Volunteer potato control in sugar beet necessary

UK - May 12, 2005

Volunteer potatoes are on the increase because of a lack and frequency of sufficiently cold winter frosts in recent years to kill them warns Dow AgroSciences.

And in future profitable sugar beet production will depend on those who can efficiently produce the highest yields. So maximising weed control, particularly of volunteer potatoes, is paramount.

"Volunteer potatoes are highly competitive in beet crops," says Colin Bowers from Dow AgroSciences. "A population of only five potatoes/m2 can reduce yield by as much as 22 t/ha, representing a loss of £648/ha at an average price of £28.80/t."

Mr Bowers points out that it is inevitable that volunteer potatoes are common in beet as Grade 1 and 2 soils suitable for beet production are also ideal for potato crops.

"Removing volunteer potatoes from beet is essential for the beet crop, as well as for following potato crops. Groundkeepers harbour eelworm and diseases, such as blight, groundkeepers that reduce the value of marketable potatoes with good skin finish."

Martin Lainsbury, a principal crop researcher for The Arable Group at Morley in Norfolk, has conducted several trials in recent years to evaluate the best method of volunteer potatoes in beet crops.

"Our 2004 trials showed treatments with Dow Shield gave better control of the groundkeepers. The best result by far was two applications of Betanal Flo, Nortron Flo and Dow Shield. But any remaining tubers in plots treated with the Dow Shield mixtures were of very low vigour and of poor viability, rendering them less competitive to the beet and more susceptible to winter kill."

For the most reliable control of volunteer potatoes in sugar beet, Dow AgroSciences recommends a split application of 0.5 l/ha Dow Shield with Betanal Flo and Nortron Flo. The first application should be made when the potatoes are between five and ten centimetres tall, and the second at ten and twenty centimetres tall 7 to 14 days after.

An alternative strategy is three applications Dow Shield at 0.35 l/ha with Betanal Flo and Nortron Flo.

"This may be more difficult given the wet weather compressing the optimal timing window," says Mr Bowers, "but the overall level of control will be enhanced in periods of extended volunteer emergence. The important part to remember, for best results on volunteer potatoes, is to apply a total of 1 l/ha of Dow Shield."

Applications of Dow Shield, in all cases, should be completed before the end of June, and the total amount for the season should not exceed 1 l/ha. Dow Shield is compatible with a wide range of sugar beet herbicides.