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Value in sponsoring herbicide stewardship program

FMC Agricultural Solutions, now the world’s fifth largest crop protection chemical company, has recently signed up as a silver sponsor of the WeedSmart herbicide stewardship program.
Dugald North, FMC development manager (crops) said the company’s acquisition of part of the DuPont Crop Protection division late last year has brought to the company a world-class discovery and development team and facilities, a pipeline of 15 synthetic active ingredients currently in development, including insecticides, herbicides and fungicides, and an extensive library of 1.8 million synthetic compounds.
Dugald North, FMC Agricultural Solutions development manager (crops) said the company has signed up as a silver sponsor of the WeedSmart herbicide stewardship program to support the ‘WeedSmart Big 6’ strategy for sustainable herbicide use.
“FMC is keenly aware of the impact herbicide resistance has on farming businesses and is fully supportive of the ‘WeedSmart Big 6’ strategy for sustainable herbicide use,” said Mr North. “We see WeedSmart as an important component of promoting herbicide use that prolongs the efficacy of our new herbicide molecules when they are released on the market.”
“The WeedSmart Big 6 combines best practice herbicide use with cultural strategies to keep weed numbers low, maintaining an environment where herbicides can perform most effectively,” he said. “Herbicide resistance is a central concern for our business and FMC is committed to prolonging the effective life of new chemistries, even if this means foregoing sales in the short term.”
Prior to the release of their new herbicide molecules, FMC has contracted the Australian Herbicide Resistance Initiative (AHRI) to conduct multi-generational resistance testing, which Mr North said will provide a scientific basis for the formulation of an effective stewardship program for individual products.
In welcoming FMC Agricultural Solutions as a silver sponsor, Lisa Mayer, AHRI centre manager and WeedSmart project leader said the promotion of sustainable herbicide use and cultural practices that drive down weed seed banks is key to securing the weed control productivity gains made by the current generation of Australian farmers.
“WeedSmart is an industry-led initiative that brings together knowledge and experience from Australian research partners, commercial entities, Government, advisers and growers to ensure Australian farmers have access to leading-edge weed management technologies and practices,” she said. “With the financial and in-kind support from sponsors secured for a further three years, WeedSmart is geared up to continue providing rural industries with insights into effective integrated weed control programs.”
Ms Mayer said gaining the support of FMC Agricultural Solutions was testament to the perceived effectiveness of the WeedSmart program in promoting practical tactics growers could implement to maintain their profitability.
“WeedSmart has become an effective conduit of information between growers within and between regions, and between growers, advisors and researchers,” she said. “We have used as many platforms as possible to raise awareness, not only of the extent of herbicide resistance but also to highlight successful management strategies that growers can implement immediately.”
“There have been many instances where growers have returned from a WeedSmart Week event or field day, or read about another grower’s success and immediately adopted practices such as harvest weed seed control, patch management, optical spray technologies or greater crop competition.”
The ‘Big 6’ WeedSmart tactics known to drive down weed numbers and drastically reduce the impact of herbicide resistance on Australian farms are: 1. Rotate crops and pastures, 2. Mix and rotate herbicide modes of action, 3. Increase crop competition, 4. Use the double-knock, 5. Stop weed seed set and 6. Implement harvest weed seed control.
FMC have joined forces with existing platinum sponsor GRDC, gold sponsors CRDC, Nufarm, Sinochem, Syngenta, Monsanto and Bayer, silver sponsors Pioneer Seeds, BASF and Dow AgroSciences and bronze sponsors Queensland Government, ICAN, Delta Agribusiness, The University of Adelaide, CropLife, Rural Directions and AGRIvision to spread the WeedSmart Big 6 message amongst growers and advisors to tackle herbicide resistance in Australia.
 

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Webinar: Pre-ems provide punch to prevent weeds

Join us for our next two-part series April 24 and 26, as AHRI’s Peter Newman chats with experts to deliver the latest on-farm strategies to help you set your crops up for success in 2018.
From wherever you are – in the paddock, ute, tractor, office – you can stream this webinar series to your smartphone, tablet or computer.  Hear from ICAN’s Mark Congreve and Uni of Adelaide’s Chris Preston who answers the Qs – how to choose and apply the correct pre-em to maximize crop yield.  Specific scenarios provided for the north and the south.  Listen to both or just tune into the webinar relevant to you.
Webinar 1:  Use Pre-ems to maximise winter crops in the North
Feat:  Mark Congreve, ICAN Rural
Date: Tuesday 24th April 2018
Time:10:30 – 11.30 am, AWST, 12.30 – 13.30 pm AEST
Why do things go wrong with pre-ems?  Herbicide choice and farming system are factors to consider, with crop safety being top of mind.  Mark takes us through the strategies to maximise pre-em performance particularly in relation to controlling ryegrass, wild oats, fleabane and sowthistle in the north and discusses how pre-ems breakdown and the implications on plantbacks and rotational crops.
Scenarios in the northern region that lead to herbicide failure will be discussed as well as strategies to mitigate risk.
Webinar 2:   Use Pre-ems to maximise winter crops in the South
Feat:  Chris Preston, University of Adelaide
Date: Thursday 26th April, 2018
Time:10:30 – 11.30 am, AWST, 12.30 – 13.30 pm AEST
Hitting weeds before the crop phase provides many more shots at the weeds.  Chris explains how to give your crop the best start and diminish the weed seedbank with pre-emergent herbicides.
 
