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Be Careful with Autumn Fungicides in Variable OSR

31 October 2011

UK - The wide variability in oilseed rape development this season means fungicide choice will require careful consideration.

With some crops very forward at up to 10 leaves, and others patchy and slow to establish in dry conditions, the advice is to be field specific when it comes to autumn fungicides, writes Farmers Guardian.

Arable Alliance agronomist Andrew Wells, who advises on crops in Nottinghamshire and Lincolnshire, says there is huge variability in development of crops in his region. Those drilled early (in August) and into moisture are forward and account for about 20 per cent of rape crops.

However, in what is currently one of the drier parts of the country, a lot of crops are at the more ‘normal' growth stage for this time of the season.

With no sign of phoma at the moment, disease prevention becomes less important for forward crops, but late phoma could affect those less forward, says Mr Wells.

"For these, I will probably apply Proline (prothioconazole) for disease prevention, rather than a product with growth regulation."

North Yorkshire-based NIAB TAG agronomist Patrick Stephenson says sufficient rain, good seedbeds and warm conditions have accelerated crop growth in the region and oilseed rape drilled a little late (mid-September onwards) ‘looks about right.'

"I'll be concentrating on dealing with any light leaf spot that comes in, and for the forward crops it will be a metconazole or tebuconazole being applied very shortly. Those less forward will have a Punch C (carbendazim + flusilazole) or Proline in a tank mix with a herbicide," he says.

Bill Barr of Prime Agriculture, who advises on crops in Bedfordshire and Northamptonshire, reckons oilseed rape is as forward as it has been for several seasons.

"In the last two years we got to mid-November and the crop growth stopped until February, but if you are looking for a bit of a PGR effect then Caramba (metconazole) or tebuconazole will be the options," he says.

Field requirements

"Metconazole is very strong and growers should avoid blanket coverage and only pick out those fields that really need it," he says.

"Otherwise, even though there is no sign of phoma as yet because of the dry conditions, I would go with prothioconazole for phoma protection and yield, and add in some tebuconazole for those fields which need holding back a little."

Robert Hurren, who advises in Suffolk for Apex Agronomy, estimates about 70-80 per cent of the rape he oversees will receive a fungicide application this autumn as most are well forward.

"This is the first year in the last four years where I can see most crops benefiting from an autumn metconazole, and while I have seen very few phoma lesions as yet, the added disease control will be welcome," he says.

TheCropSite News Desk

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