Avena fatua Apera spica-venti Bromus secalinus % calamus chamomile cumin thyme sage mint lavender lemon balm tansy Amaranthus retroflexus Centaurea cyanus Chenopodium album % 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). RESULTS 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 • 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.