Symptoms and Control Methods of Potato Viral Diseases

(1) Pathogens and Infection. The pathogenic viruses that can infect potatoes and cause losses include Potato virus X, Potato virus Y and several others. Potato mosaic virus (PVX) is a filamentous virus with a length of 520-550 nm; sometimes the central hole of the virus particle can be seen under the electron microscope. When the viral coat is formed by subunits, its cross-striations can be seen, and this is the main difference in morphological structure between it and Potato virus Y. Potato virus Y (PVY) is a filamentous virus with a length of 680-900 nm; under the electron microscope, its central hole and the cross-striations of the coat protein subunits cannot be found. It is somewhat thinner and longer than PVX. In addition, Potato virus S, Potato virus M, Potato yellow dwarf virus, and Potato spindle tuber viroid among the viroids have also been discovered. As for the routes by which potato virus infection causes potato viral diseases, the main one is sap transmission. The main vector of sap transmission is the aphid. Aphids have a probing feeding habit, that is, when an aphid contacts a plant (mainly young leaves), it first spits saliva at the landing site, pauses for a while, and then at the site with saliva sucks back the pierced-and-sucked sap together with the saliva, and only finally determines whether to continue feeding. It is precisely because of this habit that the virus, suspended in the sap, is spread by relying on the aphid as the main vector. Therefore, ordinary pesticides that kill aphids cannot solve the problem of aphid-borne viruses. By the time the aphids are killed, the virus has long since been transmitted. After PVX is transmitted through sap, the symptom it causes on potato plants is mild mosaic; after PVY is transmitted through sap, the symptom it causes on potato plants is severe mosaic; repeated infection by PVX and PVY produces obvious severe mosaic and spotted wilt on potatoes, and the impact on yield and quality then becomes serious. In actual production, it is often a composite infection, and therefore the consequences are serious. Large patches of potato necrotic spots are commonly seen. Even the harvested tubers show flesh browning.