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Ask an Expert

What can I do at harvest to reduce my future weed burden?

As crops mature and harvesters begin reaping, consider the potential fate of seeds ripening on weeds that escaped in-crop control measures.
Peter Newman, WeedSmart’s western extension agronomist, says harvest time is an important opportunity to assess weed burden across the farm and be proactive about driving down the weed seed bank.
“Harvest can either be a super-spreader or a weed suppressing event,” he says. “Small patches of weeds can quickly expand when seed is blown out the back of the harvester. On the other hand, the harvester can be a powerful weed management tool if any one of the harvest weed seed control options are implemented.”
WeedSmart’s western extension agronomist, Peter Newman says efforts made to reduce the spread of weed seed at harvest will soon pay off for growers.
Australian growers have led the world in inventing and adopting harvest weed seed control tools such as impact mills, chaff carts, chaff decks and chaff lining, all of which can reliably destroy over 90 per cent of the weed seed that enters the front of the harvester.    
“In addition to harvest weed seed control there are several other actions in the WeedSmart Big 6 that growers can implement just prior to, during and immediately after harvest that will make a measurable difference to the weed burden in future growing seasons,” says Peter. “The WeedSmart Big 6 tactics are scientifically-proven to reduce the risk of herbicide resistance through diverse herbicide use and cultural control to prevent weed seed set.”
What can I do before harvest to manage late emerged weeds?
In brief: Scout for and map weedy patches. Consider sacrificing small areas of high density weeds. Swathing can be a very effective way to stop seed set of late emerged or resistant weeds. Collect weed seeds for herbicide susceptibility testing.
The details: Growers across Australia use a variety of methods to map weeds – from the simple to the sublime. ‘Dropping a pin’ using the tractor’s GPS mapping system as you travel through a weedy section when spraying or harvesting is easy and provides useful information about the distribution of weeds in the paddock. Many growers have their own drones and use them the collect images or video footage of the crop that can be viewed or analysed to identify high density weed patches.
Collect seed for herbicide susceptibility testing – knowing what still works is vital information for planning next season’s herbicide program. There are three herbicide testing facilities in Australia that are equipped to test weed seed samples – Plant Science Consulting, CSU Herbicide Resistance Testing and UWA Herbicide Resistance Testing.
Collecting weed seed before or at harvest is the most common method used. The collected seed must be mature, from green to when the seed changes colour. Before harvest, collect 30 to 40 ryegrass seedheads or several handfuls of wild oats seed. After harvest, it is common to find seedheads still in the paddock or samples of contaminated grain can be sent for analysis.
Keep samples from different locations separate and details noted on the bag. Only use paper bags (double layer) to collect and send seed samples. Ensure bags are sealed so that the samples don’t mix during transit.
Which harvest weed seed control tool is best for my situation?
In brief: There are six harvest weed seed control tools used in Australia – impact mills, chaff decks, chaff lining, chaff carts, bale direct and narrow windrow burning. Choose the one that best suits your system and budget.
The details: Impact mills are best suited to continuous cropping situations. Residues are retained and evenly spread. Chaff decks have lower capital cost and are well-suited to controlled traffic situations. Chaff carts are popular with grain producers who also run livestock. Bale direct is also expensive but has a good fit in locations where there is access to straw markets. Chaff lining is currently the best ‘entry level’ system and can be used in CTF or non-CTF systems, with best results where the harvester runs on the same track each year. Chaff lining has essentially superseded narrow windrow burning, overcoming the time required and risks involved in burning and reducing the loss of nutrients from the system.
If you haven’t used harvest weed seed control tools before, it doesn’t take long to build and fit a chaff lining chute ready for use this harvest season.
What should I be ready to do straight after harvest?
In brief: Spraying weeds immediately after harvest is fairly common practice. Weeds present may be close to maturity or fresh germinations of summer-active weed species.
The details: Some growers get in early with knockdown herbicide applied under the cutter bar when swathing barley or canola. Consider using the double knock strategy, heavy grazing pressure and possibly a soil residual herbicide that is compatible with your planned crop rotation. Pay particular attention to any weedy patches identified before or during harvest. Stopping seed set at every opportunity is the crux of an effective weed management program.
Give some thought to what might be the underlying cause of weedy patches – fixing problems such as pH and soil nutrition imbalances, waterlogging and spray practices that routinely deliver low doses of herbicide.

Ask an Expert

How can I set up my summer crops to help manage weeds?

