Don’t ignore black grass…control it

Black grass is becoming more and more prevalent in Ireland. Control of this invasive weed should be a top priority for all farmers. The weed has taken hold in the UK and results in the destruction of winter wheat crops every year.

Many instances of the weed have been found in Ireland and while some farmers are very diligent in controlling the weed, more may not know they have it.

It is important to keep an eye out for this weed (pictured above). If you do have it in your field, action needs to be taken immediately.

Some farmers have made wholecrop silage from infested wheat crops. However, it is important to ensure that the black grass plant has not gone to seed before it is cut, as this can result in further spread of the grass weed.

Prevention and future control

The use of herbicides only results in partial control, so a mixed approach needs to be taken and cultural control methods are essential.

Knowing where your seed comes from is key; using Irish certified seed gives a large amount of security to growers.

The AHDB (Agriculture and Horticulture Development Board) in the UK has put together a list of things that can be done to control black grass. If numbers still appear in crops, a chemical method of control should be used.

However, according to the AHDB, 97% control is the most that can be achieved – through both cultural and chemical control – where the weed has taken hold.


Ploughing results in a 69% reduction of the weed. If you spot it, it is recommended to plough that field in the season ahead.

Pull it

Where the weed is in small numbers, pull it before it goes to seed; but ensure that you have removed all of the plant.

Spray it

Where the weed is in large numbers in a crop, the area affected may be sprayed off with glyphosate before the weed goes to seed. This will result in the destruction of the wheat crop, but can pay off in the long run.

Crop rotation

Crop rotation can significantly reduce the incidence of black grass. Sowing spring barley and oilseed rape in a rotation with winter wheat can reduce plant numbers significantly. Spring cropping can reduce black grass levels by 88%.

Competitive crops

Establishing a competitive crop can result in a 22-26% reduction in the grass weed, according to the AHDB.

Delay drilling

Delaying autumn drilling can reduce black grass levels by more than 31%.

Reduce seed numbers

Sowing a grass ley, cover crop or leaving land fallow can reduce seed numbers by 70-80%, according to the AHDB.

This short video below gives a summary of the AHDB’s recommendations.