associated with high soil populations of fusaria.Fusarium lateritiumwas the most frequently isolated fungus from roots of diseased velvetleaf plants collected fromfieldA, and also was the most virulent when inoculated onto velvetleaf seedlings. Results of this research indicate that velvetleaf suppression can occur naturally in the field and thatF. lateritiumis an important cause of velvetleaf mortality infieldA.

Velvetleaf is one of the most significant and fastest spreading alien weeds in Europe, and it is a difficult weed to control in conventional sugarbeet. Laboratory experiments were carried out in 2007 and 2008 and field experiments were carried out in 2006, 2007, and 2008 with the aim of finding effective herbicide combinations and optimum timing of control. Herbicides containing the active ingredients phenmedipham, desmedipham, ethofumesate, clopyralid, and triflusulfuron were all tested at different timings. Phenmedipham + desmedipham + ethofumesate gave 87% velvetleaf control in pot experiments when applied at the growth stages of velvetleaf cotyledons and one true leaf, but only 27 to 42% control in field trials. Triflusulfuron gave 76% control in pot experiments and 83 to 88% control in field experiments. The timing of the first and second herbicide applications was very important: the first application of herbicides must be at the cotyledon stage of velvetleaf. A 1-wk delay in first application reduced herbicide efficacy by 8%. A 5-d period between the first and second treatments gave 93% control, while a 10-d period between the first and second treatments gave only 77% control. Sugarbeet yield decreased by 60 to 86% due to competition with velvetleaf when a standard herbicide combination (phenmedipham + desmedipham + ethofumesate) was used, and the velvetleaf produced between 6,700 and 14,800 seeds m−2. Inclusion of triflusulfuron in the herbicide treatment significantly reduced velvetleaf seed production to between 200 and 4,700 seeds m−2. In most cases, inclusion of triflusulfuron increased sugarbeet yield. Better velvetleaf control occurred in years when the sugarbeet canopy developed early and the index of leaf area of sugarbeet was higher.

Tolpyralate, an HPPD (4-hydroxyphenyl-pyruvate dioxygenase) inhibitor, is a relatively new herbicide for weed control in corn. Field studies were conducted in 2015 and 2016 to evaluate the effective dose of tolpyralate applied alone or mixed with atrazine for weed control in corn. The treatments included seven rates (0, 5, 20, 29, 40, 50 and 100 g ai ha-1) of tolpyralate applied alone or mixed with a constant rate (560 g ai ha-1) of atrazine. The evaluated weed species were common waterhemp (Amaranthus rudis Sauer), common lambsquarters (Chenopodium album L.), velvetleaf (Abutilon theophrasti Medik), henbit (Lamium amplexicaule L.) and green foxtail (Setaria viridis L.). Overall, POST-application of tolpyralate resulted in 42-100% visual weed control, depending on the weed species and tolpyralate doses. Calculated dose of 19-31 g ai ha-1 (ED90) of tolpyralate applied alone provided 90% visual control of common waterhemp, common lambsquarters, henbit, and velvetleaf. However, addition of atrazine significantly reduced the required dose of tolpyralate to 11-17 g ai ha-1 for the same level of control of these weed species; suggesting a synergy between the two herbicides.

Velvetleaf (Abutilon theophrasti) was accidentally introduced into New Zealand in 2016 and intensive efforts are being implemented to mitigate the risk of its naturalisation. This study investigated the possibility of velvetleaf plants surviving in maize fields following silage harvest in late summer and early autumn. Velvetleaf plants were grown to maturity in a glasshouse during the summer of 2017—2018. They were left to seed and senesce naturally and, on 28 February 2018, five senesced plants were “harvested” at each height (0, 30, 50, 70 and 150 mm) with varying numbers of leaf nodes remaining (0, 0, 1, 2 and 3 pairs respectively). Velvetleaf was capable of regeneration 2—4 weeks after “harvest” from these leaf nodes. Forty percent regeneration occurred with 1 pair of nodes; 80% (2 pairs); and 100% (3 pairs). All regenerated plants subsequently produced mature seed pods with viable seed (95% germination) 6—10 weeks following “harvest”. Maize silage crops are normally cut ~100 mm above ground level. In this study, velvetleaf was able to regenerate and reproduce following simulated maize silage harvest at, below and above, normal cutting height. Growers are advised to continue management strategies for velvetleaf to prevent seed set following maize silage harvest and before sowing of the next crop or pasture.

