A product for reinforcing the natural plant defense system a mixture of one or several silicon-rich substances (A), one or more activators of plant immune system (B) and substance (C) which supply to (A) and (B) activity. Activators are substances or physical effects and substances, which transport the information about stress and provide the synthesis of non specific and/or specific stress-proteins, stress ferments and other stress-protecting substances to the plant cells. Using various forms of Si-rich substances will help plants to synthesize non-specific, specific substances and ferments which protect plants against stress. The substance (C) could serve for optimization of plant growth or for reinforcing Si or the activator component and they can be added to the new product also. The application of all these ingredients can be conducted via soil application (both broadcasting and incorporation) together with the irrigation water, by foliar applications or as dust application. The application of all the ingredients can occur together or separately at intervals, which can't be longer then 6 months.