Multiple resistance of Conyza sumatrensis to three mechanisms of action of herbicides

Alfredo Junior Paiola Albrecht,Leandro Paiola Albrecht,Luiz Henrique Saes Zobiole,Cristian Natalino Zanfrilli De Souza,Fernando Storniolo Adegas,Vinicius Gabriel Caneppele Pereira

doi:10.4025/actasciagron.v42i1.42485

Abstract

Fleabane (Conyza spp.) is an important weed in grain production systems and is currently one of the most problematic weeds in Brazil. An important factor related to weeds such as fleabane is the characteristic of herbicide-resistant biotypes developed under selection pressure, with multiple resistance previously detected for Conyza spp. Thus, the aim of this study was to demonstrate the multiple resistance of Conyza sumatrensis to the herbicides paraquat, glyphosate, and chlorimuron. From the F2 seeds of biotypes with suspected resistance to paraquat, glyphosate, and chlorimuron, dose-response greenhouse experiments were conducted for the three herbicides. Herbicides were applied when the plants had 6-8 leaves that were at a height of 8 cm. At the end of the evaluations, 28 days after application, multiple resistance to paraquat, glyphosate, and chlorimuron was observed, with resistance factors (RF50) for the control of 7.43, 3.58, and 14.35 and for the reduction of dry mass of 2.65, 2.79, and 11.31, respectively. All the established criteria for demonstrating new cases of weed resistance were met; thus, the first case worldwide of a Conyza species with resistance to herbicides with three different mechanisms of action was confirmed.

Highlights

Plants of the genus Conyza, known as fleabane, originated in the Americas, according to most reports
The origin of C. sumatrensis is hypothesized to be in the subtropical region of South America, and the species is distributed to the warm regions of continents (Thebaud & Abbott, 1995); other authors identify Indonesia as the probable place of origin (Kostermans et al, 1987)
Fleabane infestation (Conyza spp.) has gradually increased in cultivated agricultural areas in Brazil, primarily in soybean crops, becoming one of the primary weeds that interfere with this crop (Albrecht et al, 2018)

Summary

Introduction

Plants of the genus Conyza, known as fleabane, originated in the Americas, according to most reports. After the harvest of off-season corn, interval occurs before sowing soybeans, and in this period, between the planting of the crops, fleabane develops significantly (Krenchinski et al, 2019; Cesco et al, 2019). This fact is due to the high adaptability of this plant to the production systems and the evolution of biotypes resistant to herbicides, which cause increasing losses to crops (Lamego et al, 2013; Albrecht et al, 2017; Cesco et al, 2019)

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Results