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Throwing a wide net over mobile weeds

Like feral animals, ‘mobile’ weeds move easily across landscapes, taking no notice of boundary fences, land use or land tenure.

These weeds are now the subject of a pilot ‘area-wide management’ project to trial cooperative and cost-effective methods to reduce the movement of these weeds and the herbicide resistance traits they have evolved.

The cross-industry project has Australian government funding to target weeds that are a common problem to all industries in an area and have ‘mobile’ seed and pollen – that is, they spread easily. Weed species that fit the criterion include flaxleaf fleabane, feathertop Rhodes grass and annual ryegrass.

In three distinct regions – in the Darling Downs region of Queensland, the Riverina region of NSW and the Sunraysia region of Victoria – project teams are devising and implementing area-wide management programs to tackle target weeds of concern in their region.

The University of Adelaide is providing targeted herbicide resistance testing within the pilot areas and mapping the spread of weeds, based on genetic testing conducted at the University of Queensland.

Dr Rick Llewellyn, senior principal research scientist (agricultural systems) with CSIRO is leading the ‘Area wide management for cropping systems weeds’ project to better understand the importance of weed mobility, and test the opportunities for this collaborative approach. He says the idea is to draw together industries and land managers to ‘find a collaborative solution to a common problem’ where a strong value proposition can be established.

Dr Rick Llewellyn, CSIRO, says more coordinated awareness and information sharing can channel effort and innovation into weed management improvements that benefit both the individual land manager as well as the district.

“Area-wide management has been very effective in the management of invasive animal pests and for some mobile insect pests,” says Rick. “We know that some weeds are particularly good at moving across the landscape, either as contaminants or borne on the wind or in flood water – and most farmers have experienced a weed incursion from a source beyond their farm boundary. We are testing collaborative and cost-effective ways to reduce the spread of cropping weeds across diverse farming landscapes.”

Each of the three pilot areas have identified the highest priority mobile weeds to target in their initial on-ground project. In the Sunraysia region the Mallee Sustainable Farming and horticulture organisations have partnered to develop strategies that minimise spray drift while also providing effective control of important weeds like fleabane. Dr Chris Preston, The University of Adelaide, is assisting the Sunraysia project team as they investigate application techniques and product choice for summer weed control in this diverse cropping region.

“Where a range of different crops are grown in close proximity there is a risk of damage through off-site movement of herbicides. To reduce this risk, growers using some products, such as phenoxy herbicides, must work within narrow application windows; but to prevent large populations of weeds setting mobile seeds, growers need cost-effective herbicide options,” says Rick. “The area-wide management trials led by Mallee Sustainable Farming compared weed fallow control efficacy of six alternative products registered for use in optical sprayers, as well as options for better control of mobile and resistance-prone weeds like sow thistle in horticulture.”

The area-wide management trials led by Mallee Sustainable Farming compared weed control efficacy of six alternative products registered for use in optical sprayers, as well as options for better control of mobile and resistance-prone weeds like sow thistle in horticulture. Photo: Frontier Farming Systems.

In the Riverina’s Murrumbidgee Irrigation Area, the focus of the area-wide trials led by the local Irrigation Research and Extension Committee (IREC) is to reduce the movement of weed seed within the irrigation scheme through better management of channel bank vegetation.

Establishment of weed-suppressive grassed channel banks is being tested to assess its feasibility as a weed management strategy that could bring benefits to the many industries that utilise the irrigation scheme. The area-wide activities in the Riverina also attracted extra support from the wine industry with additional trials established to prevent seed set of mobile weeds in vineyards.

The Darling Downs pilot is addressing the management of drainage line and roadside vegetation, particularly where farmers are aiming to maintain weed-free fallows. The project also included the demonstration of new innovations, such as the mechanical weed chipper for control of glyphosate resistant weeds in fallows. The focus weeds in this project are fleabane and feathertop Rhodes grass, both of which can be difficult to control with knockdown herbicides such as glyphosate.

