Screening of Mediterranean wild plant species for allelopathic activity and their use as bio-herbicides

Seventeen wild plant species from the Mediterranean area (Calabria, Southern Italy) were assayed for their allelopathic activity and as potential source of new natural herbicides for weed control. The inhibitory effects of aqueous extracts of 17 Mediterranean plant spp. were studied on seed germination and root elongation of Lactuca sativa L. of these 4-species [Calamintha nepeta (L.) Savi, Hypericum hircinum L. ssp. Majus (Aiton) Robson, Artemisia arborescens L. and Euphorbia rigida Bieb] proved most inhibitory to weeds and lettuce seedlings. Root elongation proved more sensitive than seed germination. The phytotoxicity of aqueous extracts of most phytotoxic plant species persisted till 112 days. The aqueous extracts inhibited the seed germination and root growth of Chenopodium album, Sinapis alba, Echinochloa crus-galli weeds. C. album and S. alba weeds were most sensitive to all aqueous extracts, while E. crus-galli was most tolerant. In pot experiments, plant residues caused stronger inhibition in shoot than in roots. The phytotoxicity followed the order: A. arborescens > E. rigida > C. nepeta ≈ H. hircinum. These results might help in developing the natural Mediterranean plant extracts for weeds control.