Weed management can be difficult and expensive in organic agricultural systems. Because of the potentially high cost of the natural product herbicides vinegar and clove oil, their efficacy with regard to weed species growth stages needs to be determined. A further objective was to identify anatomical and morphological features of redroot pigweed and velvetleaf that influence the effectiveness of vinegar and clove oil. Research was conducted on greenhouse-grown cotyledon, two-leaf, and four-leaf redroot pigweed and velvetleaf. Dose–response treatments for vinegar included 150-, 200-, 250-, and 300-grain vinegar at 318 L/ha and at 636 L/ha. Clove oil treatments included 1.7, 3.4, 5.1, and 6.8% (v/v) dilutions of a clove oil product in water (318 L/ha), and a 1.7% (v/v) dilution in 200-grain vinegar (318 L/ha). An untreated control was included. Separate plantings of velvetleaf and pigweed were treated with vinegar or clove oil and were used to study anatomical and morphological differences between the two species. Redroot pigweed was easier to control with both products than velvetleaf. Whereas 200-grain vinegar applied at 636 L/ha provided 100% control (6 d after treatment [DAT]) and mortality (9 DAT) of two-leaf redroot pigweed, this same treatment on two-leaf velvetleaf provided only 73% control and 18% mortality. The obtuse leaf blade angle in velvetleaf moved product away from the shoot tip, whereas in pigweed, the acute leaf blade angle, deep central leaf vein, and groove on the upper side of the leaf petiole facilitated product movement toward the stem axis and shoot tip. For both species, and at all application timings, 150-grain vinegar at 636 L/ha provided control equal to that of 300-grain vinegar at 318 L/ha. As growth stage advanced, control and biomass reduction decreased and survival increased. Application timing will be critical to maximizing weed control with vinegar and clove oil.

The primary defense against seed mortality, the seed coat, is maternally derived. Hence, weed seed mortality in the soil seedbank is likely to be influenced by the maternal environment and genetics. We hypothesized that seed accessions from contrasting maternal environments (seed lots) exhibit different rates of seed mortality and that the relative differences among seed lots remain consistent across burial environments. Velvetleaf and giant foxtail annual seed mortality rates were studied in field experiments in Hickory Corners, MI, and Wooster, OH, using seed lots collected from the same locations. Seeds enclosed within mesh bags and unenclosed seeds (‘‘seeded cores’’) exhibited similar levels of seedbank persistence (r 5 0.90, P , 0.001) and seed mortality (r 5 0.65, P 5 0.006). Annual seed mortality rates ranged from 16 to 56% and 27 to 91% for seed lots of velvetleaf and giant foxtail, respectively. Relative differences among velvetleaf seed lots were consistent across burial environments in both years, whereas giant foxtail differences were consistent in only 1 of 2 yr. The relative ranks among velvetleaf seed lots varied between years, indicating that maternal environment may have influenced seed persistence more than seed-lot genetics. Within years, variation in seed mortality was predicted by changes in soil moisture in the burial environment (R 2 5 0.47, P , 0.001 for velvetleaf; R 2 5 0.34, P 5 0.007 for giant foxtail). Accelerated seed mortality was associated with moist soils (soil water potential 52 6 kPa for velvetleaf, 27 kPa for giant foxtail). These results suggest that agronomic practices affecting the maternal environment and moisture levels in the soil seedbank may promote weed seed mortality in the soil seedbank. Nomenclature: Giant foxtail, Setaria faberi Herrm. SETFA; velvetleaf, Abutilon theophrasti Medik. ABUTH.

Control of weeds growing around field edges to limit seed production is an important component of preventative weed management. POST herbicide rates that are effective on weeds growing within a dense corn or soybean canopy may not be high enough to control weeds at the edge of a field. A study was conducted from 2004 through 2006 to compare velvetleaf growth and fecundity at the edge of the field as opposed to within the crop in response to a range of glyphosate rates. Treatments included position (plot center or edge), time of emergence (VE or V4 crop growth stage) and glyphosate rate (0 to 900 g ae ha−1). Without herbicide application, velvetleaf plants grown on the edge flowered earlier, had thicker stems, and produced more seed capsules than plants grown in the center of the plots. At glyphosate application rates of 200 to 900 g ha−1, the percentage of plants surviving and reproducing was higher on the edge than within the crop. Edge plants treated with 900 g ha−1of glyphosate produced more seeds than center plants that received no herbicide. Dose–response curves were used to estimate the glyphosate rate that would reduce seed production of surviving plants to 80% of the untreated plants. Plants emerging at the VE stage were estimated to require 300 g ha−1within the corn or soybean canopy and 668 g ha−1on the crop edge, whereas plants emerging at the V4 stage would require 0 g ha−1within the canopy and 280 g ha−1on the crop edge.

The sweet potato whitefly, Bemisia tabaci (Gennadius) biotype B was first found in southern China in 1994 and has since then become a pest of increasing importance throughout the nation. The population dynamics of this invasive species and the effect of natural enemies on its population dynamics were studied in commercial cotton fields during the summers of 2003 through 2005 in Langfang, Hebei (northern China). The abundance of Bemisia tabaci was found to increase rapidly in late July, and reached its first peak in mid-August, then followed by the second peak in early September. Whitefly populations subsequently declined slowly to attain a plateau after mid-September. A total of 13 natural enemy species were discovered in association with B. tabaci in cotton fields, including dominant species such as Chrysopa sinica Tjeder, Leis axyridis Pallas, Propylaea japonica Thunberg, Orius similis Zheng, and Eretmocerus sp. Caged experiments on velvetleaf, Abutilon theophrasti Medic, one of the preferred h...

