Control of Salvinia molesta with imazamox and analysis of environmental indicators in microcosms.

The aim of this study was to assess the efficacy of imazamox for control of S. molesta and to assess the effects of plant decomposition on environmental indicators after application of this herbicide in microcosm conditions. The following rates were used: 600, 700, 800 and 900 g ai ha-1 and spray volume 50 L ha-1. Control efficacy was determined as the percentage (from 0 to 100%) of visible injury symptoms in the plants, biochemical and chemical oxygen demand (BOD5 and COD), water quality variables, chlorophyll a and pheophytin a at 0, 7, 15, 30, 45 and 60 days after application (DAA) and fresh and dry biomass at 60 DAA. Imazamox was effective in controlling 94% of S. molesta with 900 g ai ha-1; it reduced 95% of fresh weight and 92% of dry weight of plant at 60 DAA, and reduced chlorophyll a of the plants for all rates. For BOD5, there was an increase for all rates at 15, 30 and 45 DAA with restoration of the parameters at 60 DAA, and for COD, there was an increase at 60 DAA with 700 and 900 g ai ha-1. For temperature, pH, dissolved oxygen and electrical conductivity, there was no significant effect after spraying. Imazamox was effective in controlling S. molesta with 900 g ai ha-1 without causing significant effects on the physical-chemical parameters of water quality.

Electrostatic spraying of imazamox to control the floating aquatic plant Salvinia molesta and its effects on environmental indicators of water quality.

This study aimed to assess, in a microcosm condition, the efficacy of electrostatic spraying of herbicide imazamox in the control of Salvinia molesta and the effects of decomposition of plant material on water quality. The herbicide rates used were 600, 700, 800, and 900 g ai ha-1 and spray volume of 50 L ha-1 in electrostatic application. Control effectiveness was assessed at 7, 15, 30, 45, and 60 days after application (DAA), expressed in percentage (0-100%) of visible injury symptoms in the plants, biochemical oxygen demand (BOD5), chemical oxygen demand (COD), chlorophyll a and pheophytin a contents at 0, 7, 15, 30, 45, and 60 DAA, and fresh and dry biomass at 60 DAA. Imazamox was effective in controlling 63% of S. molesta with 900 g ai ha-1 in 45 DAA and 30% with 800 g ai ha-1 in 30 DAA, and reduced 82.3% and 17.5% of fresh weight and 62.6% and 9.3% of dry weight of plant at 60 DAA, respectively. The imazamox spray reduced chlorophyll a with all doses applied and increased BOD5 in 45 DAA with 900 g ai ha-1 and COD in all assessment periods, but for temperature, dissolved oxygen, electrical conductivity, and pH, there was no significant effect after spraying. The herbicide imazamox reduced S. molesta plants with 900 g ai ha-1, without causing significant effects on environmental indicators of water quality. Electrostatic spraying of herbicide can be used in management strategies of aquatic plants to reduce plant density in water bodies and maintain the colonization of plants at a level not harmful to the aquatic biota.

Sensitivity of aquatic organisms to ethanol and its potential use as bioindicators / Sensibilidade de organismos aquaticos ao etanol e seu potencial uso como bioindicadores

The aim of this research was to evaluate the feasibility for the use of the organisms Lemna minor, Azolla caroliniana, Hyphessobrycon eques, Pomacea canaliculata and Daphnia magna as exposure bioindicators for ethanol (lethal and effective concentration 50% - LC50(I)/EC50(I)). Thus, the following concentrations were used 5.0; 10.0; 20.0; 30.0; 40.0 and 50.0 mg L-1 ethanol on L. minor; 25.0; 50.0; 75.0; 100.0; 150.0 and 200.0 mg L-1 on A. caroliniana; 0.3; 0.5; 1.0; 2.0 and 3.0 mg L-1 on H. eques; 0.05; 0.10; 0.20; 0.40 and 0.80 mg L-1 on P. canaliculata; and 40.0; 60.0; 80.0; 100.0; 120.0 and 140.0 mg L-1 on D. magna. An untreated control was also kept for all organisms, with three repetitions. The increase in the ethanol concentration elevated the electrical conductivity and decreased the water dissolved oxygen and pH. The ethanol LC50 for L. minor and A. caroliniana were 12.78 and 73.11 mg L-1, respectively, and was classified as slightly toxic; 1.22 mg L-1 for H. eques (moderately toxic); 0.39 mg L-1 for P. canaliculata (highly toxic) and 98.85 mg L-1 for D. magna (slightly toxic). Thus, H. eques and P. canaliculata have showed good potential for the use as ethanol exposure bioindicators on water bodies.

