Oilseed rape weeds will require assessment before taking action

Part Article taken from the Farmers Guardian

The make-up of spring herbicide strategies for winter oilseed rape crops should depend on the success or otherwise of pre-emergence and early post-em weed control, and the consequent effects on weed populations – and whether any decent frosts occur in the next few weeks.

That is the consensus of agronomists from various parts of the UK, as forward crops outcompete grass-weeds in many crops, but broadleaved types continue to pose a problem in some.

Agrovista’s Mark Hemmant says “Most crops got off to a good start, establishing well and then benefiting from good pre- and post-em weed control.

Mild Conditions

“They have since come through the winter well advanced due to the mild conditions, and that has created some strong crop competition for weeds.  We are in a lot better position than last year, where gappy crops caused by poor establishment and pigeon and slug damage then left easy inroads for weeds to establish.

“But there were also some areas where soils were quite dry when early-sown crops were established in the latter half of August, and in many cases it affected the efficacy of residual herbicides.

“Where growers were able to apply AstobKerb, the new Dow combination of propyzamide and aminopyralid, before February 1, this has helped, but while many planned an application of Fox (bifenox) – which has an EAMU for use in oilseed rape – but delayed it I the hope of colder weather, weeds have been able to grow away.”

With the window for application now closed (end of January) and Carbetamide approved for use only until the end of February, the armoury for spring control of grass and broad-leaved weeds is much smaller, Mr Hemmant says.

“It is still possible to use one litre per hectare Fox to control weeds such as field pansy, red dead-nettle, poppy and speed-well.”

In many cases, good crop cover is doing a decent job of suppressing weed growth, he adds.  But in the absence of a run of decent frosts, farmers who are trialling the concept of companion cropping, which should also be helping suppress weed growth, may need to look at spraying to kill off the companion plants.

“Galera (clopyralid + picloram) at 0.35 litres/ha, will control mayweed, creeping thistles, sow thistle and cleavers, and can also be sued for taking out companion crop mixtures.”

Galera can be applied from the four-leaf stage of the crop up to the point just before flower buds are visible above the crop canopy, which occurs usually at the end of March or beginning of April…..

 

07 February 2014

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