Stem and root rot symptoms were noticed in two greenhouse farms on tomatoes planted in the 3rd decade of June, 2013. Diseased plants exposed suppressed growth and top wilting due to drastic decrease of water and poor transport of mineral salt. From diseased stem and root parts Phytophthora nicotianae var. nicotianae was isolated. The same species was also detected in cubs and stonewool mats. In laboratory experiments isolates of P. nicotianae var. nicotianae caused rotting of stem parts, leaf petioles, leaf blades and fruits regardless of tested cultivar. Necrosis spread even more than 8 mm per 24 hrs. Colonisation of tomato stem parts was observed at temperature range from 10 to 32.5°C as the optimum. In the greenhouse trials P. nicotianae var. nicotianae added to peat with infested stonewool caused wilting of 3-week-old tomato cultivar Admiro seedlings already after 3-day-growth and 5 days later most of plants wilted and died. The pathogen colonized stem base of seedlings on the length up to 30 mm.
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