Belfast Telegraph

Friday 28 November 2014

After 50 years, potato fields are finally free of destructive fungus

Unhealthy: potato wart fungus can lie dormant for decades
Unhealthy: potato wart fungus can lie dormant for decades

More than 700 fields across Northern Ireland have faced strict potato growing restrictions for the last 50 years — until now.

All of the 750 fields were once contaminated by Potato Wart Disease, which swept parts of Ireland in the early 20th century.

There hasn't been a case in Northern Ireland since 1959, but the fungus is so virulent that outbreaks can stay viable in the soil for more than 30 years. Therefore the fields had to be kept clear of seed potatoes, which are grown to start new potato plants.

If two or three fields in a townland were found to have the disease, the rest of the townland had to undergo the same restrictions. Exclusion from potato production was the only means to control the spread of the fungus.

All the affected fields at that time were blacklisted as contaminated and no seed potatoes could be planted. The scheduling of affected fields and surrounding townlands designated as safety zones resulted in 691 townlands being placed under restrictions with respect to potato plantings — some 70,000 hectares.

Now the restrictions are to be lifted after an announcement by Agriculture Minister Michelle O’Neill. She said: “This announcement will benefit the local potato production industry through the removal of restrictions on potato production on nearly 700 townlands.

“The availability of clean land, free of fungal disease such as Potato Wart Disease will enable producers to grow varieties in demand for home ware trade and expand the availability of land for seed export production.”

The move comes after 10 years of systematic sampling and testing of all land identified as having an outbreak of Potato Wart Disease.

From 2000 to 2011, inspectors from the Department of Agriculture and Rural Development (DARD) implemented the ambitious plan. It involved extensive soil sampling and the planting of tubers under the guidance of Plant Pathologists from the Agri-Food and Biosciences Institute (AFBI).

No viable wart has been found in any of the 750 local fields from more than 600 local townlands under test. Land that was previously infected is now disease-free.

More than 250 tonnes of soil were sampled and tested as part of the 10-year programme.

“Not all injurious plant health pests and diseases are spreading as a result of trade and climate change — some are being controlled very effectively by official measures such as the Department’s Potato Wart Disease de-scheduling programme,” the minister said.

“I welcome the fact that the north of Ireland is alone internationally in achieving de-scheduling of the entire territory through this method.”

The restrictions have meant that non-resistant varieties of potato were off limits, including traditional British Queens, Sharp’s Express and King Edwards. Newer non-resistant varieties such as Hunter and Galactica also couldn't be planted, according to Rodney Martin of the Department’s Agri-Food Inspection Branch.

“About a quarter of the varieties on the UK list would be susceptible to wart disease,” he said.

There were major outbreaks in a swathe of land from Draperstown in south Derry to Toomebridge in Antrim.

Another major outbreak zone took in the Mournes, Newry, Newcastle, Downpatrick and the southern Ards peninsula, with smaller zones around Ballycastle, the Glens and Dungannon.

“Northern Ireland is now clear,” Mr Martin said.

Factfile

Signs of wart disease appear only on the underground parts and the disease is often not noticed until the tubers are lifted from the ground.

On infected potatoes, the eyes develop into characteristic warty, cauliflower-like swellings. When formed underground, they are the same colour as the potato skin, but gradually darken with age. When infected early, tubers can become so distorted and spongy that they are almost unrecognisable.

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