Currently, nanotechnology has extensive applications in the field of medicine and agriculture, food industry, and many other areas. According to research, the activity of many metal ions and nanoparticles is similar to that of fungicides. The aim of the research presented in this paper was to determine the effect of selected plant conditioners against fungal pathogens of herbs and orchard plants, which can also affect human health. Fertilisers containing nanoparticles of silver and copper as well as ions of boron and zinc (in combination): Viflo Cal S Viflo, Viflo Chitosol Silver, Viflo Miedź-Bor, and Cynk Viflo Zn, and isolates K 425 of Colletotrichum dematium and K 651 of Phomopsis diachenii were taken for the study. The percent of fungal colony growth inhibition on PDA medium containing metal nanoparticles and ions in three different concentrations was adopted as the criterion of evaluation of the fertilisers. The in vitro experiment showed that the effect of the studied conditioners on the colony growth and sporulation of P. diachenii and C. dematium varied. Only Viflo Cal S at the highest studied concentration of 1 g·cm-3 completely inhibited the mycelial growth of P. diachenii and caused fungus cell death. None of the tested preparations had fungicidal activity against C. dematium. Cynk Viflo Zn and Viflo Miedź-Bor, regardless of the concentration, as well as Viflo Chitosol Silver at the concentrations of 0.125 g·cm-3 and 0.05 g·cm-3 stimulated the growth of C. dematium.