Susceptibility of Echinochloa populations to cyhalofop-butyl in Southern region of Brazil and impact of the weed phenology on its efficacy of control

• Main Author: Kalsing,Augusto
• Publication Date: 2017
• Other Authors: Tronquini,Sérgio Mateus, Mariot,Carlos Henrique Paim, Rubin,Rogerio da Silva, Bundt,Angela Da Cas, Fadin,Dauri Aparecido, Marques,Luiz Henrique
• Format: Article
• Language: eng
• Source: Ciência rural (Online)
• Download full: http://old.scielo.br/scielo.php?script=sci_arttext&pid=S0103-84782017000400153
• topic: barnyardgrass; development stage; imidazolinones; Echinochloa crus-galli; Echinochloa colona

ABSTRACT: Cyhalofop-butyl stands out among the herbicides in the control of imidazolinone-resistant Echinochloa species; but, rice farmers are not always satisfied with the control achieved with this herbicide. The objectives were to evaluate in regional scale the susceptibility of Echinochloa populations to cyhalofop-butyl, and quantify the effect of the weed phenology on its efficacy of control. For this, three trials were carried out under greenhouse conditions with a fully random design, using Echinochloa populations collected in rice fields in the southern region of Brazil. In two trials, the susceptibility level of 156 (2012/13 growth season) and 103 (2013/14 growth season) populations were evaluated with the application of cyhalofop-butyl at 360g ha-1. In other trial, in which treatments were arranged in a bi-factorial design (A = 6 x B = 5), it was evaluated six cyhalofop-butyl rates and five phenological stages of E. crus-galli populations. Echinochloa populations had showed differential susceptibility to cyhalofop-butyl, especially in the 2013/14 growth season, where 20 out of the 103 populations had control lower than 90%. The efficacy of this herbicide was inversely proportional to the phenological stage, and the application timing delay contributed directly to the decrease of susceptibility to the herbicide. Cyhalofop-butyl is an effective alternative to control imidazolinone-resistant Echinochloa populations, as long as the application timing occurs in the early phenological stages (2 to 4 leaves).