Bioherbicidal effects of some plant essential oils on different weed species

The inhibitory effects of plant essential oils on seed germination and on seedling growth of weeds were investigated in petri dish experiments. Essential oils were extracted from leaves and flowers of five different plant species (Artemisia vulgaris L., Mentha spicata L. subsp. spicata, Ocimum basilicum L., Salvia officinalis L., Thymbra spicata L. subsp. spicata) collected from Tokat region of Turkey. Bioherbicidal activities of essential oils were assayed in four concentrations (2, 5, 10 and 20 mu l) against eight weed species from different families (Agrostemma githago L., Amaranthus retroflexus L., Cardaria draba (L.) Desv., Chenopodium album L., Echinochloa crus-galli (L.) P.B., Reseda lutea L., Rumex crispus L., Trifolium pratense L.). All essential oils used in the experiments were highly phytotoxic on seed germination and seedling growth of the tested weeds. With increasing essential oil concentration the inhibitory effects on seed germinations and seedling growth increased. In 10 and 20 [mu l/petri dish concentrations, except for essential oil treatments of A. vulgaris and S. officinalis on R. crispus, the germination of seeds was totally inhibited. T spicata essential oil possessed the highest inhibitory effect on seed germination, whereas S. officinalis essential oil had the least inhibitory effect in 2 and 5 mu l/petri dish concentrations. In S. officinalis essential oil treatments, seedlings were shortened and thickened compared to other treatments. Similar symptoms were observed for A. vulgaris essential oil treatments on certain weed species. Inhibitory effects of essential oils also showed differences according to the weed species. A. retroflexus, E. cruss-galli and R. lutea were more susceptible, and R. crispus was more resistant to the essential oils than the other weed species used in this study.