Blight strain puts fluazinam resistance under spotlight

There was an update on blight, together with the latest thinking on cultivations, N timing and nematicide use in potatoes at the Potato Council’s winter forum at Sutton Bridge. Dominic Kilburn reports on the ways to maximise yields in the coming season.

TWO samples of a new blight strain which originated on the Continent were discovered in the UK for the first time last year.

Known as ‘green33’, and found on volunteer potatoes in a carrot field in Norfolk, research has suggested the isolate has shown some resistance to blight fungicide active ingredient fluazinam, which is widely used to control the disease in UK crops.

Less effective

David Cooke from the James Hutton Institute said trials on the new isolate had taken place in the Netherlands last year, where it was first found, and early indications were that fluazinam was less effective against the green33 isolate compared with the blue13 isolate.

However, speaking at the Potato Council’s Winter Forum at Sutton Bridge, Dr Cooke was quick to ease concerns about any fungicide resistance.

“The link between green33 and the reduced effectiveness of fluazinam is not established and continues to be under investigation,” he said. “The cause of the reduced sensitivity, or increased aggressiveness, is not yet known.”

Looking at the blight picture generally, he said 2011 had turned out to be a low blight risk season, with dry weather causing a slow start to infections around the country and only 183 outbreaks in total.

The first blight outbreak in Scotland had taken place in Fife on June 28, while in England the first outbreak occurred in Cornwall on July 13.

There had also been a big drop off in the level of the usually dominant A2 genotype 13 strain last season, with only 14.5 per cent present in the outbreaks sampled.

“There was a low number of Smith Periods, the primary inoculum was scarce and consequently the blight never really got established,” said Dr Cooke.

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