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Researchers testing herbicides on lucerne seeds

Australian farmers will soon know the effectiveness of herbicides on lucerne seeds following new research that commenced in September last year

The Herbicide resistance in lucerne seed production systems in South East of South Australia project is the first research of its kind for the lucerne seed industry and will aim to provide insights into integrated weed management strategies to safeguard the sustainability of herbicides in the industry.

The project is expected to run until May 2023 whereby weed seeds will be gathered from 100 commercial lucerne seed paddocks in the southeast of South Australia – a region that produces more than 80 per cent of the country’s commercial lucerne seed.

Once collected, the seeds will be germinated in a controlled environment and will then be sprayed to determine the levels of herbicide resistance.

Annual ryegrass (Lollium rigidum), barley grass (Hordeum glaucum and H. leporinum) and sowthistle (Sonchus oleraceus) are the three weeds selected for the study.

Currently, all three weeds have confirmed herbicide resistance throughout Australian cropping regions, however the extent of this resistance in lucerne productions regions remained unknown.

Lucerne Australa executive officer Dr Katrina Copping says the data gathered with the study will be crucial for the sector’s future.

“Basically, the research will give us access to information to extend the life of the herbicides we have available to our industry,” Copping says.

“That will make lucerne seed production more sustainable in the long run.”

Copping also says that while herbicide resistance is well documented in broadacre farming, no evidence exists regarding the impacts of it in the lucerne seed industry.

“It has been raised by industry representatives and growers because they have seen poor weed control in their lucerne seed crops,” Copping says.

“The thing about lucerne seed production is we are limited with the amount of herbicide options available to growers. A reliance on a small group of chemicals, it is one of the precursors of weed resistance development.”

AgriFutures, which supports the project through its Pasture Seeds Program, hopes the vital information garnered through the project may also be applicable for other pasture seeds industries.

Herbicides, given their efficiency and cost effectiveness, are imperative for the lucerne seed production systems, however the small-scale nature of Australia’s lucerne seed industry means there are limited available herbicide options.

Keeping weed populations controlled in order to satisfy requirements for seed certification is vital for the weeds’ export sale viability, according to Copping.

“Growers must make sure certified lucerne stands are clear of weeds and they aren’t allowed to have regeneration of volunteer lucerne seedlings in certified seed crops,” she says.

“We don’t have a lot of options and it’s a recipe for the development of herbicide resistance, based on what we know in broadacre situations.

“But unlike broadacre farmers, lucerne seed producers don’t have the option of changing to grow another crop next year due to the perennial nature of the crop.”

The project will be conducted by Plant Science Consulting – an Adelaide-based research organisation, in conjunction with AgriFutures and Lucerne Australia.

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