The experiment assess the effectiveness of two mineral oils: Sunspray 850 EC (85% mineral oil) and Sunspray Ultra-Fine (98.8% mineral oil) on tulip ‘Leen van der Mark’ fields. Tulip plants were sprayed once a week for three weeks. Mineral oils were applied at concentrations of 1.0, 1.5, and 2.0%. The oil preparations did not negatively affect the length of flower shoot and tepals of tulips grown in field. No phytotoxic symptoms were observed on leaves, however their color was altered. In all combinations protected using oils, the number of plants with virus symptoms on petals was lower than for control. No decrease in the commercial and the first choice bulb yields due to the mineral oils application were recorded. Mineral oils applied at concentration up to 2.0% had no negative contribution on the quality of produced tulip flowers. Despite of the selection made in the field, from 60 to 73% plants showed virus symptoms in control combination during plant forcing. Efficiency of oils in reducing the spread of viruses depended on the year of study and oil type. The best effects were achieved using Sunspray 850 EC at 1.5% concentration (26% virus-infected plants). The oil preparations, despite of high efficiency in reducing the virus spread, did not guarantee a full protection in the field in any year of study.

139-148