Controlling rhizoctonia with Amistar (azoxystrobin) applied in the seed-bed encourages faster potato establishment, and resulted in 20% higher yields, Syngenta trials have found.

In the trials conducted by John Purslow Agronomy, Amistar-treated plots of Markies had reached 33% groundcover two weeks after emergence compared with 20% where untreated.

The beneficial effect on crop health and vigour also helped maintain green leaf at the end of the season, when the untreated crop had begun to die back. Twelve weeks after emergence, the Amistar plots still retained 82% ground cover, when the untreated had dropped to 70%.

Rhizoctonia has a hidden effect on crop establishment and season-long vigour, Syngenta’s Tom Whitworth says. “Getting the crop growing faster is essential to optimise tuber set, while the prolonged green leaf area at the end of the season can enhance tuber size and quality.”

Yields were up to 20% higher in the Amistar-treated plots.

Treatment could also improve quality, Mr Whitworth says. Rhizoctonia stem pruning can cause late secondary tuber initiation, resulting in inconsistent tuber size and variable dry matter at harvest. “Both can adversely affect processing and cooking quality,” he says.

Amistar is the only approved treatment for soil-borne rhizoctonia and black dot.