Herbicide selectivity in herbaceous ornamental gardens of tagetes erecta L.

One of the major problems in landscaping in tropics is weed management. The herbaceous ornamental plant, Tagetes erecta L. (Asteraceae), is very popular for its beautiful flowers which can be used in landscape and also as cut flowers. The increase use of this plant and lack of selective herbicides led to the objective of this study to evaluate the herbicide metribuzin selectivity for this ornamental plant. The experimental design was completely randomized using four treatments (herbicide metribuzin doses: 0, 0.5, 1.0 and 1.5 L ha-1, equivalent to 0, 240, 480 and 720 g ha-1) and five replicates. The herbicide was applied over the seedling of T. erecta as pre-emergence of the weed seeds. Evaluations were performed at 7, 14, 21 and 28 days after application (DAA) by visual analysis of the toxicity symptoms over the ornamental, using the European Weed Research Council (EWRC) scale (1 to 9), where 1 is the total absence of symptoms and 9 to death plants. Polynomial regression statistical analysis was used. It was verified that, from the dose of 1.0 L ha-1, T. erecta plants died by 14 DAA, which the most of them had presented a very strong toxicity symptom; for the 0.5 L ha-1 treatment the plants had survived until 28 DAA. However, most of them already exhibited the high toxicity level, dying at 35 DAA. Thus, metribuzin was not suitable for T. erecta even at the lowest rate tested in this study.

Managing arable weeds for biodiversity

As a result of the recent intensification of crop production, the abundance and diversity of UK arable weeds adapted to cultivated land have declined, with an associated reduction in farmland birds. A number of questions need to be addressed when considering how these declines can be reversed. Firstly, can the delivery of crop production and biodiversity be reconciled by spatially separating cropping from designated wildlife areas? A number of subsidised environmental schemes in the UK take this approach and are focused on establishing vegetation cover on uncropped land. However, because of the lack of regular disturbance in these habitats, they are dominated by perennials and they therefore have limited potential for promoting the recovery of annual weed populations. A number of farmland bird species also rely on the provision of resources in field centres, and it is therefore likely that the recovery of their populations will rely on weed management options targeted at the cropped areas of the field. This raises two further questions. Firstly, is it possible to identify beneficial weed species that are relatively poor competitors with the crop and also have biodiversity value? Secondly, are the tools available to manage these species at acceptable levels while controlling pernicious weeds? A number of approaches are being employed to answer these questions, including predicting yield loss from weed competition models and exploiting herbicide selectivity. The further development of these tools is crucial if farmer opposition to managing weeds in crops is to be overcome. (c) 2007 Society of Chemical Industry.

Seletividade de trifluralin incorporado ao solo para batata-doce

No Estado de São Paulo, a batata-doce é cultivada em escala comercial como produto hortigranjeiro. em vista das dificuldades para o controle manual e o mecanizado das plantas infestantes da cultura, há grande interesse pelo método químico desse controle. Com essa finalidade, tanto pelo baixo custo relativo como pelas facilidades técnicas de utilização, o trifluralin desperta a atenção dos agricultores. Para avaliar a seletividade do herbicida para essa cultura, foi realizado um experimento em vasos, com doses crescentes do produto, nas seguintes concentrações: 0,00; 0,11; 0,22; 0,44; 0,88; 1,76 e 3,52 mg.kg-1 de i.a. em peso. Os resultados mostraram que, a partir da dose de 0,22 mg.kg-1 de i.a., o trifluralin interferiu negativamente e em escala exponencial sobre os parâmetros: comprimento das ramas, número de folhas, peso da massa seca da parte aérea e das raízes, avaliados aos 30 dias, revelando-se não seletivo para a batata-doce quando incorporado ao solo, em profundidades semelhantes às da zona de enraizamento das plantas.

