20 November 2001
Rape growers hit by OP restrictions
By Tom Allen-Stevens
A LEADING grain storage expert has warned growers that restrictions on the use of organophosphates in store could spell extra problems for rapeseed.
The advice comes on the eve of this years Grain 2001 event at Stoneleigh, where keeping stored crops in top condition is high on the agenda.
Controlling mite in oilseed rape has become more difficult since Actellic dust (pirimiphos-methyl) lost its approval earlier this year.
The only options now are to ventilate or dry the rapeseed, said Ken Wildey, from the Central Science Laboratory in York.
“It would seem that mites have begun to develop in seed which has been stored too wet,” he added.
Even if seed had been dried to the target moisture content for safe storage (7.5%), it may have reabsorbed atmospheric moisture over the autumn, he warned.
One option to alleviate any infestation problems is to blow cool air (below 10C) through grain, but this also has its limitations, said Dr Wildey.
“For cooling and drying, its important to remember that oilseeds require more powerful fans than cereals, as the crop is more dense.
“The alternative is to store oilseed rape at only half the depth of cereals to address this problem.”
Chemical control is now off-limits, he pointed out: Actellic, the most commonly used, has not been labelled for mite control on oilseeds for nearly two years.
“Old stocks with the original label were still able to be used until June 30 this year. Satisfar (etrimphos), is no longer distributed for use on such crops.”
Assured Combinable Crops told FWi that eliminating organophosphates on stored crops is a welcome move and encourages growers to ventilate whenever possible.
“Cheap pedestal ventilators are now widely available you can kit out an average store for under 1000,” said ACCS regional manager Bill Young.
“Despite the warm weather, there have been plenty of cold nights ideal to cool the store. Growers dont turn the fans on enough, in my opinion.”
Another option to cure a mite problem is to re-dry the surface layers of rapeseed, but growers are warned that over-drying causes brittle seed.
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