2,4‐Dichlorophenoxyacetic‐N‐methylmethanamine and haloxyfop‐P‐methyl interaction: Sequential and interval applications to effectively control sourgrass and fleabane

Abstract

Sourgrass (Digitaria insularis L.) and fleabane (Conyza spp. L.) constitute a major challenge to weed management in soybean [Glycine max (L.) Merr.] production systems in Brazil, especially when both are resistant to glyphosate and present concurrently. The aim of this study was to evaluate the interaction of haloxyfop-P-methyl [methyl(R)-2{4-{3-chloro-5(trifluoromethyl)-2-pyridyloxy] phenoxy} propanoate] and 2,4-D [2,4-Dichlorophenoxyacetic acid-N-methylmethanamine] to control sourgrass at three to four tillers and flowering stages and 12-to 15-cm fleabane at vegetative stage. The experiments were arranged in a randomized complete block design with four replicates and were conducted twice. Treatments were composed of haloxyfop-P-methyl and 2,4-D applied sequentially at 3-, 6-, and 12-d intervals.Treatments also included an untreated check, haloxyfop-P-methyl, and 2,4-D sequentially (without interval) and stand-alone applications of both herbicides. All treatments across experiments completely controlled fleabane plants, except haloxyfop-P-methyl alone. Haloxyfop-P-methyl applied ≥6 d before 2,4-D controlled flowering and three-to four-tiller sourgrass plants at rates of 50 and 100%, respectively. Based on results of this study, haloxyfop-P-methyl should be applied ≥6 d before 2,4-D in a sequential application structure to control fleabane and sourgrass (three or four tillers) when present concurrently.

Eficácia de glifosato + haloxifope-p-metílico em associação com outros herbicidas no controle de capim-amargoso

“…Alguns fatores tendem a afetar a ocorrência ou não do antagonismo entre graminicidas e latifolicidas, como por exemplo, a proporção de dose de cada produto utilizado e o intervalo entre as aplicações, quando estas ocorrem de maneira isolada para cada classe de produto (Trezzi et al, 2007, Leal et al, 2019. Osipe (2015), observou antagonismo da mistura cletodim (168 g ha -1 ) + 2,4-D apenas pela maior dose do latifolicida, a qual foi de 670 g ha -1 , ao passo que 402 g ha -1 não resultou em antagonismo.…”

“…Segundo Leal et al (2019), quando o 2,4-D foi aplicado após haloxifope-p-metílico em um intervalo mínimo de seis dias entre as aplicações, não se observou efeito antagônico por parte do latifolicida no controle de capim-amargoso no estágio de três a quatro perfilhos. Já quando o 2,4-D foi aplicado associado ao haloxifope-p-metílico ou em um intervalo de três dias ocorreu redução de eficácia.…”

“…No entanto, diversos trabalhos relatam que a mistura de latifolicidas e graminicidas apresenta antagonismo, com perda de eficácia no controle de gramí-neas, havendo a necessidade do aumento da dose do graminicida para compensar o efeito antagônico, ou então, a realização de duas operações separadas com intervalo entre elas (Trezzi et al, 2007, Leal et al, 2019. Em ambos os casos a vantagem operacional proporcionada pela mistura de tanque é colocada em xeque, havendo desta forma a necessidade de estudos prévios para determinação de práticas que visem minimizar possíveis impactos negativos.…”

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“…For the reduction of antagonism problems due to the combination of herbicides, some authors suggest increasing the dose of the ACCase inhibitor, sequential applications or the use of adjuvants in the spray solution (Mueller et al 1989;Myers and Coble, 1992). Further, another possibility aimed at reducing antagonism problems refers to the interval of about ten days for the application of 2,4-D in relation to the date of use of the ACCase inhibitor (Leal et al 2020). This that the antagonism between auxin mimics and ACCase inhibitors is not related to incompatibility of the mixture in the spray tank (Todd and Stobbe, 1980).…”

“…For areas with simultaneous infestation of fleabane and sourgrass, reports of antagonism have been common among combinations of graminicides and latifolicides, especially in relation to the control of monocotyledonous species with ACCase-inhibiting herbicides mixed with 2,4-D (Pereira et al 2018;Andreoti et al 2019;Leal et al 2020). From this context, the present study aimed to evaluate the interaction of auxin-mimic herbicides (dicamba and 2,4-D), ACCase inhibitors and glyphosate alone or in combinations in the control of glyphosate-resistant fleabane and sourgrass.…”