Alternatives for chemical management of sourgrass

Eraldo Godinho Gilo,Tiago Lima Do Espírito Santo,Cristiane Gonçalves De Mendonça,Paulo Eduardo Teodoro

doi:10.14393/bj-v32n4a2016-32786

Abstract

Intensive use of Glyphosate has been selected multiple resistant sourgrass biotypes in the areas of intensive agriculture in Brazil. Thus, it is important that viable management alternatives are evaluated for this invasion, which currently is regarded as the main problem of Brazilian agriculture. The study aimed to evaluate strategies for chemical management of sourgrass. Three trials divided according to the weed development stages were performed: Post-Initial (up to tillering), Post-Delayed (one to four tillers) and Adult-Plant (adult stage characterized by the beginning of the reproductive phase). The sourgrass seeds were collected from biotypes with evidence of Glyphosate tolerance in the municipality of Rio Brilhante – MS. In each trial were evaluated thirteen treatments and one witness, where the treatments were herbicide mixtures applications with subsequent sequential applications at different dates (7, 10 and 14 days after the first application) and the herbicides application without mixtures. Sourgrass plants are tolerant to Glyphosate and Clethodim herbicides. Formulated mixtures of Paraquat + Diuron and Haloxifop are the most suitable for controlling sourgrass plants derived from seeds, regardless of the control period. Treatments that have the Haloxyfop herbicide in the first application provided better control when compared to the other treatments with mixtures and sequential applications at all stages of applications.

Highlights

Herbicides whose mechanism of action is inhibition of phenol-piruvilshiquimato phosphate synthase (EPSPs) began to be used in Brazilian agriculture in the late 1970s, but its use began to grow only from the end of the 1980s and early 1990s with the increased use of no-till system, where prevails the maintenance of the previous crop straw in soybean, maize and wheat cropping systems (KRUSE et al, 2000). Another factor contributing to the growth of glyphosate use in Brazil was the approval of the Biosafety Law in 2005 that allowed the legalized use of genetically modified crops resistant to the herbicide (KOGER; REDDY, 2005)
Machado et al (2006) and Gemelli et al (2012) reported that beginning of the sourgrass plants development is the period of highest sensitivity, because the plants have a lower lignin content in the tissue, facilitating the control in the early stages, which was observed in this study when compared to more advanced development stages of the plants
The results found in this study corroborates the results obtained by Melo et al (2012), which found that sourgrass plants used in their work were tolerant to this herbicide after evaluating different herbicides for management of this weed in maize and found only 65% of control at 28 days after application

Summary

Introduction

Herbicides whose mechanism of action is inhibition of phenol-piruvilshiquimato phosphate synthase (EPSPs) began to be used in Brazilian agriculture in the late 1970s, but its use began to grow only from the end of the 1980s and early 1990s with the increased use of no-till system, where prevails the maintenance of the previous crop straw in soybean, maize and wheat cropping systems (KRUSE et al, 2000) Another factor contributing to the growth of glyphosate use in Brazil was the approval of the Biosafety Law in 2005 that allowed the legalized use of genetically modified crops resistant to the herbicide (KOGER; REDDY, 2005). It is a perennial, which form clumps with rhizomes, produces high amount of dispersing seeds, has a rapid early vegetative development and is highly competitive with other plants (LORENZI, 2014)

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