Using technology to put pressure on weeds

Herbicide resistant annual ryegrass has been an on-going challenge for grain producers in the Mintaro area of South Australia since the 1980s. Agricultural consultant Mick Faulkner has worked alongside growers as they tackle the problem and has been impressed with the tenacity of some growers in the area as they adopted a new attitude toward weed control. [caption id="attachment_4054" align="alignnone" width="940"]Mark Sandow (right) and his consultant, Mick Faulkner have come up with 13 weed control tactics and aim to six or seven of them in action at any one time on Mark’s farms at Mintaro SA. Mark Sandow (right) and his consultant, Mick Faulkner have come up with 13 weed control tactics and aim to six or seven of them in action at any one time on Mark’s farms at Mintaro SA.[/caption] “The growers that changed their attitude to a ‘no tolerance’ approach to weeds are the ones that have been able to gain the upper hand with herbicide resistant weeds,” he said. “This approach works because if you have no weeds you have no trouble with herbicide resistance.” When developing a weed control plan with growers Mick looks for tactics that have at least a 92 per cent control rate. The aim being to bring weed density right down and preventing any survivors from setting seed to keep reducing the weed seed bank. One grower who has fully embraced this no-tolerance policy is Mark Sandow, and in doing so he has almost eliminated herbicide resistant annual ryegrass, wild oats and wild radish from the 1900 ha of cropping land he owns and leases in the 500–600 mm rainfall zone of South Australia. “There are paddocks on Mark’s property where annual ryegrass covered 17 per cent of the area to begin with and this is now down to one per cent or less by doing everything possible to stop weed seed set,” said Mick. “Having low density and knowing where those weeds are in a paddock helps keep chemical costs right down as you are treating known problem areas, not the whole paddock.” Annual ryegrass was the first herbicide-resistant weed on the property and its resistance was confirmed 35 years ago. In the early days Mark used haymaking to manage weedy paddocks. Although he found it difficult to successfully make hay in their high rainfall conditions it did help with the weeds until better options came available. Over the last five or six years Mark has used GPS capability in his tractors to map and manage weeds. “We started using GPS to mark the location of weed patches and this gave us a better understanding of the scale of the problem,” he said. “It actually showed that the weed density was probably less than we first thought and gave us more confidence that the problem was manageable.” [caption id="attachment_4056" align="alignnone" width="940"]Mark makes the most of the technology available in the tractor to map where weeds are in the fields. When he started out he would ‘drop a flag’ but now he prefers to ‘mark lines’ to better illustrate the spread of weeds. Mark makes the most of the technology available in the tractor to map where weeds are in the fields. When he started out he would ‘drop a flag’ but now he prefers to ‘mark lines’ to better illustrate the spread of weeds.[/caption] Since then the Sandows have upgraded to the more accurate RTK GPS system and rather than ‘dropping a flag’ Mark now marks lines from one side of a weedy patch to the other. “This provides a much better weed map and we have no doubt about where the weeds are in a paddock,” he said. “When we treat these patches we use more expensive herbicides but on a much smaller area. I also check for any misses after a spray and pull out any plants that have survived.” Mark has found that most apparent ‘survivors’ have been due to reasons other than a chemical failure, but he recognises the need to physically remove older plants to prevent them setting seed. The Sandows direct drill all crops to save time and avoid erosion on some steeper areas of the farm. While not using a fully controlled traffic system Mark is still seeing benefits of keeping the most frequent traffic—the sprayer and urea spreader—on permanent tracks. “In a weedy patch the elimination of weeds is the highest priority and I am not overly-concerned if removing the weeds in that area also causes some crop losses,” he said. “Overall the crop losses are less now than they were simply because we keep to the permanent tracks and less crop is knocked down during spraying.” A very significant benefit of low weed density in a paddock is that cropping choices are much wider than if the grower is having to consider weed control as part of the rotation decisions. Mick said that with more choice, growers are able to sow crops that are likely to be the most profitable that season without being bound by weed control concerns. The Sandow’s farming system includes wheat, faba bean and canola in rotation on 2.5 m wheeltracks and sheep graze the stubble after harvest. The main soil type on the farm is red-brown earth over limestone with smaller areas of black clay. The crop rotation works well across the whole cropping area giving the Sandows more options to rotate chemical groups between cereals and broadlead crops. “We lease some cropping land from my cousin and the sheep belong to him,” said Mark. “Having the sheep graze the stubble helps keep weeds under control over summer and provides some extra feed for the sheep. In years that we don’t have sheep on a paddock it is clear to see the increase in weeds over summer. There is no doubt that they are doing an effective job.” Mark also uses narrow windrow burning in the canola crops as another weed control tactic. If there is a particularly high stubble load after back-to-back wheat Mark may also burn the stubble, although this is fairly rare. “I have tried cutting the straw under these circumstances but have noticed increased disease pressure so find burning is a better option in these paddocks, which will also help reduce the weed seed bank,” he said. Farming in a high rainfall zone means Mark is faced with several germinations of weeds over summer and autumn. He treats pre-seeding germinations as they occur using a one-off spray to remove weeds such as volunteer cereals, potato weed, salvation Jane and wild radish. “Having a clean field to sow into is essential to conserve moisture and to minimise in-crop weed pressure,” he said. “Our attitude to weeds has always been ‘if you see it, try to fix it’ and I am also willing to sacrifice a small area in a crop if that is the best way to reduce weed numbers.” After the autumn break Mark does the first spray of the season applying Sakura prior to sowing wheat and following up with Boxer Gold post-emergence in the known problem areas. “This is where the weed maps in the GPS system really show their worth,” he said. “I know that I am applying the herbicide where it is needed while keeping a lid on the cost.” Mark uses crop competition as another way to combat weeds in-crop. He and Mick choose the most competitive variety and increase the seeding rate to keep the crop density high. Mark sows all crops using a flexicoil bar with narrow point tines. The tines are set at 25 cm (10 inch) to keep the crop rows as narrow as possible while still managing the stubble and minimising the risk of herbicide damage to the crop from pre-emergent herbicides. “We find we can sow in all conditions—wet or dry—and get sufficient trash clearance using this set-up,” he said. “We plant the crops on narrow rows to increase their competitive ability without compromising yield.” Mark is also very conscious of the potential for glyphosate resistance to evolve in non-crop areas such as along fencelines. He sprays glyphosate initially, follows up with Spray Seed for any misses and then uses a hoe or pulls out any remaining weeds. Mark has removed most of the internal fences and has incorporated the land into the crop area where he keeps a close eye on any weeds that grow where the fences once were.

