Resposta de diferentes populações de Digitaria insularis ao herbicida glyphosate

Abstract

RESUMO -Objetivou-se com estse trabalho avaliar o controle químico de diferentes populações de capim-amargoso (Digitaria insularis) pelo herbicida glyphosate por meio de curva de dose-resposta, além de propor tratamentos alternativos para as populações mais tolerantes. O delineamento experimental foi o de blocos ao acaso, com quatro repetições, em esquema fatorial 5 x 9. As sementes de capim-amargoso foram coletadas em cinco locais: área de produção de grãos da Fazenda de Ensino, Pesquisa e Produção da UNESP, Jaboticabal (SP); área de produção comercial de grãos, localizada nos municípios de Campo Florido-MG e Rio Verde-GO; pomar de laranja, localizado no município de Matão (SP); e área não agrícola sem histórico da aplicação de glyphosate (Jaboticabal-SP). O glyphosate (0D, 1/4D, 1/2D, D, 2D, 4D e 8D, em que D é a dose recomendada de 1,5 kg ha -1 de equivalente ácido) e as suas associações [glyphosate + fluazifop-p-butil (1,5 + 0,25 kg ha -1 ) e glyphosate (1,5 kg ha -1 ) com sequencial de diuron + paraquat (0,20 + 0,40 kg ha -1 + 0,2% de surfatante)] foram pulverizados em plantas de sete a oito perfilhos e altura média de 20 cm. As populações de capim-amargoso de Campo Florido e Rio Verde foram consideradas suscetíveis; as de Jaboticabal e Matão, tolerantes; e a da área não agrícola, de sensibilidade intermediária. A associação de glyphosate ao fluazifop ou a sua aplicação com sequencial de diuron + paraquat foram eficazes no controle das populações mais tolerantes de capim-amargoso.Palavras-chave: capim-amargoso, controle químico, dessecação, tolerância.ABSTRACT -The objective of this study was to evaluate the chemical control of different sourgrass (Digitaria insularis) populations by the herbicide glyphosate through dose-response curves, besides considering alternative treatments to control tolerant populations. A randomized block design was used with four replications, in a factorial scheme (5 x 9). Sourgrass seeds were colleted from five locations: a grain production area located at the educational, research and production farm of UNESP, Jaboticabal-SP; a grain production area located in the agricultural area of Campo Florido, MG, and Rio Verde, GO; citrus production area located in the agricultural area of Matão, SP, and an area without previous glyphosate application (Jaboticabal-SP). Glyphosate (0D, 1/4D, 1/2D, D, 2D, 4D and 8D, where D is the recommended rate of 1.5 kg ha -1 of acid equivalent) and its associations [glyphosate plus fluazifop-p-butyl (1.5 plus 0.25 kg ha -1 ) and glyphosate (1.5 kg ha -1 ) in sequence with diuron plus paraquat (0.20 plus 0.40 kg ha -1 plus 0.2% of surfactant)] were sprayed on the 7-8 tiller plants with average height of 20 cm. Campo Florido, MG and Rio Verde, GO sourgrass populations were considered susceptible; those of Jaboticabal-SP and Matão,SP were found to be tolerant and those from the nonagricultural area were considered of intermediate sensitivity. The association of glyphosate with fluazifop, or its application in sequence with diuron plus paraquat, were effi...

Interferência de plantas daninhas na cultura do sorgo sacarino

“…The loss of IR (%) of this species can be attributed to its lower competitive ability against the weed community in the area. According to Correia et al (2010), sourgrass has slow initial growth until 45 days after emergence, so even presenting high rDe (%) and rFr (%) in the initial stages, this weed was eventually suppressed at the end of the cycle by more dominant species, such as, tropical spiderwort and guinea grass. A dominant plant is characterized by large area of ground cover, great accumulation of mass and great distribution across the area (Concenço et al, 2013a).…”

Monitoring the occurrence of glyphosate-resistant sourgrass biotypes in the south region of Minas Gerais, Brazil

“…The R/S factor corresponds to the division of LD50, LD80 or LD95 of the unknown susceptibility biotype by the susceptible biotype (Christoffoleti & López-Ovejero, 2008). Correia et al (2010) also reported glyphosate differential susceptibility of sourgrass populations, what enunciated the selection of glyphosate-resistant biotypes. In this work, doses up to 3,988 g ha -1 a.e.…”

Chemical control of different Digitaria insularis populations and management of a glyphosate-resistant population

“…Based on the Scott-Knott test at 5 % probability, means followed by lowercase letters, in the columns, compare the populations within each herbicide/ control treatment, and capital letters, in the rows, compare the herbicide/control treatments within each population. When studying the response of five populations of D. insularis to glyphosate herbicide, Correia et al (2010) reported that the populations of Campo Florido, MG, and Rio Verde, GO, both areas of grain production, were considered susceptible; the ones in Jaboticabal, SP (area of grain production) and Matão, SP (orange orchard), tolerant; and the ones in the non agricultural area were considered as having an intermediate sensitivity. For an effective control (100%) of the plants from Jaboticabal, it was necessary to apply 6.0 kg ha -1 of glyphosate.…”