Improving oilseed rape prices and two consecutive seasons of successful establishment have fuelled expectations of another rise in plantings this autumn, prompting experts to urge growers not to overlook grass weed control.
With prices edging towards £500 a tonne and confidence returning to the crop, the Agriculture and Horticulture Development Board estimated the 2026 harvested area at 358,000 hectares. Even modest increases this season would see the national crop area approach double the level recorded just two years ago.
However, more growers returning to oilseed rape will also mean more crops being drilled into fields with existing grass weed problems, increasing the importance of effective herbicide programmes.
John Cussans, weed scientist at ADAS, said oilseed rape had historically been viewed as an important ‘cleaning crop’ within arable rotations.
“There are two reasons for that,” he said. “Firstly, there is different chemistry available in oilseed rape, which is like gold dust. Also, the crop itself is so suppressive.”
He explained that oilseed rape had once played a key role in reducing blackgrass populations, but changing establishment success following cabbage stem flea beetle pressure had reduced the crop’s competitiveness.
“Rather than being the cleaning crop in the rotation, some of the worst wheat crops for grass weeds have been following oilseed rape,” he said.
“If the area is going to go up, now is a good time to revisit the grass weed control options we have in oilseed rape to bring it back into a position where it is a really good cleaning crop in the rotation.”
UPL and Corteva have jointly issued guidance recommending sequential use of the herbicides Centurion Max, containing clethodim, followed by Kerb Flo 500 or AstroKerb, which contain propyzamide.
Tom Wheelhouse, technical sales manager at UPL, said clethodim continued to provide strong control of resistant blackgrass populations.
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“In a UPL study from countries across Europe of populations sent to us because agronomists suspect there is some resistance, we found that Centurion Max provided 94% control of black grass and 97% control of Italian ryegrass,” he said.
“It shows that where field performance has been an issue, it relates to factors other than resistance.”
He advised growers to follow stewardship guidance carefully by applying products before mid-October or before crops reached six leaves, while also observing restrictions around tank mixes and application timing.
Mr Wheelhouse added that water conditioners could significantly improve herbicide performance, with trial work showing average efficacy gains of 11%.
Corteva field technical manager Hugh Guinan said flexibility would remain important given unpredictable autumn weather.
“We are getting used to using propyzamide in less than perfect conditions,” he said.
“In many cases, we need to compromise between efficacy, application conditions and date.”
He said the ideal application window was typically from late October until early December, balancing soil temperature with weed size.
Mr Cussans added that herbicides alone were not enough and that strong crop establishment remained central to successful weed control.
“All of the elements involved in establishing the crop and getting it through any cabbage stem flea beetle damage, until it forms a decent canopy, are an integral part of good weed management alongside the herbicides,” he said.
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