Farmers must be bold and take a 'zero tolerance' approach to black-grass weeds emerging this spring, according to a Norfolk farmer and agronomist.

Hutchinsons agronomist Alex Wilcox said although autumn control measures were generally very effective, due to favourable weather and soil conditions well into November, he warned that high dormancy means there is still a continued risk of fresh black-grass emergence into the spring.

He said early treatment of small susceptible weeds is crucial, but growers must also ensure black-grass is actively growing to maximise the impact of post-emergence chemical sprays – which may require patience, especially when coming out of a cold spell.

'Even where resistance to this chemistry is present in field populations, there will still be some black-grass control and there is added value from control of wild oats and a range of broad-leaved weeds,' he said.

Mr Wilcox also advised farmers to walk their fields during the winter to identify and map problem areas. 'There's got to be a zero tolerance approach towards any patches of black-grass,' he added.

For those putting problem black-grass areas into spring cropping, Mr Wilcox said minimising soil disturbance during seed-drilling is the key to avoiding a flush of black-grass within the spring crop. He said direct drilling can therefore produce good results but where drill systems disturb more soil, he advised growers to focus on establishing a competitive crop as quickly as possible.

'Delaying drilling until late March or early April when ground is warmer can work, but it isn't always suitable especially if you're disturbing more soil as it simply encourages a flush of black-grass at the same time,' he said.

'You may be better drilling earlier at a higher seed rate when conditions are cooler and black-grass isn't growing to ensure the crop is in the ground and ready to go as soon as it warms up.'

Spring black-grass control tips

• Map problem areas now ready for treatment.

• Apply post-emergence sprays early when weeds are small, but…

• Ensure weeds are actively growing.

• Don't overlook any areas of poor autumn control.

• Minimise soil disturbance when drilling spring crops (5cm depth maximum).

• Consider the wider spectrum of weed control available beyond black-grass.