Interferência Do Estádio Fenológico Do Capim-Amargoso Sobre a Eficácia Do Herbicida Glyphosate

Abstract

Considera-se que o controle eficiente de plantas daninhas com o uso de herbicidas em pósemergência depende, sobretudo, do estádio de desenvolvimento das plantas alvo no momento da aplicação. Neste sentido, o estádio fenológico das plantas é uma variável importante a ser considerada no ambiente de produção, pois interfere na eficácia do produto e exige readequação das doses recomendadas. Assim sendo, este trabalho foi desenvolvido com o objetivo de avaliar a suscetibilidade do capim-amargoso ao herbicida glyphosate influenciada pelo estádio fenológico no momento da aplicação. Para tanto, dois experimentos semelhantes foram realizados, nos quais os tratamentos foram organizados segundo esquema fatorial 8x5, em que oito foram as doses do herbicida glyphosate (0, 45, 90, 180, 360, 720, 1440, 2880 g ha-1) e cinco os estádios fenológicos do capim-amargoso. Comparado à variável massa seca, observou-se que a variável controle percentual promoveu melhor estimativa da suscetibilidade do capim-amargoso ao glyphosate, considerando-se diferentes estádios fenológicos; para esta variável o cálculo de DL80 resultou em excelente estimativa de suscetibilidade da espécie, obtendo-se a equação y = 26,276x – 112,42. Ou seja, a cada 10 unidades na escala BBCH, necessita-se de 150 g ha-1 adicionais de glyphosate para obter o mesmo DL80.

Sourgrass phenological stage and efficacy of ACCase-inhibiting herbicides

“…However, the control of adult plants with perennial clumps and presence of rhizomes is difficult. Thus, the best time for the control of D. insularis plants is up to 45 days after emergence, when the rhizomes are not fully formed (Gemelli et al, 2012;Andrade et al, 2019) and, in general, the plants are not yet at the flowering stage.…”

“…Glyphosate applications control susceptible young weeds grown from seeds; however, the control is difficult when the weeds are grown from rhizomes, (Andrade et al, 2019). Thus, the best time for controlling D. insularis plants is up to 45 days after emergence, when the rhizomes are not yet formed (Gazola et al, 2016).…”

“…The importance of sourgrass infestations in agricultural areas can be great for soybean and maize crops and citrus orchards because of glyphosate-resistant biotypes (Carvalho et al, 2011;Heap, 2019). Thus, the species, which previously had low agronomic importance due to its easy control, became one of the most competitive and important weeds in the country (Andrade et al, 2019). Lacerda and Victoria Filho (2004) found that only 128.5 g ha -1 of glyphosate were enough to control 50% (DL50) of these plants.…”

“…Barroso et al (2014) found that the herbicides quizalofop, haloxyfop, sethoxydim, and clethodim are good options for the control of sourgrass plants at initial developmental stages, showing efficacies higher than 90% at 28 days after application. An efficient control of weeds by using post-emergence herbicides depends mainly on the developmental stage of the target-plants at the time of application (Melo et al, 2012;Barroso et al, 2014;Andrade et al, 2019). However, little scientific information is available about the efficacy of ACCase-inhibitor herbicides regarding rates to be used, and about the effects of the plant phenology at the time of application.…”

Effect of low glyphosate doses on flowering and seed germination of glyphosate‐resistant and ‐susceptible Digitaria insularis

“…The number of leaves and tillers of sourgrass influences the efficacy of glyphosate, as studies show that for every three new tillers it is necessary to add 150 g e.a. ha −1 for adequate control of sourgrass 52 . More studies are needed to understand if the hormesis in weeds can increase its competitive capacity and if it has impact on the weed control.…”