Barclay Crop Protection

Tighter stubble management offers key defence against ‘green bridge’

Growers are being urged to employ tighter strategies for pre-drilling stubble management, as increased resistance to herbicides, tighter rotations and declining crop chemical options make control of weeds and volunteers more challenging.

Managing stubble correctly takes pressure off pre-and post- emergence products and helps to get autumn crops off to the cleanest possible start, points out Bryan Pickles of Barclay Crop Protection.

"Adverse weather can draw out harvest, so early-cut fields of stubble are left for long periods before drilling, allowing volunteers and grass-weeds to become established," he says.

"Selective herbicides are coming under more pressure and, with more wheat going in the ground this year, growers must concentrate on early removal of as many grass weeds as possible," he explains.

"Start cultivation as soon as possible after combining.  Something very light, followed by rolling, will provide the ideal environment for weed germination.

"On stubbles with chopped straw, the first flush of weeds should be seen seven to 10 days after cultivations and rolling.  At this point growers can break the 'green bridge' with a suitable application of Gallup 360 (glyphosate), which for many growers forms one of the most cost-effective elements of their black-grass strategy."

By making consideration on a field-by-field basis, growers can pin-point areas of concern.  Where there is a high burden of black-grass, stale seedbeds should be created, he says, to help reduce the threat of resistance. 

It's not only weeds that growers should be worried about, though.  The green bridges created by these problem areas harbour the aphids which transmit BYDV, and provide a reservoir from which to carry the virus onto the new crop. 

"Cultivating alone isn't always effective," warns Mr Pickles, "as aphids can survive for several weeks under the soil before resurfacing and potentially causing significant yield losses.  That's why a combination of cultivation and total herbicide is the best option."