Residue Estimation of Selected Herbicides for Weed Control in Greek Oregano Cultivation

Greek oregano (Origanum vulgare ssp. hirtum) is an important aromatic and medicinal crop grown in Greece, often on marginal lands. Effective weed management is essential for sustainable production, but the use of herbicides raises concerns about potential pesticide residues. Therefore, this study was conducted to evaluate the residue levels of metribuzin + pendimethalin applied and incorporated pre-planting, as well metribuzin + cycloxydim and glyphosate applied post-emergence in oregano crop grown over a three-year period in the Agrinio location in Greece. Herbicide residue analysis in the edible part of the oregano plants was performed using two validated protocols, i.e., QuEChERS and QuPPe coupled with LC-MS/MS. The analytical methods demonstrated high sensitivity, with limits of quantification (LOQ) at 0.01 mg/kg and recovery rates ranging from 71% to 102%. These results indicated that the application of the above herbicides in oregano crop grown under Greek field conditions resulted in no detectable residues above the established LOQs, strongly supporting the potential safe use of these herbicides in oregano crop and their possible use for regulatory assessments and consumer safety assurance.