Chris delves into the behaviour of pre-emergent herbicides and what pre-emergents to use when sowing your crop dry in the south? What are the characteristics of the products and how should these influence use patterns? How to manage pre-emergent herbicides in different soil types? Why don’t pre-emergent herbicides work as well on brome grass as they do on annual ryegrass? What is the current status of resistance to pre-emergent herbicides and how should this influence the way they are used?
 
Ready to register?

Use of Pre-ems in the North with Mark Congreve

Registration URL:  https://attendee.gotowebinar.com/register/12301726111335937
Webinar ID:  391-027-483

Use of Pre-ems in the South with Chris Preston

Registration URL:   https://attendee.gotowebinar.com/register/7423634619926422785
Webinar ID:  440-111-339
 
P.S. For more information about these webinars please contact Lisa Mayer at lisa.mayer@uwa.edu.au or phone 0414 841 862. For more info on weed management visit our website.
 
WeedSmart is an industry-led initiative aimed at enhancing on-farm practices and promoting the long term sustainability of herbicide use in Australian agriculture. Australian research partners, commercial entities, Government, advisers and growers have joined forces to ensure weed management remain at the forefront of global farming practise. Viable herbicide use will help secure the weed control productivity gains made by the current generation of Australian farmers.

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3-year strategy for sustainable brome grass management

Brome grass is showing off its ability to dodge and weave to evade control, making it the most costly weed in the Mallee regions of South Australia and Victoria, and increasingly problematic in other cropping areas of southern Australia.
According to University of Adelaide weed ecology researcher Dr Sam Kleemann, the increased incidence of brome grass is associated with management practices that have inadvertently selected biotypes with greater seed dormancy.

According to University of Adelaide weed ecology researcher Dr Sam Kleemann, the increased incidence of brome grass is associated with management practices that have inadvertently selected biotypes with greater seed dormancy.
“We compared the dormancy behaviour of brome grass seed collected from crop paddocks and fencelines and found that the seed from the cropped paddocks had a greater dormancy, which allowed these biotypes to thrive in no-till, cereal intense farming systems,” said Dr Kleemann. “The adoption of earlier sowing and dry sowing has also favoured this species. Brome grass has the potential to reduce wheat yields by up to 50 per cent if numbers get out of hand.”
This process of selection for biotypes that remain dormant longer and avoid pre-seeding controls such as a double-knock or cultivation, is slower but similar in effect to the evolution of herbicide resistance. Herbicide resistance levels in brome grass are currently low, however there are records in Australia of brome grass with resistance to Group A, B, C and M herbicides.
“The autumn break has traditionally initiated brome grass germinations, and this is when germination is most likely on fencelines and roadsides,” he said. “The biotypes that have persisted in cropping areas are more likely to germinate in late autumn and through winter, and some even require a period of chilling to 5 °C to break the dormancy period.”
Having evaded early control these late-germinating weeds go on to produce a large amount of seed and often lodged or shed their seed by crop harvest time, so they can also largely escape harvest weed seed control measures. The seed can remain viable for up to three years if it remains on the soil surface.
Although brome grass has proven to be successful in the no-till farming environment, dedicated research efforts have shown that brome numbers can be driven down quite rapidly using a double-break from cereals, more effective pre-emergent herbicide packages and sowing on-the-row rather than inter-row.
Trials on non-wetting sands in the Mallee have shown that sowing on the same row as the previous year improves crop establishment and the ability of the crop to compete with brome seed that is generally more abundant on the row than between the rows. The planting operation can also help break the seed dormancy by burying some of the seed, putting the seedlings in contact with the full rate of pre-emergence herbicide.
“At high brome grass densities, trifluralin is generally the least effective pre-emergent option,” said Dr Kleemann. “Better results can be expected from the more expensive Sakura + Avadex package, which resulted in 72 per cent less brome panicles than trifluralin alone in trials. In this 2015 trial the trifluralin treatment resulted in 60 brome grass panicles per metre square compared to just 16 in the Sakura + Avadex treatment.”
“Growers will need to weigh up the extra cost in herbicide compared to the likely seedbank benefits and the variability in pre-emergence herbicide performance between seasons. This is why a diverse approach to weed management is essential.”
“In years where crop competition is patchy, brome grass can exploit the opportunity and replenish the seed bank, putting increased pressure on pre-emergent herbicides the following season.”
3-year brome grass reduction rotation
Growers who are noticing increased brome grass numbers can use a three-year rotational strategy known to effectively drive down the brome grass seed bank.
Year 1 – a pulse crop to enable the use of effective pre-emergent herbicides and in-crop grass selective herbicides, followed with crop-topping to reduce brome seed set where there is no yield penalty expected.
Year 2 – canola or hay. Canola offers a similar suite of tactics to the Year 1 pulse crop, targeting brome grass germinations throughout the cropping season. Hay is a very effective option, reducing seed set by as much as 90 per cent, particularly if the hay is cut at the commencement of brome grass flowering. Regrowth after cutting hay must be controlled with grazing or knockdown herbicides, particularly in wet seasons.
Year 3 – Clearfield wheat allows the use of imidazolinone herbicides, the most effective chemistry available for brome grass control. Using this technology in a low weed situation (due to seed bank reduction in the previous two years) there is less pressure applied to this herbicide, which is known to be prone to rapid evolution of herbicide resistance in high weed density scenarios.

Growers who are noticing increased brome grass numbers can use a three-year rotational strategy known to effectively drive down the brome grass seed bank, starting with a pulse crop that is suited to crop-topping without yield penalty.
The Brome RIM tool is available for growers and advisors to test the likely effect of different management scenarios on brome grass numbers.

