Take advantage of sugar beet crop to control groundkeepers

UK - May 28, 2004

Potato producers who also grow sugar beet have a simple solution for controlling volunteer potatoes says Dow AgroSciences.

Dow AgroSciences data shows 1,100 UK farmers grow both sugar beet and potatoes.

“The high grading standards seen in potato crops today leave behind undersized tubers,” says Dow AgroSciences’ Donald Westwater. “Estimates range up to 35,000 tubers/ha remaining in the soil following harvest. These groundkeepers are a major problem for potato growers, and the easiest crop to control them in chemically is sugar beet due to the efficacy of Dow Shield^† on the weed.”

Les Sykes, technical manager at Sands Agricultural Services, believes that this year volunteer potato emergence in sugar beet crops has been greater than usual because of the early warm soils and plentiful moisture.

He advises growers apply Dow Shield (clopyralid) when the potato haulm is 5 – 10 cm high or across, but highlights that emergence is always prolonged so a sequence is important.

“The addition of ethofumesate and phenmedipham improves contact activity. But mixtures of Dow Shield with desmedipham plus or minus triflusulfuron-methyl can also significantly improve final control of both foliage and daughter tubers,” he says.

“However, it’s important not to let the potatoes get beyond the application timing as vigorously growing haulms are difficult to control.”

Mr Sykes advises that the 1.0l/ha rate of Dow Shield should be divided into two half rate applications, or three 0.35l/ha treatments applied at intervals of 7 – 10 days.

“But don’t cut the overall rate or miss part of the sequence. To be effective the full litre is required to prevent re-sprouting and to cover the emergence window.”

Many of the first applications will have gone on already so it is important to make sure these are followed up. Split treatments maximise herbicide activity on haulm growth, and pick up later flushes. Dow Shield causes a distortion in stems and foliage as effective and rapid haulm knockdown is crucial to minimise competition with the beet crop, but the primary effect is to control daughter tubers.

“Dow Shield translocates to the daughter tubers, reducing weight, number and above all viability,” says Mr Westwater.

^† Trademark of The Dow Chemical Company