The Weed's News Digest

The Weed's News email digest contains a summary of activity for the time period March 30, 2012 through April 5, 2012.
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The Weed's News Articles

Is golf the environment’s worst nightmare?

David Low / WeedsNews3136 / April 5, 2012 / 2:47:19 PM EST / 0 Comments
keep off the grass, danger![ 16 Mar 2012 by Paul Tukey] -- Few industries around the world can point to a single weekend as the date of their origin. Sure, lawn care has been around ever since kings ordered peasants to scythe their meadows for comfortable strolling, but in terms of the modern lawn care industry it really all began during the second weekend of April of 1967 — the first time the Masters golf tournament was broadcast live to America in full technicolor green. The men of America couldn’t golf like Arnold Palmer or Jack Nicklaus, or even Gay Brewer, who won the storied tournament that year, but they soon aspired to what they thought was the next best thing: an emerald green fairway front lawn of their own. And every year since then — 45 years and counting — the guys have raced out to the lawn and garden supply stores, or jumped on the phone with their lawn care company, and immediately expected Augusta National Country Club conditions for their own grass. For the professionals who care for grass, either on golf courses or in home yards, the “Augusta Syndrome” is a love-hate relationship between financial opportunity and unrealistic expectations of their patrons and customers. For the manufacturers like Scotts Miracle Gro, Bayer and others, America’s obsession with Masters green has been a pure gold excuse to print their own money.

Roads as corridors for invasive plant species: new evidence from smooth bedstraw (Galium mollugo)

David Low / WeedsNews3135 / April 5, 2012 / 1:58:42 PM EST / 0 Comments
Abstract: Roads function as prime habitats and corridors for invasive plant species, and can contribute significantly to the spread and establishment of weeds inside protected areas. Smooth bedstraw (Galium mollugo) populations have recently expanded in the abandoned agricultural fields of Bic National Park (Quebec, Canada), and may represent a threat to the preservation of plant diversity and to the quality of visitor experience. The main objective of this study was to map the distribution of the species in the park and to delineate factors influencing the abundance of the plant in fallow fields. We hypothesized that road proximity was the main factor explaining the presence and abundance (frequency of recording) of smooth bedstraw in fields. Vegetation surveys were conducted in abandoned agricultural fields, and two logistic regression models were built to examine the relationship between the presence and abundance of smooth bedstraw and environmental and historical variables. Smooth bedstraw populations were also mapped along transportation corridors. The abundance of smooth bedstraw significantly increases within 125 m (410 ft) of a paved road. The recent proliferation of smooth bedstraw in Bic National Park is likely associated with the construction of road embankments during the paving of gravel roads. The paved road network has probably acted as a dispersal corridor for smooth bedstraw, while the abandoned agricultural fields located close to the paved roads provided suitable habitats facilitating population establishment over large areas. We recommended to the park's authorities to cease paving all remaining gravel roads in the park, not only to stop smooth bedstraw invasion, but also the spread of other invasive species of concern. [Geneviève Meunier and Claude Lavoie (2012). Roads as corridors for invasive plant species: new evidence from smooth bedstraw (Galium mollugo). Invasive Plant Science and Management, 5(1):92-100,]

Performance of West African dwarf (WAD) goats fed tridax and siam Weed in ficus based diets

David Low / WeedsNews3134 / April 5, 2012 / 1:51:30 PM EST / 0 Comments
Abstract: Twelve West African dwarf goats weighing between 4.5kg to 5.5kg were used to study the effect replacement of Tridax and Siam weed in Ficus based diet. The goats were divided into three dietary treatments with attention to the body weights with four replicate per treatment. The diets were fed for a period of 25 days in order to investigate the influence of the replaced forage mixture on feed intake and nutrient digestibility, also on the level of the serum metabolites as factor of influence. Goats maintained on Ficus-Tridax forage mixture consumed more dry matter than goats fed Ficus only and Ficus-Siam mixture. The average values were 186.57g/day for Ficus, 202.56g/day for Ficus-Tridax mixture, and 145.0g/day for Ficus-Siam mixture per goat. The nature of the feed influence the digestibilities of the nutrients, the relative values of which were statistically (p<0.05) significant. The values of crude fiber digestibility in the treatment were not significantly different (p<0.05). The result of serum metabolites anaylsed showed no statistical difference (p<0.05), so all the forage feeds tested could cause no harm of significant measure to the animals, results of this study suggest that Tridax can be effectively used to feed small ruminant most especially the WAD goat and it serves as alternative browse plant for the scarce forages during the dry season. [KM Okukpe, AA Adeloye, AHA Badmos, KD Adeyemi & TO Olaniran (2011). Performance of West African fwarf (WAD) goats fed tridax and siam Weed in ficus based diets. Agrosearch, 11(1), 11-18.]

