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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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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.


Maximising the weed control value of my crop rotation

with Kevin Morthorpe, Trait & Seed Technology Stewardship Manager, Pioneer Seeds
A diverse crop rotation is the twine that holds a good farming system together and underpins an effective weed management program.  
Kevin Morthorpe, Pioneer Seeds’ Trait & Seed Technology Stewardship Manager says herbicide tolerance traits in crop hybrids can be used to maximise competition against weeds and increase the herbicide options available to growers while optimising yield and profitability of the crop sequence in rotations.

Kevin Morthorpe (left) – Pioneer Seeds’ Trait & Seed Technology Stewardship Manager, with Dr Ray Cowley – Canola Research Scientist, Corteva Agriscience and Pioneer Seeds’ Rob Wilson – Strategic Customer & Market Development Manager and Clint Rogers – Western Regional Sales Manager & Canola Product Lead at a canola research trial near Jindera in southern NSW.
Plant breeders continue to introduce herbicide tolerance traits in a number of crops in Australia, including corn, canola, pulses, cereals, grain sorghum, summer forages and cotton.
“For example, in canola there are several herbicide tolerance traits and they are primarily available in hybrids,” he says. “This means growers get both improved crop performance due to hybrid vigour and more flexibility in herbicide use patterns.”
The increased vigour of canola hybrids also generates greater biomass production and early canopy closure that suppresses growth and seed set of weeds that germinate in-crop, complementing the use of pre-emergent herbicides.
“Hybrids super-charge crop competition through a strong root system and vigorous growth,” Kevin says. “From an economic angle, hybrids optimise yield in both high input and tough environments. In fact, we see more growers selecting hybrids when producing canola in tough conditions.”
Since the release of the first herbicide tolerant canola in 1991, the popularity of herbicide tolerance has seen a 98 per cent adoption of canola varieties with tolerance to imidazolinone (Clearfield), triazine (TT) or glyphosate (RR). In the last 15 years, the area sown to hybrid canola has risen to an impressive 47 per cent in Australia. With glyphosate tolerant canola hybrids entering South Australia in 2021 and new hybrid releases, the hybrid percentage will increase further over coming years.
With glyphosate tolerant canola hybrids entering South Australia in 2021 and new hybrid releases, the hybrid percentage will increase further over coming years.
Kevin says that Pioneer Seeds have seen increasing demand for Clearfield canola in recent years following a dip in popularity. Through strategic application of herbicide tolerant traits in diverse crop rotations it seems that farmers are overcoming the resistance problems that were prevalent with the Clearfield technology and can now re-introduce these varieties and take advantage of the weed control benefits and high yields they offer, and manage herbicide residues in the soil.
“A diverse rotation of crops and pastures is one of the WeedSmart Big 6 tactics, which Pioneer Seeds endorses wholeheartedly to protect the longevity and effectiveness of herbicide tolerance traits,” he says. “Through an effective crop rotation you can tick off all the herbicide and non-herbicide tactics needed to drive down weed numbers.”
How do I make the most of a hybrid crop?
In brief: Employ best practice agronomy.
The details: Grain hybrids are vigorous plants that produce increased biomass and grain yield. To do this, they must be supported with adequate crop nutrition. When properly fed, hybrids will provide increased crop competition and achieve greater water use efficiency compared to their conventional counterparts.
Growing a hybrid crop with herbicide tolerance traits does not equate to a full weed control program. These crops must be used within the WeedSmart Big 6 framework, within a diverse crop rotation and using herbicide tactics such as double knocking alongside cultural practices such as harvest weed seed control and crop competition to reduce seed set. They also combine well with pre-emergent herbicides to achieve excellent early weed control and suppress seed set in any late germinating weeds.
Can I use hybrid crops with herbicide tolerance to fix a weed blow-out?
In brief: No. This technology is not suitable for salvage operations.
The details: When Roundup Ready canola varieties were first released there was an expectation that these traits could be used to reverse a weed infestation. This proved not to be the case.
Hybrid crops are best used in low weed density situations where they can effectively drive down the weed seedbank. They should be grown in rotations that include an effective double-break, brown manure crop or a pasture phase.
Having hybrid crop options for both summer and winter growing seasons increases the opportunities to tackle weeds throughout the year or to use different fallow herbicides while maintaining the ability to safely grow crops in the following season.
New glyphosate tolerance traits (Truflex® and Optimum GLY®) and the stacking of herbicide tolerance traits of triazine tolerant and Clearfield® (TT+CL) have expanded the safe window for herbicide application in canola.
Are residues in grain a concern when using stacked trait herbicide tolerant hybrids?
In brief: Not if the stewardship program is followed.
The details: New glyphosate tolerance traits (Truflex® and Optimum GLY®) and the stacking of herbicide tolerance traits of triazine tolerant and Clearfield® (TT+CL) have expanded the safe window for herbicide application in canola. This gives more options, more flexibility and more crop safety through the rotation.
The stewardship program for the herbicide tolerant trait hybrids describe herbicide use patterns that growers must follow to confidently avoid the accumulation of herbicide residue in the grain and ensure that Australian maximum residue limits (MRLs) will not be exceeded. [Note that MRLs in other countries may be different to the Australian MRL. Find out more at Grain Trade Australia] 
To avoid problems with crop safety within the rotation it is important to maintain accurate paddock records to avoid applying herbicide to the wrong crop variety and ensure susceptible crops are not sown into paddocks with herbicide residues in the soil.
On the flip-side, herbicide tolerance in crops increases the options for crop selection within the rotation.
Also, keep in mind the importance of controlling any volunteers from a herbicide tolerant crop in the summer fallow or following crop.