The Darling Downs area-wide weed management project is focused on the management of road-side vegetation, particularly alongside cropping paddocks.

“In each of the pilot areas we have conducted herbicide resistance testing to build a picture of the extent and pattern of resistance across the landscape, on public lands, orchards, vineyards, and on grain and cotton farms,” says Rick. “We have also used genetic testing to map related populations to determine where weeds have come from. For example, we are interested in whether the weeds in the cropping paddocks are related to those found on adjacent roadsides, or did they originate from a distant site.”

Initial findings suggest that there is not usually evidence of ‘resistance fronts’ moving across a district, but rather resistant weed outbreaks are usually scattered. This points to the importance of localised ‘neighbourly’ action to reduce the overall cost of weeds, in addition to broader regional approaches to prevent the introduction and spread of problem weeds.

The WeedSmart Big 6 tactics can be applied to area-wide management as well as within a cropping enterprise to tackle resistance through strategic patch management and diverse control methods that result in low weed densities and prevent seed set of mobile weeds.

Rick says more coordinated awareness and information sharing can channel effort and innovation into weed management improvements that benefit the individual land manager as well as the district.

“There has been an increase in the diversity of food production industries in many districts over recent decades, so there’s more and more opportunity for a collaborative approach to reduce weed costs and risks as ‘new neighbours’ become established in many dryland grain growing areas,” he says.

Research and development partners involved with the project include Grains Research and Development Corporation, Cotton Research and Development Corporation, AgriFutures Australia, CSIRO, University of Queensland, University of Adelaide, University of Wollongong, Mallee Sustainable Farming, Millmerran Landcare Group, Irrigation Research & Extension Committee Inc, together with Wine Australia, the Toowoomba Regional Council and a range of additional local industry organisations.

This project is supported through funding from the Australian Government Department of Agriculture as part of its Rural R&D for Profit program and the Grains Research and Development Corporation and the Cotton Research and Development Corporation.

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What to expect at WeedSmart Week 2021

Big 6 at WeedSmart Week 2021 – Double knock to protect glyphosate
The WeedSmart Forum is set for Tuesday 17 August, 2021 at the Civic Centre in Esperance WA. The program features growers, agronomists and researchers discussing ways to use the BIG 6 to beat crop weeds. You can register for the 3-day WeedSmart Week event here.
Greg Warren from Farm and General in Esperance will be sharing his thoughts on the control of weeds like summer-germinating ryegrass, marshmallow, fleabane and portulaca.
He says the growers around Esperance are tackling glyphosate resistance in annual ryegrass, along with brome and barley grass and other emerging weeds using a range of integrated control tactics. The double knock plays a key role in preserving glyphosate (and soil moisture) and providing a clean seed bed for planting crops.

 
Big 6 at WeedSmart Week 2021 – Increase crop competition
WeedSmart Week 2021 is set for Tuesday 17 to Thursday 19 August, 2021 in and around Esperance WA. The last two days feature local growers hosting visits to their farms and discussing how they use the BIG 6 to beat crop weeds. You can register for the 3-day WeedSmart Week event here.
One of the farms hosting a visit during WeedSmart Week is Warrakirri’s 12,800 cropping operation at Condingup. Farm manager Con Murphy has implemented a variety of tactics to combat their main weeds – annual ryegrass and wild radish. Since 2015 the farm has undergone an intensive soil amelioration program to improve the drainage and ameliorate the sandy soils across the farm.
Con says the benefits have been seen in better germination and establishment that sets their cereal, pulse and canola crops up to compete strongly with weeds. There is also a benefit at the end of the season where rain in August or September enters the soil profile without causing waterlogging, and providing a better finish for their crops.
Since 2016-17 about 80% of the farm has been ripped and a portion has been ripped 2 or 3 times because the sandy soils tend to slump after substantial rainfall events, recreating the hardpan.
Con will be showing the WeedSmart tour group how their ripping, drainage, liming and spading program has helped grow more crop and less weeds!
Listen to the podcast with Warrakirri’s Con Murphy talking about the impact of improved drainage on crop competition

