Sequential application of herbicide options for controlling Conyza sumatrensis in soybean pre-sowing

Abstract

The aim of this study was to evaluate the efficacy of sequentially applied herbicides to control Conyza sumatrensis, one of the most widely distributed weeds worldwide, in soybean pre-sowing burndown. The study was conducted under field conditions in the state of Paraná, Brazil, at 2018-2019 growing season. The experiment consisted of a randomized block design with four replicates, with 12 treatments consisting of different herbicide mixtures applied before sowing. Control of C. sumatrensis, injury to soybean plants, and variables related to agronomic performance were evaluated. The control levels were high for all treatments, except for the one that was free of saflufenacil in either of the two applications. These results highlight the importance of saflufenacil in the control of C. sumatrensis and show promise for the use of saflufenacil/imazethapyr when considering the system and other weeds. All studied treatments were selective to soybean, which showed higher injury values in the presence of diclosulam; however, this did not compromise the agronomic performance of soybean. Highlights • Application of systemic herbicides with sequential application of burndown herbicides, is essential for the control of Conyza sumatrensis (>15 cm height).• Saflufenacil, flumioxazin, and imazethapyr stand out in the control of Conyza sumatrensis.• Protox and ALS inhibitors can replace paraquat in sequential application with equal efficacy in the control of Conyza sumatrensis.

Changes in leaf structure and control of Conyza spp. by herbicides applied in the presowing desiccation of soybean

“…However, in advanced phenological stages of Conyza spp., the control of this weed can be compromised. This behavior was observed by Albrecht et al 32 , who obtained less than 60% control of Conyza spp. in applications to plants with a height of 42-65 cm.…”

“…with heights greater than 10 cm, i.e., resulted in a percentage greater than 85%, and these treatments have the association of an auxin herbicide as a common feature. This behavior was expected because in the management of Conyza spp., presowing of soybean should always be associated with the positioning of postpost-emergent herbicides, often glyphosate with auxin mimics, followed by sequential use of another contact product, aiming to control the infestation present in the eld [6][7][8][9]32 .…”

“…The herbicide halauxifen + diclosulam has adequate percentages of Conyza spp. control and has often been positioned in its management in presowing desiccation, and after the establishment of percentages higher than 85%, no regrowth of these plants has been observed 32 . However, halauxifen + diclosulam may be slower to establish high control percentages compared to other products used in presowing desiccation.…”

Identification, mapping, and chemical control of fleabane resistant to glyphosate, chlorimuron, paraquat, and 2,4-D

“…In areas with high infestation and/or herbicide resistance, two or more applications of a herbicide are required to effectively control fleabane prior to soybean planting. Glyphosate and synthetic auxin mixtures are commonly used in the first application (Albrecht et al 2022a; Cantu et al 2021; Quinn et al 2020), and burndown herbicides such as diquat, glufosinate, or glufosinate + saflufenacil in the second (Albrecht et al 2022b,c; Dilliott et al 2022).…”

Incremento na eficácia de herbicidas no controle de plantas daninhas devido a aplicação sequencial de glufosinate + saflufenacil

“…Different herbicides, in combination with glyphosate, can be effective in the control of fleabane and/or Benghal dayflower in inter-harvest management, in particular saflufenacil (Santos Junior et al, 2019;Piasecki et al, 2020;Albrecht et al, 2022a), auxin mimetics (Frene et al, 2018), and glufosinate (Tahmasebi et al, 2018). The synergistic effects of some herbicide combinations in weed control have been reported, for example, the combination of glufosinate + saflufenacil (Takano et al, 2020).…”