Beet experts stumped by low sugar disease
Beet experts stumped by low sugar disease
By Robert Harris
CAUSE of the new sugar beet disease found for the first time in the UK this season remains a mystery. That is bad news for affected growers who have already lost money.
Some experts believe the ailment is low sugar disease which first hit French crops seven years ago. Others suspect nutrient disorders are a more likely cause.
The outbreak was first identified in Teddy Maufes 109ha (270 acres) of beet at Branthill Farm, Wells-next-the-Sea, Norfolk. One in 20-30 plants were affected in all fields. Although a record yield of 68 adjusted t/ha (27.5t/acre) more than offset the 3% lower sugar content of diseased plants, he is concerned losses could be greater in a more normal year.
"We had a superb crop thanks to 5.5in of rain in June. In a more normal droughty year, or if the disease had come in earlier, it could make the difference between making quota or not." As a result, he will reduce beet area by just 2.8ha (7 acres) this season, compared with the planned 15-20 acres cut which would have maintained a 10% quota overshoot.
Weak tops, caused by premature death of leaves, saw harvesting losses of 5-7.5t/ha (2-3t/acre) when the three row Armer belt-lifter was used. A second-hand three-row Tim machine fitted with Oppel wheels soon replaced it.
Disease symptoms – erect leaves like celery stalks – were first spotted in September. Those were later killed by frost and turned black. Small arrow-shaped leaves then regrew from the middle of the crown.
"At first I thought it was boron deficiency, although we routinely apply it," says Mr Maufe. He called in his beet specialist, Suffolk-based Philip Draycott.
"That was certainly the first impression. But there was no rotting in the crown, which is a sure sign of a boron problem," says Dr Draycott.
He believes the disease is low sugar disease. "Certainly from the French slides I have seen it looks the same." Helen Smith of IACR-Brooms Barn agrees. "I believe we are dealing with the same thing."
French research suggested a phytoplasma spread by leaf hoppers was to blame. However, healthy plants have since been found to contain similar levels, so that theory has been dropped.
Dr Smith and Dr Draycott suspect a virus is to blame. Some plants contained high levels of cryptic virus, a seed-borne organism which is commonly present at low levels in healthy stock. But the patchy appearance of the disease suggests an insect or nematode is a more likely vector. No varietal or soil type effects were seen.
Tests are being carried out at Brooms Barn to test the virus theory. The ministry is also conducting its own research.
• British Sugars Mike Armstrong believes it is too early to call shots. "No conclusions have been made. But I suspect it is a physical problem, a stress effect, caused by a nutrient imbalance. Im fairly convinced it is not the same disease the French have. Any crop regrowing leaves so late would lower sugar content."
Affected growers wishing to protect their quota levels can order more seed, he adds. "Samples in affected areas did suffer a 3% fall in sugars. That has to be taken into account."
LOW SUGAR DISEASE?
* Symptoms – blackened leaves, late regrowth.
* Sugar content 2-3% down.
* High amino N levels.
* North-west Norfolk hit.
* Suspected cases south to Thetford and into Lincs.
* Plant extra beet to protect quota?
Still puzzled by low sugars in Norfolk beet are farmer Teddy Maufe (left) and agronomist Philip Draycott. Extra beet drilling this spring may be needed to compensate for potentially significant losses..
LOW SUGAR DISEASE
• Symptoms – blackened leaves, late regrowth.
• Sugar content 2-3% down.
• High amino N levels.
• North-west Norfolk hit.
• Suspected cases south to Thetford and into Lincs.
• Plant extra beet to protect quota?