Sugar beet
Weed control key to hitting high yield sugar beet target
• Target problems early for better results • Evaluate strategy on fi eld-by-fi eld basis • Base spray timings on crop growth stage
C
ontrolling weeds in sugar beet is vital for growers to achieve a low unit cost of production – as well as being key to achieving higher yields, says agronomist Pat Turnbull. “Weed control is one of the keys to higher yields and grow- ers have got to get control strat- egies right or they will always be playing catch up and in the long run this will be more expen- sive,” she says. “Hit broadleaved weeds hard and early using a mix of contact and residual acting her- bicides.
“Compromising weed control can soon tip the balance to a posi- tion that you can’t come back from and it’s the taller weeds that are the real problem. An infestation of just one tall weed species per m2 such as fat hen or redshank in a crop can potentially reduce yields by 10%.”
Bad weed control can knock yields by 30%, says Dr Turnbull. Successful control has always been about fi nding the right strat- egy. In some ways that has be- come easier – but in others it has become more diffi cult.
Hi-tech
The move towards having a sin- gle, high-tech sprayer on the farm – often covering a large area and a wide range of crops – means that
multi-pass herbicide post-emer- gence strategies with small dos- es applied at close intervals have become more of a challenge. “Growers simply don’t have the time to get so many applica- tions on the crop at such a busy time of year, so adopting a two spray programme known as ‘Broadacre’ – with robust mul- ti-active herbicide mixes – can have a positive impact on control.” Critical to the success of the ‘Broadacre’ approach is the ap- plication rate of actives trifl usul- furon-methyl and ethofumesate – the latter included as the ‘acti- vator’ – depending on the weed threat. But if weeds are bigger, or the spray has been delayed, then raising spray rates is essential.
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Multi-active herbicide mixes can have a positive impact on control
“Weed control in sugar beet must be programmed, with ap- plications timed as fl ushes of weeds emerge. And it’s important that spray timings are based on the crop’s growth stage because as the size of the beet seedlings increases, they can cope with stronger herbicide mixes,” she says. For some growers, a move that relies on a two spray Broadacre programme is perceived as risky, especially when large numbers of weeds emerge early alongside the sugar beet. As usual, strategies should be evaluated on an indi- vidual fi eld-by-fi eld basis.
Strong hits “We often recommend a broad spectrum system on some farms where the two strong hits with trifl usulfuron-methyl and etho-
22 ANGLIA FARMER • JUNE 2017
Thistles can be a problem in some crops, says Dr Turnbull (pictured below)
fumesate are used at the second and the third post-emergence timings,” explains Dr Turnbull. With this approach it’s nor- mally a grower’s preference to apply a pre-emergence herbicide and the product of choice is chlo- ridizon as a relatively cost-effec- tive start, which predisposes the weeds to post-emergence sprays and gives a little more timing fl ex- ibility, she adds. “The fi rst early post-emer- gence herbicide application must be at the cotyledon to one true leaf stage with a robust mix based on phenmedipham + ethofumesate + metamitron + desmedipham, giv- ing safety and early broad spec- trum control.”
Some growers might include
Debut (trifl usulfuron-methyl) in the fi rst application, if there is an early emergence of actively grow- ing weeds. But Dr Turnbill says it is typically most effective when applied as the second spray 10- 14 days after the fi rst. In this case, it is specifi cally targetted at brassicas, cleavers and some polygnums such as red- shank and pale persicaria – and then usually followed with a fi - nal Debut based spray. “Debut also adds to black- grass control. Both anecdotally and in BBRO trials carried out at Brant Broughton in Lincoln- shire in 2013, two applications of trifl usulfuron-methyl added to blackgrass control compared to a standard mix,” says Dr Turnbull.
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