Manawatu - the nation's food, fibre capital
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Horizons environmental programme coordinator plant security Craig Davey says the grass is already affecting farming in Waikato and is easily transferred from roadside infestations, via stock movement and infested hay.
"Like a lot of weeds, yellow bristle grass is quick to colonise bare ground. Hot, dry conditions, poor machinery hygiene practices and spraying to bare earth can all exacerbate its spread," Davey says.
"Once established, it is a prolific seeder and becomes dominant in a paddock within a few years.
The grass has poor nutritional value and stock tend to avoid it once it begins to seed, which occurs between early January and March. Evidence also suggests that the seed heads may cause lesions and ulcers to the mouths of grazing cattle.
Yellow bristle grass is likely to have been present in the Manawatu-Wanganui region for decades and has been found along the state highway network and beyond.
The grass can be difficult to identify until it produces a seed head. In open pasture, its first leaves tend to be parallel to the ground. They are yellow-green to green in colour and usually red or purple at the base.
Where yellow bristle grass is prolific, annual feed production may be reduced by up to 20% resulting in increased on-farm costs due to the need for supplementary feed and/or pasture renovation. The result is estimated to be a cast of about $1,100/ha.
Davey encourages farmers to check out the distribution map on Horizons' website as well as information on identification and control options.
"The best control is prevention; have as much other vegetation in place as possible and, in disturbed areas, instigate spraying as soon as possible," he says.
