The improvement of pre-plant treatment is possible on the basis of hot and cold mist of biopreparations. The device to treat seed tubers consists of a box made of thin metal or plywood on a loader conveyor with a rubber shutter to ensure the tightness of the treating area. Mist treatment occurs when the oncoming movement of tubers, ensuring fine droplets. Hot mist of biopreparations promotes heating of the surfaces of tubers by 1-2° C, accelerating physiological processes in them. The analysis of plant development has established that the best result is achieved by treating potato seed tubers of “Lily” variety with hot mist of biopreparations, and the highest efficiency is obtained from biopreparation Potassium humate. The value of the vegetative activity index in plants treated with hot mist of Potassium humate is 18 % higher in comparison with plants in the control plot not treated with biopreparations. The height of the stems of potato plants is 7.3 % higher in those treated with hot mist of Potassium humate than those treated with cold mist of the same preparation. In comparison with plants in the control plot, it is 75.1 % more. The number of leaves on potato bushes when treated with hot mist of Potassium humate is 13.1 % higher in comparison with those treated with cold mist of the same preparation and by 18.9 % in comparison with the values in the control plot. Studies have shown that the treatment with the mist of biopreparations helps to accelerate the development of plants, and treating with hot mist increases the physiological activity of tubers.