Big 6 at WeedSmart Week 2021 – Implement harvest weed seed control
The WeedSmart Week machinery display is set for Wednesday 18 August, 2021 at Dave Campbell’s shed near Esperance WA. The 3-day WeedSmart Week program features growers, agronomists and researchers discussing ways to use the BIG 6 to beat crop weeds. You can register for the 3-day WeedSmart Week event here.
We’ve saved the harvest weed seed control discussion for the machinery session on Wednesday 18 August. Ben White from Kondinin Group will host the machinery session with spray and harvesting gear on display including impact mills from Seed Terminator, Redekop and iHSD (both hydraulic and belt-driven), Emar chaff deck, and spray technologies including Goldacres’ G6 Crop Cruiser series 2, and weed detection technologies using drones and weed identifying cameras (green on green).
Ben White, Kondinin Group (Photo: Melissa Powell, courtesy of GRDC)
Growers doing the WeedSmart Big 6
WeedSmart Week 2021 is set for Tuesday 17 to Thursday 19 August, 2021 in and around Esperance WA. The last two days feature local growers hosting visits to their farms and discussing how they use the BIG 6 to beat crop weeds. You can register for the 3-day WeedSmart Week event here.
One of the growers who will open up their farm for a visit is Adrian Perks who farms at Condingup, 70 km north-east of Esperance. Adrian runs a continuous cropping program on his 4300 ha property, growing canola, wheat, barley, faba beans and lupins. This diverse rotation allows him to mix and rotate both chemical and non-chemical weed control tactics. Over half of Adrian’s farm is sandplain, on which he has implemented a soil amelioration program to address non-wetting to increase the competitiveness of his crops. He currently uses chaff decks for harvest weed seed control and is introducing an impact mill this season. Adrian monitors the tramtracks for weed growth and if he feels the weed pressure is too high, he uses a shielded sprayer to reduce seed set. The bus tour will include four farm visits and a machinery display.
Listen to Adrian on the Regional Update podcast.
Adrian Perkins, Condingup WA
 

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WeedSmart agronomist set to tackle high rainfall zone weeds

