A really nasty seed-borne bacterial blackleg disease, Dickeya solani is causing concern to potato farmers.

First identified in Holland in 2005, Dickeya solani is an aggressive form of another type of blackleg disease, Dickeya dianthicola that has established itself in several countries in Europe, including Spain, France and Belgium, as well as in Finland and Poland. It has also spread to the United Kingdom (specifically England and Wales) and other parts of the world.

Prior to this, as early as 1970, the less aggressive form of blackleg, Dickeya dianthicola had been reported in Holland and was already causing concern.

A Threat to Farmers

Dickeya solani causes tubers to rot and the growing plants to wilt, which is exactly what the traditional blackleg diseases do. But the damage this one causes is much worse, and it happens in a far wider range of conditions, with less bacteria present.

Farmers worldwide are warned to use only high quality seed crops since the original scourge is said to have been largely the result of the downgrading of seed crops and exportation of affected seed.

Scotland has taken a particularly hard line since the disease has never been found in potatoes of Scottish origin.

What Researchers Say

According to Jan van der Wolf and four of his Dutch colleagues, climate change is partly responsible for the “new” blackleg diseases.

They stated in research papers published in New and old pathogens of potato in changing climatein 2007, that there were as many as six new species of Dickeya, and that they were most virulent in warm climates. Another problem they identified is that water can spread the disease through the soil where rotten tubers are present, contaminating plants that were not previously affected.

Jaana Laurila and five colleagues from Finland reported in same series of papers, that some highly virulent Dickeya strains may be present in rivers and there “is a risk that they will spread into potato stocks if contaminated river water is used for irrigation of seed potato fields”.

How to Prevent This Disease from Spreading

According to the UK’s Potato Council head of seed and export, Mr Robert Burns, the rest of the world can learn from the Scottish lesson. As Dickeya solani wreaked havoc in other parts of the Britain during the first decade of this century, legislation was introduced to Scotland to force farmers to use potato seed produced in Scotland.

Wales and England, on the other hand, still import about 10% of their seed from Europe – and there is no quarantine status requiring the seed to be free from Dickeya solani.

“The best way to prevent the introduction of these non-indigenous pests is by doing all we can to stop them entering the country in the first place,” said Burns just weeks before the 2012 World Potato Congress to be held in Edinburgh.