Belinda Chase, agronomist at Dalby Rural
It has been a few years since growers on the Darling Downs have been able to plan for a summer crop. With the uncertainty surrounding planting opportunities came some hesitancy to fully invest in weed control.
Belinda Chase, an agronomist at Dalby Rural Supplies, says it is a welcome change to be actively planning for summer cropping and being more proactive with weed control leading up to planting.
“Our main weeds here over summer are feathertop Rhodes grass, barnyard grass and broadleaf species like flaxleaf fleabane and peach vine,” she says. “In terms of known resistance we have some Group 1 [A] and glyphosate resistance in barnyard grass and paraquat plus glyphosate resistance in tall fleabane. Annual ryegrass seed in hay from other states has also established in small areas, potentially bringing resistance that has evolved elsewhere.”
With more soil moisture than growers have had for several years, many have been planning ahead to manage weeds in winter fallows destined from summer crops – mainly cotton and sorghum, along with some millet, corn, mungbean and sunflower.    
“Pre-emergent, or residual, herbicides have played an important role in keeping weed numbers low in winter fallows,” says Belinda. “The next rain event will most likely also be the trigger for planting, and weed control in those early weeks of crop growth will be crucial.”
The WeedSmart Big 6 tactics can be applied to all crops to reduce the risk of herbicide resistance through diverse herbicide use and cultural control to prevent weed seed set.
What are the resistance risks with pre-emergent herbicides in summer crops?
In brief: Avoid over-using the same mode of action group throughout the crop rotation.
The details: There has been widespread use of knockdown herbicides with residual activity, such as Group 14 [G] flumioxazin (e.g. Valor), in winter fallows to maintain low weed numbers. With multiple use patterns in fallow (on its own or as a tank mix ‘spike’) and post-sowing pre-emergent in a number of summer crops, there is a risk that resistance to this mode of action could develop. There is currently no known resistance to Group 14 [G] herbicides in Australia but resistance has been identified in both grass and broadleaf species in other countries.
Valor has a plant back period of one month pre-sowing for pigeon pea, maize, sorghum and navy bean, two months pre-sowing for cotton, sunflower and mungbean and up to nine months pre-sowing for canola. It can be applied after sowing and pre-emergent to protect the crop as it establishes.
Tank mixes and co-formulations are an effective way to reduce the risk of resistance to Group 14 [G] herbicides. Significant escapes must be prevented from setting seed.
Another option for pre-emergent weed control in sorghum is s-metolachlor, a Group 15 [K] herbicide such as Dual Gold. Applied as a split application before and immediately after planting sorghum gives optimal weed control, provided the seed safener (Concep II or Epivio C) has been applied at planting.
Atrazine, a Group 5 [C] herbicide, also provides a pre- and post-emergence option for broadleaf weeds and some pre-emergent control of annual grasses like barnyard, crowsfoot, summer and love grass in crops such as sorghum and maize.
How can I best incorporate imi-tolerant summer crops?
In brief: Imi-tolerant (IT) hybrids are now available for sorghum, maize, sunflower and soybean, providing for alternative in-crop control options for a range of grass and broadleaf weeds.
The details: IT sorghum seed is in short supply this year, but there are other options to consider. Growers who have Group 1 [A] resistance in barnyard grass or who are looking for alternative products to control or suppress other key summer weeds may consider growing these herbicide-tolerant crops.
With an imi-tolerant hybrid, growers will be able to safely plant into paddocks where imidazolinone (Group 2 [B]) chemistry has been recently applied, say after an IT maize, wheat, canola or pulse crop, negating the current 12+ month plant-back requirement, which otherwise restricts the choices that growers have in summer. In this situation it is advisable to avoid applying Group 2 [B] herbicides to the current crop to break the ‘imi-cycle’ that can develop where imi herbicides are used in successive crops – resulting in a high risk scenario for the evolution of herbicide resistance.
The second major benefit is that an imi-tolerant hybrid can be planted into a paddock that has a broadleaf weed burden—a situation that would not be advisable for a non-IT variety.
Imi-tolerant (IT) hybrids are now available for sorghum, maize, sunflower and soybean.
Is patch management a good tactic for feathertop Rhodes grass?
In brief: Feathertop Rhodes grass is a serious challenge, but summer cropping can help reduce the weed seed bank.
The details: Controlling FTR can be easier in a competitive mungbean crop on narrow row spacing, than in sorghum and sunflower, which are typically grown on wider row spacings and do not quickly cover the inter-row.
Controlling feathertop Rhodes grass can be easier in a competitive crop on narrow row spacing, where the crop quickly covers the inter-row.
After applying suitable pre-emergent herbicides (if FTR numbers are low) or cultivating if FTR pressure is high, do everything you can to maximise crop competition. Consider narrower row spacing, optimal plant density, avoid planting gaps and provide adequate crop nutrition.
After the crop has established, use inter-row cultivation where necessary and harvest early. If there are areas with low density escapes of this prolific seeding weed, chipping is worthwhile before the seed sets. If patches of escapes are evident it can be very beneficial to accept a ‘short-term pain for long-term gain’ by ploughing or spraying out the affected patch of crop before the FTR plants set seed.
At harvest, record any patches of FTR and return soon after harvest to remove established plants and apply a pre-emergent herbicide to manage new germinations.
Further information

Feathertop Rhodes grass and sorghum – does this work?
Avoid getting stuck in the imi-cycle
Competitive sorghum to reduce FTR and BYG pressure


Chaff carts were made for feeding livestock

Chaff carts were invented in Canada in the 1970s as a fodder collection system, so they have always had an association with livestock. In the late 1980s they were introduced to Australia and used as one of the first harvest weed seed control (HWSC) tools to manage herbicide resistant ryegrass and wild radish in Western Australia.
Depending on the grower’s situation, chaff heaps in Australia have been burned, grazed then burned, sold as loose chaff for horse feed, grazed or knocked down then seeded through (unburned) and most recently, baled and used on-farm as conserved fodder.
Different model chaff carts incorporate more or less straw with the chaff, which can affect the feed value of the bales.
This latest method fits very well with the move to confinement feeding of sheep and brings the use of the chaff cart almost full circle. Given the long-standing association with fodder conservation, the value of the chaff as a feed source is well known, particularly for sheep.
A HWSC Calculator developed by WeedSmart western extension agronomist Peter Newman, now enables growers to quickly estimate the potential value of baling chaff from chaff heaps and feeding it out in on-farm confinement areas. Upper Eyre Peninsula mixed farmer, Bruce Heddle, instigated the addition of the new feature to the calculator and provided the energy figures from his own testing of different chaff types. Planfarm livestock consultant, Paul Omodei, worked with Peter to make sure the calculator took into account the important considerations for livestock production.
Although there is variability in feed value results, ballpark energy figures are in the order of 6.7 MJ/kg DM for wheat chaff, 7.7 MJ/kg DM for barley chaff, and 8 MJ/kg DM for canola and pulse chaff. Peter says the cost to deliver baled barley chaff to an on-farm feedlot is around 1.5 c/MJ compared to barley grain for 2.3 c/MJ, based on these feed values that Bruce Heddle provided.
“Chaff carts incorporate more or less straw with the chaff depending on the cart model, and while some extra straw makes baling and handling easier, it also reduces the feed value slightly, so that needs to be factored in,” he says. “Some growers are already set-up for hay making while others might choose to employ a contractor.”
Bruce has a contractor to bale their wheat, barley, canola and lentil chaff dumps, and feeds the bales along with barley grain and a lick feeder to sheep held in confinement from January to the end of seeding. All the chaff is beneficial although the canola and lentil chaff has the highest feed value.
Bruce says having the sheep confined during this period reduces their workload as the sheep are easy to look after and feeding out is only needed once a week. They are able to easily monitor the flock and attend to any problems quickly, and don’t have to spend time moving sheep around during seeding.
The pastures also benefit from a spell from grazing for these months, so the sheep are turned out into refreshed pasture after their confinement.
Jarred Tilley is another mixed farmer who has been making chaff bales for use in their family’s sheep enterprise at Kapunda in South Australia for the last two years. Jarred has been fencing off less productive areas on their farms and using them as confinement yards for their sheep in May and June. Their high density baler creates large bales that weigh 500 to 550 kg each from chaff dumps that are knocked down using a telehandler and then raked to save time when baling. Having their own hay-making equipment helps justify the chaff baling operation.
“We have fed 500 ewes in an 8 hectare paddock for six weeks with a diet of chaff bales, regular hay and a lick feeder,” he says. “The benefits are probably marginal for us using wheat chaff, but the canola and pulse chaff is a better feed supplement. The feed quality of the chaff is not always as good as we would like.”
Jarred says that the sheep spread the chaff out in the confinement paddocks and often leave more ground cover in those paddocks than when the sheep went in.
Chaff is a low-cost feed that is only sufficient for maintenance energy levels for sheep. Other feeds need to be included in the feed ration to promote growth or support lactation. Studies that Ed Riggall at AgPro Management conducted at multiple sites in Western Australia over three years demonstrated that sheep with access to chaff heaps from various crops gained an average of 2 kg in the first three weeks. This was 500 g more than sheep grazing stubbles where the chaff was spread out by the harvester.
Livestock containment paddocks boost productivity while stopping the spread of herbicide resistant weed seeds.
At the end of six weeks grazing the sheep with access to chaff piles had gained about 100 g, while sheep without access to the chaff piles had lost almost 2 kg compared to their starting weight. Additional benefits might be expected in a confinement feeding situation where the chaff is easier to forage and is potentially available to the stock for longer as part of a mixed ration.
By making use of the chaff within their own operations these growers are gaining benefit from a resource that is otherwise wasted, and avoid the risks associated with burning chaff heaps.
All harvest weed seed control methods provide similar levels of weed control – collecting, concentrating or destroying over 90 per cent of the weed seed that enters the front of a well set-up harvester. Australian farmers are spoiled for choice when it comes to the options for collecting and destroying weed seed at harvest and keeping downward pressure on herbicide resistance. The WeedSmart HWSC Calculator tool allows growers and agronomists to test different scenarios using their own figures to estimate the costs and benefits of the different systems available.
More information

