Аннотация:The infestation of the rhizosphere by pathogenic microorganisms is a widespread soil-ecological problem, leading to large losses of yield of tubers and root crops and reduced survival of seedlings of trees and shrubs. Suppression of these microorganisms in the rhizosphere is possible on the basis of special gel compozitions with modern plant-protecting agents (PPA), among which the most promising agents of plant protection with silver. Laboratory testing of the effectiveness of gel- silver compozitions carried out on pure cultures of pathogens late blight and black leg of potato. The study revealed the exponential dependence of a dose of the inhibitor and linear (by diameter) and nonlinear (by area) specific growth rates of microorganisms colonies. It allows to determine the values of the effective concentration of the CPP, in which there is a two-fold slowdown in the growth of the colony, varying in the case of the gels with colloidal silver in the range of 1–86 ppm on the active substance for both pathogens. For gel CPP based on ionic silver fungicidal effect was significantly (3–30 times) lower compared to colloidal forms, and for the pathogen of black leg of potato bactericidal properties of the ions and nanoparticles of silver were similar.