Identification and mapping of glyphosate-resistant sourgrass with low-level resistance to clethodim and haloxyfop

Abstract

Mapping resistant populations makes it possible to identify the evolution and dispersal of resistance cases, providing important information for control-related decision making. This study aimed to identify and map herbicide-resistant sourgrass (Digitaria insularis) populations in Brazilian regions. The results showed no glufosinate resistance, with 485 samples (96.6%) classified as putative resistant to glyphosate, while nine (1.8%) and five (1%) were considered putative resistant to haloxyfop and clethodim, respectively. Two samples were deemed putative resistant to three herbicides (glyphosate, haloxyfop, and clethodim). One of the samples characterized as a control failure for all three herbicides was used on the dose-response curve. This biotype was identified as glyphosate-resistant, with low-level resistance to clethodim and haloxyfop. Based on C50, resistance factors of 10.96, 3.26, and 3.15 were identified for glyphosate, clethodim, and haloxyfop, respectively. Mapping sourgrass resistance is vital to understand and ensure the early identification and quantification of the frequency of these plants.