10 May 2001
Don’t mix fungicides, growers warned

By Tom Allen-Stevens

A LEADING cereal pathologist has urged arable growers not to abandon their T1 fungicide applications.

Poor conditions this spring have meant many growers are way behind with their crop-spraying programme.

A fine few days are forecast and some farmers could be tempted to combine their T1 and T2 sprays now or delay them altogether until the flag leaf timing.

But Bill Clark of ADAS said: “Dont do that. Its a very dangerous tactic.

“A wet winter and spring has left a legacy of crops riddled with septoria. Get a good, robust T1 spray on, even if its only two weeks until the flag leaf emerges.”

A good triazole spay should be used, such as epoxiconazole, and rates may have to be raised on forward crops, said Mr Clark.

“You may already have lost leaf four, but you will need a high eradicant dose to protect leaf three, especially in open crops.

“But dont reduce the dose of the strobilurin its the total dose over the season that counts.”

Mr Clark advised growers to aim for a total of 1-1.25 units of strobilurin per hectare over no more than two timings.

Nor should the flag leaf spray be applied too early, he said.

“Theres a myth surrounding strob persistency: they are persistent, but only on the leaves that have already emerged when you spray.”

Twenty per cent of growers miss the ideal flag leaf timing of GS39, and can lose up to one tonne per ha of yield as a direct result.

The big yield robber this year is septoria, he says. Mildew and yellow rust levels are generally very low.

  • Full report in Crops, 26 May issue
  • Click here to visit Crops web pages

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