Rhizomania-resistant sugar beet varieties continue their steady march, with just over 40% of the UK crop now being drilled with these types, latest figures reveal.
Even so, experts believe that a great deal of rhizomania is still going undetected, resulting in further spread of the virus and damage to both yield and income.
According to Richard Powell of Syngenta, there are huge regional differences in the uptake of resistant varieties, with growers in East Anglia leading the way with almost 60% of the sugar beet area down to rhizomania-resistant types.
“That’s very different to Nottinghamshire, for example,” he says. “The Newark factory has just 17.3% of its intake in resistant varieties.”
Part of the problem is that rhizomania-resistant varieties don’t always offer enough to the grower, he explains.
“They struggle to meet the combination of yield, sugar content and bolting characteristics that’s required,” he adds. “So there’s still plenty of life in the conventional types, with a good new one, Saracen, joining the line-up for next year.”
Having said that, Mr Powell admits that great progress has been made with resistant varieties and reveals that Syngenta has its first rhizomania-tolerant entry on the 2010 NIAB Recommended List.
Aimanta is an early-maturing rhizomania resistant variety, he claims. “We see it having a place where early lifting is required, particularly on heavy land, to give a good entry for the following wheat crop.”
Mr Powell also sees a need for a late-maturing variety for the UK. “If the sugar beet area goes up, as predicted, the factories will be put under a great deal of pressure. We’re going to need varieties for both early and late lifting.”
Ian Munnery of Elsoms believes many more growers should be switching to rhizomania-resistant varieties to help prevent inoculum building up and reaching levels which could threaten resistance.
“We’re getting to the stage when the whole of East Anglia should move across. And growers in Lincolnshire should submit samples for testing – there’s a danger that they’re underestimating how much land is infected.”
On the Continent, France, Belgium and the Netherlands rely almost entirely on resistant types. “They’re gaining momentum here, but it’s slower than it should be, especially in Nottinghamshire and Lincolnshire.”
Elsom’s sugar beet trials have shown that some varieties bulk up earlier than others, making them more suited to early lifting, reports Mr Munnery.
“This is relevant to heavy-land situations,” he says. “Growers don’t have access to this sort of information from the Recommended List, so they will need to ask the breeders.
“Bobcat is another of these early lifting types, as well as being rhizomania resistant, making it a good choice for heavy land. Its consistency has been outstanding.”
Bullfinch and Levi are other rhizomania resistant choices from Elsoms, he adds.
The first double-tolerant sugar beet variety on the Recommended List, Fiorenza, will also be found at Cereals.
Breeder KWS has introduced multi-resistance to both beet cyst nematode and rhizomania in a variety. Syngenta is hopeful that Sentinel will be recommended next year.
These double-tolerant varieties are expected to take up to 20% market share within five years, both companies predict.
“It’s estimated that 5% of UK beet land is badly infected with beet cyst nematode,” says Volker Utesch of KWS. “But shorter rotations and warmer weather are expected to increase the problem.”
Yield losses of up to 30% have been recorded from the pest, he adds. “Early attack causes wilting of young plants. Heavy infection levels show up as plants are stunted, the main roots are shortened and the roots develop a bearded appearance.”
Fiorenza is lower-yielding, he admits. “But where it’s grown in infected soil, you get a yield response between 20 and 40%.”
Higher-density sugar beet crops have workload and timeliness advantages as they result in a more even crop, says Ian Munnery of Elsoms.
“Where you have a higher plant population, from using a slightly higher seed rate, you tend to get slightly smaller roots but a far more uniform crop.
“That makes all operations, such as spraying and harvesting, quicker and easier. The yield benefit of such an approach is still being evaluated in trials.”
Open, low populations are at the mercy of pests, he adds. “It would make sense to take seed rates up from their current level of 1.05 units/ha to 1.2 units/ha, as is done on the Continent. The benefits would far outweigh additional seed cost.”