Herbicide management for horseweed (Conyza spp.) control in post-emergence under flooded rice

Abstract

This study aimed to assess the efficacy of commonly used post-emergence herbicides under flooded rice fields, for Conyza spp. control. The greenhouse experiment employed a factorial setup with factor A denoting the presence or absence of a water layer post-application, and factor B representing different herbicides, to C. sumatrensis. In field trials, were applied when the rice plantation was on V3 stage. Evaluations were control (%), roots and shoot dry weight of Conyza spp., as well as injury (%), number of grains per panicle, and grain yield (ha⁻¹) of rice. The applications of imazapyr + imazapic, florpyrauxifen-benzyl, imazethapyr, penoxsulam, quinclorac, bentazon, triclopyr-butyl, saflufenacil and ethoxysulfuron followed by water layer entry led to Conyza spp. control surpassing 80% at 28 DAA. The herbicides florpyrauxifen-benzyl, quinclorac, triclopyr-butyl, and saflufenacil, without flooding after application, demonstrated Sumatran fleabane control equal to or greater than 80% at 28 DAA. Effective water layer management is crucial for Conyza spp. control in zero-grade rice cultivation areas.

Keywords:

• Flooding
• chemical control
• dry-seeded rice
• weeds
• horseweed

Acknowledgements

The authors thank the National Council for Scientific and Technological Development (CNPq) and the Coordination for the Improvement of Higher Education Personnel (CAPES) for providing research scholarships (undergraduate and graduate) during the conduct of this work. The authors would also like to express their appreciation to UruAgro Assessoria Agropecuária and the Santa Ana Farm for their valuable assistance in carrying out the field experiment in Dom Pedrito (RS). Additionally, we would like to thank Mariano Abel Trachta for English review.

Author’s contribution

The authors contributed equally to the conception, data collection, and analysis, as well as the manuscript’s writing. All authors reviewed the final version of the manuscript.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This study was funded by Research Support Foundation of the State of Rio Grande do Sul (FAPERGS) through call number 09/2023 - Gaúcho Research Program (PqG).