More than one way to kill a weed says leading researcher

Avoid killing herbicides by finding new ways to kill weeds, says researcher

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WEED WARRIOR: Associate Professor Michael Walsh from Sydney University says Australian agriculture desperately needs to develop non-chemical weed killing options to reduce herbicide use.

WEED WARRIOR: Associate Professor Michael Walsh from Sydney University says Australian agriculture desperately needs to develop non-chemical weed killing options to reduce herbicide use.

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Laser and electrical weed control have the potential to take pressure off herbicides in grain cropping regions.

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Laser and electrical weeding are the most promising non-chemical solutions to growing herbicide resistance in Australian cropping regions.

Michael Walsh, Associate Professor and director of Weed Research at Sydney University, said both laser and electrical weeding offered potentially low-energy, lightweight and cheap alternatives to chemicals.

Other potential alternative weed control technologies included solar irradiation, microwaves, heating, abrasive grit and air blast.

Dr Walsh told the Australian Farm Institute's Conservation Agriculture in 2030 webinar pressure on existing herbicides would keep rising because rainfall patterns during the past 100 years had shifted from winter to summer dominance in cropping regions.

This meant farmers were having to work harder at conserving every drop of moisture in their soils during summer to get crops through drier winters.

"We already have high levels of herbicide resistance across southern and western cropping regions, particularly in annual ryegrass," Dr Walsh said.

As well, he said glyphosate resistance in fallow weed control in northern cropping regions was becoming a major issue particularly with fleabane, barnyard grass and feathertop Rhodes grass.

"We need to change our approach to weed control. We are going to keep losing our herbicide resources if we don't change something."

Dr Walsh said other factors were impacting on herbicide usage including limited development of new products, public pressure and increasing regulation.

He said site-specific weed control ("treat the weed, not the paddock") using optic sensing technologies provided an opportunity to reduce costs by 11 to 90 per cent, depending on weed densities.

Alternative non-chemical weed control technologies using the same technologies could also reduce reliance on current herbicides.

However, physical or thermal weed technologies had to be applied directly to the target.

Optical sensing technologies such as Weedit, WeedSeeker and Weed Chipper (which Dr Walsh helped to develop) were available to detect green material in a brown field (fallow paddocks).

But the big challenge was site-specific weed control in a green crop ("green on green"), he said.

He said development of weed recognition cameras and sensing technologies was underway around the world.

Autonomous platforms were also being rolled which could be fitted with the new technologies to tackle weeds in growing crops.

However, most of them were in Europe and the US and were focused on high-value crops.

Dr Walsh said there were two major opportunities for in-crop site-specific weed control in Australia - early post-emergent and late post-emergent.

Using an average broadacre cropping area of 3000 hectares, Dr Walsh said a 34-metre boomspray equipped with weed recognition and spraying technology could easily handle the early post-emergent control "window" of three weeks.

The timeframe for weed control in late post-emergent crops was around three months which offered an opportunity to use autonomous vehicles which could cover around one ha an hour (multiple platforms would be needed).

These autonomous vehicles could do other jobs like soil and crop monitoring as well as weed recognition and targeting using a shrouded camera and constant light source, he said.

The story More than one way to kill a weed says leading researcher first appeared on Farm Online.

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