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

Abstract

Resumo -O objetivo deste trabalho foi avaliar a resistência de capim pé-de-galinha (Eleusine indica) ao glifosato, em lavouras de soja transgênica; avaliar o efeito de aplicações de glifosato em diferentes estádios de desenvolvimento; identificar práticas agronômicas associadas à seleção de biótipos resistentes; e avaliar a eficiência dos herbicidas cletodim, fluazifope-P-butílico, clomazona, glufosinato de amônio 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 vegetação, tendo-se avaliado a sua resistência ao glifosato. Os acessos resistentes foram selecionados e avaliados quanto ao efeito da aplicação do glifosato em diferentes estádios de crescimento e quanto à sensibilidade aos herbicidas. Foi aplicado um questionário aos produtores para identificação das práticas agronômicas associadas às falhas no controle. O controle de E. indica pelo glifosato é mais efetivo com a aplicação em estádios iniciais de desenvolvimento. Práticas agronômicas, como uso contínuo de baixas doses do herbicida, aplicação em estádios de desenvolvimento avançados das plantas daninhas (mais de um afilho) e a ausência de rotação de culturas foram relacionadas às falhas de controle observadas. Os herbicidas cletodim, fluazifope-P-butílico e glufosinato de amônio são alternativas eficientes para o controle de E. indica.Termos para indexação: Eleusine indica, Glycine max, dosagem, eficiência de controle, estádio fenológico, resistência ao glifosato, roundup ready. Management of goose grass on transgenic soybean, resistant to glyphosateAbstract -The objective of this work was to evaluate the resistance of goose grass (Eleusine indica) to glyphosate application in transgenic soybean crops; evaluate the effect of glyphosate applications in different growth stages; identify the main agronomic practices associated with the selection of resistant biotypes; and evaluate the effect of the herbicides clethodim, fluazifop-p-butyl, clomazone, glufosinate ammonium, and glyphosate on resistant plants. Plants that survived glyphosate application were collected on 24 properties in the state of Rio Grande do Sul, Brazil. Plants were grown in greenhouse and their resistance to glyphosate was evaluated. The resistant accessions were selected and evaluated as to the effect of glyphosate application on different growth stages and to their sensitivity to the herbicides. A questionnaire was given to producers in order to identify agronomic practices associated with control failures. The control of E. indica by glyphosate is more effective at initial growth stages. Agronomic practices, such as continued use of low doses of glyphosate, application on advanced weed growth stages (more than one tiller), and absence of crop rotation were related to the observed control failures. The herbicides clethodim, fluazifop-p-butyl, and glufosinate ammonium are efficient alternatives to control E. indica.

Goosegrass Resistant to Glyphosate in Brazil

“…Glyphosate applications in goosegrass in early development stage (E1) usually imply more effective, because it is the moment of greatest susceptibility of these plants to herbicides (Ulguim et al, 2013). One of the goosegrass characteristics is its rapid tillering capacity, as the stadium of 2-3 tillers and 5-6 tillers can be reached at nine and twenty-four days after its emergence (DAE) respectively (Takano et al, 2016).…”

“…In this sense, complementary measures handling with herbicides should be designed to reduce the selection pressure, such as the association and the use of herbicides with different mechanisms of action (Shaner, 2000;Johnson and Gibson, 2006).Research papers show that ACCase inhibitors are one of the alternatives for goosegrass control (Ulguim et al, 2013). However, it is important to remember that goosegrass resistance to this mechanism of action has been previously reported in Brazil (Vidal et al, 2006), which shows that the continuous application of graminicides may not be effective in all situations.…”

“…However, it is important to remember that goosegrass resistance to this mechanism of action has been previously reported in Brazil (Vidal et al, 2006), which shows that the continuous application of graminicides may not be effective in all situations. Alternatively, other mechanisms of action may exhibit effectiveness in controlling these populations, such as GS-GOGAT inhibitors, carotenoid synthesis inhibitors (Ulguim et al, 2013), cell division inhibitors, and photosystem I inhibitors (Molin et al, 2013).…”

Evaluation of the Mechanism Responsible for the Low-Level Resistance to Glyphosate in Goosegrass

“…The fact that the LLR biotype has not shown an increase in phloem diameter may represent greater ability to Accumulation of shikimate (mg mL tolerate the herbicide application, especially in the 1-2 tiller stage. It should be noted that the application of glyphosate in that biotype at that stage provided 74% control (Ulguim et al, 2013). Other studies should be conducted to confirm this characteristic, especially those involving the application of glyphosate radioisotopes and evaluation of its translocation.…”

“…The cases of goosegrass resistance to glyphosate reported in the literature are due to the change of the gene encoding the EPSPs enzyme (Powles and Yu, 2010 7 on goosegrass by herbicide application in advanced stages of development (Ulguim et al, 2013). The control of Conyza canadensis resistant to glyphosate was greater than 80% when the herbicide was applied in 10 cm high plants, whereas when the plants were treated with the herbicide at 15-20 cm height, the control did not reach 50% (Vangessel et al, 2009).…”