Cortisol response to acute stress in jundiá Rhamdia quelen acutely exposed to sub-lethal concentrations of agrichemicals

Exposure to agrichemicals can have deleterious effects on fish, such as disruption of the hypothalamus-pituitary-inter-renal axis (HPI) that could impair the ability of fish to respond to stressors. In this study, fingerlings of the teleost jundiá (Rhamdia quelen) were used to investigate the effects of the commonly used agrichemicals on the fish response to stress. Five common agrichemicals were tested: the fungicide - tebuconazole, the insecticide - methyl-parathion, and the herbicides - atrazine, atrazine + simazine, and glyphosate. Control fishes were not exposed to agrichemicals and standard stressors. In treatments 2-4, the fishes were exposed to sub-lethal concentrations (16.6%, 33.3%, and 50% of the LC50) of each agrichemical for 96 h, and at the end of this period, were subjected to an acute stress-handling stimulus by chasing them with a pen net. In treatments 5-7 (16.6%, 33.3%, and 50% of the LC50), the fishes were exposed to the same concentrations of the agrichemicals without stress stimulus. Treatment 8 consisted of jundiás not exposed to agrichemicals, but was subjected to an acute stress-handling stimulus. Jundiás exposed to methyl-parathion, atrazine + simazine, and glyphosate presented a decreased capacity in exhibiting an adequate response to cope with stress and in maintaining the homeostasis, with cortisol level lower than that in the control fish (P < 0.01). In conclusion, the results of this study clearly demonstrate that the acute exposure to sub-lethal concentrations of methyl-parathion, atrazine + simazine, and glyphosate exert a deleterious effect on the cortisol response to an additional acute stressor in the jundiá fingerlings. © 2008 Elsevier Inc. All rights reserved.

Ecotoxicologia do glifosato e surfactante aterbane® br para guaru (Phalloceros caudimaculatus)

Aquatic macrophytes are important components of aquatic ecosystems, but these plants have become a problem due to their occurrence in different regions. Some studies aimed to demonstrate the effectiveness of herbicides to control these macrophytes; however, few studies report the possible ecotoxicological effects. The objective of this study was to estimate the acute toxicity (LC (I)50;96h) and assess water quality variables for glyphosate in the Rodeo® formulation, Aterbane® BR surfactant and mixtures of glyphosate + 0.5% and 1.0% of surfactant, for the guaru fish (Phallocerus caudimaculatus). The guaru was exposed to increasing concentrations of glyphosate and a mixture of glyphosate + 0.5 and 1.0% of surfactant. The mixture of glyphosate and glyphosate + 0.5 and 1.0% of surfactant showed (LC (I)50;96h) > 975.0 mg L -1. For the surfactant, the rate was 5.81 mg L -1. The glyphosate and mixtures of glyphosate + 0.5% and 1.0% of surfactant caused a decrease in pH and dissolved oxygen and increased the electrical conductivity of water. Glyphosate in the Rodeo® formulation and the mixtures with surfactant Aterbane® BR can be classified as practically nontoxic, whereas surfactant Aterbane® BR can be considered as moderately toxic to guaru.

Dessecação de Crotalaria juncea no outono

The objective of this study was to evaluate the effect of glyphosate applied alone and in mixtures with 2.4-D or metsulfuron methyl in the desiccation of mature plants of Crotalaria juncea during the fall season, in a field crop. Two experiments were carried out using a randomized experimental block design, in a 4 × 3 factorial scheme, with four replications. Treatments in the first experiment were formed by four doses (0.00, 0.54, 1.08 and 1.62 kg ha -1) of glyphosate, associated with three doses (0.00, 0.806 and 1.209 kg ha -1) of 2 , 4-D. In the second experiment the same doses of glyphosate were studied associated with three doses (0.0 4.0 and 8.0 g ha -1) of metsulfuron-methyl. Visual evaluations of plant poisoning, score number of plants with regrowth and dry matter of plants were determined. It was concluded that glyphosate applied alone or in association with 2.4-D or metsulfuron-methyl, regardless of the applied doses, was ineffective in the desiccation of mature plants of Crotalaria juncea.

