Control of glyphosate resistant hairy fleabane (Conyza bonariensis) with dicamba and 2,4-D

Abstract

-Auxyn type herbicides such as dicamba and 2,4-D are alternative herbicides that can be used to control glyphosate-resistant hairy fleabane. With the forthcoming possibility of releasing dicamba-resistant and 2,4-D-resistant crops, use of these growth regulator herbicides will likely be an alternative that can be applied to the control of glyphosate resistant hairy fleabane (Conyza bonariensis). The objective of this research was to model the efficacy, through dose-response curves, of glyphosate, 2,4-D, isolated dicamba and glyphosatedicamba combinations to control a brazilian hairy fleabane population resistant to glyphosate. The greenhouse dose-response studies were conducted as a completely randomized experimental design, and the rates used for dose response curve construction were 0, 120, 240, 480, 720 and 960 g a.i. ha -1 for 2,4-D, dicamba and the dicamba combination, with glyphosate at 540 g a.e. ha . Herbicides were applied when the plants were in a vegetative stage with 10 to 12 leaves and height between 12 and 15 cm. Hairy fleabane had low sensitivity to glyphosate, with poor control even at the 960 g a.e. ha -1 rate. Dicamba and 2,4-D were effective in controlling the studied hairy fleabane. Hairy fleabane responds differently to 2,4-D and dicamba. The combination of glyphosate and dicamba was not antagonistic to hairy fleabane control, and glyphosate may cause an additive effect on the control, despite the population resistance.Keywords: Conyza bonariensis, dose-response, glyphosate-resistant hairy fleabane, weed resistance.RESUMO -Os herbicidas mimetizadores de auxinas como dicamba e 2,4-D são alternativas para o controle de buva resistente ao glyphosate. Com a possível futura liberação comercial de culturas resistentes ao dicamba e 2,4-D, a aplicação destes herbicidas reguladores de crescimento será uma provável alternativa de controle de buva resistente ao glyphosate. O objetivo desta pesquisa foi modelar por meio de curvas de dose-resposta a eficácia do dicamba e 2,4-D isolados e dicamba em associação com glyphosate para controle de uma população de buva resistente. Um estudo de doseresposta em casa de vegetação foi conduzido em delineamento experimental inteiramente casualizado, sendo que as doses utilizadas para a construção das curvas de dose-resposta foram de 0, 120, 240, 480, 720 e 960 g i.a. ha -1 de para o dicamba e o 2,4-D isolados e dicamba associado com 540 g e.a. ha -1 de glyphosate. As doses utilizadas para o glyphosate isolado foram de 0, 180, 360, 540, 720 e 960 g e.a. ha -1. Os tratamentos herbicidas foram aplicados quando as plantas estavam no estádio vegetativo de 10 a 12 folhas e altura entre 12 e 15 cm. A buva apresentou baixa sensibilidade ao glyphosate, pois não foi controlada mesmo na dose de 960 g e.a. ha -1 de glyphosate. O dicamba e o 2,4-D foram eficazes no controle da população de buva estudada. A buva responde de forma diferenciada ao 2,4-D e dicamba e será importante determinar as doses apropriadas de cada herbicida para controle de buva resistente ao glyphos...

Influence of Adjuvants on the Surface Tension, Deposition and Effectiveness of Herbicides on Fleabane Plants

“…In this context, the different reports about glyphosate-resistant fleabane (Conyza spp.) species stand out (González-Torralva et al, 2012;Soares et al, 2012;Byker et al, 2013;Mellendorf et al, 2013;Moretti et al, 2013). Therefore, it is important to search for new ways to apply glyphosate, both by the association with other herbicides (Gandolfo et al, 2012) or by the addition of adjuvants to the spraying mixture, in order to improve the effectiveness of the applications (Iost and Raetano, 2010;Maciel et al, 2011).…”

Spectrum of Weed Control With 2,4-D and Dicamba Herbicides Associated to Glyphosate or Not

“…A similar situation occurs for fleabane plants (Conyza spp. ), which are more easily controlled when glyphosate is associated to 2,4-D or dicamba (Owen et al, 2011;Soares et al, 2012). Vink et al (2012), in experiments with glyphosate-resistant Ambrosia trifida, verified that dicamba is an excellent option to control the species.…”

“…doses are enough to control fleabane (Conyza canadensis) and, among auxinic herbicides, the one promoting higher fleabane control levels is diglycolamine salt-based dicamba, followed by dimethylamine salt, 2,4-D ester and 2,4-D amine, respectively (Kruger et al, 2010). Fleabane responds in a different way to 2,4-D and dicamba, and dose determination for each herbicide is fundamental (Soares et al, 2012). The authors also state that, even in resistant plants, glyphosate addition may cause additive or synergic effect on control.…”

O desenvolvimento de culturas tolerantes ao herbicida diclorofenoxiacetato: revisão de literatura

“…Alguns trabalhos demonstram a eficiência do 2,4-D no controle de plantas daninhas de difícil manejo com outros herbicidas, como, por exemplo, Conyza bonariensis, Conyza canadensis e Amaranthus palmeri resistentes ao glyphosate (Soares et al, 2012;Kruger et al, 2010). Entretanto, em algumas espé-cies, apenas o uso do 2,4-D pode não ser suficiente para controlar todos os indivíduos.…”