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Resistance testing informs herbicide use plans

Matt and James Toscan have been growing cotton for seven years at Darlington Point in the Murrumbidgee. Speaking to their CottonInfo Regional Extension Officer, Matt Toscan outlined how they are managing the threat of resistant weeds.
The primary weeds encountered on their farm are barnyard grass, blackberry nightshade, sowthistle, fleabane, annual ryegrass and thistles.
Matt Toscan.
Matt and James have tested barnyard grass, sowthistle and ryegrass for resistance over recent years. The barnyard grass and sowthistle were found to be susceptible to glyphosate (Group M), while the ryegrass was found to be resistant to by glyphosate and Group A herbicides.
To counter the threat of further incursion and resistance, Matt and James have an integrated weed management strategy (IWM) that is developed over the full course of the year, in close consultation with a crop consultant. The summer crop program is decided in July–August, and the winter crop program in March–April.
“We recognise that weed resistance is a threat to the long-term cropping viability of intensive irrigation areas, which is why an integrated weed management approach is so important to us,” said Matt. “There are no new herbicides, so we need to preserve our chemical options by making use of non-chemical control tactics.”
“Weed control in cotton will never be as easy as it is right now, while we are a new area and can rely on glyphosate for summer weed control. Being so easy and effective is both a strength and a weakness in the current weed control system. We need to think long term and use multiple tactics.”
The Toscan’s take a whole farm approach to management of weeds, with particular attention paid to non-cropped areas, such as the sides of fields, channels, roadways, drains and bankless channels.
Their IWM strategy involves a range of control measures, including pre- and at-plant residuals, pre-emergent knock downs, post-emergent herbicide applications and chipping, particularly for ryegrass and milk thistle. The pre-emergents are used sparingly, due to the possible cold conditions at the start of the crop. Not all control measures have worked, so the strategy has evolved over time.
“We’ve learnt that spraying in less than ideal conditions can result in spray application failures – like spraying barnyard grass when it is too hot. Timing of applications is critical: there can be advantages re timing with aerial application,” James said.

Growers
Matt and James Toscan

Cropping area
Total hectares: 4200 ha. Cotton: 1100 ha irrigated

Soil type
Majority Grey/brown self-mulching clay with some Transitional Red brown earth

Rotations
Two-year rotation: cotton (summer); durum wheat (winter); fallow (summer and winter); cotton (summer)

Source: CottonInfo Weed Control case studies
Further information: CottonInfo weed management page

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Using IWM to keep one step ahead of resistance

Ben Thomas has been growing cotton for 15 years across three properties, two irrigated and one broadacre, at Warren in the Macquarie Valley. Speaking to his CottonInfo Regional Extension Officer, Ben Thomas outlined how he is managing the threat of resistant weeds.
The most common weeds found on Ben’s properties are fleabane, windmill grass, barnyard grass, sow thistle, turnip weed and ryegrass. Fleabane and windmill grass are the biggest challenges at present, with Ben expecting ryegrass, sow thistle, barnyard grass and feathertop Rhodes grass to emerge as issues in the future.
Ben Thomas
The threat of resistance is a core reason why Ben has an integrated management plan in place, developed with consultant Andrew Cooper of Landmark.
Ben’s approach is to control weeds in his irrigated cotton through a range of tactics including pre-emergent knock downs, post-emergent herbicide applications, layby residuals and cultivations. Chipping is used if required.
The pre-emergents and laybys are used sparingly, as high disease levels and cold temperatures can lead to a slow start for the cotton, and he does not want to put any additional stress on the plant.
He calculates that the cost for controlling weeds ranges from $50 to $80 per hectare across his fallow, broadacre and irrigation country.
Through CottonInfo, Ben has tested for resistance in fleabane, ryegrass and other weeds.

Grower
Ben Thomas

Cropping area
Total hectares: 6000 ha. Cotton: 1500 ha irrigated

Soil type
Cracking clay

Rotations
Two-year rotation: cotton (summer); winter cereal or legume (winter); long fallow (sum- mer and winter); cotton (summer)

Source: CottonInfo Weed Control case studies
Further information: CottonInfo weed management page

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Adjuvants’ role in combatting herbicide resistance  

Andrew Somervaille, Jubilee Consulting has been evaluating the performance of herbicides for more than three decades and says the role of adjuvants is often either over-rated or under-estimated. This may seem a contradiction, but the fact is that sometimes adding an adjuvant is beneficial and sometimes it is detrimental; and there is an art to knowing how to best deploy these additives.
When weeds are susceptible to the applied herbicides, the effectiveness of adjuvants generally goes un-noticed. However, correctly applied adjuvants can reduce the impact of low level herbicide resistance by helping to maximise the amount of herbicide taken up by the plant.<!
Andrew Somervaille, research agronomist with Jubilee Consulting suggests growers and advisors should not overlook or over-rate the use of adjuvants.
“In the best case scenario, the correct use of an adjuvant can optimise performance of a single herbicide, or a herbicide mix,” he says. “This results in the most efficient control of the target weeds, minimises seed set and reduces weed numbers into the future. All research points to low weed numbers as the only sustainable way to manage herbicide resistance.”
“In the worst case scenario, the incorrect use of an adjuvant can reduce herbicide performance, may compromise the physical compatibility of mixtures and can alter the function of tank mix components,” says Andrew. “This may result in a sub-lethal dose of herbicide being applied, which is known to amplify herbicide resistance if there are low levels of resistance present in the weed population.”
“Once populations are highly resistant then the impact of adjuvants is reduced,” says Andrew. “This highlights the importance of being very deliberate and calculated when making recommendations or decisions about adjuvants.”
In one experiment Andrew conducted with two formulations of glyphosate, he measured the negative effect of the adjuvant when in the presence of 2,4-D to control awnless barnyard grass. “We know there is antagonism between 2,4-D and glyphosate in a tank mix in some situations that results in a reduction in the level of control expected from glyphosate alone,” he says. “What we observed in this experiment was that one glyphosate+surfactant formulation mixed with 2,4-D achieved just over 80% control while a second glyphosate+surfactant formulation mixed with 2,4-D achieved 94% control.”

