Sistemas de manejo de plantas daninhas utilizando o novo herbicida pyroxasulfone visando ao controle químico de gramíneas em sojaWeed managemet systems using the new herbicide pyroxasulfone aiming at grass control in soybeans Resumo -Em face do crescente número de problemas de gramíneas com resistência aos herbicidas inibidores da EPSPs e da ACCase, é muito importante avaliar alternativas de manejo com herbicidas de outros mecanismos de ação. O objetivo deste trabalho foi avaliar sistemas de manejo contendo o novo herbicida pyroxasulfone visando ao controle de capim-pé-de-galinha (Eleusine indica) e capim-amargoso (Digitaria insularis) e a seletividade para a cultura em aplicações antecedendo a semeadura da soja. O delineamento utilizado foi o de blocos ao acaso, com onze tratamentos e quatro repetições. Todos os tratamentos com herbicidas residuais foram aplicados na segunda dessecação, sete dias antes da semeadura da soja. Cada sistema de manejo contou com duas dessecações sequenciais e uma aplicação em pós-emergência da soja. O melhor controle inicial (até 28 dias após a semeadura) de capim-pé-de-galinha foi observado nos tratamentos contendo pyroxasulfone, embora após a terceira aplicação de herbicidas todos os tratamentos tenham proporcionado excelente controle.No caso de capim-amargoso, a terceira aplicação em pós-emergência da cultura não resultou em nenhum incremento de controle e os melhores resultados foram obtidos com tratamentos que continham herbicidas residuais utilizados na segunda aplicação de dessecação, exceto com chlorimuron-ethyl. Os resultados indicam que a utilização de pyroxasulfone associado a outros herbicidas com atividade residual é uma ótima opção para controle simultâneo de capim-pé-de-galinha e de capim-amargoso, sendo tais tratamentos seletivos para a cultura da soja.Abstract -Due to the increasing number of grasses selected for resistance to the EPSPS and ACCase inhibitors, new alternatives with effective and selective herbicides from different mechanisms of action must be developed. This work was carried out to evaluate weed management systems containing the new herbicide pyroxasulfone aiming at controlling goosegrass (Eleusine indica) and sourgrass (Digitaria insularis) in applications immediately prior to soybean sowing. The design used for the randomized blocks, with eleven treatments and four replicates. All residual herbicides were applied at the second burndown application, seven days prior to soybean sowing. In each system, two sequential burndown applications followed by one post-emergence application were sprayed in each treatment. The best level of initial (up 28 days after crop sowing) control of goosegrass was observed with treatments with pyroxasulfone, although after the third herbicide application all systems provided excellent control of this weed. Concerning to sourgrass, the third post-emergence Morota et al. Rev. Bras. Herb., v.17, n.2, e584, abr./jun. 2018 2/10

The destruction of cotton stalks after harvesting is a prophylactic measure aimed at reducing the population of insects and disease inoculants that may remain in the crop residues and remaining cotton plants. The objective of this work was to evaluate integrated methods of management of the cotton stalks, combining mechanical and chemical control, to promote the eradication of cotton stalks. A 7x5 factorial experiment was installed where seven different methods of mechanical control of cotton stalk and five herbicide treatments were tested. The percentage of control (visual scale of 0 to 100%) and the number of plants regrowth per meter were evaluated at 14, 28 and 50 days after herbicide application treatment. At the end of the experiment, the size of the regrowth was evaluated at 50 days. The methods of management with mowing associated with an application on the stalk followed by another application to plant regrowth’s and mowing with two sequential applications in the sprouts, for the herbicidal treatments 2,4-D + glyphosate in association with [imazapic + imazapyr]) or saflufenacil, promoted the highest control rates of cotton stalks. Aiming at the effectiveness and speed of control, the management with the application of the treatment with 2,4-D + glyphosate + saflufenacil on the stalk, after mowing, associated to another application in the regrowth, provided 100% control at 14 days after the last application and totally inhibited the regrowth of the stalks, and was considered the most effective in the destruction of cotton stalks.

