It was investigated, that mixed infection of buckwheat distributed in various ecological regions of Ukraine, the pathogens that belong to different taxonomic groups have different and peculiar morphological and structural properties. First was shown that buckwheat is affected by buckwheat burn virus (BBV) together with Mycoplasma. Mixed infection leads to proliferation of sepals, clarification of the flowers petals, reduction and greening of petals, hypoplasia or hypodevelopment of stamens and pistils: all of this can lead to partial or complete sterility.