Potato fungicide’s label expanded to cover black dot

A broad-spectrum fungicide used to control early and late blight in potatoes can now be used also to control black dot, another common potato plant disease.

Syngenta Canada on Monday announced the expanded label for its Group 11 azoxystrobin fungicide Quadris.

Black dot, found most often on tubers, can "significantly" impact potato production by affecting a plant’s vascular system, causing the plant to wilt, Syngenta said. The disease can also cause rotting in potato roots, shoots and stolons, leading to early plant decline, discoloured tubers and reduced yields.

On potato plant foliage, symptoms of black dot are "nearly indistinguishable" from early blight, while on tubers, black dot produces blemishes sometimes mistaken for silver scurf, Syngenta said.

The expanded label covers Quadris for control of black dot when applied as a foliar spray on a seven- to 14-day interval, starting prior to disease establishment, at a rate of 500 to 800 millilitres per hectare — the same rate and interval as for control of early blight.

No more than three applications of Quadris per hectare per season should be made, nor should more than 2.4 litres of Quadris be applied per hectare per season, the company said.

Quadris’ other label uses on potatoes include a tank mix with Bravo 500 to control early blight; an in-furrow tank mix with Ridomil Gold, to control rhizoctonia stem, stolon canker and black scurf and suppress pink rot; and an in-furrow application to control silver scurf.

Related story:

Potato blights develop fungicide resistance, March 17, 2009

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