EN
The aim of two year field investigations was to evaluate the effect of seed-potato dressing and plants spraying treatments with biotechnical preparations (Biosept 33 SL – a.s. extract of grapefruit, Biochikol 020 PC – a.s. chitosan) on infection of potato tubers by Rhizoctonia solani and Helminthosporium solani. As a standard fungicide Vitavax 2000 FS (a.s. karboxin and thiuram) was used. During the vegetation period applied biotechnical preparations lowered both the deegre of tuber infection and percentage share of infected tubers by R. solani and H. solani.