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Spraing - Mop Top

Potato Mop Top Virus (PMTV)




Potatoes and certain weed species such as black nightshade


Brown arcs in the tuber flesh and raised rings on the tuber surface, but no foliage symptoms in the year of infection. Plants grown from infected seed have stunted stems (mop top), plus yellow spots and 'V' shaped markings on the leaves.


The virus is carried by spores of the powdery scab fungus (Spongospora subterranea) which may be introduced with the seed tuber or survive in the soil from previous crops. In the soil it can survive inside the fungal spore for over 15 years.

Favourable Factors

Cool, damp soils in June/July. Foliage symptoms are particularly apparent in cold springs.


30-50% of plants from infected tubers exhibit foliage symptoms, but the disease is generally of little economic importance in the UK.


Identification and Management of potato diseases

Find out more information on the key disease threats to your potato crop. For each disease you will find out the importance of the disease in terms of potential yield penalty, how to identify the disease in its early stages and our advice on the best control strategies.

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