What are some blue-sky weed control technologies?
Herbicide resistance is driving a global innovation upsurge in non-herbicidal weed control technologies. Some have been in the wings for a while, while others are very new.
Professor Michael Walsh, Gulbali Institute at Charles Sturt University, says there has been a distinct increase in research, development and commercialisation efforts to bring growers novel technologies that target weeds in broadacre cropping systems.
“The move to reduced tillage systems has essentially removed cultivation and burning as weed control options for grain growers, resulting in a reliance on herbicides,” he says. “With the development of weed detection technologies, there are new opportunities to cost-effectively use physical weed control tools to target weeds in crops and fallows.”
While on a six-month Fulbright scholarship at Kansas State University and Texas A&M, Professor Walsh investigated several new technologies that could be realistic options for Australian broadacre farmers.
“There are some very promising results from the evaluations of novel techniques such as electric weeders and directed energy using blue light and mid-wave infrared radiation,” says Michael. “Other opportunities for targeted control include reproductive interference of weeds using gametocides and harnessing the power of allelopathy for weed suppression and nitrification inhibition.”
The WeedSmart Big 6 strategy promotes diverse herbicide and non-herbicide weed control tactics to keep weed numbers low in cropping systems. The latest weed control tactics and technologies will feature at WeedSmart Week in Port Lincoln on 29–30 July 2024.
How realistic is electrical weeding?
High-voltage currents cause resistive heating, resulting in plant cells rupturing as the charge passes through the treated plant, killing the weed or suppressing growth. Researchers from the West Australian Department of Primary Industries and Regional Development (DPIRD) leading a three-year project found that electro-weeding achieved control similar to herbicides, and that the technique was more effective on broadleaf weeds than on grass weeds. The project included conducting numerous field trials of a commercial electric weeder, the AGXTEND XPower (36 kW) powered by Zasso™, which demonstrated that ‘electro-weeding’ provides effective weed control in fallow and non-crop situations such as fence lines.
High-voltage electro-weeding is a slow process, operating at speeds of around 2–9 km/h. An Australian company, Azaneo, is developing a promising low-powered (<3 W) pulsed electrical weeding system that may allow faster ground speeds while providing comparable results on target weeds.
Electro-weeding technology could be coupled with weed detection technology and robotic platforms for more efficient application.
Can heat + blue light be used for HWSC?
Researchers at Global Neighbor, a company based in Ohio, are developing a system that uses high-intensity (440 nm) wavelength blue light to damage chloroplasts in the above-ground structures of weeds and mid-wave infrared (MWIR) wavelengths to damage above-ground and potentially below-ground plant tissue. The same combination effectively kills weed seeds in processed chaff fractions at harvest.
This technology is still in the early prototype stage. Preliminary testing with a benchtop system at the University of Western Australia has identified high efficacy (>90%) of the system on annual ryegrass seed present in wheat chaff. Further testing of the system against other weed species and various chaff types is needed to understand the potential for this technology as a harvest weed seed control system in Australia.
What about chemicals that interfere with different plant processes?
Two groups of chemicals that could have a role in weed management are gametocides and allelopathic chemicals. There is enthusiasm for exploring new use patterns of previously known chemicals and newly discovered chemicals with these properties.
Gametocides are chemicals used in hybrid seed production to prevent pollination. Some of these chemicals could be used to stop weed seed set. In addition to reducing the quantity of weed seed produced, this could also stifle the spread of herbicide-resistance genes across a landscape.
Allelochemicals are produced naturally in various crop and weed species (including canola and barley) and exuded by plant roots or leached from plant residues, suppressing the growth of other plant species. There is a considerable, ongoing interest in isolating these exudates for potential use as herbicides or genetic traits for breeding more competitive crop species.
Several plant species also produce root exudates that reduce biological nitrification in the nearby soil, effectively preserving more plant-available nitrogen for the plant’s use. It is possible that commonly grown crop species and endemic weeds of Australian cropping systems also carry these weed suppression or nitrification inhibition traits.
Combining weed suppression with biological nitrification inhibition (BNI) has the potential to provide paddock-wide weed suppression while boosting crop growth. This could be achieved through plant breeding or as applied products.
GRDC Update Paper – Novel weed control technologies
GRDC Update Paper – Evaluation of electric weeder in Australia
Field trials in Western Australia of a commercial electric weeder, the AGXTEND XPower (36 kW) powered by Zasso™, demonstrated that ‘electro-weeding’ provides effective weed control in fallow and non-crop situations, such as fence lines. Image: DPIRD.
