Early drilling could be behind East Anglian light leaf spot infection

A field of oilseed rape in Norfolk. Researchers have found light leaf spot infections in oilseed rap

A field of oilseed rape in Norfolk. Researchers have found light leaf spot infections in oilseed rape in East Anglia. Picture: Matthew Usher. - Credit: Matthew Usher

Scientists have reported early signs among East Anglian oilseed rape crops of a fungal disease which can stunt growth and halve yields.

The first commercial samples of light leaf spot were found by the Bayer SpotCheck initiative in Thetford and Clacton, Essex.

Environmental consultancy ADAS has been sampling leaves for the scheme since October with phoma, fungus which causes the disease, present in trial and commercial samples.

The first positive commercial results all came from leaves supplied by farmers from East Anglia and south Lincolnshire. Bayer said it is still eastern counties taking the brunt of the disease, but light leaf spot is now being picked up as far west as Somerset and Herefordshire.

One theory is that unseasonable drilling times have exposed plants to infection.

ADAS plant pathologist Julie Smith was surprised to see the disease so early, with positive results obtained from the first batch of samples.

'It confirms what we have suspected: that light leaf spot can be present in the crop much earlier than symptoms express themselves in the field,' she said.

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Bayer's Darren Adkins said he believed seeing light leaf spot so early this season could be as a result of early drilling.

He said: 'The first positive samples have all come from areas where cabbage stem flea beetle is a concern.

'With good conditions during late July and early August many farmers took the opportunity to get crops drilled. These crops have been exposed from an early stage.

'What is also of note is that positive samples have been recorded from Barbados, Elgar and DK Exalte – all varieties that have better resilience against the disease.'

Mr Adkins urged growers to be vigilant and use a second application of fungicide to safeguard against phoma reinfection and light leaf spot, especially where crops have been in the ground for some time.

He said: 'Light leaf spot is as damaging as any oilseed rape disease and if it gets in then there is no curative option.

'The gap to stem extension can be long and we have seen the disease continue to cycle over a series of mild winters.

'There is still nothing better than Proline275 (prothioconazole) for light leaf spot and it has to be the base in light leaf spot control strategies.'