12 December 1997

Low sugar disease more widespread?

SUSPECTED low sugar disease originally seen in north Norfolk (Arable, Nov 21) is now thought to be more widespread.

But the sometimes severe disease symptoms are still causing confusion in the industry.

Colleagues and growers reckon the disease has shown up in areas as far south as Thetford, reports Wolsingham-based Cropcare agronomist Peter Single.

Philip Draycott, a Suffolk-based independent sugar beet specialist, also suspects the disease may be more widespread. "I saw similar symptoms away from the west Norfolk area. Next year I will be looking out for it more."

Some crops have been hit hard, with all plants showing symptoms, says Mike Asher of IACR-Brooms Barn. "If sugars are all down by 2-3%, those crops are going to show a pretty poor performance. But generally disease is at pretty low levels, and should not be a major problem for most growers."

British Sugar tests confirm low sugars, says BSs Mike Armstrong. "We found sugar contents typically fell by 2.5%." Amino N rose too, above that normally seen in lower sugar samples.

Root yields do not seem to have suffered unduly, he adds. But weak tops mean big losses can arise if belt lifters are used.

Dr Draycott, who identified the first case in a crop of beet grown by Teddy Maufe at Branthill Farms, Wells-next-the-Sea (Farmer Focus, p59), is convinced that low sugar disease is the cause.

"All the symptoms I have seen are exactly the same as the French have reported. And the 2-3% drop in sugar content is identical to French results."

However, blackened leaves in the centre of plants found in Norfolk are not characteristic of French symptoms, Dr Asher maintains. And molecular diagnostic tests to expose the suspected causal agent, a mycoplasma transmitted by leaf-hoppers, have proved negative.

"It could be that the tests are too specific, or we are dealing with a new strain."

He has not ruled out nutritional disorders brought on by the unusually wet June. &#42

LOW SUGAR DISEASE

&#8226 Spread beyond Norfolk?

&#8226 All roots affected in some crops.

&#8226 Sugar content 2-3% down.

&#8226 Amino-N up.

&#8226 Blackened, young leaves. Older leaves turn brown and die.

How sweet is your beet this harvest? Low sugar disease (Arable, Nov 21) has now been confirmed across much of Norfolk and is suspected further afield. Symptoms could be masked by this years heavy crop, warn experts.