Recent summer showers have brought about a new flush of weed growth in recently harvested paddocks, including the notable emergence of flaxleaf fleabane.
The hardy perennial weed has proliferated throughout 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 BCG after the 2011 floods.
The research confirmed what many farmers have already discovered – normal rates of regularly used summer weed control herbicide brews do not satisfactorily kill fleabane. In most cases, but particularly when the weed is greater than 30cm tall, a double knock (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 the widespread adoption of no-till farming practices and increased incidences of summer rainfall had contributed to the emergence of fleabane in the region.
He said the seed can persist in the ground for up to 18 months and seedlings will only emerge from the top one centimetre of soil, which partly explains why the weed has prevailed in no-till systems.
But more troublesome for farmers 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.”
Growers requiring specific information on the best herbicide mixes and rates to use to control fleabane are advised to speak to their advisors. BCG research is also available at: https://www.bcg.org.au/controlling-fleabane/ or phone BCG on (03) 5492 2787.
This article was published in the Stock and Land on January 12, 2017.