Influência da cobertura de aveia-preta e milheto sobre comunidade de plantas daninhas e produção de soja

The success in weed control by using straw depends on the management time, straw quality and quantity. The objective of this research was to evaluate the suppressor effect of black-oats and millet straw cover on the incidence of weeds and on the productivity of the soybean crop. The experiment was carried out during the years 2006 and 2007, in an area from the Farm of Education, Research and Production of FCAV-UNESP, Jaboticabal Campus, in a completely randomized block design, with four replications. Treatments consisted of different types of black oats and pearl millet straw management before soybean seeding (without management, obtained by machine cut, desiccated using glyphosate desiccation and with paraquat) and different periods of straw deposition (0, 15, 30 e 60 days before soybean seeding). The weed population and the characteristics of soybean growth and production were evaluated. The deposition of black oats and pearl millet straw provided reductions in weed density and dry mass, and this effect was more effective when the deposition occurred until 15 days prior to soybean seeding. The suppressor effect of black oats straw was more pronounced than that of pearl millet straw, regardless of the drying method, although the millet had a greater dry matter production. No significant differences were found between the drying methods and the straw effectiveness.

Cover crop termination timing on rice crop production in a no-till system

Measuring shikimic acid accumulation in response to glyphosate applications can be a rapid and accurate way to quantify and predict glyphosate-induced damage to sensitive plants. The objective of this paper was to evaluate the effect of cover crop termination timing by glyphosate application on rice (Oryza sativa L.) yield in a no-till system. A factorial experiment, arranged in a split-plot design, was conducted for 2 yr. Treatments consisted of cover crops (main plots) and timed herbicide applications (subplots) to these cover crops (30, 20, 10, and 0 d before rice planting). There was a decrease in rice yield from 2866 kg ha-1 to 2322 kg ha-1 when the herbicide was applied closer to the rice planting day. Glyphosate application on cover crops increased shikimate concentrations in rice seedlings cultivated under palisade grass (Brachiaria brizantha), signal grass (B. ruziziensis), guinea grass (Panicum maximum), and weedy fallow (spontaneous vegetation) but not under millet (Pennisetum glaucum), which behaved similarly to the control (clean fallow, no glyphosate application). Glyphosate applications in the timing intervals used were associated with stress in the rice plants, and this association increased if cover crops took longer to completely dry and if higher amounts of biomass were produced. Millet, as a cover crop, allowed the highest seedling dry matter for upland rice and the highest rice yield. Our results suggest that using millet as a cover crop, with glyphosate application far from upland rice planting day (10 d or more), was the best option for upland rice under a no-tillage system. © Crop Science Society of America.

Intervalos de chuva na eficiência de herbicidas aplicados em pós-emergência

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Eficácia da mistura de glifosato a outros maturadores na cana-de-açúcar (Saccharum spp.)

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Thiametoxam em cana-de-açúcar manejada com maturadores

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Nitrogênio no sistema solo-planta após a dessecação de brachiarias

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Maturação induzida, alterações fisiológicas, produtividade e qualidade tecnológica da cana-de-açúcar (Saccharum officinarum L.)

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Controle químico e deposição da calda de pulverização em dois estágios de desenvolvimento de plantas de Typha subulata Crespo & Peres-Moreau f

Pós-graduação em Agronomia (Agricultura) - FCA

Alterações hematológicas e hormonais em fêmeas de jundiá (Rhamdia quelen) provocadas por estresse mecânico e contaminação da água por herbicida a base de glifosato

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Recuperação de pastagem de Brachiara decumbens degradada com a introdução de estilosantes campo grande

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Eficácia da soja geneticamente modificada MON 87701 × MON 89788 com a expressão da proteína Cry1Ac no controle de Anticarsia gemmatalis (Hübner) e Pseudoplusia includens (Walker) (Lepidoptera: Noctuidae)

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Avaliações dos tecidos hidrorrepelentes de equipamentos de proteção individual após usos e lavagens em condições de campo

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)