Cyst nematode losses are often going unnoticed

2 June 2000




Cyst nematode losses are often going unnoticed

MANY growers are overlooking control of beet cyst nematode, which is an increasing problem in the UK, according to one breeder.

"The nematode can be extremely damaging," says Mike Coy of the English Sugar Beet Company. "Yield losses can be 30% or more."

Growers concerns about rhizomania seem to be distracting them from the nematode issue, he maintains. Yet in yield loss terms with tolerant varieties, rhizomania is less of a problem.

"There is always talk about the yield penalty of rhizomania tolerant varieties but it is only 2-3%. Current nematode tolerant varieties carry a 10% yield penalty in the absence of the pest."

Inspections of UK crops infected with rhizomania alerted Mr Coy to the nematode problem.

"When I went to look at the crops, a lot of the damage was due to nematodes rather than rhizomania and I do not think the growers were aware of that. It used to be an issue years ago, but it seems to have been forgotten about."

More late liftings, poor stubble hygiene in cereal crops, and a reduction in the use of nematicides are behind the rise, he maintains. More oilseed rape in sugar beet rotations could also be to blame, as the beet cyst nematode multiplies rapidly on both crops.

First sign of an infestation will be patches of crop wilting in the heat of the day, initially recovering at night; but as damage becomes more severe, wilting becomes permanent. Outer leaves turn yellow and die and new leaves are small.

"If you pull up these plants you will see bearding on the root and thousands of cysts on the root hairs."

While some growers should consider planting tolerant varieties or using nematicides, for most, lengthening the rotation to one in four or five years and taking more care to keep fields free of weed beet in sugar beet crops is their best bet, he advises.

"The yield gap with tolerant varieties will be closed no doubt, but it is a more difficult hurdle than rhizomania," he says. &#42

Andrew Swallow

This beet seems fine, but nematodes could be eating into profits more than growers realise, suggests Michael Coy. Breeding resistant varieties, however, is proving harder than with rhizomania.

BEET CYST NEMATODE

&#8226 On the increase in UK.

&#8226 Chemical control costly.

&#8226 Tolerant varieties 10% yield lag.

&#8226 Hygiene and rotation controls.


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