Smart strategies for radish
GroundCover™ Issue: 104 | Author: Melissa Williams
Owners: Simon and Dahnie Smart,
trading as EF Smart Pty Ltd
Manager: Shaun Earl
Location: ‘Wicka’, Chapman Valley
Farm size: 13,500 hectares (arable)
Rainfall (average annual): 380 to 400 mm
Soil types: yellow sandplain, red loam/clay
Soil pH: 5 to 6
Crops grown 2012: wheat (9900ha), canola (1735ha), lupins (1241ha) and barley (322ha)
Efforts to eradicate wild radish have intensified on the property of Simon and Dahnie Smart at Chapman Valley, near Geraldton, as costs to control this scourge escalate to about $50 per hectare.
Across the northern agricultural region, radish is the hardest and most costly weed to kill and it is fast developing resistance to a wide range of herbicide actives.
Shaun Earl manages the Smarts’ farm and says the family is closely monitoring wild radish resistance and implementing a range of chemical and non-chemical strategies to combat this problem.
“We know there is partial radish resistance on this property to all chemicals but we don’t have plants with full resistance,” he says.
In the past few years there has been a reliance on a double in-crop spray of pyrosulfotole, using Velocity® and Precept®, and this has achieved highly effective radish control.
But Shaun says there is concern about the longevity of this strategy in the face of potential weed resistance.
He says with no new herbicide options on the radar, the newer actives are being rotated through a range of crop types and varieties across seasons.
Shaun says results of the GRDC-funded Regional Cropping Solutions Network trials held on their property in 2012 that investigated a range of herbicide mixes and sequences were interesting.
The trial plots at the Smarts’ farm showed that a two-spray strategy using Velocity® first – at recommended label rates – in any of about 20 herbicide combinations resulted in effective radish control and uncompromised crop yields.
But Shaun says the success of the older chemical actives used in the second sprays should be treated with caution due to seasonal effects.
He says record dry conditions at the start of the growing season and through to July meant weeds were struggling and that was why the older chemicals worked well.
“In a normal-rainfall year, these combinations wouldn’t have been as effective,” he says.
“And in some cases in the trials last year, it took 70 to 80 days for the weed plants to die.
“I am sceptical that these older chemicals can still be used effectively. In our experience, in a normal season they only achieve a partial kill.
“It does not seem to be worth the risk and in the longer run could end up costing a lot of money. But, in saying that, I would like to see the sequencing trials repeated in a more ‘normal’ rainfall year to see if there can be more novel spray strategies that would be effective.”
In the meantime, the Smarts will continue with one or two winter sprays depending on rainfall, using the pyrosulfotoles, a summer spray with glyphosate and the introduction of a range of mechanical weed seed removal systems.
Chaff carts were used for the first time during the 2012 harvest in an attempt to reduce the weed seedbank.
In the past three years, spray capacity has doubled with the purchase of top-of-the-range boomsprays.
A WeedSeeker® optical weed sensor system is now used from October through to May for summer weed control.
“Our radish control program is massive and year-round costs us about $50/ha,” Shaun says.
He says systems are continually being refined and for optimal radish control the Smarts have found good success with boosting boomspray capacity to cover the ground faster, killing in-crop weeds when small (two to three-leaf stage), using recommended water rates when spraying (80 to 110 litres/ha), spraying between 9am and 4pm, and continually tidying up weeds using the WeedSeeker® system and Roundup® in-crop and during the summer months.
0429 108 425
End of Ground Cover Issue 104 (Western Edition)
Read the accompanying Ground Cover Supplement:
Ground Cover Issue 104 - Herbicide Resistance Supplement
GRDC Project Code PLN00006
Region West, North, South