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What’s the benefit of a double paraquat knockdown?

The ‘double knock’ strategy has long been used and promoted as a valuable tool in the battle against glyphosate resistance in weeds, with paraquat typically applied to control weeds that survived the ‘first knock’ of glyphosate.  
James Jess, research and technical services manager, Western AG in Ballarat, says growers in his client group and beyond have used a double paraquat application to great effect this year, and avoided a very serious blow-out of glyphosate resistant annual ryegrass.
James Jess, research and technical services manager, Western AG in Ballarat. (Source: Syngenta)
“The 2020 season did not provide an opportunity for an effective pre-seeding knockdown and growers across the higher rainfall zones of Victoria found many large, well-tillered ryegrass plants flourishing in their crops,” he says. “We sent samples to Peter Boutsalis at Plant Science Consulting and the results of the Quick Test showed high levels of glyphosate resistance.”
The live plant samples sent to Plant Science Consulting were tested for their response to rates from 2 to 5 L/ha of 600 g active ingredient glyphosate, and many survived rates of 4 L/ha and above. Given the high level of resistance, Western AG put down a trial to compare a range of double knock options so they could give their clients more confidence going into the 2021 season.    
“We knew that the surviving plants growing in fields across the district would be setting a huge amount of seed and that growers would face a devastating situation unless we took decisive and effective action in 2021,” says James. “In the badly infested patches growers also took measures to reduce the amount of seed entering the seed bank at the end of the 2020 season using hay cutting or harvest weed seed control. In paddocks with mainly glyphosate susceptible ryegrass, desiccating feed barley is also a good way to drive down weed numbers.”
‘Double-knock to protect glyphosate’ is one of the WeedSmart Big 6 tactics, which will be the centre of discussion at WeedSmart Week in Esperance, WA in August this year. This flagship event always attracts growers from interstate keen to see how other farmers are keeping weed numbers low in different systems. Early bird registration is now open.
What double-knock options did you trial?
In brief: 1. Glyphosate followed by paraquat and 2. two sequential paraquat applications.
The details: A series of timings were also tested for both the double knock options. Each of the ‘second knocks’ were applied 3, 7 and 12 days after the first knock application.
The two paraquat applications either 3 or 7 days apart were clearly effective in the trial, with the first paraquat application providing 90 per cent control of the glyphosate resistant ryegrass. This means that in a year where it is not possible to implement a double knock, we know that a single application of paraquat at robust rates will still do a good job of reducing weed numbers.

Get more details from the Western AG trial site report.
What advice did you give your clients going in to the 2021 season?
In brief: Delay seeding and implement a double paraquat knockdown.
The details: It was essential to get on top of the glyphosate resistance in ryegrass and avoid a blow-out. Last season the resistance level was high but the plants were still mainly found in manageable patches. Given the amount of seed that was likely added to the seed bank and potentially spread during harvest, it was essential that extra emphasis was put on having a clean seedbed going in to the 2021 season.
Once an effective knockdown has been applied we then recommend growers use a pre-emergent herbicide to reduce weed emergence when the crop is young. Later germinations are then suppressed by the competitive crop. In our trial we used Sakura incorporated by sowing (IBS), which provided excellent early weed control.
Has the recommendation been adopted successfully?
In brief: Yes, rapid and widespread adoption.
The details: There was immediate adoption of this tactic in response to the situation that emerged last season in the high rainfall zone of Victoria. Over 70 per cent of the Western AG client base in the higher rainfall western districts of Victoria implemented a double-paraquat application pre-seeding to target glyphosate resistant ryegrass before seeding the 2021 winter crop. This high level of adoption was a result of the strategy being actively promoted to clients, with the trial results giving growers the confidence to implement the recommendation.
The Western AG double knock trial last year provided growers with the confidence they needed to take decisive action on glyphosate resistant ryegrass before seeding the 2021 crop.
The blow-out was a real eye-opener for growers about how important it is to keep weed numbers low and the resistance mechanisms in play for all agricultural chemicals – not just herbicides.
The double paraquat tactic is also a good knockdown prior to sowing Roundup Ready canola to meet the stewardship requirements for using the RR technology.
Although resistance to paraquat is currently quite rare in annual ryegrass, it has been found in situations where paraquat has been applied at sub-lethal rates over a long period of time. There have also been new cases of paraquat resistance confirmed, and identified as developing, in ryegrass populations in WA, SA, Victoria and NSW this year.
With this in mind, a simple switch to double paraquat as a pre-seeding knockdown is not recommended as a standard practice but rather as a strategic tactic to contain glyphosate resistance in ryegrass. Once that has been achieved, a set of diverse strategies, including herbicide mixes, must be implemented and any survivors must be removed before they set seed.
Resources

Western AG Double knock field demo results – 2020
Double paraquat and RR canola – Podcast with Mark Lawrence 

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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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