Increasing weed flora in Danish beet, pea and winter barley fields

David Low / WeedsNews3132 / April 5, 2012 / 1:39:23 PM EST / 0 Comments
Abstract: In Denmark, several political initiatives have been taken to reduce use of pesticides and fertilizer in order to avoid unwanted side effect of the increasing cropping intensification. Based on two nation wide surveys we investigate flora changes and discuss the changes in relation to biodiversity, crop yield, agricultural management and climate. Our assumption is that the surveys are representative for the country. We present frequency analyses of 90 species recorded in 157 fields surveyed in 1987–89, and in 167 fields surveyed in 2001–04. Based on 4910 circular sample plots in unsprayed areas, we studied flora changes in four crops and showed that the frequency of many weed species have increased. Particularly some winter annual species (e.g. Veronica arvensis L. and Viola arvensis Murray), grass weeds (Poa annua L., Apera spica-venti (L.) P. Beauv.) and nitrophileous species (e.g. Capsella bursa-pastoris (L.) Medik, Cirsium arvense (L. Scop.), Galiumaparine L., Fallopia convolvulus (L.) Á. Löwe, Tripleurospermum inodorum (L.) Sch. Bip.) have been favoured. Some weeds have declined in some crops but increased in other crops (e.g. Chenopodium album L., Geranium pusillum L.), while only a few species declined in one crop without increasing in other crops (e.g. Elytrigia repens (L.) Desv. ex Nevski; Sinapis arvensis L). Our data indicate that continuously increasing productivity (increasing yields) seems to be possible simultaneously with enhancing the frequency of the wild flora in arable crops. [Christian Andreasen & Henrik Stryhn (2012). Increasing weed flora in Danish beet, pea and winter barley fields. Crop Protection, 36, 11-17,]

Cryptic speciation, genetic diversity and herbicide resistance in the invasive aquatic plant Hydrilla verticillata (L.f.) Royle (Hydrocharitaceae)

David Low / WeedsNews3131 / April 5, 2012 / 1:20:35 PM EST / 0 Comments
Abstract: Hydrilla verticillata (L. f) Royle (Hydrocharitaceae; commonly "hydrilla") is a submersed aquatic plant with a cosmopolitan distribution. It is a nonindigenous, highly invasive weed that causes serious ecological and economic harm in the United States, and consequently is of great management concern. Repeated use of the herbicide fluridone has led to the evolution of resistant strains in Florida hydrilla populations. I developed a standard method to screen the nuclear phytoene desaturase (pds) gene for three previously identified mutations that confer resistance. I screened accessions from the US and other countries and detected hydrilla with pds mutations from five localities in Florida and one in Georgia. All pds mutations were found only in US dioecious hydrilla, and all were located on the same homologous allele. Using this new method, lake managers may have hydrilla tested for resistance-conferring mutations prior to choosing a control treatment. Hydrilla is a monotypic genus with H. verticillata comprising the sole species. I used phylogenetic and morphological analyses to identify and delineate three cryptic species within the genus Hydrilla. These lineages, based on the geographic areas found, are 1) an Indian/Nepal/US dioecious species; 2) a Japan/Korean/European species; and 3) an Indonesian/Malaysian species that is found also as an escape in Australia. All data indicated that US dioecious plants originated from India, a result consistent with previously published phenetic analyses. The diploid parents of triploid US monoecious hydrilla were not identified definitively, but this taxon is most likely a hybrid of the Indian and Indonesian lineages. Sufficient genetic variation within invading populations may be necessary for successful colonization of new geographical regions. Hydrilla verticillata, which reproduces largely by asexual means, is an invasive aquatic weed in the United States, and a non-indigenous colonizer in China and Europe. I used data from six microsatellite loci to compare genetic diversity and structure within and among non-indigenous (US, China, Europe), and indigenous (Australia, India, Indonesia/Malaysia, Korea) hydrilla populations. The population genetic structure of hydrilla reflects the asexual reproductive history of the genus, the invasion history in different regions, and genetic divergence among hydrilla lineages that are in fact distinct species. Polyploidy and hybrid vigor are hypothesized to contribute to the success of introduced US and Chinese populations. [Benoit, Lori Kim (2011). Cryptic speciation, genetic diversity and herbicide resistance in the invasive aquatic plant Hydrilla verticillata (L.f.) Royle (Hydrocharitaceae). PhD Thesis, University of Connecticut, 117 pages.]