Andrew says that although some herbicide products are manufactured with an adjuvant included as part of the formulation, there may still be a benefit gained from adding another type of adjuvant prior to application, depending on the other products in the mix, the water quality or the target weed.
In another experiment, Andrew investigated the effect of different adjuvants (LI 700 and Liase) on the efficacy of a RoundUp Power Max (glyphosate) and Amicide (2,4-D) mix. The results clearly showed that while Liase improved the performance of the mix, LI 700 reduced performance to less than 80% control of barnyard grass.

Grower experience, research trials and computer modelling all point toward high levels of herbicide performance, coupled with the removal of survivor plants, to reliably and sustainably extend the useful lifespan of herbicides by removing potential carriers of resistance traits.
“Even small incremental losses in control at the ‘top end’ can have a large effect on the total seed-bank load,” says Andrew. “While 95% control might still be considered a good result from a herbicide application that could have potentially achieved 98% control, this three per cent loss in efficiency could be the start of a substantial increase in weed numbers and allow herbicide resistance to gain a foothold.”
Keeping weed numbers low allows the targeted use of more expensive products (e.g. through an optical sprayer), makes manual control methods economical, and even allows the use of less efficient products to maintain or slightly reduce numbers while adding diversity to the program (provided there is no cross-resistance).
What adjuvants do
An adjuvant may modify the physical, chemical and biological activity of the herbicide on the target. For example, an adjuvant may be added to improve the physical properties of the spray such as its spray quality, or to allow products to dissolve or mix in water. Adjuvants may also alter the chemical properties of the formulation to counter poor water quality or activate certain components in the herbicide, and from a biological perspective an adjuvant may be used to influence uptake through the plant cuticle and even movement across cell membranes.
Very small amounts of surfactants are required to achieve adequate ‘wetting’ of the plant surfaces and adding more surfactant will not necessarily increase the performance of foliar applied herbicides. However, some adjuvants (including surfactants) are added specifically to activate the active ingredients and so are an essential component of the formulation or mixture.
Adjuvants can play an incremental role in improved herbicide performance and assist with keeping weed numbers low and reducing the risk of sub-lethal resistance traits. However, their use does not over-ride the need for correct chemical use and application under the right conditions.
The same adjuvant may even perform different functions when included in different mixes or added to different formulations. There are also specific responses in certain weeds to certain surfactants, some giving superior results and other inferior. It is not possible to give rule-of-thumb recommendations – each scenario needs to be examined carefully, taking into account the target weed species, the condition of the weeds, the water quality and the specific herbicide formulations.
They are not always beneficial and can result in sub-lethal doses being applied if they are not used correctly. Combinations of surfactants can modify the functions of the individual components and it cannot be assumed that the effects are additive to herbicide performance.
Also, be aware that the characteristics of the leaf cuticle are not the primary limiting factor associated with the uptake of foliar applied herbicides. Plant stress is usually the main limiting factor and this may only be partly overcome through the use of an adjuvant.
Clearly, it is not a simple matter of making recommendations or decisions to include an adjuvant. Growers and their advisors need to have an appreciation of the chemistry behind the adjuvant’s use and the way that it may impact on the uptake of the herbicide into the target weed.
Useful resources
Adjuvants – Oils, surfactants and other additives for farm chemicals

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Weed control program has expanded crop choices

Darren and Leanne Eather have been growing cotton east of Narrabri for some 20 years. Speaking to their CottonInfo Regional Extension Officer, Darren Eather outlined how they are managing the threat of resistant weeds.
Darren encounters a range of weeds each season, particularly fleabane, windmill grass, liverseed, barnyard grass, turnip, milk thistle and volunteer cotton.
Darren Eather
Darren’s approach to weed management varies between his irrigated and dryland cotton, and is tailored field by field and crop by crop.
In his dryland crop, he strategically uses rotations to control weeds, along with different chemical modes of action. He applies a pre-plant residual herbicide, followed by an at-plant residual and glyphosate as a pre-emergent knock down.
“For grass control, Group D chemicals were our preferred option in order to rotate chemistries. However, we’ve found that windmill grass in particular is not consistently controlled and we get some escapees, which is why we’ve moved towards Group As as an alternative. We’re finding it is providing good control,” Darren said.
In his irrigated country, he combines cultivations with two or three applications of post-emergent glyphosate. He aims to meet with his consultant each year following picking to discuss his approach.
Darren tends not to apply a layby residual, due to the long-lasting effects and subsequent reduction of options. He believes weed control in non-crop areas of his farm is very important, and actively manages this.
“We purchased a farm around a decade ago where we had a very serious issue with black oat and black bindweed,” Darren said. “As a result, we were unable to grow chickpeas on that farm. Now, 10 years later, with a good strategy of weed control and careful crop selection we have controlled the weeds in our system to the stage where we can now grow chickpeas.”

