Cropping

Time is right to target wild radish growth

Grain Central, September 5, 2022

Wild radish is one of the most competitive weeds and allowing it to go to seed means up to eight years of weed seed lying dormant in the paddock. Photo: GRDC

SOUTHERN growers are being urged to check for wild radish, with the lead-up to harvest the optimum time to stop seed-set of this problematic and competitive broadleaf weed.

Grains Research and Development Corporation (GRDC) manager weeds Jason Emms said before harvest is 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,” Dr 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.

Weed expert John Stuchbery said now was the time growers should check for wild radish that survived herbicide applications, and late-germinating plants.

“It is important to stop these seeding and topping up the seed bank,” Mr Stuchbery said.

Dr Mike Ashworth. Photo: AHRI

“Growers can apply a follow-up in-crop herbicide with a different mode of action if the window for herbicide has not passed.”

He said that now is also the right time to plan for crop topping or desiccating prior to harvest, and for harvest weed seed control.

This research has been compiled into the Wild Radish Fact Sheet that details measures growers can take to control the weed.

University of Western Australia research agronomist Mike Ashworth works as part of the Australian Herbicide Resistance Initiative and 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,” Dr 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.

Long-term planning, with a focus on reducing the weed seed bank is key to successful control of wild radish.

Source: GRDC

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