Agronomic productivity and nitrogen requirements of alternative tillage and crop establishment systems for improved weed control in direct-seeded rice

David Low / WeedsNews3129 / April 4, 2012 / 11:49:49 AM EST / 0 Comments
Abstract: Weed control is a primary concern in direct-seeded rice, particularly for herbicide-resistant weed species which stand to threaten the long-term sustainability of California rice systems. In a four-year field study we evaluated the potential for improved weed control using no-till stale seedbed practices in water-seeded (WS) and drill-seeded (DS) rice establishment systems. In addition, as the agronomic performance of alternative tillage and crop establishment methods is not well understood, we assessed the productivity of these systems and estimated economic optimum nitrogen (EON) rates based on yield response to nitrogen (N) trials. Establishment system treatments included: water-seeded conventional tillage (WS conventional), water-seeded conventional tillage stale seedbed (WS stale), water-seeded no-till stale seedbed (WS no-till stale), drill-seeded conventional tillage (DS conventional), and drill-seeded no-till stale seedbed (DS no-till stale). Compared to the WS conventional system, WS stale and WS no-till stale treatments significantly reduced sedge weed biomass by 59 and 95%, respectively. Although redstem (Ammannia spp.) was not controlled, alternative WS systems reduced grass weed biomass by more than 99% when present. Within DS systems, no-till stale seedbed practices significantly reduced watergrass (Echinochloa spp.) biomass by 75% in the first two years but did not improve watergrass control during the second half of the study. Grain yields were not different for conventional and alternative rice establishment systems each year when N was applied at 168 kg N ha−1 and weeds were fully controlled. However, yields were significantly lower for alternative establishment systems compared to the WS conventional system when no N fertilizer was applied, likely as a result of greater soil N losses. The response of grain yield to N rate was significantly different among systems and estimated EON rates indicated that WS stale and WS no-till stale systems required an increase of 30–35 kg N ha−1 to maximize yields and returns to N compared to the WS conventional system. Results from this experiment demonstrate that alternative tillage and crop establishment systems can lead to improved weed control while remaining viable from an agronomic and economic standpoint in California. Provided N rates are close to optimal and WS and DS establishment methods are selected to target weed species of concern, these findings suggest that no-till stale seedbed practices should be considered as a component of integrated weed management strategies in direct-seeded rice moving forward. [ C.M. Pittelkow, A.J. Fischer, M.J. Moechnig, J.E. Hill, K.B. Koffler, R.G. Mutters, C.A. Greer, Y.S. Cho, C. van Kessel & B.A. Linquist (2012). Agronomic productivity and nitrogen requirements of alternative tillage and crop establishment systems for improved weed control in direct-seeded rice. Field Crops Research, 130, 128–137]

Seed bank persistence of genetically modified canola in California

David Low / WeedsNews3128 / April 3, 2012 / 7:32:06 PM EST / 0 Comments
Abstract: Introduction Canola, which is genetically modified (GM) for tolerance to glyphosate, has the potential to become established as a new glyphosate resistant weed, thus reducing the effectiveness of glyphosate. Methods Volunteer from dormant canola seeds produced thousands of plants per hectare in the fourth year (2011) following a 2007 crop harvest. This occurred with no additional canola seed production since the 2007 harvest. Results Volunteer plants following harvests of annual crops are typically only a problem for the first year after harvest. In California, glyphosate is the core herbicide on over a million hectares of high value row, tree, and vine crops and new glyphosate resistant weeds reduce the effectiveness of glyphosate. Conclusions The combination of dormant seed and herbicide resistance makes GM glyphosate-resistant canola a new and difficult California weed which was first observed in the winter of 2009. [Douglas J. Munier & Kent L. Brittan & W. Thomas Lanini (2012). Seed bank persistence of genetically modified canola in California. Environ Sci Pollut Res, on-lin Jan 19, DOI 10.1007/s11356-011-0733-8]

New effects of Roundup on amphibians: Predators reduce herbicide mortality; herbicides induce antipredator morphology