Growers
Darren and Leanne Eather

Cropping area
Total hectares: 3,000 ha.
Cotton: 400 ha irrigated and 300 ha dryland

Soil type
Vary from deep black soils to river loams and some hard setting soils

Rotations
Two-year rotation: Irrigated – cotton (summer); wheat (winter); long fallow (summer and winter); cotton (summer)
Dryland – Cotton (summer); chickpeas, canola, wheat (winter); long fallow (summer and winter); cotton (summer)

Source: CottonInfo Weed Control case studies
Further information: CottonInfo weed management page

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Efficient herbicide use pays off

He is faced with a series of weeds each season, including barnyard grass, fleabane, milk thistle, red pig weed, peachvine, feathertop Rhodes grass, bathurst burr, black oats, phalaris and turnip weed. Resistance has been confirmed in barnyard grass (resistant to Group M herbicides – glyphosate) and black oats (resistant to Group A).

Tristram Herstlet, Reardon Farms and Michael Brosnan B&W Rural
Tristram expects to have additional problems with resistance in the future, particularly with feathertop Rhodes grass and glyphosate.
To manage the existing and potential future resistance threats, Tristram has implemented an integrated approach to weed management, in collaboration with consultant Michael Brosnan of B&W Rural at Mungindi.
“We regularly discuss our weeds management program with our agronomist. By the time we plant cotton, we have a program in place and know what we want to do,” Tristram said.
“Our strategy is threefold: to minimise future resistance, prolong the use life of each herbicide, and avoid the problem of weed shifts.
“We do this by having different tactics, such as rotating our chemical groups, cultivation, crop rotation and farm hygiene. We are well aware of the dire consequences of having multiple grass and broadleaf weeds resistant to glyphosate – and we are currently managing two cases of resistance, in barnyard grass and black oats,” Tristram said.
Tristram takes a holistic approach to integrated weed management.
“We use control methods at a whole farm level, at a management unit level, down to an individual field basis. And we apply as many options as possible to try and control the weeds that are resistant, and prevent further resistance developing,” Tristram said.
“We use a Group L treatment instead of glyphosate (Group M) to give the field a break. More recently, we are using a Group K as a post-plant, pre-emergent in cotton. We intend to follow this with cultivation. We haven’t felt that we’ve needed a layby (a residual herbicide used to control weeds in-crop) as the other control methods are currently working.
“We also have a range of other tactics. All of our contractors are required to have clean gear when they come on farm. We practice ‘Come Clean Go Clean’ primarily for disease protection, but an added benefit is weed management.
“We also use chippers, predominately in non-crop areas, but also in-crop if necessary, such as if fleabane has become an issue. We try to keep everything spotless, as the fewer the weeds, the fewer the seeds for next year.”
Tristram believes the future of weed management lies in robotics and microwave technology.
“On our dryland areas we use a camera spray system, which we purchased in 2016. The driver behind the purchase was the ability to spray the dryland fallow area when cotton is in, and the ability to put on higher rates of chemical to kill fleabane without using a hormone,” Tristram said.
“The system was a serious investment – a total of $640,000, including a tractor, sprayer and boom – but we’re spraying at the moment and it costs only $5 per hectare with this new system, versus $11.60 per hectare with a full boom.
“Based on this, we’re saving around $2,000 per day in chemical with the new system. Most importantly, we’re really happy with the results: the cameras work on the chlorophyll in the plants, and the results are fantastic: we’re getting a good weed kill,” he said.

Source: CottonInfo Weed Control case studies
Further information: CottonInfo weed management page

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Getting weeds early is key

Tom and Charm Arnott have been growing cotton on ‘Fairfield’ at Boggabilla for 24 years. Speaking to their CottonInfo Regional Extension Officer, Tom Arnott outlined how they are managing the threat of resistant weeds.
They encounter a wide range of weeds in their farming operations, including peachvine, barnyard grass, chinese lantern, feathertop Rhodes grass, fleabane, sesbania, climbing bellvine, pigweed, milkthistle, turnip and native vetch. Tom finds climbing bellvine a particular challenge in cotton, because once it is in the crop it is difficult to control, wrapping around the cotton and causing issues at harvest.
Tony Taylor, Taylor Ag Consultancy and Tom Arnott “Fairfield” Boggabilla
Tom is working with consultant Tony Taylor to implement an integrated weeds management strategy.
“Resistance in weeds is already impacting on our business. We have seen how quick it can get away and it can be hard to get back. There’s also a cost associated with trying to get back,” Tom said.
“As a result, Tony and I are mapping out a strategy to combat resistance. It’s our first year, so it’s very much a work in progress. To date, I have relied on an over the top glyphosate application and a light cultivation for weed control. We’ve learnt that spraying when the plants are too big doesn’t work – you have to get in when they’re small.
“We are now implementing a residual program, which will involve using selective pre-emergents at planting to target hard-to-kill weeds on a field-by-field basis.
“We will then use a mix of glyphosate in a double- knock approach, and conduct a more aggressive cultivation with discs and knives to cultivate closer to the plant line.
“We’ll also apply a broadleaf ‘layby’ (a residual herbicide used to control weeds in-crop) to all fields to control late weeds coming through.
“We also chip weeds: particularly in the school holidays, with the whole family doing their bit. I always have a hoe in the ute!”
Tom found the recent CRDC, CottonInfo and ICAN weed management workshops useful in learning strategies to control glyphosate-resistant weeds.
“There was plenty of information, and a lot of experience among the growers in the group. It was good to kick around ideas and talk to the agronomists,” Tom said.

