Seed treatment is the main method of protecting plants from infectious diseases. The article presents data on the production of a double compound based on methylene diurea and paraaminobenzoic acid and the study of its physicochemical characteristics. The chemical interaction in the three-component water-salt system methylenediurea (MDU) – para-aminobenzoic acid (PABA) – water was studied using the isothermal method of physicochemical analysis. The crystallization region of the new binary compound, the active substance, was established at a molar ratio MDU: PABA = 1:2. The formation of the double compound is confirmed by X-ray phase and IR spectroscopic methods of analysis. From the obtained X-ray phase analysis data, it follows that the reference lines of the double compound and their intensity differ from the X-ray patterns of the initial components. The IR spectra of MDM and PABA are characterized by intense absorption in the region of 3500-3390 cm-1 , 2000-500 cm-1 and 3500-3345 cm-1 , 1800-500 cm-1 , respectively. In the IR spectra of the new double compound MDM•2PABA, the absorption intensity in the region of 1800-500 cm-1 increases. A decrease in the absorption region of the stretching vibration of CO groups from 1626, 1626.3 cm-1 to 1612 cm-1 is observed in the case of the double compound MDM•2PABA. The results of the studies indicate the formation of a new compound. It is shown that the double compound has low hygroscopicity under summer, autumn, spring and winter storage conditions, high swelling and moisture capacity, and low solubility.