Seletividade de associações e doses de herbicidas em pós emergência do trigo

Abstract

Resumo -As principais plantas daninhas encontradas na cultura do trigo são o nabo e o azevém, e seu controle em pós-emergência é baseado em herbicidas inibidores da enzima acetolactato sintase (ALS) e acetil coenzima A carboxilase (ACCase) que, em função da resistência, limita as opções de controle. Associações de herbicidas têm sido utilizadas em pós-emergência do trigo, porém, seus efeitos na cultura são pouco conhecidos. O objetivo deste trabalho foi avaliar a seletividade de associações de herbicidas e doses aplicados em pós-emergência do trigo. Foram realizados três experimentos a campo em sistema de semeadura direta, no delineamento de blocos ao acaso com três repetições. Os experimentos foram conduzidos nos municípios de Santa Bárbara do Sul-RS, Cruz Alta-RS e Tupanciretã-RS. Foram estudadas doses e associações entre os herbicidas 2,4-D, metsulfuron-methyl, iodosulfuron, piroxsulam e saflufenacil aplicados no perfilhamento do trigo. As variáveis avaliadas foram fitotoxicidade aos sete, 14, 21 e 35 dias após a aplicação (DAA), rendimento de grãos (kg ha -1 ) e peso hectolitro dos grãos de trigo (PH), sendo os dados dos três experimentos analisados de forma conjunta. Aos 35 DAA as maiores fitotoxicidades foram observadas para metsulfuron-methyl na dose de 9 g i.a. ha -1 e para saflufenacil associado ao metsulfuron-methyl. Os resultados de rendimento de grãos demonstraram que a associação entre 2,4-D e metsulfuron-methyl, saflufenacil isolado ou associado à metsulfuron-methyl e o iodosulfuron-methyl foram seletivos para o trigo. O aumento da dose de metsulfuron-methyl (6 e 9 g i.a. ha -1 ) e a dose de registro de piroxsulam causaram redução significativa na rendimento de grãos de grãos de trigo na média dos três experimentos. O PH dos grãos de trigo não foi influenciado pelos herbicidas estudados. Palavras-chave: Triticum aestivum, mistura de herbicidas, mistura em tanque, resistência Abstract -The main weeds in wheat are wild radish and ryegrass, and its post-emergence control is based on herbicides inhibiting the enzyme acetolactate synthase (ALS) and acetyl coenzyme A carboxase (ACCase), which as a function of resistance limits the control options. Herbicide combinations have been used for post-emergence of wheat; however, the effects of herbicidal combinations are poorly understood. The objective of this work was to evaluate the selectivity of Piasecki et al. Rev. Bras. Herb., v.16, n.4, p.286-295, out./dez. 2017 287

Selectivity of 2,4-D salts to barley plants applied at distinct phenological crop stages

“…When comparing the application between crop development stages for each treatment, it was found that the tillering stage and after the first node for 2,4-D amine and the first node stage for 2,4-D choline demonstrate the highest barley grain yields. The 2,4-D amine was reported to not affect grain yields of wheat (Piasecki et al, 2017) and barley (Karpinski et al, 2018), which corroborates in parts with what was observed in this work.…”

“…Post-emergence application of the herbicide 2,4-D amine for barley weed management has caused phytotoxicity of less than 5% in barley plants (Vargas & Roman, 2005) and 10% in wheat crop (Piasecki et al, 2017). These studies corroborate in part with the results found in the present work.…”

“…Plant tolerance to the herbicide 2,4-D is related to limited translocation via phloem mediated by auxin receptors (T1R1/ AFB), which govern biochemical and transcriptional responses (Piasecki et al, 2017). In plants, the T1R1 protein is involved in herbicide perception and substrate recognition, and it acts in the regulation of ethylene and abscisic acid synthesis.…”

“…Among the direct and indirect effects already described by the use of 2,4-D, phytotoxicity, altered nutrient uptake, downregulation of plant defense mechanisms, and reduced grain yield components stand out (Galon et al, 2014;Piasecki et al, 2017;Skelton et al, 2017). The herbicide 2,4-D can be marketed in amine, choline, and ester salt formulations, the latter of which is no longer marketed in Brazil (Contiero et al, 2016).…”

Seletividade e eficácia de herbicidas aplicados à cultura do trigo

“…However, in the South of Brazil, the herbicides used in the post-emergence of wheat predominantly belong to ACCase and ALS inhibitors (MICHELON et al 2021). Therefore, the most recommended for weed control in wheat and available in larger quantities are the ALS inhibitors (PIASECKI et al 2017). However, these herbicides are the ones that have shown many cases of resistant weeds in recent years (HEAP 2021), and in some countries, the concern lies in the time required for chemical control to show an effect on infective species in wheat crops (WALSH 2019).…”