Grains Research and Development

Date: 02.09.2013

Target fleabane in early spring

Author: Deanna Lush
Map of GRDC Southern Region Thumbnail

NSW DPI senior weeds research scientist Dr
Hanwen Wu says there are seven species of
fleabane but the three most common in
southern Australia are flaxleaf, tall and
Canadian fleabane.

PHOTO: Deanna Lush

Moving the main battle against fleabane to earlier in the season when plants are seedlings, rather than late spring and summer, is the key to improving control.

New South Wales Department of Primary Industries senior weeds research scientist Dr Hanwen Wu says there are seven species of fleabane, but the three most common in southern Australia are flaxleaf, tall and Canadian fleabane.

“Of these three common species, flaxleaf fleabane is the most predominant in cropping regions,” he says. “But it is easy to confuse the different fleabane species, particularly when plants are in early growth stages.”

The tools to control fleabane include herbicide, strategic cultivation, crop and pasture competition, mowing and grazing.

Fleabane

Fleabane has spread rapidly because:

  • it can flower and set seed over
    an extended period of time;
  • each plant can contain up to
    110,000 seeds;
  • seeds are easily dispersed by wind,
    surface water run-off and through
    water movement in irrigation
    channels and other waterways;
  • there is no dormancy required for
    the seed to germinate. Once seeds
    drop onto the soil surface, emergence
    occurs if climatic conditions are
    favourable;
  • peak seedling emergence occurs
    with mild wet springs and autumns,
    which were common in 2010, 2011
    and 2012; and
  • mature plants have a unique
    protective leaf structure, which
    restricts foliar herbicide uptake. 

Dr Wu says in-crop management to tackle plants while they are small should be the first and most effective strategy. Currently, Amicide® Advance 700 is the only registered in-crop option for control of fleabane up to the six-leaf stage in cereals. FallowBoss® TORDON is a new in-crop option that will be available from October 2013.

The most consistent and widely adopted double-knock for fleabane control in fallow is a mix of glyphosate and 2,4-D as the first application, followed several days later by a paraquat or paraquat and diquat-based product as the second knock.

The double-knock is more reliable than single-knock treatments across seasons, especially on older fleabane.

If populations are dense and herbicide is ineffective, strategic cultivation to pull out plants and bury seeds can be used where there is an appropriate opportunity within a farm system.

For most effective control in fallow, grain
growers should apply double-knock herbicide
applications at this fleabane size or smaller,
rather than on mature plants.

PHOTO: Ben Fleet

Fleabane is a poor competitor, so improved crop or pasture competition can be an effective non-chemical option for reducing fleabane.

IMAG Consulting agronomist Cameron Corke, from Forbes, NSW, says early control, when the weed is young and small, is easier than when plants are larger. But if control is attempted on bigger plants, a double-knock is still an effective option in summer fallow.

He says drier conditions have seen the decline of fleabane in the past year, to the point where some growers believe they have the weed under control. But he says a wet summer will test the extent to which weed control has improved.

More information:

Dr Hanwen Wu,
02 6938 1602,
hanwen.wu@dpi.nsw.gov.au

A fact sheet on Flaxleaf fleabane is available at: www.grdc.com.au/GRDC-FS-FlaxleafFleabane

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Region South, North