Essential oils as bioherbicides: effects of orange and citronella oils on weed germination and early growth

BACKGROUND Increasing selection of herbicide‐resistant weed biotypes has intensified the search for alternatives to the intensive use of synthetic herbicides. Among these alternatives, essential oils (EO) have attracted attention because of their allelopathic potential and low environmental impact. This study evaluated the effects of different doses of EOs extracted from orange ( Citrus sinensis ) by hydrodistillation and steam distillation, and from citronella ( Cymbopogon nardus and C . winterianus ), on the germination and early development of Eleusine indica , Digitaria insularis , Euphorbia heterophylla , and Amaranthus hybridus . RESULTS The EOs analyzed were characterized primarily by oxygenated monoterpenes and terpene hydrocarbons, notably citronellol, citronellal, geraniol and limonene. Citronella EOs caused strong inhibition of germination and vigor, resulting in near‐total seedling suppression from 10 mL L −1 onward. By contrast, orange EOs exhibited moderate effects, with partial and dose‐dependent reductions in germination and early growth, and the weed species differed in their susceptibility to the EOs. CONCLUSIONS The combined results indicate that citronella EOs exhibit high bioactivity and stand out as promising candidates for bioherbicide development, whereas orange EOs show a less intense but relevant allelopathic effect, supporting their potential use as complementary tools in sustainable weed management strategies.