IN the lead up to grain harvesting across southern Australia, growers are planning their weed management activity to control one of the most problematic and competitive broadleaf weeds – wild radish – and its seed is on the hit list.
Grains Research and Development Corporation (GRDC) weeds manager Dr Jason Emms said before harvest was the ideal time to stop seed-set of wild radish, control late-spring germinations, undertake crop-topping with registered herbicides and plan for harvest weed seed control.
“Growers in the region have told us they are concerned about wild radish developing resistance to routinely used herbicides,” Mr Emms said.
“To help prevent this, growers need to deploy a mix of tactics throughout the year to prevent seed set and to minimise the chances of herbicide resistance developing.”
If left unchecked, immature green plants present in high densities can interfere with harvest and mature seed can return to the seed bank, creating an ongoing problem.
GRDC has invested in multiple projects over the past 25 years to identify solutions to control wild radish.
This research has been compiled into the Wild Radish Fact Sheet that details measures growers can take to control the weed.
Weed expert and fact sheet author John Stuchbery said now was the time for growers to check for wild radish which may have survived herbicide applications and late-germinating plants.
“It is important to stop these seeding and topping up the seed bank,” Mr Stuchbery said.
“Growers can apply a follow-up in-crop herbicide with a different mode of action if the window for herbicide has not passed.”
He added now was also the right time to plan for crop topping or desiccating prior to harvest and for harvest weed seed control.
University of Western Australia research agronomist Dr Mike Ashworth, who currently works as part of the Australian Herbicide Resistance Initiative which is funded by GRDC, said growers were well-positioned to get on top of wild radish.
“In Western Australia, back in the 2000s many growers were not able to crop because of wild radish – but now they have it under control,” Mr Ashworth said.
“It is a war that can be won with attention to detail and the biggest Achilles heel is harvest weed seed control.”
Seed generated from one year of wild radish can leave enough seed dormant to fuel eight more years of weed infestations.
Harvest weed seed control systems such as seed destructors can intercept and pulverise up to 95 per cent of wild radish seed.
Growers who use harvest weed seed control systems including seed impact mills, chaff carts and chaff decks can reduce the wild radish seed bank over time, giving themselves the upper hand.
There are also herbicides registered that can be applied pre-harvest that are effective against wild radish, these are detailed in the GRDC Pre-harvest herbicide use fact sheet.
Long-term planning, with a focus on reducing the weed seed bank is key to successful control of wild radish.
