Yellow bristle grass (Setaria pumila) is a native of southern China and spreads rapidly through clean pasture. It is now present throughout the North Island and in Nelson and Marlborough in the South Island, and models have shown that it has a wide potential distribution throughout much of the country. It is particularly invasive in Waikato, where it can cover 20-40% of the ground within five years of invading the pasture.
The new edition of the Ute Guide, developed with funding from DairyNZ and the MAF Sustainable Farming Fund (SFF), updates findings since the 2006 edition on the behaviour of the plant and seed, the mechanism by which it is spread, the extent of its current and potential distributions and suggestions for long-term management of yellow bristle grass (YBG).
The guide’s recommendations for management include strategies for roadsides and small and large infestations.
One of the key recommendations is that damage to pastures at the time when YBG germinates, between October and December, should be reduced as much as possible. In addition, to minimise its spread it is crucial that pastures and roadsides are not grazed when the seed heads are present.
For pastures dominated by YBG, complete renewal is the best option. As part of pasture renewal, it is important to go through two summers of cropping, with plants such as chicory or turnips, where grass weeds are easily controlled. This depletes the reservoir of YBG seed in the soil so it will not rapidly reinvade the new pasture.
General recommendations for grazing include avoiding overgrazing, which can open pastures to weeds, and ensuring that stock are not moved from infested to clean paddocks when YBG is seeding.
One exciting update in this edition of the guide is promising new research that suggests selective herbicides may be available to control YBG. In the past, selective weed sprays were not thought to be an effective option.
Several herbicides are currently being investigated, with the herbicide called Puma® S showing the best potential for selective control at this stage. AgResearch Scientist Dr Trevor James is currently working with the proprietor Bayer CropScience to register its use in New Zealand pastures. Puma® S is a registered trademark of Bayer.
Note for editors: Content can be attributed to Dr Trevor James, AgResearch
For more information contact:
Dr Trevor JamesSenior Scientist, AgResearch Ruakura07 838 email@example.com
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