Download the HSWC costs calculator
More lambs, less weeds in confinement systems
Sheep can turn weed seeds and chaff into cash
Ben & Emily Webb case study


Throwing a wide net over mobile weeds

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.
More resources

Area wide management of weeds project updates
Social attitudes to area-wide management – Preliminary report, Darling Downs


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157: Regional Update – Alex Davies, Farmer, York, WA

We head to the Western Region in this episode and catch up with Today WA farmer, Alex Davies. Alex is based in York and has a continuous cropping farming system and also runs sheep.
Alex also shares with us his experience about how the last three seasons have gone with having a Harrington Seed Destructor and the positive impact it has had on helping in reducing weed burdens on his farm.
You can follow Alex on Twitter here.


155: Why crop topping is a great tool to prevent weed seed set

It’s hard to believe that harvest is just around the corner! In light of this fast approaching reality, we wanted to talk about crop topping and spray topping.
Each of our WeedSmart Extension Agronomists provide a rundown on what to look out for in their cropping regions in regards to crop topping, swathing and desiccation.
WeedSmart Southern Extension Agronomist Greg Condon guest co-hosts for this podcast.

Paul McIntosh, Northern Region: crop topping or swathing/windrowing winter pulses, e.g. faba beans – jump to listen at 18:00
Jana Dixon, High Rainfall Zone:  crop topping barley and spray topping pastures – jump to listen at 30:00
Chris Davey – desiccation and crop topping pulses – jump to listen at 41:30
Greg Condon – crop topping canola – jump to listen at 55:00

Dr Chris Preston, University of Adelaide, also joins us to explain the mode of action classification system changes from a letters system to numbers system and what it’ll mean for growers.
Dr Chris Preston explains the changes to MoA classification for herbicides in Australia from letters to numbers.
Helpful links

GRDC Pre-Harvest Herbicide Use Fact Sheet
Global Herbicide Classification Look-Up
Recent WeedSmart Content

News Article: Chaff carts were made for feeding livestock
Ask an Expert Article: How can I set up my summer crops to help manage weeds?  Our expert is Belinda Chase, who is an Agronomist with Dalby Rural Supplies
Webinar recording: Mixed farming – does it really help control resistant weeds? Greg Condon hosts and Agronomist Craig Drum is our guest presenter.

I promised a holiday picture of sea lions, and I’m going to deliver. Here’s a playful sea lion who hung out with me when I was snorkelling in Jurien Bay.
Sweet sea lion in Jurien Bay (Jessica Strauss).


154: Regional Update – Angus Dalgliesh, Agronomist, Dalby, Qld

Angus Dalgliesh, grower and agronomist with Nutrien Ag Solutions, joins us on the Regional Update today.
Angus recently presented on our webinar What’s next in the North for weed control?
Today he provides an update on what to be looking out for with weeds at the moment and into the near future.