O objetivo deste estudo foi avaliar a viabilidade do uso dos organismos teste Lemna minor, Azolla caroliniana, Hyphessobrycon eques, Pomacea canaliculata e Daphnia magna como bioindicadores de exposição ao etanol (concentração letal e efetiva 50% - CL50(I)/CE50(I)). Assim, foram utilizadas as seguintes concentrações: 5,0; 10,0; 20,0; 30,0; 40,0 e 50,0 mg L-1 de etanol para L. minor; 25,0; 50,0; 75,0; 100,0; 150,0 e 200,0 mg L- 1 (A. caroliniana); 0,3; 0,5; 1,0; 2,0 e 3,0 mg L-1 (H. eques); 0,05; 0,10; 0,20; 0,40 e 0,80 mg L-1 (P. canaliculata ) e 40,0; 60,0; 80,0; 100,0; 120,0 e 140,0 mg L-1 para D. magna, todos com controle em triplicata. O aumento da concentração do etanol elevou a condutividade elétrica e diminuiu o oxigênio dissolvido e o pH da água. A CL50 do etanol para as macrófitas L. minor e A. caroliniana foi 12,78 e 73,11 mg L-1, respectivamente, sendo classificado como ligeiramente tóxico; para o H. eques, foi de 1,22 mg L-1 (moderadamente tóxico); 0,39 mg L-1 para o P. canaliculata (altamente tóxico) e 98,85 mg L-1 para D. magna (ligeiramente tóxico). Assim, o H. eques e o P. canaliculata apresentaram potencial para uso como organismos bioindicadores de exposição do etanol em corpos hídricos.

Atrazine levels in the Jaboticabal water stream (São Paulo State, Brazil) and its toxicological effects on the pacu fish Piaractus mesopotamicus.

The aim of this study was to determine the environmental concentration of atrazine (ATZ) in five streams located in the north of São Paulo state (Brazil) and evaluate its toxicological impact on young specimens of the pacu fish Piaractus mesopotamicus. Samples of water were collected on three occasions between 2010 and 2011, corresponding to periods signifying the beginning, middle, and end of rain season. ATZ levels were estimated by a high-performance liquid chromatography coupled with a mass spectrometry (HPLC-MS/MS) triple quadrupole. Later, the quotient of environmental risk (QR) was determined based on the medium lethal concentration (LC50 48 h), non-observable effect concentration (NOEC), and the estimated environmental concentration (EEC) of ATZ detected in the environment. Histological changes in gills and liver were also studied, along with the brain activity of the enzyme acetylcholinesterase (AChE). The highest concentration of ATZ measured was 10.4 µg L(-1). The ATZ LC50 (48 h) for young P. mesopotamicus was 24.46 mg L(-1) and the QR was classified as "safe". Although the QR indicated that ATZ could be safe for the tested species, it caused many histological alterations in the liver and gills of the exposed specimens, and an increase in the AChE levels.

Copper sulfate acute ecotoxicity and environmental risk for tropical fish / Ecotoxicidade aguda e risco ambiental do sultado de cobre para peixes tropicais

The aim of this study was to estimate copper sulfate acute toxicity and to determine death percentage and environmental risk on guppy fish (Phallocerus caudimaculatus), zebrafish (Brachydanio rerio), mato grosso (Hyphessobrycon eques), and pacu (Piaractus mesopotamicus). Fish were exposed to 0.01, 0.03, 0.05, 0.07, 0.10, and 0.30 mg L-1 (guppy), 0.05, 0.07, 0.10, and 0.30 mg L-1 (zebrafish), 0.07, 0.10, 0.20, and 0.30 mg L-1 (mato grosso) and 9.5, 10.0, 10.5, 11.0, 11.5, and 12.0 mg L-1 (pacu) of copper sulfate, with triplicate control. The estimated 50% average lethal concentrations (LC50; 96 hours) were 0.05 (guppy), 0.13 (zebrafish); 0.16 (mato grosso) and 10.36 mg L-1 (pacu). Copper sulfate was extremely toxic for guppy, highly toxic for zebrafish and mato grosso and lightly toxic for pacu and presents environmental risk of high adverse effects on the guppy, zebrafish and mato grosso and moderate adverse effect to the pacu. Therefore, the guppy fish, zebrafish, and mato grosso are important alternatives for copper sulfate toxicity evaluation in waterbodies.

