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Weeds challenge sparks search for non-herbicide tools

GRDC Nuffield Scholar Mitch Henderson in a crop of PBA Hallmark XT (PBR) medium red lentils on his family’s continuously cropped farm near Wilkur, Victoria.
Photo: Brad Collis

Mitch Henderson uses multiple tactics to manage weeds on his family’s farms near Berriwillock, Wilkur, Brim and Werrimull in Victoria.

The 33-year-old and his family deploy different tactics to delay the onset of herbicide resistance.

In 2021, after using narrow windrow burning for several years, the Hendersons bought two Seed Terminators to kill herbicide-tolerant weed seeds at harvest.

Generally, the family runs a rotation of wheat/barley/lentils. This is sometimes followed by oaten hay if there has been unsatisfactory control of grass weeds.

“If we don’t use the Seed Terminators, we always burn narrow windrows to target weeds that have escaped herbicide control,” Mitch says.

“We tend to pick up a small amount of soil when harvesting lentils, so it will be interesting to see how quickly the weed seed mills wear over time.”

Mitch plants the medium red lentil PBA Hallmark XT across about 39 per cent of the farm because it is well-adapted to the soils, high-yielding and allows Group 1 and 2 herbicides to be used to control in-crop weeds.

After a pre-emergent herbicide is applied, the lentils are sown using knife points and press wheels set on 204.8-millimetre (12-inch) row spacings.

He targets grass weeds with an early spray. A second grass herbicide is often applied with a fungicide targeting Ascochyta blight. A spray for heliothis then follows, and a second fungicide spray is applied if required. Paraquat is used to desiccate the lentils before harvest.

“We’re using herbicides from Group 1 and 2 in our lentils for in-crop grass control,” Mitch says. “These herbicides have a high level of risk for developing herbicide resistance, which isn’t ideal.”

To delay the onset of resistance, he recently bought an Agrifac self-propelled boomspray fitted with the AiCPlus camera system. The system uses artificial intelligence to detect and spot-spray weeds in crops and fallows.

“I’ll be interested to see how the spot-spraying system works to kill weeds that survive the first spray in our lentils,” he says.

Another tactic embraced is a Weed-It camera sprayer to selectively control summer and autumn weeds.

With an annual average rainfall of 300 to 350mm, the Hendersons take a leave-no-survivors approach to prevent weeds from robbing moisture and nutrients from the soil.

To explore weed management technologies under development to take the pressure off herbicides, Mitch applied for a 2020 Nuffield Scholarship. GRDC supported his study tour seeking non-herbicide weed control innovations.

Although most technologies were prototypes, he was hopeful gear from the US and Australia would become commercially available within the next five years.

“I love a challenge and am always looking for practical ways to improve business profit,” he says.

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