Virus Diseases - PVX (Mild mosaic), PVY (Severe mosaic), PLRV (potato leaf roll virus),

Symptoms   Symptoms produced vary significantly with the variety grown, strain of virus and the time of infection, from mild mosaics or mottles to stunted plants with leaf drop streak.  In some cases tubers may be deformed, or show internal blemishes.

 Sources and Factors Favouring Development

PVY, PVX and PLRV can all be spread through planting infected seed tubers.  PVY and PLRV can be introduced to, or spread within crops by aphid vectors, whereas PVX spreads by contact from plant to plant by machinery.

Control          The use of certified seed from areas where aphid populations are low is the principle means of controlling PLRV and PVY viruses.  Approved insecticides for the control of aphid vectors must be strategically applied through out the growing season to minimise the development of resistant strains of aphid. ELISA testing seed can also provide a useful means of identifying stocks that have high levels of virus.