Prevention is much better than cure when it comes to Yellow Bristle Grass, writes Federated Farmers Policy Advisor, Dr Lisa Harper.

Yellow Bristle Grass is an invasive annual grass, causing ulcers in grazing animals and affecting pasture quality.

Early summer is the best time to act to avoid it becoming a problem at your place.

Originally from Asia, Yellow Bristle Grass (YBG) is now found from Auckland to the Manuwatu. This invasive pest is a serious concern to many farmers.


An aggressive plant, it out competes ryegrass and can quickly become dominant in a paddock, with the potential to spread by up to 70 per cent in some cases.

The seed heads cause lesions and ulcers to the mouths of grazing animals.

Read more from Federated Farmers here.

Stock avoid the plant when it's in seed, leading to both a serious loss in farm productivity and rapid spread of the weed.

Where yellow bristle grass has become established, annual feed production can be reduced by 30 per cent or more, with associated costs for replacement supplementary feed or pasture renovation.

Germination usually starts in October and peaks in mid-November. YBG is a prolific seeder, with distinctive seed-heads appearing from December onwards.

Seeds can be spread in contaminated hay or maize and via animals in manure and attached to fur.

Prevention is much better than cure, so learning to recognise the plant and watching for its appearance (especially on road sides bordering your property) is key.


A useful 'Ute Guide' is available from DairyNZ to help identify the weed, even when it's not showing its distinctive seed heads.

As YBG likes to grow in gaps, avoid pasture damage such as pugging and over-grazing, especially during its peak germination period.

Spraying in early summer can be effective, before YBG has a chance to seed. Some selective herbicides are available; Dockstar has recently been registered for use against YBG.

Roadside spraying practices have contributed to YBG's spread, with competing plants being sprayed out at the time of year when YBG becomes most active.

This increases the risk of it spreading into farmers' paddocks; keep an eye on your roadsides and act before it crosses the border into your place.

Federated Farmers has been working with councils to improve spraying practices on road sides, but to get on top of YBG, we need every landowner to secure their own properties by practicing good 'farm-gate' biosecurity and working with contractors on maintaining clean equipment between farms.