Case Studies

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Case Study

Elton and Pam Petersen, Moonie Qld

A SwarmFarm robot, ‘Oscar’, has added another dimension to Elton and Pam Petersen’s integrated weed management program, which features the majority of the WeedSmart Big 6 tactics.
In two summer fallows the Petersens have regained control of glyphosate resistant feathertop Rhodes grass (FTR) and awnless barnyard grass (BYG) that was threatening their 2000 ha dryland cropping operation at Moonie, on the Western Downs.
Elton and Pam Petersen, ‘Traighli’ near Moonie on the western Darling Downs.
The Petersens have achieved this remarkable feat after deploying ‘Oscar’ with a 12 m weedIT boom attachment. In the 20 months that Oscar has been spraying weeds in the summer fallow, ‘he’ has clocked up over 3000 hrs and passed over more than 25,000 ha.
Elton and Pam purchased ‘Traighli’, a 2370 ha grain and cattle property 5 km north of Moonie, on the western Darling Downs, in 2015. Previously they had farmed on the Fraser Coast growing sugarcane, soybeans and pineapples, and running cattle.
At the time of purchase, weeds that adapt well to conservation cropping systems had established populations that were impacting on the profitability of grain production. Elton’s initial plan was to use cultivation and blanket spraying to regain the upper hand, particularly of the herbicide resistant summer-growing grass weeds.
“Cultivation certainly helped reduce weed numbers, but was never intended to be a long-term, sustainable solution to manage these weeds. It was also too costly to use the blanket sprayer frequently enough to prevent seed set,” said Elton. “We were interested in optical spot spraying technology and everyone we spoke to who used this technology gave very positive feedback – except that it was still not practical to spray as frequently as is required to target small weeds.”
After further investigation the Petersens decided to invest in technology that would maximise the efficacy of the optical spot sprayer in their weed control program.
“Our choice was between a 36 m tow-behind weedIT boom and a 12 m weedIT boom mounted on a SwarmFarm robot,” said Elton. “We saw the robotic platform as a way for us to really hit our grass weed problem hard and to drive down the weed seed back as quickly as possible, with minimal operator input.”
The Petersens with SwarmFarm founders Andrew and Jocie Bate and SwarmFarm team members Tom Holcombe and Jarrod Jackson.
“In such a short space of time we have dramatically reduced the seed bank to the point where Oscar can work for up to 40 hours scouting and spraying weeds without the spray tank needing to be refilled,” said Elton. “This fact alone is incredibly important. It gives us much more freedom without compromising the weed management program.”
Elton has also experienced a significant mind-set change to weed management as a result of deploying Oscar. Applying constant pressure to small, fresh weed seedlings has seen the weed seed bank dwindle as no new seed has been produced for two summers.
When blanket spraying, Elton knew he was compromising on water and chemical rates in the interests of saving money and time. He said the focus was always on trying to make the spray operation more efficient and this often resulted in some weeds being larger than ideal when the herbicide was applied.
“With a tow-behind optical boom we would have improved our chemical and water application rates but not solved the frequency and consistency problem we had with the blanket spray system,” he said. “Automation brings the consistency. If Oscar goes out spraying and finds only a few weeds it only costs us $0.50/ha in diesel, and we are paying for the machine whether we use it or not.”
In the 2020/21 summer fallow, chemical costs totalled just $12.80 per ha for all the summer weed control and the pre-plant knockdown spray. Elton says this is equivalent to the cost of a single blanket spray in the past.
“In our old system we were never on top of resistant weeds and although the new system probably has similar costs, we are achieving a much better result,” said Elton. “We have essentially invested in technology that does a better job with less chemical – the long-term benefits have been realised more quickly than we dared to hope. The saving in chemical cost is even greater than I expected.”
Summer fallow spray program
In the 2020-21 summer fallow Oscar completed seven passes of the whole farm between mid-November 2020 and May 2021. For the 25-week fallow period, the property received around 650 mm of rainfall (more than the annual average for the property), with the longest stretch without rain being just 10 days. Being able to send Oscar out spraying almost immediately after rain has allowed the Petersens to treat each new germination of weeds while still very small. Elton also has Oscar set to only spray when the conditions are cool, to maximise herbicide uptake.
BYG sets seed very quickly, even quicker than FTR, so there is no opportunity to stop seed set other than killing the seedling before it seeds. Elton believes he is on track to eradicate both of these grass weeds within the next few years and will be able to reduce or eliminate the use of Group A herbicide in the summer fallow.
He says they are currently applying Group A herbicide in three passes, but each round is only using one drum of Group A product, across the 2000 ha cropped area.
The other fallow sprays are glyphosate immediately after harvest and after the first rain (for crop volunteers) and then the pre-seeding knockdown.
“This property is heavy grey cracking clay soil and melon hole country, so we have really noticed a difference in being able to access the paddocks with such a light machine much sooner after rain than is possible with a tractor,” said Elton. “Everything is centred on hitting weeds when they are very small and at their most susceptible to herbicide. This has resulted in a large reduction in the amount of chemical used.”
Another feature that Elton uses to enhance the efficacy of the pre-plant herbicide treatment is to slow Oscar down and increase the sensitivity of the optical detection to ensure that the very smallest of weeds are ‘seen’ and sprayed. This essentially saves them the cost of a pre-plant blanket knockdown.
Very clean fallow in the background compared to two passes that were missed due to an error in the robot’s instructions.
Winter weed control tactics
The Petersen’s winter cropping program is limited to growing chickpea, wheat and barley, so although they rotate the available chemistry, their options are restricted. When the opportunity arises they plant a summer crop followed by a winter fallow to target black oats and phalaris.
“We do one in-crop spray in wheat to target these grass weeds and are aware of the risk of Group A resistance in black oats, and a second in-crop spray is to control broadleaf winter weeds,” says Elton. “We use robust rates and ensure there are no survivors. A targeted winter fallow program would also go a long way to reducing the impact of herbicide resistance in black oats.”
Chickpea crops are now sown on the same 375 mm (15 inch) row spacing as the cereals, which is proving beneficial in both higher yield and weed suppression compared to the 760 mm (30 inch) spacing used previously in chickpea. Pre-emergent herbicide is applied ahead of chickpeas and in summer crops.
“We set our planting date to avoid frost risk and want to get the crop in as quickly as possible and have the option to use moisture seeking techniques in dry years,” says Elton. “You can’t overestimate the effect of canopy closure on weeds and evaporation.”

SwarmFarm: Targeting small weeds all year

Case Study

Single family, Coonamble NSW

Tony and Sharon Single farm with Tony’s parents John and Mary, south east of Coonamble in northern NSW with views of the Warrumbungle Range.
Across the 4500 ha cropping area at ‘Narratigah’, the weed numbers are low as a result of the Single’s ‘farming moisture’ philosophy, which involves planting whenever there is sufficient subsoil moisture to establish a competitive crop on their heavy clay soils. Their location allows a mix of summer and winter cropping, so if there is an opportunity for a summer crop they take it, even if that might result in missing the winter crop.
Tony (left) and John Single use their Single Shot weed detecting drone to scout for and map weeds to create a prescription map for their tractor mounted boomspray.
“Farming moisture is our risk management strategy and it has paid off time and time again,” says Tony. “We are really farming with probability and by reducing our risk we have been able to maximise profits. If there is insufficient subsoil moisture we just don’t plant. This means we have very few failed crops and we take advantage of the intermittent winter fallows to run down the seedbank, particularly for winter-active grass weeds.”
Tony says the area has a slightly summer dominant rainfall pattern but rainfall is very variable. The main crops grown are wheat, chickpea and sorghum, along with any other crop that might fit a certain planting opportunity.
While their cropping decisions are very water responsive, there can be situations where the need for ground cover outweighs other considerations. This can occur after a chickpea crop and if they feel it is necessary, Tony and John will plant a crop just to produce stubble, knowing that the yield will most likely be low.
“Generally, if it is too dry to plant we will choose to fallow to build up the soil moisture profile knowing that this is the least-risk strategy and gives the best result in the long term,” says Tony. “We can effectively gain good weed control for the full 12 months through the use of cropping and fallowing in both winter and summer.”

