As a result of the conducted researches it is set that external signs of display of silvery favus in Ukraine as well as symptoms of diseases, are tipical for other geographical areas. However, the differences in terms of display of disease has been found out. N.D. Khrobrikh (1952), M.V. Bordukova (1957), A.L. Ambrosov and others (1980) specify that illness begins to show up already in the period of collection. It is marked by the Byelorussian researchers, that at once after collection of tuber of potato does not have signs of illness, and the presence of infection shows up only in a few days in the moist terms of storage as  a sooty blotch of blue mold. Our supervisions show that at the optimum terms of development of exciter (enhanceable humidity of soil 90-100%) of sign of display of silvery favus showed up already in the period of harvest. However mainly the first typical signs of silvery favus were observed only in 4-6 weeks if it is a breach of storage, and illness reached at maximal development at the end of storage  (April-May). In this period on-the-spot tubers of potato appeared  spots of grey or mouse-grey to the color with silvery brilliance, rounded, by a size 1-10 mm in a diameter. Often spots covered considerable part of surface of tuber, especially in its end. On-the-spot spots were well noticeable with a naked eye ultrafine dim black points are sclerotic of exciter which were in the staggered cages of hide of tuber for peripheries of spot.

Rotting under spots was not observed. On tubers, with the mionectic turgor of spot became protuberant in a center and pressed on edges, as a result of what acquired the type of rings. The surface of tubers shriveled thus. After our supervisions of sign of silvery favus especially characteristically showed up on tubers with a smooth light hide, at becoming green tubers and as a result of moistening their water.

It is set that on outside of healthy tubers after holding them in a moist chamber during 10-14 days blue mold exciter of silvery favus was formed.

In depositories black sooty blotch of blue mold usually appeared at the end of storage. A raid was concentrated, mainly, on the border of sick and healthy fabric. It is explained that in the center of spot there is dying off of cages of periderm and mushroom unable to form spore, that is why in the center of spot more light, and for peripheries – dark. A raid consisted of phial ides, that formed on a sclerotium a bunch for 2-5 sht.

For determination of specific belonging of exciter we studied the morphological features of macroconidium, mycelium although it is practically impossible to set specific belonging to mycelium. Therefore we used sizes and forms of macroconidium, amount of membranes, character of crookedness, form of overhead cage and others like that.

The mycelium of exciter of illness is widespread only in the cages of periderm. At first it light, then grows brown. In separate cages, usually, it is on the edges of spots. There are umber bulges which show by itself compression of hyphen of mushroom – sclerotium. Phialide lines, cylinder, darkly olive with partitions. Conidia of inversely- clavate with 2-8 partitions, narrowed on a top, brown, in bases with an umber or black scar, from above light.

The source of infection of silvery favus can be as sick seminal tubers so soil which contains an infection. But a tuberous infection however is basic in pathogenesis of silvery favus, as the use of infectious garden material results in the increase of losses of harvest, than landing of healthy tubers is in the infected soil.

The infection of daughter's tubers of potato takes place in soil, beginning from the moment of potato formation and to the harvest, and, foremost, from a maternal tuber which young tubers are close located round.

It is known that the damage of integrity of periderm of tuber is instrumental in latent penetration of pathogens of other origin. In this connection, we are conduct research in relation to the study of influence of primary infection of Helminthosporium solani on a defeat a bacterium Pectobacterium carotovorumi by the mushroom of Fusarium oxysporum.

It is set that the defeat of tubers substantially strengthened their receptivity silvery favus to mushroom and bacterial illnesses. The analysis of the got results are the higher degree of defeat of tubers silvery favus, the greater amount and top mark of defeat their exciters of fusarium dry and bacterial soft rot.

Key words: exciters, culture, illnesses, potatoes, sort, harmfulness, terms of development.