David Low / WeedsNews3127 / April 3, 2012 / 4:10:51 PM EST / 0 Comments
Abstract: The use of pesticides is important for growing crops and protecting human health by reducing the prevalence of targeted pest species. However, less attention is given to the potential unintended effects on nontarget species, including taxonomic groups that are of current conservation concern. One issue raised in recent years is the potential for pesticides to become more lethal in the presence of predatory cues, a phenomenon observed thus far only in the laboratory. A second issue is whether pesticides can induce unintended trait changes in nontarget species, particularly trait changes that might mimic adaptive responses to natural environmental stressors. Using outdoor mesocosms, I created simple wetland communities containing leaf litter, algae, zooplankton, and three species of tadpoles (wood frogs [Rana sylvatica or Lithobates sylvaticus], leopard frogs [R. pipiens or L. pipiens], and American toads [Bufo americanus or Anaxyrus americanus]). I exposed the communities to a factorial combination of environmentally relevant herbicide concentrations (0, 1, 2, or 3 mg acid equivalents [a.e.]/L of Roundup Original MAX) crossed with three predator-cue treatments (no predators, adult newts [Notophthalmus viridescens], or larval dragonflies [Anax junius]). Without predator cues, mortality rates from Roundup were consistent with past studies. Combined with cues from the most risky predator (i.e., dragonflies), Roundup became less lethal (in direct contrast to past laboratory studies). This reduction in mortality was likely caused by the herbicide stratifying in the water column and predator cues scaring the tadpoles down to the benthos where herbicide concentrations were lower. Even more striking was the discovery that Roundup induced morphological changes in the tadpoles. In wood frog and leopard frog tadpoles, Roundup induced relatively deeper tails in the same direction and of the same magnitude as the adaptive changes induced by dragonfly cues. To my knowledge, this is the first study to show that a pesticide can induce morphological changes in a vertebrate. Moreover, the data suggest that the herbicide might be activating the tadpoles' developmental pathways used for antipredator responses. Collectively, these discoveries suggest that the world's most widely applied herbicide may have much further-reaching effects on nontarget species than previous considered. [Relyea, Rick A. 2012. New effects of Roundup on amphibians: Predators reduce herbicide mortality; herbicides induce antipredator morphology. Ecological Applications, 22:634–647.]

Thermophilic anaerobic digestion of cattle manure reduces seed viability for four weed species

David Low / WeedsNews3126 / April 1, 2012 / 7:10:47 PM EST / 0 Comments
Abstract: Anaerobic digestion of manure and other biowaste has been gaining public attention for producing biogas as a renewable energy. More digestate materials after harvesting biogas available will be used as biofertilizers, soil conditioners and amendments for land application. However, digestate is required to be free of weed seeds. The effect of anaerobic digestion on the survival of weed seeds has not been studied extensively. This study examined four weed seeds, wild oats (Avena fatua L.), wild buckwheat (Polygonum convolvulus L.), wild mustard (Sinapis arvensis (DC.) L.C.Wheeler) and volunteer canola (Brassica napus L.) that were placed in batch cultures with feedlot cattle manure at 55℃ for 7 and 24 hours. The results showed that after being subjected to anaerobic digestion for 7 hours, wild oats, volunteer canola and wild mustard had zero viability. Wild buckwheat had remaining viable seed after the 7 and 24 hour anaerobic digestion treatment as shown by the tetrazolium test. However, the remaining viable wild buckwheat seeds were considered to be incapable of normal growth and development.[Eckford R E, Newman J C, Li X, Watson P R. Thermophilic anaerobic digestion of cattle manure reduces seed viability for four weed species. Int J Agric & Biol Eng, 2012; 5(1): 71-75. DOI: 10.3965/j.ijabe.20120501.009]

