30 August 2002

Wet summer fuels seedling blight risk

WET weather at flowering and now at harvest means seedling blight is a big risk in home-saved cereal seed, prompting experts to urge growers to test seed and treat as necessary.

Wet weather splashed Fusarium and Microdochium seedling blight infection on to ears at flowering, says Simon Edwards, pathologist at Harper Adams University College.

Subsequent humid weather has provided ideal conditions for those infections to develop. "With such conditions at these critical times, high Fusarium and Microdochium infection is likely."

Diagnostic testing of cereal ears confirms the high risk, says Syngentas Iain Hamilton. Assessments in July showed 95% of samples infected with M nivale, compared with just 18% last year, when conditions were far drier at flowering. Fusarium infection is also more widespread, affecting 91% of samples, compared with 67% last year.

The tests suggest little difference between varieties or regions and infection levels were little different whether T3 ear-sprays had been applied, probably reflecting the need for high rates and accurate timing for good control.

Mr Edwards advice is to test or treat seed before planting. In HAUC trials looking at M nivale infection effective seedling blight control with seed treatment Beret Gold (fludioxonil) led to significantly less foot rot right through to ear emergence, he notes.

He warns against repeated use of untreated seed. "The only reason seed diseases in general have not been high in recent years is because seed has been routinely treated. The increasing trend to only test seed could cause a build-up of soil-borne inoculum long term."

In Scotland Valerie Cockerell from the Official Seed Testing Service agrees that conditions there have favoured Microdochium infection. "Growers should test seed they intend to save as a matter of course."

Jane Thomas of Cambridge-based NIAB agrees. "In terms of saving seed from this years crops, it is essential to test."

North Lincs mobile seed cleaner Mike Gibson, of Gibson and Faulding, echoes that view. He operates two, high-tech three-stage cleaners that can help separate out fusarium-infected seed on the basis of size and weight. But he still urges growers to treat.

"I am happy just to clean seed. But there is no point because you cant Hoover out bunt and you cant guarantee soil is free of bunt." At low seed rates effective treatment costs just £3.70/ha (£1.50/acre) after cleaning. &#42