Taísa Dal Magro

Manejo de capim pé-de-galinha em lavouras de soja transgênica resistente ao glifosato

O objetivo deste trabalho foi avaliar a resistencia de capim pe-de-galinha (Eleusine indica) ao glifosato, em lavouras de soja transgenica; avaliar o efeito de aplicacoes de glifosato em diferentes estadios de desenvolvimento; identificar praticas agronomicas associadas a selecao de biotipos resistentes; e avaliar a eficiencia dos herbicidas cletodim, fluazifope-P-butilico, clomazona, glufosinato de amonio e glifosato nas plantas resistentes. Plantas escapes ao tratamento com glifosato foram coletadas em 24 propriedades, no Rio Grande do Sul. As plantas foram cultivadas em casa de vegetacao, tendo-se avaliado a sua resistencia ao glifosato. Os acessos resistentes foram selecionados e avaliados quanto ao efeito da aplicacao do glifosato em diferentes estadios de crescimento e quanto a sensibilidade aos herbicidas. Foi aplicado um questionario aos produtores para identificacao das praticas agronomicas associadas as falhas no controle. O controle de E. indica pelo glifosato e mais efetivo com a aplicacao em estadios iniciais de desenvolvimento. Praticas agronomicas, como uso continuo de baixas doses do herbicida, aplicacao em estadios de desenvolvimento avancados das plantas daninhas (mais de um afilho) e a ausencia de rotacao de culturas foram relacionadas as falhas de controle observadas. Os herbicidas cletodim, fluazifope-P-butilico e glufosinato de amonio sao alternativas eficientes para o controle de E. indica.

Cyperus difformis L. resistance to pyrazosulfuron-ethyl herbicide and option control

Cyperus difformis L. é planta daninha ocorrente em lavouras de arroz irrigado, que tem apresentado dificuldade de controle devido à resistência a herbicidas inibidores de ALS. O objetivo da pesquisa foi estimar a dose necessária para controlar 50% da população (C50) e reduzir 50% da produção de massa da parte aérea seca (GR50) em biótipo resistente e suscetível de C. difformis e avaliar o controle destes biótipos com herbicidas alternativos recomendados para a espécie. Para isso, foram conduzidos dois experimentos em casa de vegetação, em delineamento experimental completamente casualizado, com quatro repetições. O experimento I constou de biótipo resistente (CYPDI 9) e suscetível (CYPDI 8) de C. difformis e doses do herbicida pyrazosulfuron-ethyl, correspondendo a 0; 0,5; 1; 1,5; 2; 2,5; 3; 4; 6; 8; 16; 32 e 64 vezes a dose registrada (20 g ha-1). As variáveis avaliadas foram controle visual e massa da parte aérea seca (MPAS) aos 28 dias após a aplicação dos tratamentos (DAT). No experimento II os tratamentos constaram dos biótipos (CYPDI 9 e CYPDI 8), nove herbicidas: azimsulfuron (6g ha1); bentazon (900g ha-1); bispyribac-sodium (48g ha-1); carfentrazone-ethyl (40g ha-1); ethoxysulfuron (72g ha-1); glyphosate (900g ha-1); penoxsulam (36g ha-1); propanil (3600g ha-1) e pyrazosulfuron-ethyl (20g ha-1) e testemunha que não recebeu herbicida. As variáveis avaliadas foram: controle visual aos 14, 21 e 28 DAT, área foliar (AF) e MPAS aos 28 DAT. A resistência do biótipo de C. difformis ao pyrazosulfuron-ethyl é elevada e inviabiliza seu controle pelo herbicida e, os herbicidas carfentrazoneethyl, bentazon e propanil, detentores de mecanismos de ação alternativos ao pyrazosulfuron-ethyl, controlam o biótipo resistente de C. difformis. Palavras-chave: Acetolactato sintase, ALS, C50, junquinho

Associations of Herbicides on the Simultaneous Control of Horseweed and Italian Ryegrass