Resistance status
Herbicide resistance is considered the biggest threat to their business even though they currently have resistant weeds well under control. Glyphosate resistance was first confirmed at ‘Narratigah’ in 2005 in annual ryegrass, and Tony and John are also aware of some small areas of glyphosate resistant barnyard grass.
“These are our most important weeds and keeping a lid on resistance is crucial to prevent them becoming limiting factors in our cropping choices,” says Tony. “We also have other weeds including milk thistle, fleabane, blow-away grass and feathertop Rhodes grass – the full suite of northern region weeds really.”
Tony says their efforts to consistently drive down the weed seed bank, and having regular winter fallows, minimises the impact of herbicide resistance on their business.
“Our weed seed bank is low and weeds do not dictate our cropping decisions,” he says. “Ryegrass has a relatively long growing season so we have ample opportunity to stop seed set through a winter fallow. There are also several chemical options for use with our spot spraying technology and new pre-emergent herbicide options too, along with cultural controls such as chipping.”
“We are more concerned about the implications of resistant barnyard grass, which washed in from up-stream. Barnyard grass has the ability to germinate and very quickly set seed, making it more difficult to contain.”
To avert the risk of more seed being deposited by overland flow, the Singles have constructed a number of diversion banks on the up-stream side of their cropping area to divert water.
Tony is also noticing ‘rate creep’ as weeds like milk thistle that are slow to metabolise herbicide, become harder to control. He says they are needing to use a higher rate of paraquat in the double-knock applications. The Singles are managing this through regular double-knocking in fallow and strategically using saflufenacil with paraquat to enhance control.
Black oats currently has a low resistance profile due to the use of winter fallows and fop chemistry is still effective in many paddocks.
The Singles use their proprietary drone weed mapping system ‘Single Shot’ to scout for and map weeds, helping them to better plan for and implement each herbicide application.
Their integrated weed management system is an excellent example of the WeedSmart Big 6 in practice.
#1 – Diversity in cropping
The combination of winter cereals, winter pulses and summer cereals provides many opportunities for controlling weeds pre-season and in-crop.
“The decision to plant sorghum is driven by weed and disease pressure in winter crops,” says Tony. “In a paddock that is becoming difficult to manage, we would rather change to sorghum than turn to a heavy reliance on pre-emergent herbicides and in-crop spraying of winter weeds in winter crops. Swapping to a summer crop gives us the opportunity to target problematic weeds using a winter fallow phase.”
This practice, plus the persistent drought in recent years, has resulted in more fallow area and allowed them to drive down the weed seed bank of annual ryegrass and black oats. It is now very rare for them to target grass weeds in-crop in winter cereals.
Using their drone and sensor to scout for and map weeds in the fallow periods has been a powerful tool to attack the weed seed bank in both summer and winter. Decoupling the weed detection and spraying operations opens up opportunities for more diverse weed control.
Tony and John can use the drone to map the presence of weeds just before, or soon after, significant rainfall events. Once they are able to get on the paddocks with the sprayer they can target previously existing weeds with spot spraying an effective herbicide mixture while applying a blanket rate to the new germination of weeds following the rain.
Knowing exactly what is in the paddock before they start spraying means they can consider a wider range of potential chemical options or techniques. Once the plan is made, they know how much product they will need and the cost. Knowing that they will only be treating say 5 ha in a paddock, they can afford to use chemicals that they would never consider for a blanket spray application.
#2 – Mixing and rotating MOA
Tony and John use some preemergent chemistry strategically in fallows to maximise weed control diversity while keeping their options open for cropping.
They aim to use a preemergent application to control key broadleaf and grass weeds after harvest, which takes the pressure off glyphosate without compromising planting opportunities the following autumn.
A combination of soil residual herbicides such as picloram, Balance and Flame has given good results early in the summer fallow, followed with a pre-sowing double knock of glyphosate and paraquat, giving a total of five chemical groups targeting fallow weeds. When it suits the program, they use chemistry mixes such as Sharpen + paraquat in the double knock, increasing the modes of action and increasing the efficacy of the treatment on the weed spectrum.
In addition to the use of preemergent chemistry, winter grass weeds are also targeted in broadleaf crops, usually with clethodim (Group A, Group 1), but the Singles are aware of the resistance risk and are looking to introduce Clearfield canola as alternative means of grass control in break crops, and to bring more diversity to their system.
Using their drone mapping technology, Tony and John can merge multiple flights of a paddock during the year into one map to show the location of all the weeds detected. This map can then be used to apply a site-specific soil residual herbicide for the next season to say 15 to 20 per cent of the paddock. In treating smaller areas, they can afford to consider chemistry that might otherwise be too expensive, add more diversity to chemicals used and reduce their plant-back risks.
#3 – Crop competition
The Singles consider crop competition to be their #1 weed control tactic, simply because it is the only one that provides season-long in-crop weed control.
“We do everything we can to maximise the crop’s ability to suppress weeds,” says Tony. “This starts at planting, where we have invested in planting gear with moisture seeking capability so we can plant crops on time and ensure good establishment. We take great care to ensure there are no gaps for weeds to exploit, and always square-off the headlands.”
Planting at 330 mm row spacing allows for inter-row sowing and stubble retention, and planting rates are chosen to maximise yield – with long-season wheat sown at 40 to 60 plants/m2, and later plant wheat sown at 80 to 100 plants/m2. The slope of each paddock dictates the tramline direction to be perpendicular to the overland flow, which results in most paddocks being sown north south.
For all crops Tony aims to achieve 100% knockdown prior to planting with a double knock treatment, followed with a well-established, vigorous crop.