Seletividade de herbicidas: I - utilização do método de testemunhas pareadas em experimento com cana-de-açúcar

Este trabalho objetivou comparar a precisão experimental dos delineamentos em blocos casualizados e blocos casualizados com testemunhas pareadas na avaliação da seletividade de herbicidas em soqueira de cana-de-açúcar de terceiro corte, cultivar RB835089. Os delineamentos utilizados foram o de blocos casualizados convencional e o de blocos casualizados com testemunhas pareadas, com quatro repetições. Os tratamentos foram diuron + hexazinone, azafenidin + hexazinone, metribuzin e isoxaflutole e testemunha capinada. Avaliaram-se na cana-de-açúcar a altura, o estande, o rendimento de colmos e o ATR (Açúcar Teórico Recuperável). O delineamento em blocos casualizados com testemunhas pareadas foi mais eficaz que aquele com testemunha tradicional. Constatou-se também que, para comparação das médias dos tratamentos, o teste t foi mais sensível que o teste de Tukey, pois apresentou, com maior precisão experimental, mais tratamentos com diferenças em relação à testemunha.

Eficiência fotossintética de cultivares de cana-de-açúcar e de diferentes espécies de plantas daninhas após a aplicação do diuron

O objetivo deste trabalho foi avaliar a eficiência fotossintética, através da taxa de transporte de elétrons, de seis espécies de plantas daninhas e três cultivares de cana-de-açúcar após aplicação do herbicida diuron em pós-emergência inicial. Os cultivares utilizados (PO8862, SP80-3280 e RB83-5486) foram cortados em gemas e plantados em vasos com capacidade de 12 litros. A semeadura das seis espécies de plantas daninhas - Brachiaria decumbens, Digitaria horizontalis, Panicum maximum, Ipomoea grandifolia, Ipomoea hederifolia e Merremia cissoides - foi realizada para obter 25 plantas por vaso. A aplicação do herbicida diuron em pós-emergência inicial das plantas daninhas e dos cultivares de cana-de-açúcar foi realizada na dose de 3,0 kg ha-1, com adição de 0,2% de surfatante. As avaliações da taxa de transporte de elétrons no fotossistema (ETR) das plantas após a aplicação foram realizadas com auxílio de um fluorômetro portátil. Para as espécies de plantas daninhas, a ETR foi avaliada após intervalos de 2, 4, 24, 48, 72, 96 e 144 horas após a aplicação. Quanto aos cultivares de cana-de-açúcar, os intervalos avaliados foram de 2, 24, 48, 72, 120, 168 e 240 horas após a aplicação. de maneira geral, as reduções dos valores da ETR indicaram o nível de sensibilidade dos diferentes cultivares de cana-de-açúcar e das diferentes plantas daninhas ao diuron, e a intoxicação foi detectada antes ou mesmo sem a presença dos sintomas. A classificação da sensibilidade dos cultivares de cana-de-açúcar foi em ordem decrescente: PO-8862, SP80-3280 e RB83-5486; para as plantas daninhas, as espécies mais sensíveis foram M. cissoides, I. grandifolia e I. hederifolia, seguidas das gramíneas D. horizontalis, P. maximum e B. decumbens.

Resposta de plantas daninhas ao óleo fúsel aplicado em pós-emergência inicial e tardia

This work aimed to study weed response to fusel oil rate applied at early and late post-emergence. The following species were studied at late and early post-emergence: Ipomoea hederifolia, Ipomoea quamoclit, Euphorbia heterophylla, Digitaria spp., Cenchrus echinatus and Panicum maximum.. The experiment was arranged in a completely randomized design with six treatments and four replications. Fusel oil, an alcohol distillation byproduct, was applied at rates of 50, 125, 250, 375 and 500 L ha(-1), plus control without application. The plots were constituted by polyethylene containers with 3 L capacity, filled with topsoil land from a fallow area. Visual symptoms of intoxication were verified at 7 and 30 days after application (DAA) and dry weight at 30 DAA. The variables were submitted to variance analysis according to the design, adjusting the data to obtain the dose-response curve by polynomial regression. The studied species were susceptible only to the application of 500 L ha(-1) of fusel oil at early or late plant post-emergence. The species Digitaria spp. was susceptible and E. heterophylla tolerant to fusel oil applied at early post-emergence, while the other species were moderately tolerant. E. heterophylla was susceptible, Digitaria spp., C. echinatus and P. maximum moderately tolerant and I. hederifolia and I. quamoclit tolerant to fusel oil applied at late post-emergence.

