Published on 23/11/2021
On the upside, however, December is the ideal time to spray YBG infestations before they flower and drop another massive generation of seed into existing pastures.
That’s the advice from Nufarm, which says the only thing worse than paddocks that turn yellow with YBG flowers this summer is knowing they will look even worse next season.
Left unchecked, yellow bristle grass can become a serious production limiting weed.
One reason for this is that it is a highly-aggressive, annual-seeding weed which spreads rapidly through pasture, reducing feed quality in late summer and autumn.
Cows don’t willingly eat YBG, leading to low pasture utilisation. Grazing avoidance then leads to a massive seed set, rapid re-infestation and an opening for other weeds.
Researchers have counted up to 20,000 seeds per square metre in severe YBG infestations, ranging down to 5-10,000 seeds/m2 under light infestations.
A key recommendation for best practice control of known infestations is to stop YBG plants setting seed. This is a critical step in preventing the weed from spreading further.
Techniques include early mechanical topping (before viable seeds are set), heavy grazing or chemical control with a herbicide.
Dockstar® herbicide from Nufarm is registered for this use, and when applied to YBG after it has emerged from the ground, but before seed heads are visible, has proven very effective.
Paul Addison, technical specialist for Nufarm, says Dockstar has a nil stock withholding period, which is a real bonus for farmers trying to coordinate timely YBG spraying with their summer grazing rotation.
As a result, once the recommended pre and post spray timings are observed, pastures sprayed with Dockstar can still be grazed on a rotation as short as 21 days.
Previously, the earliest return time for paddocks sprayed for YBG control has been 35 days – seven days required between grazing and spraying, plus a 28 day stock withholding period.
Dockstar also requires at least seven days between grazing and spraying, plus a gap of at least 14 days after spraying to the next grazing - this maximizes YBG control and minimizes pasture suppression.
Recommended rates for Dock-star are 1.5-2.0 litres/ha, with no adjuvants or other products added to the herbicide.
While YBG seed heads are easy to spot, identifying the weed as a young plant can be more difficult, and since Dockstar will not control seeding YBG, it’s important farmers can distinguish YBG from other grasses before it flowers.
“Look for a flattened, hairless leaf sheath; long hairs at the base of rough-edged leaves and reddish-purple colouring at the base of the sheath,” Paul Addison advises.
After spraying, Dockstar is likely to cause temporary yellowing and growth suppression of some pasture species, including ryegrass and clover.
YBG typically germinates between October and December, so another useful tool for reducing populations is to encourage better pasture competition at this time of the year.
By reducing or avoiding pasture damage before and during the period of YBG germination, there are less likely to be bare patches where YBG has enough space and light to take hold.
For more detail contact your Nufarm territory manager.