#4 – Double knock
The Singles started using the double knock tactic twenty years ago in their winter fallows, and introduced it to summer fallows about ten years ago.
“The double-knock strategy hasn’t added significantly to our overall weed control costs,” he says. “When we first started using the double-knock we counted it as a direct cost to the system, but we now see the second knock with paraquat as a preemptive strike on future weeds – an investment in lowering the weed seed bank, and we are picking up savings with lower volumes of chemical required in subsequent weed control applications.”
The double knock tactic is now embedded in their weed management strategy and they have invested in spray gear to allow them to cover their area within the recommended 7 to 8 day window. Tony says the high level of control they achieve with the double knock means there are fewer and fewer weeds each year and this reduces the cost of the operation, particularly now they have the capacity to spot spray weeds with highly consistent weed detection.
“This tactic puts a significant dent in the weed seed bank and reduces the number of large and potentially stressed plants being sprayed,” says Tony. “This makes it a very effective resistance tool, particularly for our hard to kill weeds.”
#5 – Stopping seed set
The Singles are aiming for 100 per cent weed control in fallow, particularly for annual ryegrass and BYG, by managing paddocks in a site specific way at a square metre level using their drone scouting technology.
“The drone can effectively scout for weeds at a rate of 200 ha/hr, which makes it very quick and easy to scout a paddock and then go out and chip the five or so plants that might be left growing in a paddock,” says Tony. “This moves us closer to achieving 100 percent weed control. We have really driven down our weed numbers and significantly reduced the impact of herbicide resistance in our operation.”
Occasionally, Tony will drive along the tramlines in the side-by-side and chip out any grass weeds in chickpeas that have either escaped control or germinated late in-crop. Then prior to harvest, Tony and John look for any patches of weeds that have escaped control and take action to prevent seed set.
“If we find there is a patch of weeds getting away from us we don’t hesitate to sacrifice small areas of the crop to prevent seed set,” says Tony. “In 2020 we had a three or four hectare patch of ryegrass and decided to use a small slasher to mow the crop and weeds then sprayed the area with paraquat. That way we made sure the weeds did not set seed and prevented the spread of resistant weed seed at harvest.”
The Singles do not spray any selective herbicides outside their cropped area and prior to harvest they slash a 2 m width of crop along fencelines to stop the header bringing weeds into the paddock from the fenceline.
#6 – Harvest weed seed control
Several years ago, the Singles trialed narrow windrow burning for harvest weed seed control but decided that the negative effects outweighed the weed control benefits.
“For us, ground cover is supremely important for erosion control, reducing evaporation and increasing infiltration through the heavy clay soils,” says Tony. “We are watching the developments in impact mill technology and will most likely go down that path if we feel harvest weed seed control is needed in the future.”

Case Study

Kurt Mayne, Rolleston Qld

Preserving the option for opportunity cropping is critical for Rolleston grain grower Kurt Mayne, but this means he needs to be careful with pre-emergent herbicides in his fallow weed control program.

Kurt and his family operate a 6000 ha mixed farming operation of dryland grain production and backgrounding steers for feedlots at ‘Broken Plains’, 13 km east of Rolleston in Central Queensland. They grow chickpea and wheat every winter and summer crops when the opportunity presents on the 1400 ha of farmed country previously used for finishing cattle on leucaena (AKA tagasaste).
Kurt Mayne bought a secondhand 36 m weedIT in early 2019 and can now spot spray their entire cropping area within two days.
Wanting to keep one step ahead of herbicide resistance, Kurt took the opportunity to join a GRDC Grower Solutions study tour that included attending the 3-day WeedSmart Week event in Narrabri in 2018.
He returned from the tour convinced that he needed to take extra steps to minimise the risk of herbicide resistance before it began to impact on his crop choices and profitability.
“Optical spraying technology was the tactic that really stood out for me on the study tour,” says Kurt. “We bought a weedIT boom soon after I returned from the trip and I have been impressed with the benefits that have come with the addition of an optical sprayer to our weed control program.”
“In our farming system it is hard to incorporate pre-emergent herbicides in the fallow because that can restrict our options for opportunity cropping over summer,” he says. “The optical sprayer makes fallow weed management much more effective, and when that’s combined with pulses in the rotation we are able to keep on top of grass weeds like feathertop Rhodes grass, which was getting increasingly difficult to manage.”
The main weeds at ‘Broken Plains’ are feathertop Rhodes grass (FTR), milkthistle and fleabane – all notoriously hard to kill in fallow situations. Kurt bought a secondhand 36 m weedIT in early 2019 and can now spot spray their entire cropping area within two days. He also uses a tow-behind sprayer for their broadacre spray applications.
Kurt says the pressure from FTR had led to an increasing need for cultivation to stop seed set and he saw that optical spray technology would mean he could reduce the amount and frequency of cultivation.
“We use the weedIT to spot spray weeds with a double knock of glyphosate plus a Group I [Group 18], followed with paraquat; targeting these hard to kill weeds when they are small,” says Kurt. “No residuals are used in fallow because they can limit our options for summer cropping particularly.”
“The aim is to keep the fallows weed-free so we have low weed numbers at planting,” he says. “Once a crop is planted we do use residuals to give it the best chance to grow ahead of any weeds that might emerge on the planting rains.”
The weedIT has markedly reduced the amount of chemical applied in the fallow and reduced the time needed to do an application across the cropped area. Kurt is finding it much easier to apply the double knock tactic for glyphosate within the optimal timeframe.
“Being able to get a proper double knock done when you need to, means you can get on with other jobs, knowing that you have done the best control treatment possible on the weeds,” says Kurt.
Crops and varieties are chosen to maximise yield potential and this also means there is maximum suppression on weeds. Their crops are sown on 50 cm row spacing in a 12 m controlled traffic system, except for sorghum, which is grown on 1.5 m spacing.
“We are basically farming moisture here, so if there is suitable rainfall we want to be in a position to take that opportunity to plant,” he says. “Sorghum and mungbean are the usual summer crop options, and we aim to be cropping for 10 months of the year if conditions allow.”
In drier years the winter crops are sown deep, about 15 cm, to access available moisture. Chickpeas are particularly well suited to moisture seeking planting techniques. Kurt grades his own chickpea and wheat seed to remove weed seeds and ensure that the largest and most vigorous seeds are planted. He buys in mungbean and sorghum seed each season to maximise seedling vigour and establishment, and ensure the seed is weed-free.
Chickpeas are particularly well suited to moisture seeking planting techniques. Kurt grades his own chickpea and wheat seed to remove weed seeds and ensure that the largest and most vigorous seeds are planted.
Kurt uses a tyned planter and a single disc for nitrogen application. He has recently embarked on a program to apply ‘deep P’ across the cropped area. The phosphorus is applied about three months before planting at a rate of 250 kg/ha MAP at a depth of about 30-45 cm using a dozer. He has been very impressed with the crop response to the phosphorus application, which has clearly demonstrated that low phosphorus levels have been a constraint on production.
The Maynes are seriously considering adding harvest weed seed control to their weed management program. Kurt sees real benefits in the chaff deck system that delivers the chaff onto the tram lines – both as a weed control tactic and a means of reducing the frequency of tram line renovation.
On the cattle side of their business the Maynes buy in about 1600 feeder steers and run them for less than 12 months on 2800 ha of buffel and leucaena pasture.

