29 November 1996

Top fungicide good as ever for Stritici

BRITAINS most popular fungicide remains as effective as ever at controlling Septoria tritici.

No shift in sensitivity has been recorded in France or Germany either, according to a three-year study on Folicur (tebuconazole) carried out by maker Bayer.

"There were rumours in France that its efficacy was slipping," says the companys Karl-Heinz Kuck. "Our results, and half a dozen independent ones, clearly show they are completely wrong."

A total of 1500 samples from 60 locations in the three countries showed no evidence of reduced sensitivity, he says. Continuing work this year confirms that result.

Dr Kuck believes the question mark over its performance in France was due to intense disease pressure and timing.

Disease pressure

"Disease pressure was huge. Although there were no problems in the field, in ITCF trials when tebuconazole was applied late in one shot it was found to be less persistent than Opus. "OK, weve seen its limits. Timing is very important, and if tebuconazole is applied too late its efficacy might be limited. At the proper timing and dose its control is adequate."

However, due to the intensive use of the DMI group of fungicides, of which tebuconazole is one, monitoring should continue, adds Dr Kuck. That is confirmed by laboratory tests carried out by the Central Science Laboratory on isolates of S tritici in 1992, 1994 and 1995.

COMPOUNDS being developed which stimulate resistance in plants to inoculate them against future disease attacks offer several advantages over traditional chemical control. But whether they are accepted by farmers remains to be seen.

Many traditional pesticides are toxic, non-specific and leave residues, says Gary Lyon of the Scottish Crop Research Institute. They also suffer from resistance problems, and the public are concerned about their use.

Chemicals which stimulate the plant to produce defence mechanisms in the absence of disease – elicitors – are generally not toxic, and are environmentally-friendly. And because they act on a "multi-component" system in the plant to provide the so-called systemic acquired resistance (SAR), and have no direct fungicidal action, it is difficult to see how resistance could develop, he says.

Their success depends on how growers perceive them, he adds. "If farmers expect the same levels of disease control and eradication achieved by conventional pesticides, then they may fail. However, in the context of environmental protection demands and integrated crop protection, these compounds may offer a highly cost-effective option."

Natural compounds derived from fungi could be used in organic systems. And where buyers demand low or zero residue levels, they could be used alone or in combination with reduced dose fungicides.

One such SAR-inducing chemical which works on a range of plants was launched by Ciba at Brighton.

CGA 245704 was tested widely in wheat in Germany last year, and used alone showed good activity against disease provided it was applied early, says Dr &#42 Kessman of Ciba-Geigy. It needs to be applied to plants before disease becomes established, to allow time to stimulate a response in the plant, he explains.

CONSUMER concerns remain at the top of the biotech agenda judging by a discussion at the conference

The general conclusion was that the public had to be educated if the technology was to progress. Environmental concerns also had to be addressed.

The debate was fuelled by the recent soya bean furore, in which American-grown, genetically modified herbicide-resistant beans had been mixed with conventional produce and imported into Europe. Consumers no longer had a choice in the matter.

One Austrian delegate said that had caused a drop in soya bean throughput of 30% in his country. That should serve as a lesson to all, said James Gilmour of the SAC.

Lack of understanding was the key. One of the main concerns was the name – biotechnology raised all sorts of suspicions of mad scientists working away in the clouds, said Harriet Kimbell, deputy chairman of the Consumers Association.

"To some people, gene technology is one of the most exciting intellectual endeavours ever. But to a considerable number of people, it is the ultimate in scientific arrogance and misguidedness."

Consumers saw themselves trapped between scientists and manufacturers, she said. They did not regard the new technology as safe – the BSE fiasco meant they were unlikely to take much notice of official bodies which told them otherwise.

It was no good explaining that many medicines are a product of biotechnology. "There is a big difference between food and medicine. People will go to hell and back if they are ill – look at chemotherapy."

Environmental safety was another key concern which would be hard to dispel. DDT was once thought of as safe. "But industry took a long time to admit it was not as good as they first thought."

Dr Gilmour thought the public were rightly suspicious about unknown effects. "It may be desirable to move a gene from A to B. But do you know everything about that gene. What else might it do once it is moved. Where are the checks and the balances?"

Ethical concerns also had to be addressed – although they may have no factual basis, they were a real concern among some people, said Ms Kimbell. David Atkinson of the SAC agreed.

Labelling was a key issue – consumers had to be given the choice, at least until they were used to a product, he believed.

Ms Kimbell agreed. "For scientists to say weve tested it and we think its safe, so it must be, is infuriating. Its happening with soya. It is so arrogant to think something like that can be introduced without being labelled. You may not think it is necessary, but boy is it necessary now. There may be a big backlash which will undo all the good work you have tried to do over the last few years."

Information was vital. If customers were told a certain amount, they tended to trust more, she said. "Aim to provide consumers with accurate and reliable information on which they can base their views and make choices. They have the right to make that choice."

Zenecas tomato paste, which was introduced last year to two supermarket chains was a good example, delegates agreed. "It went down very well," said the companys Ray Elliott. "We mounted a careful campaign with the retailers. Full labelling for the consumer is the best way forward."

Growers had to become involved in the debate, said farmer John Lampitt. "Biotechnology offers a wide range of opportunities. It can increase competitiveness, by increasing output and lowering costs. There are exciting possibilities for extending the growing season and availability of produce in some crops. And there are exciting opportunities in designer oilseed crops, and other non-food crops.

"We want safety, but we want to be sure if there is the opportunity to be had, we can use it. But the customer is king. His concern has to be addressed." Labelling and segregation of commodities was important. Government must also establish a regulatory framework to protect the consumer and the environment, he said.

Trials dispel fears of tebuconazole resistance, says Karl-Heinz Kuck.