INTERVAL BETWEEN SEQUENTIAL HERBICIDE TREATMENTS FOR SOURGRASS MANAGEMENT

Rafael Romero Mendes,Denis Fernando Biffe,Jamil Constantin,Hudson Kagueyama Takano,Rubem Silvério De Oliveira Junior

doi:10.1590/1983-21252020v33n301rc

Rafael Romero Mendes, Denis Fernando Biffe + Show 3 more

Open Access

https://doi.org/10.1590/1983-21252020v33n301rc

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Abstract

ABSTRACT More than one herbicide application is usually necessary to manage glyphosate-resistant sourgrass in advanced stages of development efficiently during off-season fallow periods. The objective of this study was to determine the best interval between two sequential applications to control sourgrass, based on the number of days and tiller-height after the first treatment. Two experiments were conducted based on these criteria. Experiment 1 consisted of one application of glyphosate + clethodim (1140 ae ha-1 + 108 g ha-1) followed by glyphosate + clethodim or paraquat (400 g ai ha-1) at an interval of 10, 17, 24, 31, 28, or 45 days. Experiment 2 was conducted with the same herbicide treatments, but using the tiller-height as the criteria for the second application, which were 2-5, 6-10, 11-20, 21-30, and >30 cm. None of the treatments resulted in total sourgrass control during the evaluation period. Overall, treatments with glyphosate + clethodim in the second application were more efficient than paraquat. The most effective interval between sequential applications of glyphosate + clethodim was observed at 17 to 24 days. For paraquat, the best interval for the second application was 6-10 days. The most effective performances based on the tiller-height were found at 620 cm tall for glyphosate + clethodim and 6-10 cm tall for paraquat.

Highlights

Sourgrass (Digitaria insularis (L.) Fedde) is a C4 species that belongs to the Poaceae family
Since 2008, GR sourgrass populations have been selected by frequent glyphosate treatments (CARVALHO et al, 2011) and surveys have shown that 57% of sourgrass populations are GR (LÓPEZ-OVEJERO et al, 2017)
Glyphosate-resistant sourgrass has been reported at the experimental site (LÓPEZ OVEJERO et al, 2017)

Summary

Introduction

Sourgrass (Digitaria insularis (L.) Fedde) is a C4 species that belongs to the Poaceae family. Most species from the Digitaria genus exclusively reproduce from seeds, but sourgrass can propagate vegetatively from rhizomes (GAZOLA et al, 2016). This defines sourgrass as a perennial grass that is able to grow and self-reproduce over the whole year under appropriate conditions (OREJA, FUENTE, FERNANDEZ-DUVIVIER, 2017). The adoption of no-till systems and reduced soil plowing (FIDALSKI; YAGI; TORMENA, 2015) have made herbicides the primary tools for sourgrass management across grain fields. Commercialized glyphosate-resistant (GR) crops such as soybean and corn have led to the increased use of this herbicide. Since 2008, GR sourgrass populations have been selected by frequent glyphosate treatments (CARVALHO et al, 2011) and surveys have shown that 57% of sourgrass populations are GR (LÓPEZ-OVEJERO et al, 2017)

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