Management of Resistant Conyza spp. During Soybean Pre-sowing

V.J.S Cesco,A.J.P Albrecht,F.H Krenchinski,R Nardi,L.P Albrecht,D.M Rodrigues

doi:10.1590/s0100-83582019370100039

V.J.S Cesco, A.J.P Albrecht + Show 4 more

Open Access

https://doi.org/10.1590/s0100-83582019370100039

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Abstract

ABSTRACT: Horseweed (Conyza spp.) is a weed with a considerable presence and frequency throughout Brazilian crops, as well as presenting difficult chemical control. The objective of this study was to evaluate the efficiency of herbicide management, through single and sequential applications, in controlling Conyza spp., at two development stages with 4 to 6 leaves (3 to 5 cm) and 20 leaves (15-20 cm). The analyzed variables were: control percentage (7, 14, 21, and 28 days after application), dry matter content (28 days after application) and regrowth percentage (21 days after application). Data were submitted to analysis of variance at 5% probability and when there was a difference, the means were submitted to the Scott-Knott test. For Conyza spp. plants with a height between 3 and 5 cm and 4 to 6 leaves, the best treatments were T4, T8, T9, T10, T11, T12, T13, and T14, presenting a control percentage above 90%, 7 days after application. For Conyzaspp. plants with a plant development of 15 cm in height and 15 to 20 leaves, the highest control percentages and lowest regrowth percentages were with treatments T9, T13, and T14.

Highlights

Horseweed (Conyza spp.) is a weed with a considerable presence and frequency throughout Brazilian crops, as well as presenting difficult chemical control
The objective of this work was to evaluate the efficiency of herbicide management, in single and sequential applications, at two stages of Conyza spp. plant development
Saflufenacil showed better horseweed control, and this is due to the fact that it has a rapid desiccation action, just as the other protoporphyrinogen oxidase (Protox) inhibitors, due to its weak acid character; it shows a certain translocation, limited to the phloem, but very evident by the xylem

Summary

Introduction

Horseweed (Conyza spp.) is a weed with a considerable presence and frequency throughout Brazilian crops, as well as presenting difficult chemical control. For Conyza spp. plants with a height between 3 and 5 cm and 4 to 6 leaves, the best treatments were T4, T8, T9, T10, T11, T12, T13, and T14, presenting a control percentage above 90%, 7 days after application. Plants with a plant development of 15 cm in height and 15 to 20 leaves, the highest control percentages and lowest regrowth percentages were with treatments T9, T13, and T14. Para as Conyza spp. com desenvolvimento vegetativo de 15 cm de altura e de 15 a folhas, as maiores porcentagens de controle e menores porcentagens de rebrote foram para os tratamentos T9, T13 e T14. Horseweed produces large numbers of seeds, ranging from 150 to 200 thousand per plant, which have characteristics and structures that allow an easy dispersion (Kissmann and Groth, 1992)

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