Toxicity of aqueous extracts of Ilex paraguariensis A.St.-Hil. about Euphorbia heterophylla L.

Abstract

BACKGROUND: The escalating challenge of herbicide-resistant weeds, exemplified by Euphorbia heterophylla L. (wild poinsettia), threatens agricultural sustainability in Brazil. Overreliance on synthetic herbicides has led to environmental degradation and increased production costs, necessitating eco-friendly alternatives. RESULTS: This study explores the phytotoxic potential of aqueous extracts (decoction and infusion) from Ilex paraguariensis A.St.-Hil. (yerba mate) as a bioherbicide against E. heterophylla. High-performance liquid chromatography (HPLC) identified nine major compounds in aqueous extracts (decoction and infusion), with caffeine and neochlorogenic acid being the most abundant. In vitro assays demonstrated that both decoction and infusion extracts at concentrations 4% and 6% completely inhibited seed germination and seedling formation of E. heterophylla, with lower concentrations (2%) significantly reducing germination speed and increasing mean germination time. Glasshouse experiments revealed mild to moderate leaf damage (scales 2–3) from 4% extracts, without affecting height or true leaf emergence. Field trials indicated temporal stability in development, with extracts promoting slight biomass increases (root/shoot ratio) and modulating antioxidants and pigments (chlorophyll A, cholorphyll B, carotenoids), showing positive correlations with growth traits and less severity than glyphosate. CONCLUSION: Aqueous extracts of I. paraguariensis exhibit strong allelopathic potential against E. heterophylla, particularly during germination, offering a biodegradable bioherbicide option for integrated pest management. While less toxic to mature plants, their selectivity and scalability warrant further field optimization to enhance sustainable agriculture, reducing environmental impacts and herbicide resistance. © 2026 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.