Growers
Tom & Charm Arnott

Cropping area
Total hectares: 1400 ha. Cotton: 1400 ha irrigated

Soil type
Black clay Vertosol

Rotations
Two-year rotation: cotton (summer); double crop winter cereal or chickpeas (winter); long fallow (summer and winter); cotton (summer).

Source: CottonInfo Weed Control case studies
Further information: CottonInfo weed management page

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News

Diverse approach to feathertop Rhodes grass control

As an early adopter of zero tillage and controlled traffic farming in Central Queensland, Brendan Swaffer is fully convinced of the benefits, and is well aware of the potential impact of weeds like feathertop Rhodes grass.
Since taking over the family farm near Clermont in 2007, Brendan and his wife Jody have been building a robust cropping program with wheat and chickpea in winter and, if soil moisture permits, dryland cotton and sorghum in summer across their 4000 ha of cultivation.
Brendan and Jody Swaffer, Clermont have reintroduced tillage to their zero till controlled traffic farming system to manage weedy patches, primarily feathertop Rhodes grass. Dryland cotton has also been a useful addition to the rotation and provides another opportunity to manage FTR.
“In the summer fallow our main weeds are summer grass, Johnson grass and fleabane but we are most concerned with the small patches of feathertop Rhodes grass that are appearing,” says Brendan. “We are using a mechanical and chemical double knock to manage these patches of FTR and it has been very effective for us in preventing its spread.”
Early in summer Brendon targets any patches of persistent weeds – mostly feathertop Rhodes that has survived under the winter crop. Starting with cultivation of the affected areas, Brendan then follows up a few days later with an application of metolachlor (Group K) to provide short-term residual control of any new germinations that are triggered by the cultivation.
“We might spend two days ploughing but only cultivate 150 ha in total,” he says. “For the rest of the year we carry a hoe in every vehicle and stop to chip out small areas of weeds when we see them. We have been enjoying the enormous benefits of zero till and controlled traffic since the 1990s – there is no going back to full cultivation, but it is a useful management tool to target weedy patches before they get out of hand.”
Preventing seed set for a couple of consecutive seasons is known to rapidly rundown FTR seedbank as the seed on the surface or even slightly buried only persists for 12 to 18 months.
Adding dryland cotton to their rotation has also helped minimise the spread of FTR. The Swaffers produced cotton in four of the five summers from 2010–11 to 2014–15, which enabled the application of Roundup Ready Plantshield to keep pressure on FTR and reduce seed set.
Brendan has built in several non-glyphosate weed control measures including cultivation, along with other knock-down and residual herbicides, to take the pressure off glyphosate in their farming system.
“Feathertop Rhodes grass is not a problem in conventional systems but the more area farmed the more difficult it is to keep clean,” he says. “It also seems to prefer scrub soils that are a bit lighter textured than the open downs country and alluvial soils we have on this property, giving us a slight advantage.”
The fallow starts with spraying out sorghum in June with glyphosate to kill the crop, make harvest easier and kill the weeds. During summer, Brendan applies glyphosate, 2,4D-amine and small amount of metsulfuron (Group B) as a tank mix to target weeds when they are small and actively growing after a rainfall event. The metsulfuron is targeting parthenium and can also provide an additive effect on glyphosate when applied in a tank mix.
After each spray application Brendan looks for, and manages any survivors or areas where the sprayer has missed, to minimise the number of weeds that escape and set seed later in the season. In recent years he has moved to more robust rates to ensure efficient weed control and to avoid the need to go over a paddock a second time.
With the variable rainfall experienced in Central Queensland, chickpeas are now the Swaffer’s most reliable crop, using moisture seeking planting techniques. “We can plant in April or early May on rain received in February by planting the chickpea seed up to 18 cm deep,” says Brendan. “Chickpea is the only crop that has a long coleoptile that allows emergence from such depth.”
Planting chickpea on 50 cm rows using moisture seeking techniques has established chickpea as the Swaffer’s most reliable crop. Brendan has found that a post-plant pre-emergence application of Terbyne (Group C) controls weeds up to canopy closure and no other in-crop herbicide is needed until the crop is desiccated prior to harvest.
“Emergence can take three weeks, but we can establish a crop on stored moisture and have it up and away before in-crop rain initiates a fresh flush of weed germination, giving the crop a distinct competitive advantage.”
The timing of a moisture seeking planting needs to factor in the frost risk in the district to avoid having the chickpea crop flowering when there is a high chance of frost.
In some years there is moisture higher in the profile, allowing both chickpea and wheat to be planted about 10 cm deep. Wheat is also planted a little later in the Clermont district than in other areas of CQ, to avoid frost. Most growers prefer to accept the small yield penalty for planting later rather than risking a crop failure.
“Strzelecki wheat is a slow maturing spring wheat of semi dwarf habit that is popular in CQ due mainly to its longer coleoptile length that allows us to plant to a depth of 10 cm,” he says. “But this variety is about to be re-classified to Hard 2 instead of Prime Hard and so many growers will be looking for alternative wheat for the future,” he says.
Strzelecki wheat has been a mainstay variety in the Clermont district because of its ability to emerge from a depth of 10 cm. A change in classification of this wheat will most likely drive growers to look for a replacement variety suited to the conditions.
Higher levels of crop competition can be achieved in the winter crops compared to the summer crops, with chickpea and wheat both sown on 50 cm rows. Brendan plants chickpea in his cleanest paddocks and uses a post-plant pre-emergence application of Terbyne (Group C) to control weeds up to canopy closure. No other in-crop herbicide is applied except for desiccation for harvest management. Brendon avoids using Balance due to the long plant-back period and the need for a lot of rain to breakdown the residual.
Sorghum crops are sown on single skip metre rows, with cotton planted in double skip configuration of 2 in and 2 out to optimise yield and quality. Brendan previously planted sorghum in solid 1 m single rows but has changed to planting a single skip – 2 in and 1 out – and increased intra-row plant density. The soil on the Swaffer’s property requires about 200 mm of steady soaking rain to fill the profile and initiate a summer crop planting. Last season there was no summer crop planted due to a lack of soil moisture however the outlook year is looking more promising for sorghum but they have not planted cotton this season.
“We are concentrating on achieving even intra-row spacing using a double disc precision planter to increase weed competition within the row,” he says. “This also promotes even maturity and reduces tillering. The combined effect encourages a shorter flowering period and makes grub and midge control easier, along with reducing the risk of ergot infection.”
Sorghum is planted in January and early February following an application of glyphosate, Dual Gold and 2,4D, provided there is no cotton planted nearby. Brendan also applies atrazine and fluroxypyr to provide in-crop weed control. Metolachlor applied in the fallow ahead of cotton provides some residual weed control but the main in-crop weed control strategy is RR Plantshield. Brendan puts far greater emphasis on timeliness of weed control than on specific rates and products.
At harvest, Brendan uses perforated screens in the header to remove as much Mexican poppy, and turnip weed seed and soil as possible out of the chickpea grain sample. He also keeps about 100 t of both chickpea and wheat seed that has been graded hard to ensure the cleanest possible seed goes back in the ground the following season.
Brendon does all his own spraying with a John Deere 4030R self-propelled sprayer and likes to keep their spray technology up to date. He considers the sprayer to be their main tractor now and changes the sprayer unit every 5 years or so to always have new gear that works well and minimal downtime.
“Our groundwater is quite hard so we use ammonium sulfate, especially when spraying out sorghum with glyphosate,” says Brendan. “Although we now have more access to rainwater, storing water is very costly so we have been assessing the difference between rain water and groundwater this year in terms of cost and efficacy on weeds. We expect to invest more in rainwater storage in the future.”
Being in full control of the spray program means Brendan can ensure his neighbours are always informed regarding cotton plantings and he only sprays when conditions are suitable. “When sensitive crops are nearby it is all about working in the right conditions and being careful about product selection,” he says.
Other resources
Mark Congreve explains the key features of FTR, considerations when developing a control strategy, fallow herbicide options and fallow application recommendations in a new series of Grains Research and Development Corporation (GRDC) Know More videos.

