Add a knockdown now to control your fleabane
From the July 2012 edition of Agriculture Today.
Coonamble district agronomist Rohan Brill checks crop competition with fleabane.
There are two distinct windows in-crop for the use of herbicides to control the weed.
For early post-emergent aplications (generally prior to Z31) the pyridine group of herbicides (e.g. picloram, clopyralid, aminopyralid) are the best option to provide residual control of late winter-early spring germinating fleabane plants.
“A knockdown component can be added to these products to broaden weed control spectrum for both broadleaf and grass weeds,” according to Coonamble district agronomist, Rohan Brill.
Research at Trangie Agricultural Research Centre undertaken last year, revealed the application of clopyralid (e.g. Lontrel) early post-emergent for label weeds also gave excellent control of fleabane – applied early August and measured post-harvest – and the product is compatible with many other herbicides registered on wheat and canola.
Mr Brill said with the pyridines being residual herbicides, plant-back periods need to be adhered to with pulse crops generally having the longest plant-back periods.
“For late post-emergent applications, (after Z31) – which is about the time in most areas where fleabane becomes established – crops need to be monitored closely using a threshold that you would be willing to accept in the fallow,” he said.
“While one to two fleabane plants per square metre may not affect the yield of the crop, control of fleabane at this stage is relatively cheap and effective – but weed escapees from this period become the headache of the summer fallow.”
At the cereal growth stages after Z31 and generally prior to booting, knockdown Amicide Advance is generally the best bet.
In-crop herbicides for fleabane control are effective for two reasons – firstly, they target the weed when small and secondly, they enable the added effect of crop competition to assist with control.
Further trials at Trangie Agricultural Research Centre last year, showed that a doubling of row spacing from 33 centimetres to 66cm also doubled the fleabane population in the early fallow period.
Growers considering machinery purchases in the near future should strongly consider looking at relatively narrow row spacing (eg 25cm) to reduce pressure on herbicides.
Contact Rohan Brill, Coonamble, (02) 6822 1000, firstname.lastname@example.org