Efeito da palha na disponibilidade do herbicida amicarbazone na solução do solo em áreas cultivadas com cana-de-açúcar

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Selectivity of the herbicide flazasulfuron applied after postemergence in sugarcane (Saccharum spp. L.) crop

The selectivity of the herbicide flazasulfaron was evaluated when applied at two rates (50 and 100 g/ha) with and without surfactants (Aterbane or Agral at 0.2% v/v). The treatment was applied at early (three leaves) and late (five to six leaves) stages of the postemergence of sugarcane plants (var. RB845257) grown in two soils (sandy and clay) with good moisture status before and after application. Despite the toxicity symptoms, especially at the late stage with the higher rate of application in the sandy soil, the herbicide did not affect the growth nor the stalk yield. The presence of the surfactants had no effect on the toxicity symptoms.

Endothall species selectivity evaluation: northern latitude aquatic plant community

Species selectivity of the aquatic herbicide dipotassium salt of endothall (Aquathol® K) was evaluated on plant species typically found in northern latitude aquatic plant communities. Submersed species included Eurasian watermilfoil (Myriophyllum spicatum L.), curlyleaf pondweed (Potamogeton crispus L.), Illinois pondweed (Potamogeton illinoensis Morong.), sago pondweed (Potamogeton pectinatus L.), coontail (Ceratophyllum demersum L.), elodea (Elodea canadensis Michx.) and wildcelery (Vallisneria americana L.). Emergent and floating-leaf plant species evaluated were cattail (Typha latifolia L.), smartweed (Polygonum hydropiperoides Michx.), pickerelweed (Pontederia cordata L.) and spatterdock (Nuphar advena Aiton). The submersed species evaluations were conducted in 7000 L mesocosm tanks, and treatment rates included 0, 0.5 1.0, 2.0, and 4.0 mg/L active ingredient (ai) endothall (dipotassium salt of endothall). The exposure period consisted of a 24-h flow through half-life for 7 d. The cattail and smartweed evaluation was conducted in 860 L mesocosm tanks, and the spatterdock and pickerelweed evaluations were conducted in 1600 L mesocosm tanks. Treatment rates for the emergent and floating-leafed plant evaluations included 0, 0.5, 2.0 and 4.0 mg/L ai endothall, and the exposure period consisted of removing and replacing half the water from each tank, after each 24 h period for a duration of 120 h. Biomass samples were collected at 3 and 8 weeks after treatment (WAT). Endothall effectively controlled Eurasian watermilfoil and curlyleaf pondweed at all of the application rates, and no significant regrowth was observed at 8 WAT. Sago pondweed, wildcelery, and Illinois pondweed biomass were also significantly reduced following the endothall application, but regrowth was observed at 8 WAT. Coontail and elodea showed no effects from endothall application at the 0.5, 1.0, and 2.0 mg/L application rates, but coontail was controlled at 4.0 mg/L rate. Spatterdock, pickerelweed, cattail, and smartweed were not injured at any of the endothall application rates.

FLUXOFENIM USED AS A SAFENER ON SORGHUM SEED FOR S-METOLACHLOR HERBICIDE

This study aimed to evaluate the efficiency of protective fluxofenim seed treatment of sorghum hybrids DKB510 and SCG340, in order to increase the selectivity to the herbicide S-metolachlor applied pre-emergence and to determine the activity of detoxification enzyme glutathione S-transferase (GST). This work was divided into two stages. The first step consisted of field evaluation of the effectiveness of the shield to reduce visual symptoms of plant injury caused by the herbicide and the second determined the activity of GST. It was compared the susceptibility of sorghum seeds to the herbicide by means of visual assessment of injuries at 3, 7, 15 and 30 days after emergence (DAE), root dry weight and shoot at 10 DAE, and determination of activity GST. The treatments were: application of the safener dose at 0 and 40 mL per 100 kg of seed, and spraying of the herbicide S-metolachlor at rates of 1,440 and 2,880 g a.i. ha(-1), and a control without herbicide. The safener use to seed treatment for both sorghum hybrids (DKB510 and SCG340) increased tolerance to the herbicide S-metolachlor in two doses, and the best results were obtained at a dose of 1,440 g ha(-1). The GST enzyme activity showed an increase when using the fluxofenim prior to application of the herbicide S-metolachlor at a dose of 1,440 g ha(-1) for the two hybrids.