O objetivo deste estudo foi estimar a toxicidade aguda, determinar a porcentagem de mortalidade e o risco ambiental do sulfato de cobre para o peixe guaru (Phallocerus caudimaculatus), zebrafish (Brachydanio rerio), mato grosso (Hyphessobryconeques) e pacu (Piaractus mesopotamicus). Para realização dos ensaios com sulfato de cobre foram utilizados: 0,01; 0,03; 0,05; 0,07; 0,10 e 0,30 mg L-1 (guaru), 0,05; 0,07; 0,10 e 0,30 mg L-1 (paulistinha), 0,07; 0,10; 0,20 e 0,30 mg L-1 (mato grosso) e 9,5; 10,0; 10,5; 11,0; 11,5 e 12,0 mg L-1 (pacu) como controle em triplicata. A concentração letal média 50% (CL50; 96h) estimada para o guaru foi de 0,05, para o paulistinha foi de 0,13 para o mato grosso foi de 0,16 e para o pacu foi de 10,36 mg L-1. O sulfato de cobre foi classificado como extremamente tóxico para o guaru, altamente tóxico para o paulistinha e mato grosso e ligeiramente tóxico para o pacu e apresenta risco ambiental de elevado efeito adverso para o guaru, paulistinha e mato grosso e moderado efeito adverso para o pacu. Assim, conclui-se que o guaru, paulistinha e mato grosso são importantes alternativas para avaliação da toxicidade do sulfato de cobre em corpos hídricos.

Efeitos tóxicos de surfactantes fitossanitários para o peixe mato grosso (Hyphessobrycon eques) / Toxic effects of phytosanitary surfactants for jewel tetra (Hyphessobrycon eques)

Os surfactantes são moléculas anfipáticas que reduzem a tensão superficial da água e fazem parte dos componentes inertes das formulações de produtos fitossanitários. Assim, os objetivos deste trabalho foram: estimar a concentração letal (CL(I)(50;96h)); classificar e avaliar a qualidade da água durante os testes de toxicidade aguda dos surfactantes: Agral®, Aterbane® BR, Ag-Bem®, Energic®, Fixade® e Gotafix® para o peixe mato grosso (Hyphessobrycon eques); e os sinais de intoxicação nos animais. Para tanto, os peixes foram aclimatados por dez dias em sala de bioensaio. Os animais foram expostos aos surfactantes em DIC com três repetições. A CL(I)(50;96h) do surfactante Agral® foi 3,29 mg L-1; do Aterbane® BR, 8,21 mg L-1; do Energic®, 2,34 mg L-1; do Gotafix®, 4,37 mg L-1; do Fixade®, 3,38 mg L-1 e do Ag-Bem®, 34,95 mg L-1. As variáveis de qualidade da água não foram alteradas. Os peixes apresentaram aumento do batimento opercular após a exposição; 4 e 24h, perda da capacidade de arfagem; 48h, batimento opercular lento e 72 e 96h, recuperação. Os surfactantes Energic®, Agral®, Gotafix®, Aterbane® BR e Fixade® podem ser classificados como moderadamente tóxicos e o Ag-Bem® como pouco tóxico para H. eques e este organismo apresenta sinais de intoxicação semelhantes para todos os surfactantes.

