8 June 2001
Keep up weed beet control – BS

By Andrew Swallow

LATER drilling may mean that weed beet is less of a problem than last year, but growers must not be tempted to ease back on control, says British Sugar.

“It is a menace that is difficult to contain,” warns BSs Simon Fisher. “If you leave some bolters, the problem will get worse.”

Last year BSs crop survey revealed 64% of fields had a weed beet problem, continuing a dramatic rise in area affected over the past five years.

Plants shed about 1500 seeds, so leaving even one bolter per square metre is storing up trouble. At a density of 8 bolters/m2, yield loss hits 50% in a dry year.

“Even in a wet year, the yield loss is still significant and it does not take long to reach that level of infestation, just a couple of rotations,” warns Mr Fisher.

Institute of Arable Crop Research Brooms Barns Mike May says tractor hoeing in the beet crop should be a standard treatment for those with weed beet problems.

“Typically it will give 70% control and should ideally start when the largest weed beet have two true leaves.

“After this stage, plant stems can bend around blades and survive.”

Control of bolted stems is the next stage. Where numbers of weed beet are low, 100-1000/ha (40-400/acre) pull them, says Mr May.

“If the plants have not started to set seed, then pull them up, break the stem close to roots and drop them in the field to save time,” he says.

Where seed has set, it must be removed from the field, but it is better not to let it get to that stage, he adds.

“In most cases it is better to walk fields twice before the weed beet set seed than trying to walk only once, but having to carry plants off.

At 1000-10,000/ha (400-4000/acre), weed wiping with glyphosate is the preferred option and likely to be 90% effective if carried out properly, says Mr May.

Really high populations, over 10,000/ha (4,000/acre) should be cut, he advises.

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