Applicability of root electrical capacitance (EC) measurement for monitoring of crop–weed competition was studied in a pot experiment. Maize (Zea mays L.) was grown both alone and with Echinochloa crus-galli or Abutilon theophrasti in different densities with regular measurement of root EC. Plants were harvested 42 days after planting to determine above- and belowground biomass. Depending on weed density, E. crus-galli-A. theophrasti interaction reduced the root EC of maize by 22–66% and 3–57%, respectively. Competitive effect of crop on weeds and intraspecific competition among weeds could also be detected by EC values: E. crus-galli was less sensitive both to the presence of maize and to intraspecific competition than A. theophrasti. Strong linear correlations between root dry mass and root EC for crop and weeds (with R2 from 0.901 to 0.956) were obtained by regression analyses at the end of the experiment. EC monitoring informed us on the emergence time of competition: E. crus-galli interfered with maize root growth a week earlier then A. theophrasti, and increasing weed densities accelerated the emergence of competition. In conclusion, the simple, non-destructive EC method should be considered a potential in situ technique for pot studies on crop–weed competition, which may partially substitute the intrusive techniques commonly used in agricultural researches.

Cover crops influence on canopy structure and light interception of maize (Zea mays L.) and velvetleaf (Abutilon theophrasti Medik), was studied in a field experiment. Treatments included planting of bean (Phaseolus vulgaris L.), soybean (Glycine max (L.) Merr.) and berseem clover (Trifolium alexandrium L.) as cover crops at the same date and 21 days after maize. Sole cropping of maize under weed- free and weedy conditions were also included in this experiment. All tested cover crops significantly reduced leaf area density and height of velvetleaf up to 50 %, while maize leaf area density increased in the presence of cover crops. Among cover crops, bean and soybean were the most effective in reducing velvetleaf leaf area density and height. Bean and soybean also strongly reduced absorbed light by velvetleaf by up to 80 % compared to clover. Maize grain yields were significantly influenced by cover crops planting in the inter row space. Compared to weeds free plots, only treatment with soybean as a cover crop resulted in similar maize grain yields, while maize intercropping with bean and clover significantly reduced maize yields. Delayed planting of cover crops, 21 day after maize, increased maize grain yield compared to cover crops and maize planting at the same time.

Large numbers of field-collected tobacco budworms Heliothis virescens L., and/or bollworms Helicoverpa zea (Boddie) (heliothines) might be difficult to obtain depending upon host plants available to the insects. Of the >95 cultivated and wild plants that have been identified as their hosts, some are highly attractive to these insects, some are also widely available and of those, some could be used to collect large numbers of both insect species. However, the reliability of these plants in space and time in providing abundant samples of larvae and/or moths is not well understood. We studied naturally-occurring heliothine populations over a 3-year period in 2 different geographic locations in plots of garbanzo bean (Cicer arietinum L.), upland cotton (Gossipium hirsutum L.), and velvetleaf (Abutilon theophrasti Medikus) finding that garbanzo bean produced significantly higher numbers of tobacco budworm and bollworm larvae and adults as compared to the other 2 plant species. Tobacco budworm larvae w...

We investigated the germination, growth rates and uptake of contaminants of four plant species, barnyard grass (Echinochloa crusgalli), sunflower (Helianthus annuus), Indian mallow (Abutilon avicennae) and Indian jointvetch (Aeschynomene indica), grown in soil contaminated with cadmium (Cd), lead (Pb) and 2,4,6-trinitrotoluene (TNT). These contaminants are typically found at shooting ranges. Experiments were carried out over 180 days using both single plant cultures and cultures containing an equal mix of the 4 plant species. Germination rates differed among the species in single culture (92% for H. annuus, 84% for E. crusgalli, 48% for A. avicennae and 38% Ae. indica). In the 4-plant mix culture, < 20% of seeds germinated for all 4 species. E. crusgalli and H. annuus grew slightly faster in the four-plant mix culture than in single culture, whereas A. avicennae and Ae. indica grew much slower in the 4-plant mix culture. In both single and 4-plant mix cultures, Cd concentrations in the roots of A. avicennae and E. crusgalliwere high, and Pb concentrations were high in A. avicennae and H. annuus. Cd and Pb concentrations in shoots were low to negligible in both treatment cultures for all species, except E. crusgalli in the 4-plant mix culture. The concentrations of TNT and its metabolites, 2-amino-4,6-dinitrotoluene (2ADNT) and 4-amino-2,6-dinitrotoluene (4ADNT) were high in H. annuus, Ae. indica and A. avicennae. Total Cd removal from soil differed among species, with E. crusgalliremoving the most (50.1%) followed by H. annuus(41.3%), Ae. indica(41.1%) and A. avicennae(33.3%). The four-plant mix removed more Cd (25.8%) than a no-plant control (12.9%). Pb removal was negligible for all plant species. All plant species rapidly removed TNT and its metabolites, regardless of whether the culture was single or mixed. From in these results, we conclude that a phytoremediation for the removal of heavy metals and TNT from contaminated soils should use a single plant species rather than a mixture of several plants.