ESSENTIAL OILS IN THE CONTROL OF WEEDS: the search for alternative methods to chemicals

• Grant number: 24/13350-4
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: December 01, 2024
• End date: November 30, 2025
• Field of knowledge: Agronomical Sciences - Agronomy - Crop Science
• Principal Investigator: Patrícia Andrea Monquero
• Grantee: Geovana Rocha Marzochi
• Host Institution: Centro de Ciências Agrárias (CCA). Universidade Federal de São Carlos (UFSCAR). Araras , SP, Brazil

Abstract

Currently, there is growing concern about finding alternative methods to chemical products for pest control. In the context of weeds, this becomes especially important due to the increase in cases of herbicide-resistant biotypes in Brazil. The aim of this study is to evaluate the inhibitory potential of essential oils (EOs) on the germination and development of weeds. The experiments will be conducted in the laboratory, using EOs of pear orange (Citrus sinensis) obtained by different extraction methods, as well as citronella oil (Cymbopogon nardus) from Ceylon and (Cymbopogon winterianus) from Java. The weed species selected include both monocotyledons, such as crowfoot grass (Eleusine indica) and bitter grass (Digitaria insularis), and eudicotyledons, such as milkweed (Euphorbia heterophylla) and caruru (Amaranthus hybridus). The experiments will be organized in a completely randomized design, with four replicates per treatment, following a 4x5 factorial scheme. Four EOs will be tested (two from Pêra orange and two from citronella) at five different concentrations (0, 10, 25, 40 and 60 ml L-1) for each weed species. Three approaches will be used: in the first, the seeds will be placed in Petri dishes with filter paper soaked in different concentrations of the EOs, to assess the germination percentage, the germination speed index and the length of the radicle. In the second, the weed seeds will be pre-germinated in sterilized boxes, and when they emit the radicle, they will be exposed to the different concentrations of the EOs, and the development (radicle and aerial part) will be evaluated at 7 DAA after treatment, and osmotic control will also be carried out using polyethylene glycol 6000 (PEG 6000). In a third experiment, the effect of the Pêra orange and citronella EOs on post-emergence weeds will be evaluated and, for this purpose, when the seedlings have at least two to three true leaves, the concentrations (0, 10, 25, 40, 60 ml L-1) of the EOs will be applied with a mini-spray. Visual phytointoxication will be assessed at 4, 8 and 12 DAA, using scores ranging from 0 (no symptoms) to 100% (plant death). After 12 DAA, the seedlings will be removed and their length, root area and biomass will be quantified.