Difficult weed’s a growing problem

Flaxleaf fleabane threat increases


Grains
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Weeds like flaxleaf fleabane have proliferated in the Mallee and Wimmera in recent years.

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ACT NOW: Birchip Cropping Group contract services manager Cameron Taylor says growers should control flaxleaf fleabane early and protect future yields.

ACT NOW: Birchip Cropping Group contract services manager Cameron Taylor says growers should control flaxleaf fleabane early and protect future yields.

Summer showers have brought about a flush of weed growth in recently harvested paddocks, including the emergence of flaxleaf fleabane.

The hardy perennial weed has proliferated in the Mallee and Wimmera in recent years. And, as farmers are discovering, it is not a simple weed to manage.

The best way to control fleabane – which saps both nutrients and moisture from the soil and is notoriously hard to kill –  was researched by Birchip Cropping Group (BCG) after the 2011 floods.

The research confirmed what many farmers have already noticed: normal rates of regularly used summer weed control herbicide brews do not satisfactorily kill fleabane. In most cases, particularly when the weed is greater than 30cm tall, a second spray is necessary to achieve an adequate result (95 to 97 per cent control).

BCG corporate services manager Cameron Taylor said despite the difficulties, it was important to eliminate the weed from paddocks in order to avoid yield penalties in next season’s crop and subsequent seed set.

“Fleabane has a deep tap root and, like all summer weeds, it will use valuable stored moisture and nutrients in the soil,” he said.

“It is also a prolific seeder and because seeds are most commonly dispersed by wind, they can travel substantial distances if seed set is not prevented.”

Mr Taylor said widespread adoption of no-till farming and higher summer rainfall had contributed to the emergence of fleabane.

He said the seed could persist in the ground for up to 18 months. Seedlings only emerge from the top 1cm of soil, which partly explains why it has prevailed. More troublesome is the weed’s habit of germinating during the growing season.

“This is a major problem as fleabane is much easier to control when the plant is young,” Mr Taylor said.

“When it germinates during the growing season, there are limited options for control until the crop has been harvested and by then the weed plant is quite mature.”

BCG’s research is available at www.bcg.org.au/controlling-fleabane.

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