Goal. To establish the effect of a multicomponent preparation of biologic origin on seed potato productivity and viral diseases infestation in condition of southwestern Forest Steppe of Ukraine.
 Methods. Field method — the trial plots were set in selection-seed production rotation of Bukovinian state agricultural research station of Carpathian region Institute of agriculture NAAS. Laboratory-field method — determining crop capacity and tubers structure in a yield. Visual method — plants infestation assessment. Comparative-calculated method — to determine the potato stands productivity and viral diseases infestation degree.
 Results. Avatar-2 Zahyst is a system-contact preparation of virulicidal, fungicidal, and antibacterial action. It is recommended for use on grain, technical, vegetable-, and fruit crops. The preparation is used for pre-sowing seed treatment, as well as for vegetating plants treatment. When determining the seed potato productivity depending on the biopreparation Avatar-2 Zahyst implementation, no significant difference in tubers yield was established; on the variety Slauta it stayed within 34.5—36.3 t/ hа, and on the variety Kimmeria 36.7—37.4 t/ hа. No any significant difference was established also in quantity and tubers mass per one bush, as well as in one tuber average mass, and tubers fractional composition in a harvest. When determining plants infestation with viral diseases, it was established, that the biopreparation Avatar 2 Zahyst application has influenced the decrease of seed potato stands infestation. The variety Slauta damage on the variant with seed poisoning and three-times spraying during vegetation made 2.5%, which is by 2—3% lower than on the control variant. The infestation of plants where only seed poisoning was implemented made 3—4%, when of those where three-times preparation application was carried out during vegetation — 2.0—4.0%, which is by 0.5—2.5 and 1.5—2.5% lower than the control variant, respectively. The same tendency was observed during the variety Kimmeria investigation.
 Conclusions. The use of the biological product Avatar-2 Zahyst does not give a significant difference in the yield of tubers. The introduction of the biological product Avatar 2 Zahyst influenced the reduction of the incidence of viral diseases in potato seed plantations.