Phytotoxic effects of Hesperozygis ringens (Benth.) Epling (Lamiaceae) essential oil on Amaranthus viridis L. (Amaranthaceae)

Synthetic herbicides have been causing damage to health and the environment, and this has driven studies on more sustainable alternatives. The present study evaluated the phytotoxic potential of Hesperozygis ringens essential oil (EO) on Amaranthus viridis , an infesting plant. The following concentrations of the EO (emulsified in Tween® 80) were tested: 1%, 3%, and 6% as well as three controls (water; water + Tween® 80; herbicide EnlistDuo® Colex-D). The experiments, conducted in a greenhouse and in the field, evaluated germinative parameters (percentage, average time, germination speed, and percentage of seedling formation), physiological parameters (chlorophyll content, photosynthetic capacity, electrolyte leakage), and anatomical changes. The EC₅₀ of EO on A. viridis was determined. The data were submitted to ANOVA and either LSD-Fisher test (p < 0,05) or Kruskal-Wallis test for non-parametric data. Results revealed a dose-dependent effect, and the concentrations of 3% and 6% were the most effective, with reduced germination percentage, time, and speed, reduced chlorophyll contents and photosynthetic capacity, increased electrolyte leakage, leaf necrosis, and severe anatomical damages. In the field, 6% of EO caused severe necrosis and total wilting in a shorter period than the herbicide. EC₅₀ showed higher sensitivity to the EO in the germinative phase (EC₅₀=2.11–3.09%) compared to already established plants (EC₅₀=2.57–5.52%). H. ringens EO showed significant phytotoxic potential against A. viridis , both in the greenhouse and under field conditions, comprising a sustainable and promising alternative for the management of infesting plants, in line with the principles of sustainable agriculture.