Pyroxasulfone is a new herbicidal molecule with residual activity to be used in Brazilian agricultural areas, it is necessary to gather information about its behavior in the soil, as well as its persistence in the environment and the risk of environmental contamination. The objective of this work was to evaluate the sensitivity of species to pyroxasulfone in order to select potential plants to be used as bioindicators in herbicide soil activity experiments. Greenhouse experiments were conducted with four species as potential bioindicators including lettuce (Lactuca sativa), cucumber (Cucumis sativus), sorghum (Sorghum bicolor), and tomato (Solanum lycopersicum). The preemergence pyroxasulfone treatments at 0, 3.125, 6.25, 12.5, 25, 50, and 100 g a.i. ha -1 . The percentage of injury of the treated species was evaluated by a visual scale of 0-100% at 7 and 14 days after treatment (DAT). We also evaluated the effect of the herbicide on plant height, root length, shoot fresh biomass, root fresh biomass, and total fresh biomass. Using the non-linear regression models was possible to estimate the dose of pyroxasulfone required to obtain 50% of the response for the analyzed variable (I 50 ). I 50 values were used to determine the susceptibility of the species evaluated. The pyroxasulfone dose-response experiments revealed three species with potential for bioassay studies. Overall, Lettuce was the most sensitive to herbicide. Sorghum may be useful species to detect pyroxasulfone soil activity based on plant height measurements (I 50 = 9.7 g a.i. ha -1 ). Cucumber also showed to be a potential candidate as bioindicators. Tomato was considered tolerant of pyroxasulfone doses evaluated.

Para aumentar o espectro de controle das plantas daninhas na cultura do milho, a formulação de herbicidas com princípios ativos de diferentes mecanismos de ação é uma alternativa importante. Objetivou-se avaliar o controle promovido pelo novo herbicida Calaris®, mistura formulada de [atrazine+mesotrione] aplicado em pós-emergência das plantas daninhas, de forma isolada ou em mistura com outros herbicidas. Os experimentos foram conduzidos em casa de vegetação, um para cada planta daninha avaliada, em delineamento inteiramente casualizado com 16 tratamentos e quatro repetições. As sementes das plantas daninhas (Conyza bonariensis, Urochloa decumbens, Cenchrus echinatus, Digitaria horizontalis, Urochloa plantaginea, Ipomoea grandifolia, Euphorbia heterophylla, Bidens pilosa, Glycine max e Commelina benghalensis) foram semeadas em vasos com volume de 5 dm3 a uma densidade de 20 sementes por vaso. Os tratamentos herbicidas foram aplicados em pós-emergência e foram constituídos por [atrazine+mesotrione] isolado ou em mistura com glyphosate, tembotrione e nicosulfuron; atrazine isolado ou em mistura com glyphosate, mesotrione, tembotrione e nicusulfuron; glyphosate isolado e testemunha sem aplicação. A aplicação dos tratamentos de cada experimento foi realizada em datas distintas, levando em consideração o estádio de desenvolvimento das plantas daninhas. Avaliou-se a porcentagem de controle em relação às plantas daninhas aos 7, 14 e 28 dias após a aplicação dos herbicidas. A nova formulação herbicida [atrazine+mesotrione] controlou de forma eficaz a maioria das plantas daninhas avaliadas, exceto Cenchrus echinatus e Urochloa decumbens, entretanto, o controle eficaz foi obtido quando em associação com outros herbicidas, principalmente ao glyphosate.

In the current scenario of resistance of weeds to glyphosate in grain and fiber production systems, imidazolinone-resistant soybean is shown as an option in the rotation of biotechnology events and herbicide action mechanisms through the application of [imazapic+imazapyr]. However, due to its persistence in the soil, the herbicide may harm the subsequent crop. The objective of this work was to evaluate the residual activity of the herbicide [imazapic+imazapyr] applied in pre-emergence in soybean cultivation on cotton in succession. The experimental design was a randomized block design with five replicates, using seven concentrations (0; 6.25; 12.5; 25; 50; 100 and 200%) of the recommended dosage of the herbicide [imazapic+imazapyr] ([78,75+26,25] g ha-1). The cotton was sown 112 days after application of the herbicide with accumulated rainfall of 637 mm during the soybean cycle, totalizing 1,043 mm until the cotton harvest. There was no significant difference for the analyzed variables. It is concluded that the BRS 8482cv soybean cultivar is resistant to double of the recommended dosage ([157.5+52.5] g ha-1) of [imazapic+imazapyr], and its residual soil activity does not affect cotton cv. TMG 42 WS, in the 112 day interval between pre-emergence herbicide application in soybean cultivation and sowing of cotton.