Controlling black grass in crops – ‘the answer is not in a herbicide can’

Irish tillage farmers can learn from the mistakes made by UK farmers in regards to the control of black grass, according to the ADAS’s Sarah Cook.

The UK-based consultant, who spoke at the Teagasc National Tillage Conference, said that black grass has become a major issue on farms in the UK.

This is especially the case in winter wheat and oilseed rape crops, she said.

“Black grass is a noticeable grass weed which is mainly found in the eastern counties of the UK, but it is moving to the north and west.

“Over 60% of tillage farmers say that the severity of black grass has increased in the last five years. It has also been a build up of tolerance to herbicides,” she said.

Cook also said that some farmers in the east of England are spending over €120/ha on herbicides to control black grass, while others are destroying crops to stop it from spreading.

We estimate that there 33,000ha of wheat was sprayed off last year in the UK due to black grass problems.

The crops specialist said that black grass can cause reduced yields, as winter wheat crops will see yields reduce by 63%. 

She said that farmers in the UK have started to drill crops earlier and she recommended that Irish farmers should not follow suit, as early drilling causes an increase in black grass populations.

Cook also advised Irish farmers to avoid using post-emergence sprays as herbicide resistance is already present in Europe for most weed grasses.

Herbicide usage is not sustainable in the long run.

“In England 97% of black grass is resistant to commonly-used herbicides, but there has been no field resistance identified for pre-emergence sprays.

“The answer is not in a herbicide can, it may appear to be, but in the long run with resistance issues it is not the answer.

However, she said that pre-emergence herbicides can play a big role in the control of black grass.

She also said that leaving a gap between crops by delaying drilling allows tillage farmers to use a non-selective herbicide which can kill 75% of black grass plants.

The ADAS representative also suggested that farmers use a crop rotation to deal with grass weeds in their tillage crops, but these rotations should be economically viable.

“Chopping and changing between spring and autumn cropping will give a better level of control.” she said.

Ineffective black grass controls
  • Continuous autumn cropping
  • Same cultivation type every year
  • Early drilling in August and September
  • Poor crops
  • Continued use of post-emergence herbicides

Comments

Please be considerate of others when commenting. All comments posted are subject to our commenting policy. Comments violating this policy will be removed without notice.