Harvest weed seed control in a nutshell

*Note: In Australia we call the whole machine a harvester, not just the cutting front.
At harvest time many weeds that have grown in the crop still have seed held in the seed head. These seeds enter the harvester along with the grain and most exit the harvester and are spread across the paddock in the chaff and straw.
Collecting these weed seeds at harvest and either destroying them or depositing them in a known location where they can be monitored and controlled later, is an excellent way to stop weeds in their tracks.
Brome grass is the most costly weed for Mallee farmers to manage, even though herbicide resistance in brome grass is currently low in the region.
If you are considering adding harvest weed seed control (HWSC) to your weed control program there are excellent resources on the WeedSmart website to help guide you through the initial decisions and the implementation of this important weed control tool.
Key messages:

Decide on which system fits your farm best.
Get maximum weed seed into the header.
Know how to manage the collected weed seed.

Which system is best?
HWSC is being rapidly adopted in Australia and other countries around the world. There are six systems currently being used on Australian farms and they have all been developed by farmers. Research has demonstrated that all are very effective weed control tactics, achieving over 80 per cent control and for some nearly 100 per cent.
There are six systems currently used to collect and manage weed seed at harvest:

chaff carts
chaff lining
chaff decks (chaff tramlining)
impact mills
Bale Direct
narrow windrow burning

While they are all effective, they vary considerably in capital and ownership cost, nutrient removal costs, operational costs and labour costs. Some HWSC tactics involve the purchase of substantial machinery – such as an impact mill, chaff cart or chaff deck – but the operational and labour costs might be lower than methods such as narrow windrow burning, which involves low set-up costs but higher nutrient losses and labour costs associated with burning. Invariably narrow windrow burning is the most expensive option in the long-run due to the high nutrient removal cost.

To calculate the cost of each method for your farm you can use a calculator developed by AHRI’s Peter Newman.
The HWSC tools all involve some modification to the harvester. The simplest modification is for chaff lining and narrow windrow burning, where a simple chute is attached to the rear of the harvester to direct the residue into a band on the ground, running the same direction as the harvester has travelled. These chutes are often constructed and fitted on-farm.
All the other systems are commercial modifications that are fitted to the harvester – chaff decks and impact mills – or trail behind the harvester – chaff cart and Bale Direct.
WeedSmart resources:

Videos from the HWSC course outline the science and practice of HWSC
Calculating the cost of HWSC
Stepping into chaff lining
Using your harvester to destroy weed seeds

Get the weed seeds into the header
Harvest weed seed control only works on weed seed that enters the header. Getting the weed seed into the header relies on the seed being held in the seed head at the time of harvest. The seed head must also be at harvestable height.
Consider the weed spectrum and the likelihood of seed capture. Even if some seed has shed, chances are there will be other seed heads that have not yet shed and even this will assist with reducing the amount of seed entering the seed bank.
There are four chaff-only systems and two all-residue systems.
The chaff-only systems – chaff carts, chaff lining, chaff decks and impact mills – require the harvester to be set up to separate chaff and straw, and to keep the weed seed in the chaff stream. This may require modifications to the harvester rotor and sieves and the installation of a baffle to keep the weed seed in the chaff stream.
If you choose the Bale Direct system or narrow windrow burning, all the straw and chaff ends up in the same place, so no other modification to the harvester is needed.
WeedSmart resources:

Harvester setup for HWSC
Getting weed seed into the chaff stream
Using HWSC in different weed spectrums

Manage the weed seed after harvest
If you choose an impact mill as your HWSC tool then the tactic is completed in one pass at harvest, with nothing extra to do. All the residue is spread in the field and the weed seeds are rendered unviable.
All the other HWSC tools involve some action after harvest to remove or destroy the weed seed collected at harvest.
Chaff decks deposit the weed seed-laden chaff in one or both harvester tramlines or wheeltracks. Some growers find that the chaff rots and the weed seeds die, but in other environments growers find that it is necessary to control weeds that germinate in the tramlines using herbicide or non-herbicide tactics applied just to the tramlines.
Chaff carts can be emptied as they fill in the paddock or emptied at a central point. Many growers use chaff piles as a high nutrient value stockfeed, others burn the piles and others leave them unburned in the paddock and sow through them the following season.
Chaff lines are usually left unmanaged with the expectation that the following crop will provide adequate competition to the weeds to minimise weed growth and seed production.
The Bale Direct system results in large bales of crop residue that can be sold into suitable markets. Distance to market is usually an important factor in the success of this system for HWSC.
Narrow windrow burning uses fire to destroy the weed seed in the Autumn following harvest. There are significant labour costs and safety risks to consider along with the loss nutrients and ground cover.
Key resources to learn more:

Diversity Era online course – Harvest weed seed control 101
Kondinin Group Residue Management at Harvest – Weed Seed Options research report
Kondinin Group Harvest Weed Seed Warriors research report

Grower experiences:

Chaff decks and chaff lining in a high rainfall zone
Keeping pressure on brome grass with HWSC



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