Article
News

Planned approach to rotations helps manage weeds

Ross, Ingrid, David and Margot Uebergang have been growing cotton for 27 years at Miles on the Darling Downs. Speaking to their CottonInfo Regional Extension Officer, Ross Uebergang outlined how they are managing the threat of resistant weeds.
They combat a series of weeds each year, in both their cotton and winter crops, including fleabane, feathertop Rhodes grass, barnyard grass, liverseed grass, bladder ketmia, black pigweed, caustic creeper, caltrop, volunteer cotton, milk thistle, fireweed, black oats and phalaris. Bellvine is an emerging problem on the farm, one Ross Uebergang suspects may become a larger problem down the track.
Ross Uebergang, Jess Mickelborough and Tim Richards
The Uebergangs are yet to do any resistance testing – something Ross hopes to implement this season – but suspect they may have resistant grass weeds.
As a result, they have implemented a whole-of-farm approach to integrated weed management, involving multiple weed-control tactics.
“If you keep relying on one tactic no matter what it is, a problem is going to arise,” said Ross. “We are trying to manage resistance and also the buildup of problem weed seeds. If we don’t, resistant or hard-to-kill weeds will bring the whole farming system unstuck.”
“For us, grasses are the main problem. We have barnyard grass and feathertop Rhodes grass and we’re unsure if they’re resistant or just hard to kill,” he said.
Ross doesn’t rely on glyphosate: his approach includes pre-plant residuals, pre-emergent knock downs, and ‘laybys’ (residual herbicides used to control weeds in- crop), plus non-herbicide tactics including cultivations and spot chipping.
“Our current strategy is to apply a residual six-weeks prior to cotton planting and then to pre-irrigate to allow the volunteers and other hard-to-kill weeds to emerge.
“We follow this with pre- and post-planting knockdowns, which include gramoxone (Group L). In crop, we apply two Group M (glyphosate) sprays and a Group A spray to target feathertop Rhodes grass and will also apply in-crop residual chemicals with shield spray in problem fields.
“After picking, we mulch and rootcut and then do heavy tillage passes to remove ratoon cotton and compaction and then the system starts again. For fields going into fallow, a layby is applied immediately post winter harvest, keeping fields clean for first flush of spring grasses,” said Ross.
“We review our practices every year. Pre-season and post-season we have a meeting with our consultant, Tim Richards of MCA, to review our strategy.
“This is where we work out our rotations and fields, highlight problem areas and develop our residual program. We have a whole farm approach, but treat fields separately due to different weed spectrum and soil types.
“This is our third season of implementing this weed control program and it has really streamlined the whole operation of growing the crop, resulting in greater timeliness of operations which equates to better yields,” he said.
Tim Richards of MCA says a successful integrated weed management system means taking a long-term approach.
“If a grower is looking further ahead than just this season and is willing to commit to a rotation, then it is easy to implement an integrated weed management system like this one. The spin-off benefit of such a system is superior operational timeliness, as we have – and are adhering to – a plan,” Tim said.

