Trials were on-going to investigate whether Amistar (azoxystrobin) or Shirlan (fluazinam) applications had any additional benefits against a range of potato skin blemishes, SAC researcher Stuart Wale said at Potatoes in Practice 2006.

In-furrow applications of Amistar are currently used for activity against black dot and black scurf, while Shirlan has a specific off-label approval against powdery scab.

Both were now being tried against a range of blemishes including silver scurf, skin spot, black scurf and black dot, he explained. “We expect Amistar to do black dot and black scurf, but will it do the others?”

Shirlan had been shown to have some effect against silver scurf as a tuber treatment, but also affected crop growth. “It might be you still get an effect if you mix it with soil as you would with an off-label approval.”

Results were not available as yet against those blemishes but an unexpected reduction in common scab levels had been observed on resistant varieties in the field. “Both products reduced severity by about 50% on Romano and Sante.”

But no effect had been seen in susceptible varieties Maris Piper and Kerr’s Pink. “We’re don’t know how it is working – powdery scab is a bacterial infection – it is an odd result,” he said.