The experiments carried out in vitro have showed that among many oils that have been investigated some of them retarded the growth of bacterium Erwinia carotovora subsp. atroseptica (peppermint, caravay and thyme oils at cocentrations 0.25 to 1.0%, thuja oil -at concentrations 2.0 and 4.0%, juniper oil -at concentrations 0.25 and 0.5%), and Pseudomonas lachrymans (peppermint, carovay and thyme oils at concentration 1.0%, thuja oil at concentrations 3.0 and 4.0%), and Pseudomonas phaseolicola (thuja oil at concentrations 3.0 and 4.0%, juniper oil at concentrations from 0.25 to 2.0%. The efficient effect on Pythium sp. and Fusarium sulphureum was noted after the usage of peppermint, carovay, and thyme oils. In greenhouse experiments peppermint and thym oils at concentrations 0.5 and 1.0% have showed efficient influence on the growth limitation of cucumber damping off. In the field experiments dressing of cucumber seeds with thuja oil emulsion at concentration 2.0% significantly decreased the growth of angular leaf spot of cucumber seedlings.