Enhanced green leaf retention from strobilurin fungicides can significantly improve oilseed rape yields and oil content, even in the absence of disease, according to Syngenta.

Last year was the first season for Amistar use in oilseed rape and results of field trials found applications of 0.8litres/ha gave an average yield benefit of 0.35t/ha where no disease was present, with a margin over treatment cost of £29.50/ha, says the firm’s Rod Burke.

This compares to 0.4t/ha extra where disease was present.

“To build yields in the key post-flowering period, you need to extend greening and maintain green leaf as long as possible.

Amistar maintains green leaf for 20-30 days longer and its timing flexibility allows it to be sprayed pre-flowering, which means there is no need to travel during flowering and risk more damage to the crop.”

In low disease situations, he suggests using the product at growth stage 59 (yellow bud), but where sclerotinia or alternaria protection is needed, application should be delayed until early to mid-flowering (GS60-65).

“Effective disease management must be prophylactic.

If the strategy is not to travel through a crop in full flower consider earlier application, but expect a reduced level of control.”

Field trials last season also found that average oil contents were 0.85% greater in Amistar-treated crops, compared to “standard fungicides” such as boscalid and iprodione + thiophanate.

This is due to better green leaf retention and improved pod fill, notes Mr Burke.

Glencore’s oilseeds trading manager, Nick Oakhill believes better use of fungicides is one way of improving UK oilseed rape yields.

Growers need to adopt similar attitudes to those in Germany and France, where oilseed rape is regarded as a mainline crop and average yields are 0.25-0.75t/ha higher, he says.

“Growers seem to think 3t/ha is all oilseed rape can produce and adjust inputs according to this.

But in some cases, yields as high as 7t/ha have been achieved and a national average of 4t/ha is achievable with a bit more attention.”

He believes a two-tier seed market is likely to develop involving industrial and specialist human consumption varieties – such as the low linoleic acid varieties, Nexera and Splendor.

paul.spackman@rbi.co.uk