Weed control challenge for potato growers

RAPIDLY emerging weeds from warmer soils are set to pose a challenge for potato growers forced to delay planting due to poor conditions.

Faster establishment means extra vigilance is needed to avoid any phytotoxic growth check. This is especially the case for some pre-emergence herbicide options that require a prolonged period from application to first emergence.

“Using Defy on all varieties and all soil types will give growers greater flexibility in their application timing and options,” claims Glenn Wilkinson, potato technical manager for Syngenta.

Trials have shown Defy + Retro tank mix can be safely used up to 10% crop emergence, ensuring the crop can get away in a clean weed free seedbed, Mr Wilkinson said.

There should be ample soil moisture to achieve very high levels of weed control this spring. Growers could select residual tank-mix options along with Defy + Retro according to the prevailing weed spectrum, variety and soil type.

The rapid emergence of weeds likely to occur following the delayed spring planting also meant growers and agronomists would be seeking to control actively growing, vigorous weed populations at a later application timing.

“The new higher rate of Retro approved for this spring will give faster and more robust kill of larger weeds. Retro is the only diquat herbicide approved for use at up to 4.0 l/ha.”

Meanwhile, application trials have identified the company’s new Syngenta long-life potato nozzle, launched last year, could improve results with Defy residual herbicide applications on potato seedbeds.

“The angle of spray helps to achieve all-round coating of any clods in the seedbed, which will enhance weed control. Operators should fit them to face forward and backwards along the spray boom to give the optimum coverage.”

Syngenta trials have demonstrated cloddy seedbeds created during cultivations pose a real problem for effective pre-emergence herbicide sprays applied with a standard flat fan nozzle.

When spraying with a standard flat fan nozzle at 12 km/hr, a soil clod casts a shadow three-quarters of its size where no spray lands; so a 50mm (2”) clod creates a 38mm (1.5”) untreated shadow area.

But spraying with angled long-life potato nozzles – fitted to face forward and backward along the spray boom – eliminated the clod shadow and gave complete coverage, said Mr Wilkinson.

The long-life nozzle was “less drifty” compared to conventional flat fan nozzles, giving a more even spray pattern. “This can increase the number of spray days available to growers and may be crucial in a difficult spring.”

Importantly for potato growers, the spray pattern was more forgiving of boom height, which could improve herbicide coverage along the sides of the bed ridges and furrows.