Case Study

Messina family, Mullewa WA

Mullewa growers Andrew and Rod Messina have been on a long and dedicated journey of weed management. Their 12 thousand ha dryland cropping enterprise is based on a predominantly sandplain soil type and the region generally expects 250 to 350 mm annual rainfall, but seasonal variability is often a challenge.
The most recent innovations to be tested and adopted are real-time and localised herbicide application technology and impact mills for harvest weed seed control.
The soils and rainfall limit the Messina’s crop choices but they use the available options of wheat, canola and lupins to their best advantage for herbicide and non-herbicide tactics to keep downward pressure on the weed seed bank.
Mullewa farmer Andrew Messina says it’s amazing how quickly weed numbers come down after two or three years of integrated weed management practices, including harvest weed seed control. Photo: Fiona Mann
“We have been doing whatever we can to reduce the seed bank for weeds, and we’ve been doing that for a long time now, particularly with mouldboard ploughing and harvest weed seed management,” Andrew said. “Weeds rule broadacre farming, there are no two ways about that – weeds and rainfall.”
Over the years their efforts to reduce the weed burden across their controlled traffic farming operation have also included narrow windrow burning, chaff carts, autumn tickles, crop topping and double knocking glyphosate.
“We find that when we buy a new property it always has a lot of weeds but after two or three years of integrated weed management practices, including harvest weed seed control, it’s amazing how quickly weed numbers come down,” Andrew said.
Wild radish has always been the main weed challenging crop production on the Messina’s Spring Park Farms on the Eradu sandplain east of Geraldton. When herbicide resistant wild radish populations established on the farm the Messinas added pre-emergent to the in-crop herbicides in their weed management strategy.
In 2020 the family sold their collection of chaff carts and bought three Integrated Harrington Seed Destructors (iHSD) in anticipation of a harvest dominated by cereals across 10,000 ha. The impact mills performed well through the 2020 harvest and the Messinas are very pleased to have dispensed with burning chaff dumps for harvest weed seed control.
At the same time they have also moved into camera spot-spraying technology, initially for summer and fallow spraying but also for future potential for in-crop spot-spraying.
Teaching technology to recognise weeds
Their new 8000-litre Agrifac Condor Endurance II machine is equipped with weed-identifying cameras developed by French firm Bilberry, allowing for real-time weed detection and tailored herbicide application.
“To have mechanically driven weed destructing mills on our harvesters, and this camera technology … it’s the most exciting thing I have seen in my farming life,” said Andrew.
The system – called AiCPlus – uses optical cameras and microprocessors to identify weeds ahead of the 48-metre spray boom. Individual nozzles are then triggered as the boom passes overhead to spot spray the weeds. The cameras are fixed at 3 m apart, with each linked to the independent operation of nozzles within a set of 12 nozzles.
Green-on-brown is the only commercially available technology available for this machine at present, but the Messinas have been busy assisting the system’s developers to trial its green-on-green capabilities.
Arriving on farm in January 2020, a little later than expected, the Messinas used it to finish the summer weeds program on about 400 ha of their sandplain soils. Once the crops were planted, they then used it for nine days in young wheat crops in July and then again in August, traversing 14,000 ha at an average speed of 19 km/h.
AiCPlus uses optical cameras and microprocessors to identify weeds ahead of the 48-metre spray boom. Photo Fiona Mann
Its target was wild radish growing in paddocks of Scepter, Devil, Chief and Zen wheat. With each pass, the cameras captured images that depicted both the crop and weed at different times of day and under various light conditions. These images are being used to better inform the algorithm behind the technology. In 2021 the Messinas will be working with Bilberry to gather images to identify blue and white lupin in wheat crops.
For the trial, they had allowed the radish plants to grow to a size that the cameras could easily detect, approximately 10 cm2, with the sprayer first being put to work on a paddock with a high weed burden, something that they would not usually do.
In paddocks with high weed burdens, their aim is to knock out weeds early in their growth via a blanket spray, in a bid to conserve crop-available moisture. This would usually occur around the three-leaf stage in wheat.
Andrew expects the efficiencies from green-on-green technology to come in subsequent sprays that targeted the low number of radish plants from later germinations.
As a result of the family’s persistent weed-fighting efforts, most of their paddocks host only low densities of radish. In these paddocks, Andrew said a blanket spray would generally not be necessary.
Having the impact mills fitted to their harvesters gives the Messinas full confidence to be involved with the development of the weed identification and spraying technology because they know that any weeds that escape treatment will be destroyed at harvest.
“But when we were walking through the paddock, most of the weeds had been hit,” said Andrew.
The 48 m Agrifac sprayer runs on the same trams as the harvester rather than the trams used by their other sprayers. By going to a wider boom and operating at 19 km/hr they can get over the same area as their 36 m sprayers running at 26 km/h.
Addressing soil constraints
The family started exploring soil constraints in 2008, mainly to determine if soil acidity, aluminium toxicity or nutrient deficiencies were limiting yields.
Testing uncovered pH levels of around 5.3 to 5.5 at the surface and 4.4 to 4.6 at depth (30 cm). Non-wetting properties and compaction were also identified as potential limiting factors.
They then embarked on a liming and mouldboard ploughing program to adjust the pH, treat non-wetting and bury weed seed. Their soils now feature pH levels in the range of 5.5 to 6.2.
“For the past five years we have been deep ripping to depths of 60 to 70 cm prior to seeding wheat to maximise the ability of crops to access moisture and nutrition in the profile,” said Andrew. “We also spread two tonnes of lime per hectare ahead of the ripper every three years.”
The overall result is better soil, better crop competition and less weeds. Andrew says the deep ripping has the potential to bring weed seed back to the surface, but this has only been evident on the edge of tram lines in a couple of paddocks where brome grass has re-surfaced.
Stopping seed set at every opportunity
The Messinas aim to stop seed set at every stage of the crop production and weed life cycle.

Mouldboard ploughing and liming re-set the seed bank and removed soil constraints related to pH and non-wetting.
Deep ripping ahead of planting (autumn tickle) stimulates a germination of weeds that are treated with a knockdown herbicide or double knock. Deep ripping also opens up the sandy profile to accept soil moisture and incorporate lime every three years. This encourages roots to seek nutrients and moisture and sets the crop up to compete well with weeds and reach the yield potential for the season.
Pre-emergent herbicides are applied to give the crop a head start on weeds.
One or two post-emergent sprays are applied as required in wheat for wild radish control. The AiCPlus camera sprayer will change broadacre spraying into spot-spraying for this key weed.
Lupins and canola are crop-topped if required but crop-topping has not been necessary in recent years.
All crops are treated with harvest weed seed control. The Messinas have achieved excellent weed seed control since they began with windrow burning in 1997 then moved to chaff carts in 2012 and now use iHSD impact mills.
Summer spraying will now focus on spot-spraying with the AiCPlus camera sprayer.