Surfactants are amphipatic molecules that reduce the surface tension of water and make up the inert components of pesticide formulations. Thus, the objectives of this study were: to estimate the lethal concentration (LC(I)50;96h); classify and evaluate water quality during testing of the following surfactants: Agral®, Aterbane® BR, Ag-bem®, Energic®, Fixade® and Gotafix® for jewel tetra (Hyphessobrycon eques); and the signs of intoxication in the animals. For this, the fish were acclimated for ten days in the bioassay room. The animals were exposed to the surfactants in an entirely randomized design with three replications. The LC(I)(50;96h) of surfactant Agral® was 3.29 mg L-1; Aterbane® BR 8.21 mg L- 1; Energic® 2.34 mg L-1; Gotafix® 4.37 mg L- 1; Fixade® 3.38 mg L-1; and Ag-bem® 34.95 mg L-1. The variables of water quality were unchanged. The fish showed an increase in the opercular beating after exposure; 4 and 24 hours, loss of gasping ability; 48 hours, slow opercular beating; and 72 and 96 hours later, recovery. The surfactants Energic®, Agral®, Gotafix®, Aterbane® BR and Fixade® can be classified as moderately toxics, and Ag-Bem® as slightly toxic for H. eques; this organism shows similar intoxication signs for all surfactants.

Crescimento e esporulação de Bipolaris euphorbiae cultivado sob diferentes condições nutricionais / Growth and sporulation of Bipolaris euphorbiae cultivated under different nutritional conditions

Apesar de ser considerado um potencial bioagente de controle do amendoim-bravo (Euphorbia heterophylla L.) em cultivos de soja no Brasil, pouco se conhece sobre as características nutricionais do fungo Bipolaris euphorbiae Muchovej & Carvalho. O objetivo deste trabalho foi avaliar diferentes fontes de carbono (glicose, amido, sacarose, lactose e maltose), de nitrogênio (nitrato de sódio, nitrato de amônio, sulfato de amônio, fosfato de amônio dibásico, cloreto de amônio), de fósforo (fosfato de potássio monobásico, fosfato de potássio bibásico, fosfato de cálcio, fosfato de sódio, ácido fosfórico, fosfato de amônio) e a suplementação do meio de cultivo com fontes orgânicas de macro e micronutrientes, para o crescimento e a esporulação de B. euphorbiae. O amido proporcionou o maior crescimento, sendo também considerada a fonte de carbono mais favorável para a esporulação. O melhor crescimento e esporulação de B. euphorbiae foram obtidos usando o nitrato de sódio como fonte de nitrogênio e fosfato de potássio monobásico e fosfato de cálcio como fonte de fósforo, embora as demais fontes de fósforo analisadas, exceto o ácido fosfórico, tenham igualmente favorecido a esporulação. A suplementação do meio de cultivo com peptona e extrato de levedura resultou em melhor crescimento e esporulação do fungo e a adição de vitaminas favoreceu a produção de conídios.

Bipolaris euphorbiae Muchovej & Carvalho is considered a potential bioagent for control of selvage peanuts (Euphorbia heterophylla L.) on soybean crops in Brazil. However, little is known about the nutritional characteristics of this fungus. The main objective of this research was to evaluate different sources of carbon (glucose, starch, sucrose, lactose and maltose), of nitrogen (sodium nitrate, ammonium nitrate, ammonium sulphate, bi-basic ammonium phosphate, ammonium chloride), of phosphorus (monobasic potassium phosphate, bi-basic potassium phosphate, calcium phosphate, sodium phosphate, phosphoric acid, ammonium phosphate) and addition of organic sources of macro and micronutrients as supplement in the culture medium for the growth and sporulation of B. euphorbiae. Starch was the carbon source that promoted the greater fungus growth and was considered the most favorable to sporulation. The nitrogen source sodium nitrate and the phosphorus source monobasic potassium phosphate and calcium phosphate provided the best growth and sporulation of B. euphorbiae, but the others phosphorus source analyzed, except phosphoric acid, favored the fungus sporulation. The supplementation of the culture medium with peptone and yeast extract promoted a better growth and sporulation of the fungus and the addition of vitamins favored the production of conidia.

Toxicidade aguda e efeitos histopatológicos do diquate na brânquia e no fígado do Piauçu (Leporinus macrocephalus) / Diquat acute toxicity and histopathological effects on Leporinus Macrocephalus's gliss and liver

