Test results have confirmed a major shift in the bacterial species causing blackleg in Dutch seed potatoes, with a new species being found in two-thirds of seed crops investigated.

Blackleg is a soft rot caused by a number of different bacteria which include pectobacterium and dickeya species and can lead to severe in store losses.

See also: Tips on breaking the potato blackleg cycle

This seed-borne disease is the focus of inspections of seed crops, some of which are exported to countries such as the UK.

Back in 2014, researchers reported the first case of blackleg being caused by Pectobacterium carotovorum subs brasiliense in the Netherlands.

Of all bacterial-diseased plants the Dutch General Inspection Service (NAK) for seed investigated in 2015, 67% were found to have this strain.

Before 2014, Dickeya species dominated, but last year, they were found in 21% of the diseased plants, says the service.

The bacterial species Pectobacterium atrosepticum and Pectobacterium wasabiae were each found in about 6%.

More downgrades

In addition to the shifting species, NAK says last year saw an increase in the area downgraded because of blackleg.

NAK downgraded 15% of seed potato fields to a lower class during inspections, the highest percentage in four years.

Since 2009, there had been a downward trend in class downgrades due to blackleg.

However, this trend has been broken last year, said Jaap Haak, coordinator inspections at the NAK, at a recent growers’ meeting.

“Due to the heavy rains in June, more seedlings became infected with bacterial disease,” he says.

This pieces is based on an article that appear on Farmers Weekly’s Dutch sister magazine Boerderij’s website.