How to manage black-grass in arable crops

A dominance of autumn-sown arable crops and herbicide resistance mean black-grass has become a major headache for many farmers. However, a combination of non-chemical management approaches can still deliver good levels of control, especially when combined with chemistry.

Managing weeds in arable rotations – a guide

Why has black-grass become such a problem?

Most black-grass emerges within crops, rather than before drilling, making it a tough target:

  • 80% of black-grass emergence occurs in early autumn (August to October)
  • Virtually all oilseed rape and, usually, more than 50% of winter cereals are sown before the end of September

Selective post-emergence herbicides no longer offer reliable control:

  • Multiple herbicide resistance now occurs on virtually all farms where herbicides are used against black-grass
  • Control has relied increasingly on weather-dependent pre-emergence herbicides
  • Additionally, high-risk management could drive the selection of resistance to the non-selective herbicide glyphosate

How to achieve high levels of black-grass control

  • Combine non-chemical control methods with herbicides to improve overall control and protect efficacy
  • Monitor weed populations to inform short-, medium- and long-term management
  • Conduct resistance tests (on weed seeds or plants) to establish which herbicides are likely to be the most effective
  • Consider the relative control cost of herbicides and non-chemical methods (herbicides may not be the cheapest option)
  • Avoid over-reliance on glyphosate to reduce resistance risks
  • Tailor control to each field
  • Aim for fewer than five surviving plants/m2

Basic black-grass biology

Integrated control strategies require a good understanding of black-grass weed biology. With a focus on its life cycle, our dedicated black-grass biology page will help you identify the chinks in the armour of this arable weed.

Arable weeds: Basic black-grass biology

Herbicide resistance

Regular use of black-grass herbicides is associated with resistance. Detected in almost every county in England and at a low frequency in Wales and Scotland, it is essential to control weeds with resistance in mind. The Weed Resistance Action Group page includes the latest information on resistance status and management guidance.

Herbicide resistance in black-grass

Integrated management

About 95–100% black-grass control is required to prevent populations increasing. There are many non-chemical control methods available. In isolation, none provides complete control. Our science-based information shows you how to stack the options for high levels of control.

Integrated management of black-grass