A concentração letal (CL 9I) 50-96h e os efeitos histopatológicos do diquate para o piauçu (Leporinus macrocephalus) foram avaliados em três experimentos conduzidos em condições de laboratório. Os peixes foram expostos ás concentrações de 0; 12; 18; 24; 30; 36; 42; 48; 54 e 60 mg de diquate/L e a histologia da brânquia e do fígado avaliada nos peixes sobreviventes. A concentração letal (CL 9I050-96h) foi de 34,76 mg/L. Nos tratamentos controle, 12 e 18 mg/L as brânquias dos peixes estavam revestidas por epitélio estratificado que em intervalos regulares formaram as lamelas secundárias, constituídas por duas camadas de células epiteliais pavimentosas, células pilares, células-cloreto e células mucosas. Nos tratamentos com 24, 30, 36, 42 e 48 mg/L ocorreu hiperplasia das células de revestimento, das mucosas e das células cloreto no espaço interlamelar. No tratamento com 54 mg/L verificou-se edema subepitelial e fusão apical das lamelas secundárias. O fígado do piauçu nos tratamentos controle e 12 mg/L apresentaram arranjo cordonal dos hepatócitos. Nos tratamentos com 18, 24, 30, 36, 42, 48 e 54 mg/L ocorreu congestão no interior dos capilares sinusóides. Nos tratamentos com 48 e 54 mg/L constatou-se a presença de grânulo de glicogênio no interior da célula, início de necrose dos hepatopâncreas, congestão e fusão celular. O diquate mostrou-se pouco tóxico para o L macrocephalus, e as alterações histopatológcas que ocorreram na brãnquia e no fígado dos peixes são reversíveis.

Weed interference on maize (Zea mays) under no tillage system.

A field trial was carried out in Brazil in March 2002 with the aim to evaluate the effects of different timing and extension of weedy period on maize productivity. The hybrid Pioneer 30K75 was sowed under 7 t ha(-1) mulching promoted by glyphosate spraying. The treatments were divided in two groups: In the first group, weeds were maintained since the maize sowing until different periods in the crop cycle: 0, 14, 28, 42, 56, 70, and 150 days (harvesting time). In the second group, the maize crop was kept weed free for the same periods of the first group. Weed control was done through hand hoeing. A complete randomized blocks experimental design with five replications was used for plots distribution in the field. Nonlinear regression model was used to study the effects of weedy or weedfree periods on maize productivity. Weed community included 13 families and 31 species. Asteraceae, Poaceae, and Euphorbiaceae were the most abundant families. Results showed that under no tillage condition with 7 t ha(-1) mulching at sowing time, the maize crop could cohabit with weed community for 54 days without any yield lost. On the other hand, if the crop was kept weed free for 27 days, the weed interference was not enable to reduce maize production. According to these results one weed control measure between 27 and 54 days after crop emergence could be enough to avoid any reduction in maize productivity.

Germination and mycelial growth of Bipolaris euphorbiae Muchovej & Carvalho as influenced by herbicides and surfactants

Bipolaris euphorbiae Muchovej & Carvalho can be combined with herbicide in order to control a large spectrum of weed species, being a strong candidate for the biocontrol of Euphorbia heterophylla L. (milk weed). The fungus release can be combined with herbicide in order to control a broader spectrum of weed species. Thus. Laboratory experiments were set up to study the feasibility of using tank mixes of B. euphorbiae spores with herbicides or surfactants recommended for soybean. Mycelial growth and conidia germination were evaluated in PDA medium enriched with the herbicides oxasulfuron (80 g/ha), glyphosate (4 L/ha), bentazon (1.5 L/ha), fomesafen (1 L/ha), chlorimuron-ethyl (80 g/ha), lactofen (1 L/ha) and imazetaphyr (1 L/ha), and the surfactants Energic (2 ml/L), Aterbane (2.5 ml/L), Silwet L-77 Ag (1 ml/L), Herbitensil (2 ml/L) and Natur LÆóleo (10 ml/L). Dilution of the herbicides at 50 percent and 25 percent were evaluated based on solution consumption of 300 L/ha. The surfactants were evaluated only in the recommended concentrations. Mycelial growth was not affected by bentazon and fomesafen and slightly by oxasulfuron. However, glyphosate and the surfactants Energic, Herbitensil and Aterbane strongly reduced its growth. The reduction observed on imazetaphyr enriched medium was intermediate and the NaturÆóleo promoted mycelial growth. All of the surfactants allowed B. euphorbiae conidia germination equivalent to that reached in the presence of water. Energic and Herbitensil caused an expressive retardation on spore germination. The germinative process only began after 120 minutes in the presence of Herbitensil. In relation to the herbicides, it was observed that only in the presence of glyphosate and imazetaphyr the conidia germination did not follow the trend of the treatment with water.