For the first time, potato wart disease has been discovered in potatoes grown on Prince Edward Island, Canada.
Only a handful of tubers have been discovered with the disease but the finding has greatly upset the Island potato industry.
An investigation is now under way to find the source of the problem. The site, reportedly in the field of a large grower, has been put under quarantine.
A fungus, Synchytrium endobioiticum, it can survive in the soil for years. Tubers are infected at the "eyes" by motile, haploid, uniciliated zoospores produced by the sporangia. The invaded tissue is stimulated to active division, giving rise to the characteristic warts.
The disease was discovered in South America and was transported on potatoes to Europe in the late 1700s.