Digitaria insularis control by using herbicide mixtures application in soybean pre-emergence

Abstract

Sourgrass (Digitaria insularis) is one of the main weeds in the soybean crop. In order to control its growth, an increase of herbicide rates is required to simplify its management as it a plant with high vegetative capacity and seed production. It implies to select the herbicide-resistent Digitaria insularis biotypes. Nevertheless, some information is still contrasting the antagonist of synthetic auxinic herbicides, associated with glyphosate and ACCase inhibitors mixtures, for the control of weeds resistant or tolerant to herbicides. This study aimed to evaluate the D. insularis control, with a mixture of herbicides applied in soybean pre-emergence, with sequential application in soybean post-emergence, and to check possible antagonism between ACCase inhibitors herbicides with synthetic auxins and other latifolicides. The experiment was conducted in Palotina, Paraná (Brazil) and Corpus Christi, Canindeyú, (Paraguay.) The treatments consisted of associations of glyphosate, ACCase inhibitors (clethodim, haloxyfop), and latifolicides (2,4-D, triclopyr, dicamba, carfentrazone, saflufenacil, chlorimuron). A randomized block design was used. Only in Palotina, the weed control was satisfactory after sequential application in post-emergence. An antagonism for all synthetic auxins was observed with glyphosate+clethodim or haloxyfop mixtures, in both locations. As a result, in Palotina an efficacious control of perennial D. insularis was found in pre-emergence burndown for some mixtures such as glyphosate+ACCase inhibitor added to carfentrazone, saflufenacil, or chlorimuron. Antagonism was observed for all synthetic auxins, in both locations. In Corpus Christi, the herbicide associations were not effective, even with the postemergence application in soybean of glyphosate+clethodim. With ineffective control for treatments composed with synthetic auxins, the post-emergence application in soybean increased the weed control with satisfactory final controls for all treatments.

Distribution, characterization and chemical management of noxious shrub weed (Dichapetalum stuhlmannii Engl) in cashew in southeastern Tanzania

“…The synergism of glyphosate and triclopyr have been observed on different weed species [ 20 , 33 , 70 ]. In addition, the synergism of glyphosate and other auxin mimic/synthetic auxin have been reported in various weeds management practices [ 55 , [71] , [72] , [73] ]. On the other hand, the efficacy of the mixture of glyphosate plus triclopyr was found to be at par with the efficacy of a single glyphosate.…”

“…Opoku-ameyaw et al [ 52 ], reported the regrowth of weeds after three to four months of double herbicide application. Bauer et al [ 71 ], described a single application of herbicides as influencing early regrowth of certain weeds including Digitaria insularis. Growing of leguminous plants such as Mucuna shows low residual effect of herbicides and soil fertility due to low intra-weed competition [ 75 , 76 ].…”

Herbicide resistance status of sourgrass

“…However, GS seedlings over 45 days old, which have begun to tiller and clump together, also become difficult to control (Andrade Jr et al, 2018). Clethodim, fluazifop-p-buthy, tepraloxydim, clethodim, fenoxaprop-P-methyl, paraquat, haloxifop-P-methyl and imazapyr, when tested on sourgrass plants with up to two tillers, have demonstrated control levels exceeding 90% (Bauer et al, 2021;Correia et al, 2012;Correia et al, 2009;Zobiole et al, 2016;Barroso et al, 2014;Petter et al, 2015). However, once the plant has formed clumps and developed numerous propagation structures, control efficacy decreases to approximately 50% due to regrowth (Procópio et al, 2006).…”

“…The problem is exacerbated when sourgrass exhibits glyphosate resistance, as GR plants do not incur fitness penalties compared to glyphosatesusceptible (GS) plants (Martins et al, 2017;Pereira et al, 2017). These characteristics collectively make the control of sourgrass very challenging (Bauer et al, 2021).…”

Agronomic implications of paraquat ban in Brazil

“…The low performance of combinations of herbicides with an immediate contact effect, such as diquat, with systemic herbicides, has been reported (Wehtje et al, 2008). In addition, there is antagonism between ACCase inhibitors and synthetic auxins (Underwood et al, 2016;Webster et al, 2019;Bauer et al, 2021) or between ACCase inhibitors and ALS inhibitors.…”