Factors affecting thermal weed control

David Low / WeedsNews3124 / March 31, 2012 / 9:39:50 AM EST / 0 Comments
Abstract: Early thermal weed-control measures were known to be rudimentary and hazardous. Thermal weed control has progressed in sophistication, application, and efficiency and has resulted in many commercial systems available for common row-cropping applications. Flame weeding for established turfgrass is not effective because of the inability to treat weeds without injuring the turfgrass system. Aesthetically this type of treatment would be unacceptable. Therefore, past thermal weed control measures can be refined to utilize direct soil heating by flame from propane burners for the production of a stale seedbed. Initial soil-sterilization and flame heating studies conducted in 2009 and 2010 demonstrated a high potential for reducing weed populations before turfgrass establishment. Many factors can alter the efficacy of this type of thermal treatment including seed heat tolerance, seed depth, thermal conductivity, and soil moisture content. For acceptable weed control utilizing this method, adequate soil temperatures need to be achieved. Planting depth in a Marvyn loamy sand (Fine-loamy, kaolintic, thermic Typic Kanhapudult) and seed heat tolerance research was conducted to evaluate germination and emergence of weed seeds. Large crabgrass (Digitaria sanguinalis), Virginia buttonweed (Diodia virginiana), and cocks-comb kyllinga (Kyllinga squamulata) emerged from 8, 6, and 2 cm maximum planting depths, respectively. Temperature and duration effects on weed germination experiments resulted in 0% germination of large crabgrass, Virginia buttonweed, and cocks-comb kyllinga at 120, 250, and 120°C, respectively, for 5 second heat exposure. Heat transfer studies utilizing a PL8750 Poultry House Flame Sanitizer (Flame Engineering, Inc; LaCrosse, KS) in Marvyn loamy sand at 0.1 volumetric water content (θ) resulted in only surface temperatures adequate to prevent weed germination. Further experimentation resulted in a thermal conductivity of 0.96 W m-1 K-1. Compilation of results shows potential for effective present application of thermal weed control in turfgrass management. [Jared Adam Hoyle (2012). Factors affecting thermal weed control. PhD Dissertation, Auburn University, Alabama.]

Impact of maize formulated herbicides Mesotrione and S-metolachlor, applied alone and in mixture, on soil microbial communities

David Low / WeedsNews3123 / March 30, 2012 / 11:54:37 PM EST / 0 Comments
Abstract: In order to reduce the amounts of pesticides used, and thereby their associated risks, new generations of less environmentally dangerous molecules with lower weight are currently being used in the mixtures sprayed on crops. Few studies have been made, however, to analyse their impact on the soil, and more particularly on the microorganisms living in the soil which maintain the essential functions of this ecosystem. By taking a microcosmic approach, we were able to assess the impact of the maize herbicides “cocktail” Mesotrione and S-metolachlor on global soil microbial activity, biomass, and structures, by using the formulated compounds, respectively, Callisto and Dual Gold (both registered brands of Syngenta). Our results highlighted a synergetic effect in “cocktail” microcosms resulting in an increase in the Mesotrione herbicide dissipation time and in an impact on the microbial community at onefold field rate equally to more than a single herbicide used at tenfold field rate. [Pierre Joly, Pascale Besse-Hoggan, Frédérique Bonnemoy, Isabelle Batisson, Jacques Bohatier & Clarisse Mallet (2012). Impact of maize formulated herbicides Mesotrione and S-metolachlor, applied alone and in mixture, on soil microbial communities. ISRN Ecology, Volume 2012, 9 pages, doi:10.5402/2012/329898]

Developmental exposure to diuron causes splenotoxicity in male Sprague-Dawley rat pups

David Low / WeedsNews3122 / March 30, 2012 / 11:43:24 PM EST / 0 Comments
Abstract: This study investigated whether perinatal exposure to diuron [3-(3,4-dichlorophenyl)-1-1-dimethylurea] might exert adverse effects on rat lymphoid organs. Pregnant Sprague-Dawley (SD) rats were exposed to diuron at 500, 750 or 1250 ppm in the diet from gestational days (GD) 12–21 and during lactation. At postnatal day (PND) 42, male pups were euthanized and thymus, spleen, mesenteric lymph node and femur were collected for histopathological analysis. Food consumption and body weight gain were significantly reduced in dams exposed to 1250 ppm during gestation period. Also, Diuron at 750 and 1250 ppm produced: (1) increased relative spleen weight associated histologically with severe congestion in red pulp, (2) enhanced extramedullary hematopoiesis and hemosiderosis as well as (3) depletion of lymphoid follicles in white pulp. Flow cytometric analysis revealed a significant reduction in B lymphocytes (CD45RA+) in male pups but T lymphocytes (CD4+, CD8+ and CD4+/CD8+) were not markedly affected. Thus, data suggest that Diuron-induced maternal toxicity in dams exposed to high dose and perinatal exposure to this herbicide produced spleen toxicity as evidenced by a reduction in B lymphocyte number in male SD pups. [Alexandre Domingues, Tony F. Grassi, Ana L.T. Spinardi-Barbisan & Luís F. Barbisan (2012). Developmental exposure to diuron causes splenotoxicity in male Sprague-Dawley rat pups. Journal of Environmental Science and Health, Part B: Pesticides, Food Contaminants, and Agricultural Wastes, 47(5), DOI:10.1080/03601234.2012.657054]