29 September 1995

Upgrade advice on resistance, demands ADAS

By Robert Harris

ANTI-RESISTANCE guidelines for fungicide use are impractical and often too expensive for farmers to adopt.

Better advice is needed from researchers and manufacturers, delegates were told at last weeks conference on the future of fungicides in cereal production organised by the British Crop Protection Council and the Society of Chemical Industries.

Growers are being given a mixed message, said ADAS national cereal specialist, Bill Clark. "Theres too much hesitation when it comes to talking about resistance. We are all walking on eggshells. Researchers dont want to upset the manufacturers, because they are often partly funding the work." Companies are often reluctant to admit problems to preserve product share, he added.

Sensitivity shifts

Talk of "sensitivity shifts" means little to farmers, and they are difficult to see in the field. And once resistance is detected, farmers see little benefit in adopting methods to avoid it.

"You can debate whether there is a shift in sensitivity. Field control failure exists. But it doesnt feature in the official literature. I would suggest that some of the scientists and workers are not clear what the results of their work mean. More research is needed.

"Historically, advice has not been very good. Very few anti-resistance strategies have any practical significance. Arable farmers are generally not interested in resistance until something happens."

Advice to avoid repeated use of products with the same mode of action and alternate them instead is unrealistic, says Mr Clark. "Farmers havent a choice. On the face of it, there look to be lots of groups and products to choose from, but in practice the mainstay are azoles."

The "strange trend" of mixing them is mainly commercially based, he added. "A lot of the time they dont fit with anti-resistance strategies."

Recommending other formulated mixes is fine in theory. "But farmers are businessmen – they are running a very tight ship. They cant afford to use them out of altruism."

Advising farmers to stick to label recommendations is equally unrealistic. "Farmers are aware that the label dose is very robust and largely there to stop litigation. Often such recommendations are way over the optimum rate."

More research is called for to provide farmers with practical advice on the way to use fungicides to prevent diseases developing resistance on the farm. Current recommendations miss the mark, says one expert.