A new approval for the contact herbicide Retro means potato growers can use double the rate this season.

Raising the dose to 4 litres/ha would give more robust control of larger weeds and produce a cleaner seed-bed to speed emergence, said Syngenta’s technical manager, Glenn Wilkinson.

“The higher rate will be valuable for growers who wait until as close to emergence as possible before applying their residual herbicides, when there may already be significant weed populations established,” he said.

Tank-mixing Retro (diquat) with Defy (prosulfocarb) would help burn off established weeds and minimise effects on the crop, he explained.

Reduced linuron rates meant most growers waited to apply as close to emergence as possible to achieve the best residual activity. “This makes the role of Retro particularly important,” he said

The approval is targeted specifically at black bindweed, cranesbill and other difficult to control weeds.