Effect of water stress on the efficiency of herbicides in controlling pasture weeds

• Grant number: 25/13402-7
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: September 01, 2025
• End date: August 31, 2026
• 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

Chemical control of weedy grasses in pastures, such as Sporobolus indicus (SI) and Paspalum virgatum (PV), is hindered by their morphological similarity to forage grasses and the scarcity of selective herbicides. Water stress, especially water deficiency, compromises herbicide efficacy by altering plant structures and reducing absorption, which justifies the development of this study. The main objective of this project is to evaluate the effects of water deficiency on the efficacy of the herbicides hexazinone and haloxyfop-methyl in the control of SI and PV, as well as to investigate the morphological and anatomical changes resulting from this interaction. The experiments will be conducted at the Weed Science Laboratory of UNESP - FCAV, in Jaboticabal (SP), using a randomized block design with five replications. Each experiment will correspond to one weed species (SI and PV), which will be subjected to the application of the herbicides hexazinone, haloxyfop-methyl, and an untreated control, followed by five water deficiency periods: 0, 3, 6, 9, and 12 days without irrigation after application. The applications will be carried out in the post-emergence stage, with visual evaluations of weed control at 7, 14, 21, 28, 35, and 42 days after application. At the end of the experimental period, the dry mass of the aerial parts and roots of the remaining plants will be determined. For treatments showing regrowth, anatomical analyses of leaf and root tissues will be conducted through transverse and paradermal sections observed under light microscopy. Data will be subjected to normality and homogeneity tests, followed by analysis of variance and, when applicable, fitted using regression models. It is expected that the results will help to understand the influence of water stress on herbicide efficacy in invasive grasses, contributing to more effective chemical management strategies in pastures.