26 January 1996

More fungicide needed to keep septoria at bay

Making more of fungicides and the potential of precision farming were key topics at a recent ADAS conference in Harrogate. Robert Harris reports

TOO little fungicide is being applied to the UK wheat crop to control septoria, restricting yield and pegging profits. Using more will repay the cost even in a low disease year.

So says Bill Clark, ADASs Cambridge-based cereal pathologist. "Yield response to fungicides is similar to the nitrogen response curve," he explains.

"The more fungicide you apply, the more yield increases, until you reach the optimum point where the cost of the extra fungicide equals the extra yield. Growers need to be at or just beyond that point."

Home-Grown Cereals Authority-funded work at ADAS Rosemaund using Folicur (tebuconazole) to protect Riband against septoria suggests most growers apply less than the optimum.

"In 1994, a low disease year, we found that 1.5 litres/ha over the season gave the highest yields. Last year, also a low disease year, the optimum was 1.25 litres/ha. I doubt anyone put that much on." Typical commercial rates would have totalled 0.75-1litre/ha, saving between £15-23 compared with the trial, says Mr Clark.

But in 1994 applying that level pulled yield down by 0.5t/ha (0.2t/acre), worth £50. Even in the droughty 1995 season growers would have covered the cost of the extra fungicide by a "few £". "You dont have to save much yield to cover cost of the fungicide."

Optimum doses vary between products. He advises use of modern products like epoxiconazole (Opus), tebuconazole or cyproconazole (Alto). "A half-rate application is as good as or better than full rates of many older products."

Precision is the key… Better fungicide timings and modern mapping techniques can both help farmers improve their lot, says ADAS.