17 May 1996

Beet seed treatment offers added bonus – thrips control

By Andrew Blake

EVIDENCE is mounting that Gaucho (imidacloprid) seed treatment is helping sugar beet resist this years unprecedented thrips attacks.

But with many crops at a standstill in the cold, dry weather some growers are playing safe by using additional spray insecticides.

Brooms Barn entomologist Dr Alan Dewar says the signs are that the armour provided by Gaucho, used mainly against aphids and virus yellows, is providing an unexpected benefit in a season when its main advantage could be reduced.

"After the cold we have had this winter and spring, with some sharp frosts in May, I did wonder whether the large number of growers who have used Gaucho would see any benefit, because the aphid and virus yellows risk is low."

But several cases of split-field treatments have highlighted the chemicals impact on thrips.

Andrew Dunning has 17ha (43 acres) of sugar beet at Monckton Walk Farm, Newbald, York. Thrips are common pests on peas and occasionally on sugar beet, he says. "But this years attack is totally unexpected in numbers and sheer earliness."

Side-by-side treatments in one field confirm Gauchos merit, he maintains. "Where we have used it the seedlings are OK." An area sown with last years seed treated with Force (tefluthrin) is surviving, but only with the help of a dimethoate insecticide spray, he reports. But a 1ha (2.5-acre) strip sown with untreated seed for a Brooms Barn trial has been lost.

Norfolk-based AICC member, Pat Turnbull, says she is convinced of the anti-thrips benefits of Gaucho. "It has been very useful. I have got some fields where it has been used only on part of them and there is noticeably a lot less damage," says Dr Turnbull.

Temik (aldicarb), used widely in the area to counter Docking disorder, has not been so effective against thrips, she reports.

Simon Fisher, fieldsman at British Sugars Bury St Edmunds factory, echoes her views on Gaucho and the pest. "It has definitely been useful." But a few treated fields have had enough damage to tempt some consultants to advise spray treatments, he says.

Robert Rush believes Gaucho has provided an added bonus in the shape of thrips control on the 150ha (370 acres) of beet at Hall Farm, Shimpling, Bury St Edmunds.

But with the whole area so treated direct comparisons are not possible, he admits. "But I have heard of people who have had to re-drill because of thrips."

Despite the absence of damage, however, he treated the whole crop with cypermethrin as a precaution.n


&#8226 High numbers, very early.

&#8226 Some re-drilling necessary.

&#8226 Gaucho giving useful control.

&#8226 Slow growing crops mean growers have used sprays, too.

Drilling beet treated with Gaucho looks to have bought an added bonus for many growers this season – control of thrips, an unexpected threat in East Anglian fields.