PHYTOTOXIC EFFECT OF ESSENTIAL OILS FROM TEMPERATE CLIMATE HERBS AGAINST SELECTED WEED SPECIES Stokłosa A., Kulig E., Puła J. H. Kołłątaj University of Agriculture, Kraków, Poland INTRODUCTION Interest in the ecological methods of weed management is increasing. Among them an important role play chemicals extracted from plants of known or observed allelopathic potential. Essential oils, composed of various groups of chemicals, are the crucial component of medicinal plants. They show mostly antibacterial and antifungal properties, and recently also their insecticidal and phytotoxic potential has been shown i.e. clove oil or lavender oil (Stokłosa et al. 2012). Our study aimed at assessing the phytotoxic potential of essential oils extracted from herbal species, cultivated and wild ones, from a temperate climate against germination of weeds. MATERIAL AND METHODS Herbal plants were collected from South-Eastern Poland. Essential oils were extracted using Clavenger apparatus. There were 9 essential oils tested: mint, lavender, cumin, lemon balm, thyme, sage, chamomile, calamus and tansy. In a Petri dish bioassay their phytotoxic potential was tested against six common weeds: Avena fatua, Apera spica-venti, Bromus secalinus, Amaranthus retroflexus, Chenopodium album and Centaurea cyanus. There were 5 doses of oil used and control (distilled water with 5% acetone): 0.2; 0.6; 1.2; 2.4; 7.2 g/L. After 6 days of growth the percentage of germinated seeds, their root and coleoptile length were measured. The experiment was repeated twice. The chemical composition of essential oils was assessed using GC/MS method. The statistical analysis was carried out using a non-linear regression (Ritz and Streibig, 2005). % Avena fatua Apera spica-venti Bromus secalinus Amaranthus retroflexus Chenopodium album Centaurea cyanus mint lavender cumin lemon balm thyme sage chamomile calamus tansy RESULTS ESSENTIAL OIL (%) MAIN CONSTITUENTS % Cumin (2.15) limonene 34.8 carvone 63.2 Lavender (2.85) linalool 36.8 α-terpineol 5.6 linalyl acetate 36.0 lavandulyl acetate 1.6 Lemon balm (0.13) citronellal 2.3 neral 28.2 geranial 40.2 Mint (2.55) menthone isomenthone 6.7 menthol 24.0 piperitone 1.5 menthyl acetate 7.7 piperitenone oxide 9.6 Chamomille (0.5) (E)-β-farnesene 32.9 α-bisabolol oxide B 15.5 bisabolone oxide A 11.1 chamazulene 3.7 α-bisabolol oxide A 7.3 Sage (1.64) 1,8-cineole 10.3 α-thujone 27.6 β-thujone 12.8 camphor viridiflorol 3.3 Caraway (2.1) α-selinene 4.0 shyobunone (isomer) 5.7 δ-cadinene 4.2 (Z)-asarone 3.4 zierone 3.1 acorenone 5.5 Thyme (2.35) p-cymene 7.2 γ-terpinene 4.5 thymol 72.9 carvacrol Tansy (1.55) sabinene 1.3 artemisia ketone 3.9 6.3 46.8 umbellulone 11.2 Table 1. Seedlings mean shoot (above) and root (below) length after 6 days of germination in the presence of the highest and the lowest dose of essential oil Weed species Control Mint lavender Cumin Lemon balm Thyme Sage Chamomile Caraway Tansy 0.2 7.2 Apera spica-venti 16.2 10.8 0.3 8.5 6.7 2.6 4.9 5.0 Avena fatua 61.7 37.6 9.5 31.6 4.7 62.0 3.6 40.8 27.9 8.3 15.5 4.3 41.5 Bromus secalinus 23.9 2.5 14.6 4.8 10.0 5.6 3.0 5.8 4.0 11.5 0.9 Amaranthus retroflexus 27.7 16.4 3.5 3.7 2.3 5.9 7.8 Chenopodium album 29.0 3.8 21.7 15.1 15.8 5.2 7.6 8.7 19.4 Centaurea cyanus 38.7 9.0 12.8 13.8 5.4 6.5 4.6 1.1 CONCLUSIONS: Essential oils substantially inhibited the germination and development of weed seedlings. The most inhibiting effect displayed cumin and thyme oils. The effect of oil depended on weed species, type of oil and its dose. Wild oat (Avena fatua L.) was least susceptible to the most of oils except cumin and thyme oils. Weed species Control Mint Lavender Cumin Lemon balm Thyme Sage Chamomile Caraway Tansy 0.2 7.2 0. Apera spica-venti 16.2 8.6 8.4 5.4 2.9 6.6 3.2 Avena fatua 52.9 31.0 3.4 34.7 7.3 57.8 4.4 37.7 33.5 4.7 30.9 2.5 41.4 Bromus secalinus 44.8 2.6 21.3 11.3 15.3 3.7 3.0 11.7 4.9 18.6 0.8 13.4 Amaranthus retroflexus 7.9 22.9 7.5 4.0 10.9 16.8 10.74 Chenopodium album 28.1 16.0 15.1 6.3 1.5 8.5 12.6 14.7 Centaurea cyanus 39.9 16.5 19.4 14.2 7.7 13.2 5.8 6.1 0.6