Iron(III) Porphyrin Covalently Supported onto Magnetic Amino-Functionalized Nanospheres as Catalyst for Hydrocarbon and Herbicide Oxidations

This work describes the covalent immobilization of an ironporphyrin, 5,10,15,20-tetrakis(pentafluorophenyl)porphyrin iron(III) chloride (FeTFPP), onto maghemite/silica magnetic nanospheres covered with aminofunctionalized silica. The resulting material (gamma-Fe2O3/SiO2-NHFeP) was characterized by diffuse reflectance infrared spectroscopy (DRIFTS) and UV-Vis absorption spectroscopy. The catalytic activity of this magnetic ironporphyrin was investigated in the oxidation of hydrocarbons (styrene, (Z)-cyclooctene and R-(+)-limonene) and an herbicide (simazine) by hydrogen peroxide or 3-chloroperoxybenzoic acid. Hydrocarbon and simazine oxidation reaction products were analyzed by gas chromatography (GC) and high performance liquid chromatography (HPLC), respectively. This catalytic system proved to be efficient and selective for hydrocarbon oxidation, leading to high product yields from styrene (89%), cyclooctene (71%) and R-(+) -limonene (86%). Simazine oxidation was attained with 100% selectivity for a dechlorinated product (OEAT), while several oxidation products were obtained for the same catalyst in homogeneous media. The catalyst can be easily recovered through application of an external magnetic field and washed after reaction. Catalyst reuse experiments for R-(+)-limonene oxidation have shown that the catalytic activity is kept at 90% after 10 consecutive reactions.

Iron(III) porphyrin covalently supported onto magnetic amino-functionalized nanospheres as catalyst for hydrocarbon and herbicide oxidations

This work describes the covalent immobilization of an ironporphyrin, 5,10,15,20- tetrakis(pentafluorophenyl)porphyrin iron(III) chloride (FeTFPP), onto maghemite/silica magnetic nanospheres covered with aminofunctionalized silica. The resulting material (γ-Fe2O3/SiO2-NHFeP) was characterized by diffuse reflectance infrared spectroscopy (DRIFTS) and UV-Vis absorption spectroscopy. The catalytic activity of this magnetic ironporphyrin was investigated in the oxidation of hydrocarbons (styrene, (Z)-cyclooctene and R-(+)-limonene) and an herbicide (simazine) by hydrogen peroxide or 3-chloroperoxybenzoic acid. Hydrocarbon and simazine oxidation reaction products were analyzed by gas chromatography (GC) and high performance liquid chromatography (HPLC), respectively. This catalytic system proved to be efficient and selective for hydrocarbon oxidation, leading to high product yields from styrene (89%), cyclooctene (71%) and R-(+)-limonene (86%). Simazine oxidation was attained with 100% selectivity for a dechlorinated product (OEAT), while several oxidation products were obtained for the same catalyst in homogeneous media. The catalyst can be easily recovered through application of an external magnetic field and washed after reaction. Catalyst reuse experiments for R-(+)-limonene oxidation have shown that the catalytic activity is kept at 90% after 10 consecutive reactions.

Plasma control of morpho-dimensional selectivity of hematite nanostructures

Highly controllablefabrication of the nanowire, nanocone, and mixed nanowire/nanowall arrays of iron oxide (hematite, α-Fe2O3) nanostructures in a simple, environment-friendly process is achieved by exposing the metal foils to low-temperature oxygen plasmas. Very dense forests of thin (≈50 nm) and long (up to several μm) nanowires are grown on the electrically biased substrates, whereas the use of the electrically insulated substrate resulted in the formation of a mixed array of nanowires and nanowalls. The proposed mechanism of the nanostructure growth is supported by the numerical simulations demonstrating the key role of the plasma environment in the growth morphology selection.