Every locality has its own spectrum of weeds, and growers face different opportunities and challenges regarding the control tactics they can employ.
The WeedSmart Big 6 approach is a practical way to ensure that an integrated weed management program is put in place that disrupts weed seed production and the evolution of herbicide resistance.
Commencing in January 2021, Jana Dixon has joined the WeedSmart team of extension agronomists, with a focus on applying the Big 6 to manage weeds in the high rainfall cropping systems of southern Australia – from Esperance in WA to south-eastern SA, Tasmania and south-western Victoria.
Jana will add to the dedicated and experienced extension agronomists on the WeedSmart team with Peter Newman in the Western region, Chris Davey in the South, Greg and Kirrily Condon in the East and Paul McIntosh in the North.
Jana Dixon has joined the WeedSmart team of extension agronomists, with a focus on applying the Big 6 to manage weeds in the high rainfall cropping systems of southern Australia – from Esperance in WA to south-eastern SA, Tasmania and south-western Victoria.
Jana hails from the Mid North of SA, and began working at Pinion Advisory (previously Rural Directions) while she was studying agriculture at the University of Adelaide. She has been employed full-time at Pinion Advisory since January 2019 as an agribusiness consultant, based in Clare, and spends most of her time delivering agronomy and farm business advice to clients from a wide range of cropping regions in South Australia.
Pinion Advisory is a foundation WeedSmart sponsor and Jana has been involved in two WeedSmart Week events already – the first as a participant and grower group organiser at the Horsham event in 2019 and then as the local organiser for WeedSmart Week 2020 in Clare.
In welcoming her to the WeedSmart team, program manager Lisa Mayer says Jana brings energy, commitment and insight to deliver communications focussed on the southern region’s high rainfall regions.
“Growers in the southern high rainfall zones are facing some serious issues with herbicide resistance influencing their farming decisions,” says Ms Mayer. “Jana will be engaging with agronomists, growers and researchers in each of the distinct high rainfall zones to understand the complexities and look for practical ways to apply the WeedSmart Big 6 in various cropping scenarios.”
“We plan to deliver WeedSmart Week in Esperance, part of Western Australia’s high rainfall cropping zone, in August 2021 and Jana will play a key role in the planning and delivering of our annual 3-day flagship event.”
Jana says her experience with the WeedSmart program has been very positive and she has been particularly impressed with the support the program has from all sectors of the grains industry.
Newly appointed WeedSmart extension agronomist, Jana Dixon (green cap) leading discussions with farm visit host, Ben Marshman, Owen SA, and growers and agronomists attending WeedSmart Week 2020 in Clare.
“I have spoken to many growers and agronomists who have found real value in the information that the WeedSmart program delivers,” she says. “For many it is as much about considering another operator’s philosophy on dealing with weeds, and taking a fresh look at their own systems, rather than just learning about a new tactic or the traits of a new herbicide in isolation from the big picture.”
She says the high calibre of industry people who contribute their time and expertise to the program is testament to the value WeedSmart has to agribusiness, growers, agronomists and researchers alike.
In taking on the responsibility for delivering information tailored for the high rainfall zones Jana says she is pleased to have an extensive network of contacts through Pinion Advisory, with offices in a number of high rainfall areas to provide easy access to local agronomists and growers. She is also aware that there are major differences in weed spectrums and farming systems in each high rainfall zone and plans to take full advantage of the opportunity this role presents to expand her understanding of different approaches to weed management.
“The long and favourable growing season and the associated prolonged periods of weed germination, is a key factor that I see potentially impacting on a grower’s weed management strategies in these regions,” she says. “On the other hand, access to highly diverse rotations and a focus on crop competition are two strategies that can play an important role in achieving excellent weed management in these regions.”
“I am keen to engage with anyone working and farming in the high rainfall zones to build my knowledge and understanding,” she says. “And to create opportunities to develop and extend the WeedSmart Big 6 strategies, both herbicide and non-herbicide, that work in each area and in different situations.”
WeedSmart is the industry voice delivering science-backed weed control solutions with support from the Grains Research and Development Corporation (GRDC), major herbicide, machinery and seed companies, and university and government research partners, all of whom have a stake in sustainable farming systems.
You an follow Jana on Twitter and keep up to date with the HRZ here.

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Never cut the herbicide application rate

Scientific studies have demonstrated that resistance can rapidly evolve in weeds subjected to low doses of herbicide. Some weeds can develop resistance within a few generations.
Full rates when mixing herbicides too!
When mixing herbicides it is important that each product is still applied at the full label rate to ensure high mortality.
Applying different chemicals in one mix can provide an additive advantage. It is important to understand the mode of action of each herbicide on the plant when preparing a herbicide mix. This is just as important for pre-emergent grass weed mixes as it is for post-emergent mixes aimed at broadleaf weed control. ALWAYS READ THE LABEL.
Surrounding weed seeds with a combination of pre-emergent herbicides with different modes of action can give a high level of control and help extend the useful life of all the chemicals used. The high level of control must be supported with additional control measures for all survivors. All products with different modes of action must be applied at full label rates for this to be an effective strategy.

 
Mixing two chemicals with the same mode of action can achieve some additional efficacy, however, the mix should deliver the combined full rate to ensure a lethal dose. The amount of stubble present and crop safety are all important considerations when mixing chemicals. For example, when using a tank mix of Avadex® and trifluralin to control ryegrass in wheat, the rates used will vary depending on the sowing system and level of stubble retention. Be sure to get good advice.
Many herbicides on the market are a combination of two or more modes of action within the one product. These products must be applied at the full label rate to be effective. Having dual action does not negate the need to change herbicide products and rotate modes of action. Repeated use of any single strategy will reduce the effectiveness of that strategy over time.
 

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