Weed competition negatively affects grain yield on wheat and soybean crops. Due to better practicality and timesaving it is usual the association of broadleaf herbicides with graminicides to control monocot and dicot weeds. However, little is known about the deleterious effects of broadleaf herbicides on graminicides. Thus, the objective of this experiment was to evaluate the effects of simple, double and triple association of broadleaf herbicides with graminicides to control of Italian ryegrass and horseweed. The experiment was conducted into greenhouse on completely randomized experimental design with four replications. The treatments consisted of the graminicides clethodim and clodinafop; the broadleaf herbicides 2,4-D, metsulfuron and saflufenacil and non-selective glyphosate, sprayed isolated and in double and triple association to be compared with a control. The variables evaluated were control (%) at 21 and 28 days after treatments (DAT), and dry weight (g) at 28 DAT. The isolated graminicides and the broadleaf herbicides controlled both Italian ryegrass and horseweed respectively. At the double association of broadleaf with graminicides herbicides, 2,4-D antagonized the effect of clodinafop, and glyphosate mixed with clodinafop decreased the control of the graminicide on Italian ryegrass. At the triple herbicide association, when mixed with glyphosate, metsulfuron decreased the control effect of Italian ryegrass by clethodim. The association of broadleaf herbicides with graminicides is effective on the control of monocot and dicot weeds, but it depends on which herbicide used for the combination. When it is evident the antagonism between broadleaf herbicides and graminicides, the detrimental effects go on grass control.

Safening effect of bentazon over phytotoxicity of ALS inhibitors herbicides on two cultivars of common beans

The experiment aimed to test the crop selectivity and postemergence weed control on common beans. The treatments consisted of cloransulam, and imazethapyr isolated and tank-mixed with bentazon, a weedy control and a weed-free control for comparison of the cultivars Agronorte (ANfc9) and IPR Uirapuru of common beans. The experiment was conducted on a field, on a complete randomized block experimental design with four replications. The variables analyzed were crop injury, weed control, first pod height, pod number, 1000 grains weight and crop yield. Each cultivar behaves differently with the ALS herbicides. The cultivar ANfc9 was more tolerant to the ALS herbicides than IPR Uirapuru. Bentazon tank-mix with cloransulam or imazethapyr decreased the level of crop injury and no antagonism was observed to weed control.

Chemical control of Lolium multiflorum: effect of biotype and time of spraying

Different herbicides were tested to control two biotypes of Lolium multiflorum, an important weed of annual and perennial crops, applied onto 3-4-leaf and pre-flowering stages. Regardless of stage and biotype, the highest efficacy (>85%) was obtained with paraquat and paraquat+diuron. Any of the tested herbicides promote effective control (>85%) of L. multiflorum when applied to 3-4-leaf plants. When applied in pre-flowering, in addition to paraquat and paraquat+diuron, only glyphosate and iodosulfuron can promote effective control (>85%), but with dependence the biotype. The herbicides paraquat and paraquat+diuron are the most recommended for the control of L. multiflorum.

Seletividade do herbicida oxyfluorfen em pré-transplante na cultura do brócolis

As most vegetables, broccoli (Brassica oleracea var. italica) suffers great loss of productivity in the presence of weeds; an appropriate weed management being necessary. The objective of this study was to evaluate the selectivity of oxyfluorfen herbicide applied in pre transplant of broccoli, hybrid Avenger, on different transplantation periods. The experiment was carried out in a greenhouse, in Universidade de Caxias do Sul, situated in Vacaria, Rio Grande do Sul State, Brazil, from August to October 2012. The experimental design was completely randomized in a factorial 11x2 with three replications. The factor A was composed of 11 periods of transplantation (0 to 10 days after application of the product) and the B with and without herbicide (3 L/ha). We evaluated visual symptoms of phytotoxicity in plants, plant height, weight of fresh mass of shoots and dry weight of shoots and root. Plant material was collected from all treatments and analyzed 30 days after transplantation. The herbicide oxyfluorfen does not cause phytotoxic effects on broccoli, hybrid Avenger, when applied to soil in pots, under pre-transplanting.