BASF Agricultural Solutions UK

Resistance testing is vital to help control black-grass on farm

  • Resistance testing should be taken to reduce risk and help support decisions on how to control black-grass.
  • Testing for resistance acts as an early warning sign to a bigger problem down the line.
  • By testing black-grass seed, you will know what you are dealing with.

The benefits:

  • Knowing what you are dealing with will help to determine the most appropriate herbicide program and can save money on potentially wasteful herbicides.
  • Get a picture of what herbicides will be effective in your field to aid both short & long-term management of black-grass.
  • Monitor resistance development on your farm and evaluate the most appropriate control tactics.

When to sample:

When sampling black-grass seed for resistance testing

make sure the seed is ripe

. Black-grass seed is

ready for sampling when the seeds are brown and the seeds fall off the panacle on their own

when gently brushed with your hand; you won’t need to force seed off the plant. This is normally 2nd-3rd week of July and when 10-20% of seeds have already shed.

How to sample


  • Collect a small mug of seed. Collect just the seeds; avoid collecting intact heads as they are unlikely to be ripe
  • Do not collect from the edge of the field. Collect a representative sample from across the field; across 2-3 tramlines and across an area of 100m.
  • Where patches of black-grass occur in the field, sample the patches and mix together; the bigger the area the better.
  • When you collect a mug of seed, allow the seeds to dry in a container for a few days.
  • Transfer seed to a paper envelope.
  • Samples are ready for sending.

Sampling black-grass for resistance testing

Resistance tests are only as good as the sample collected and the extent to which it represents the suspect population. Follow the guidelines above to ensure your seed sample is suitable.

Click here to read the WRAG guidelines for sampling black-grass

Deciding which field(s) to have tested

Ideally fields should be tested every 3 years to coincide with a typical 3 year rotation. Understanding the resistance profile of the black-grass population in the field will help to optimise control measures.

If cost is a prohibitive factor in testing then the following points can be used as a guide when selecting sites:

  • Fields that have never been tested before
  • Fields tested 5+ years ago
  • Fields with continuous cropping (i.e. winter wheat only)
  • Fields where control of black-grass is poor
  • Fields where suspected resistant patches are still very small/discrete
  • Fields with the worst yields

If sending black-grass samples for resistance testing, please download this form, complete it and send the form with your black-grass seed sample to ADAS Boxworth at the address on the form. Click here.

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