This case study is based in part on an original article written by Ann Rawlings with permission from the Society of Precision Agriculture Australia ( and other sources.


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Mixed farming – does it really help control resistant weeds?

In this webinar, WeedSmart Southern extension agronomist Greg Condon looks at the mixed farming system and explains how the Big 6 principles encourage diverse weed management. Greg focuses on solutions in the medium rainfall zone whilst grower and agronomist Craig Drum focuses on the high rainfall zone.
Both Greg and Craig share real-life examples of clients who successfully controlled resistant weeds by using a mixed farming system, whilst remaining profitable.
Topics covered include:

What the WeedSmart Big 6 looks like in a mixed farming system
How to be profitable whilst reducing the seedbank of resistant weeds
Harvest Weed Seed Control opportunities: baled chaff, chafflines
4 examples of clients who successfully controlled their resistant weeds using mixed farming


Rod Birch on how the Big 6 is keeping weeds at bay at Catalina Farms

Catalina Farms is approximately 13,000 ha of 100% cropping, with 65% wheat, with the other 35% comprising of 20% canola and 15% lupins. The longterm rainfall is about 330ml per year and around 250-280ml of growing season rainfall.
Taking on a new property usually has its challenges, but there can be upsides too. Some of the challenges at Koobabbie were related to the fact it had been a livestock property and cropping machinery had never having been run through it. However, Rod explained that they have had some great news about the herbicides they are able to use.
Through the University of Western Australia’s resistance testing service, run by Dr Roberto Busi at AHRI, they found out some older chemistries were still effective, which was a pleasant surprise. Daniel Birch explains below in the Regional Update Podcast what they found out and how they used this information in their planning.

Video breakdown

1:10 Crop rotations – Rod’s favourite rotation is Lupins – wheat – canola – wheat. It provides a lot of diversity for Modes of Action, as well as allows for nitrogen to go back into the soil through the lupin phase.
2:10 Crop Competition – the Birches are big fans of crop competition and it’s an essential part of their approach to controlling weeds.
3:00 Double knock – conditions haven’t been suitable for a double knock since 2016, but when the opportunity arises, it’s an important tool.
4:21 Mix and rotate herbicides – the crop rotations used at Catalina allow for really diverse chemical groups to be used, which is a great tactic to keep resistance at bay.
5:52 Stopping weed seed set – the Birches are trying to eliminate as many weeds in the crop as possible. Crop topping is a tool that they employ, as well as late spraying where necessary.
6:49 Harvest weed seed control – seed destruction is on the horizon at Catalina, but logistically has been a bit tricky.
7:21 Acquiring Koobabbie – it has been exciting for the Birches to be able to introduce more diverse rotations. They’ve been able to use Modes of Action which have never been used before.
9:48 Soil amelioration  – liming has been a really beneficial tool for Catalina Farms. They also put out pot ash and gypsum. Deep ripping has also been a great tool to remove the compaction layer.
11:29 Big 6 benefits  – controlling weeds is such an important strategy at Catalina Farms. Rod Birch said “We’ll never have a ceasefire on the war on weeds!”.



WeedSmart Week Forum Day Videos

List of videos

Interviews with the Esperance Pioneers. Chair: Lisa Mayer, interviewing Neil Wandel & Theo Oorschot
Rotating buys you Time, mixing buys you shots
Efficacious use of the new pre-ems, Brent Pritchard
Delivering regionally focused research
Crop competition in wheat and canola, Hugh Beckie
Summer weed control
Strategies for control of ryegrass, marshmallow, fleabane, portulaca, Greg Warren
Farmer Experience
Rotations to stop seed set and preserve chemistry, Tom Longmire
Soil Amelioration, Tom Edwards
Crop competition: Reduced row spacing, higher seeding rates, east-west sowing, precision seed placement & competitive varieties, Theo Oorschot
Farmer Experience – Utilising crop competition strategies and the Big 6, Mic Fels
Weed control – farmer systems discussion panel – Chair: Peter Newman, with Mark Wandel and Laura Bennett
What’s next in spray technology? Andrew Messina
What’s next in spray technology 2? Guillaume Jourdain
Innovation Panel – Chair: Ben White, with Guillaume Jourdain, Andrew Messina
Stacking the Big 6 in farming systems in WA presented by Greg Condon, with Peter Newman

Fact Sheets

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Fact Sheet

Changes to herbicide Mode of Action (MoA) names

The global MoA classification system is based on numerical codes which provides infinite capacity to accommodate new herbicide MoA coming to market, unlike the alphabetical codes currently used in Australia.
Farming is becoming increasingly global. Farmers, agronomists and academics around the world are now, more than ever, sharing and accessing information to assist them to grow crops, while managing sustainability issues such as herbicide resistant weeds. It’s important then that the herbicide MoA classification system utilised in Australia be aligned with the global classification system. This will ensure more efficient farming systems into the future and allow Australian farmers and advisors to access the most up-to-date information relating to managing herbicide resistance.
CropLife Australia is working with key herbicide resistance management experts, advisors and the APVMA to ensure farmers and agronomists are aware of the planned changes.
The numerical classification system should be fully implemented by the end of 2024.
You can find further information by reading the factsheet and visiting the CropLife website here.

Fact Sheet

Sustainable glyphosate use in winter grain cropping systems in southern Australia

The number of glyphosate resistant weed species present in winter grain crops, along fencelines and in irrigation channels in Australia.

You can reduce the risk of glyphosate resistance in weeds if you follow the recommended practices in this factsheet.

Fact Sheet

Sustainable glyphosate use in Australian vegetable production

The number of glyphosate resistant weed species present in Australian vegetable production systems is increasing.

You can reduce the risk of glyphosate resistance in weeds if you follow the recommended practices in this factsheet.

Fact Sheet

Sustainable glyphosate use on roadsides, railways, public utilities and parks

The number of glyphosate resistant weed species present on Australian roadsides and railway lines is increasing.

You can reduce the risk of glyphosate resistance in weeds if you follow the recommended practices in this factsheet.

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