8 June 2001

Weed beet growing trouble, claims BS

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 a sq m is storing up trouble. At a density of eight bolters a sq m 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.

IACR 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. "Control is likely to be about 90% if wiping is carried out properly," says Mr May.

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

"The best machines are those that tend to macerate the weed beet into small pieces so they will not regrow. Cutter bars top the beet, but large pieces can still set viable seed unless they desiccate on top of the crop," he warns. &#42

BEATING WEED BEET

&#8226 Hoe when weed beet plants have two leaves.

&#8226 Under 1000 bolters/ha: Pull before seed set.

&#8226 1000-10,000/ha: Wipe with glyphosate.

&#8226 Over 10,000/ha: Cut.