Efficacy of Herbicides in Controlling Capim-Capeta and Capim-Navalha and in the Selectivity of Capim-Colonião

• Grant number: 24/08437-3
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Effective date (Start): August 01, 2024
• Effective date (End): July 31, 2025
• Field of knowledge: Agronomical Sciences - Agronomy - Plant Health
• Principal Investigator: Pedro Luis da Costa Aguiar Alves
• Grantee: Andrey Batalhão de Oliveira
• Host Institution: Faculdade de Ciências Agrárias e Veterinárias (FCAV). Universidade Estadual Paulista (UNESP). Campus de Jaboticabal. Jaboticabal , SP, Brazil

Abstract

The presence of weeds in pastures can significantly compromise biomass productivity by competing for resources such as water, light, and nutrients, and also reduce the quality of the available forage for livestock. The use of chemical control through herbicide application is a common practice to mitigate this issue, providing a quick and efficient response in reducing infestations. However, the management of molecules is crucial to ensure control efficiency, avoid weed resistance, and minimize environmental impacts. Thus, with the potential ban on atrazine, a molecule proven effective for these crops, new molecules are being studied. Therefore, our objectives are to: 1) evaluate the efficacy of imazethapyr, clethodim, haloxyfop-p-methyl, hexazinone, and glyphosate in controlling Sporobolus indicus at two development stages; 2) assess the selectivity of metsulfuron, atrazine, and gapper alone and in combination in the crops of Panicum maximum and Urochloa brizantha, as well as the effectiveness in controlling Paspalum virgatum and Sporobolus indicus; and 3) verify whether florpyrauxifen-benzyl has the potential to replace atrazine for weed control while maintaining crop selectivity. The project will be conducted at the Weed Science Laboratory, located in the Department of Biology at the Faculty of Agricultural and Veterinary Sciences - UNESP, Jaboticabal Campus. To achieve the objectives, the efficacy of imazethapyr, clethodim, haloxyfop-p-methyl, hexazinone, and glyphosate will be evaluated in controlling Sporobolus indicus at two development stages: initial stage (2-3 leaves) and tillering stage (4-5 tillers), using a 5x6+T factorial system with a completely randomized design. The dosages for imazethapyr will be 4x, 6x, 8x, 10x, 12x, and 16x the recommended dose on the product label, while for the others, the dosages will be 0.25x, 0.5x, 1x, 2x, 4x, and 8x the recommended dose. In the second experiment, the effect of different doses and mixtures of metsulfuron and atrazine on the control of Sporobolus indicus and Paspalum virgatum, and the selectivity of Panicum maximum and Urochloa brizantha, will be evaluated, as well as the potential of florpyrauxifen-benzyl to replace atrazine for weed control. The experimental design will be completely randomized, with a 4x10 factorial system, including ten control and/or selectivity treatments (1 - metsulfuron at recommended dose; 2 - atrazine at recommended dose; 3 - gapper at recommended dose; 4 - 3.0 L atrazine + 13.3 g ha-1 metsulfuron; 5 - 3.0 L atrazine + 9.0 g ha-1 metsulfuron; 6 - 3.0 L atrazine + 6.6 g ha-1 metsulfuron; 7 - 0.3 L gapper + 13.3 g ha-1 metsulfuron; 8 - 0.3 L gapper + 9.0 g ha-1 metsulfuron; 9 - 0.3 L gapper + 6.6 g ha-1 metsulfuron; 10 - Control). Control percentage, phytotoxicity, and plant dry matter will be assessed at 7, 14, 21, 28, 35, and 42 days after application.