Alternatives for chemical management of sourgrass

Abstract

Intensive use of Glyphosate has been selected multiple resistant sourgrass biotypes in the areas of intensive agriculture in Brazil. Thus, it is important that viable management alternatives are evaluated for this invasion, which currently is regarded as the main problem of Brazilian agriculture. The study aimed to evaluate strategies for chemical management of sourgrass. Three trials divided according to the weed development stages were performed: PostInitial (up to tillering), Post-Delayed (one to four tillers) and Adult-Plant (adult stage characterized by the beginning of the reproductive phase). The sourgrass seeds were collected from biotypes with evidence of Glyphosate tolerance in the municipality of Rio Brilhante -MS. In each trial were evaluated thirteen treatments and one witness, where the treatments were herbicide mixtures applications with subsequent sequential applications at different dates (7, 10 and 14 days after the first application) and the herbicides application without mixtures. Sourgrass plants are tolerant to Glyphosate and Clethodim herbicides. Formulated mixtures of Paraquat + Diuron and Haloxifop are the most suitable for controlling sourgrass plants derived from seeds, regardless of the control period. Treatments that have the Haloxyfop herbicide in the first application provided better control when compared to the other treatments with mixtures and sequential applications at all stages of applications.

Selectivity of herbicides in native forest species of cerrado

“…Therefore, the need for researches on weed control in reforestation areas with native tree species is clear (DOUST et al, 2008;MACHADO et al, 2013). Thus, identifying herbicides selective to native species would allow the use of more practical methods for controlling invasive plants and would facilitate the use of these species in commercial plantations or agroforestry systems (BRANCALION et al, 2009 (TEODORO et al, 2015;GILO et al, 2016;SANTO et al, 2017). Thus, this study aimed at assessing the selectivity of glyphosate and imazapyr in native seedlings present in Cerrado, such as Schinus terebinthifolia (Anacardiaceae), Peltophorum dubium (Fabaceae) and Handroanthus albus (Bignoniaceae).…”

Control of conyza bonariensis with glyphosate associated to adjuvants applied with different spray nozzles

“…The application techniques to be adopted in order to obtain a good uniformity of phytosanitary product applications, thus ensuring the solution deposition on the target, should be selected according to the weed morphological parameters which are present in the growth area, such as their height, shape and leaves size (GILO et al, 2016). Adding to this, the combination of adjuvants with herbicide solutions, especially glyphosate, has become a common practice that aims at increasing control efficiency and reducing the dose of the product, since the adjuvants act on the physicochemical features of the solution, increasing the surface wettability and reducing superficial tension and the contact angle of the drop, as well as enhancing the penetration capacity of the active ingredient through the plant cuticle (RODRIGUES-COSTA et al, 2011;MINGUELA;CUNHA, 2010).…”

ALTERNATIVAS DE CONTROLE QUÍMICO PARA CAPIM-AMARGOSO (Digitaria insularis) NA CULTURA DO MILHO

“…Dentre as plantas daninhas de difícil controle, que têm aumentado de importância no sistema de sucessão soja-milho safrinha, o capim-amargoso (Digitaria insularis) é a espécie que mais merece atenção por parte dos produtores de soja e milho (Licorini et al, 2015). Esta espécie se caracteriza por ser uma planta de difícil controle, em função de sua velocidade de crescimento, da dificuldade de controle de plantas entouceiradas, de sua adaptabilidade a diferentes condições edafoclimáticas, e do aumento da população de biótipos resistentes ao glyphosate no Brasil (Gilo et al, 2016;Carvalho et al, 2011;Mondo et al, 2010;Machado et al, 2006). O primeiro registro de biótipo de capim-amargoso resistente a glyphosate foi realizado por Adegas & Gazziero, em 2008, em uma lavoura de soja no município de Guaíra, na região oeste do Paraná (Heap, 2017).…”

“…Por meio de resultados de pesquisas, vários trabalhos indicam que, para dessecação de plantas adultas de capim-amargoso em pré-plantio, o glyphosate deve ser associado a herbicidas de ação graminicida que se caracterizam por inibirem a enzima acetil-coenzima A (ACCase), intercalados por uma aplicação de produto de contato ou novamente por outro produto de ação graminicida (Zobiole et al, 2016;Gilo et al, 2016;Correia et al, 2015;Gemelli et al, 2013). Resultados obtidos para a cultura da soja GR indicam a necessidade de aplicações sequenciais de herbicidas de ação graminicida para o controle de plantas de capim-amargoso entouceiradas resistentes ao glyphosate ou uma única aplicação para plantas pequenas (Barroso et al, 2014).…”

“…Entretanto, tem sido observada ineficácia no controle de plantas adultas e de biótipos resistentes de capim-amargoso (Correia & Durigan, 2009). A entrada de cultivares de milho tolerante a haloxyfop-pmethyl e ammonium-glufosinate no mercado poderá auxiliar no manejo desta infestante, tendo em vista a eficiência já relatada destes produtos em outras culturas e/ou na dessecação pré-plantio (Gilo et al, 2016;Gemelli et al, 2013). Desta forma, torna-se necessá-rio ampliar o conhecimento sobre os herbicidas disponíveis para serem utilizados na cultura, assim como sobre novas alternativas de controle químico que poderão ser implementadas em função da inserção de genes de tolerância a herbicidas no milho.…”