Growers
Ross and Ingrid Uebergang, David and Margot Uebergang, Uebergang Agriculture

Cropping area
Total hectares: 1100 ha. Cotton: 400 ha irrigated

Soil type
Clay loam, brigalow belah, deep cracking self-mulching clays

Rotations
Three-year rotation: cotton (summer); covercrop back into cotton (winter, then summer); barley or wheat (winter); fallow (summer and winter); and cotton (summer)

Source: CottonInfo Weed Control case studies
Further information: CottonInfo weed management page

Article
News

Are you going spraying or killing weeds?

Spray drift is of great concern for sensitive crops and environments, along with the fact that if the spray doesn’t hit the intended target, you do your dough and your weeds live.
Bill Gordon, spray application consultant with Nufarm Australia says the focus of spraying herbicide needs to be on doing the job right so the weeds receive the correct dose and die, and this includes reducing the air borne fraction to a bare minimum.
Bill Gordon, Nufarm spray application consultant says most growers are implementing best spray practice when it comes to boom height and nozzle selection but the temptation to spray at higher speeds and into the night can over-ride common sense at times.
“In many cases this means not spraying at night if the wind speed is too low,” he says. “Many product labels prohibit night spraying due mostly to the risk of spray drift. Our studies have shown that with a coarse spray quality drift may travel up to 300 to 400 metres during the day after any inversion has broken, but spraying at night can leave up to five times as much chemical in the air using the same products, nozzles and ground speed. This can result in spray drifting 10 to 20 kilometres or more at night, and this is unacceptable for other farmers, the community and the environment.”
Mr Gordon says most growers are implementing best spray practice when it comes to boom height and nozzle selection but the temptation to spray at higher speeds and into the night can over-ride common sense at times.
“The flip side of this is that it is becoming more evident that using Delta-T as the main determinant of safe day-time spraying conditions may not be the best approach,” he says. “What really matters most is the wind speed and whether the weeds are stressed or not.”
“If the weeds are not stressed on a hot day, due to ample soil moisture, then spraying at a higher Delta-T may still be effective and safe, with course droplets surviving quite well and not becoming air-borne.”
This can essentially increase the number of daytime hours available to growers to get the job done without spraying at night or early in the morning when the risk of spray drift is the highest.
“Getting onto paddocks as soon as possible after rain and using up the daytime hours to target priority paddocks will maximise weed control and minimise spray drift risk,” says Mr Gordon. “Spraying can continue into the evening in summer if the soil remains warm and the wind speed stays above 12 km/hr. If the wind drops off, then spraying should cease, usually by about 10 pm through to a few hours after sunrise.”
The bottom line is that it is very difficult to determine a safe night-time spraying conditions.

When environmental conditions are borderline in terms of wind turbulence, the safe spray window can be extended slightly through the use of coarser sprayer quality where the proportion of droplets less than 150 microns is 10 per cent or less, keeping drift to a minimum. The trade-off, however, is reduced efficacy when using very coarse droplet size, particularly when the target is small, vertical or hard to wet.
“When buying new nozzles, check them against the new standard, which shows spray quality with adjuvants rather than water only,” says Mr Gordon. “The GRDC has recently updated and published the 2017 Nozzle Selection Chart for growers to use as a reference. Using the correct nozzle and adjuvant combination can have a positive impact in reducing spray drift and maintaining efficacy.”
[A new factsheet provides advice to help growers meet the new 2,4-D application requirements]
“Reducing ground speed by just 5 km/hr can also make a big difference to spray coverage and efficacy of weed control, particularly if there is a high stubble load present,” he says. “Water sensitive paper, in combination with apps such as ‘SnapCard’, is a good way to test the coverage, penetration and spray pattern achieved under different conditions, such as different ground speeds.”
Mr Gordon’s rule of thumb for effective weed control when applying fully translocated products (e.g. glyphosate and Group I) is a minimum of 6–8 per cent coverage, while coverage of 10–12 per cent or more is required for contact herbicides. “Pre-emergent herbicides are the most difficult to judge due to the number of variables involved in their effective application, but as a rule of thumb I generally look for coverage of at least 15–20 per cent,” he says.
Getting onto paddocks as soon as possible after rain and using up the daytime hours to target priority paddocks will maximise weed control and minimise spray drift risk. Spraying can continue into the evening in summer if the soil remains warm and the wind speed stays above 12 km/hr. If the wind drops off, then spraying should cease, usually by about 10 pm through to a few hours after sunrise.
If you are going out killing weeds, you need to get everything right.
Bill Gordon’s 10 Tips for Reducing Spray Drift

Choose all products in the tank mix carefully.
Understand the product mode of action and coverage requirements.
Select (and check) the coarsest spray quality that will provide effective control.
Expect that surface temperature inversions will form as sunset approaches and will likely persist overnight and even beyond sunrise on many occasions. DO NOT SPRAY.
Use weather forecasts to inform your spray decisions.
Only start spraying when the sun is about 20 degrees above the horizon and when the wind speed has been above 4–5 km/hr for more than 20–30 minutes, and clearly blowing away from any adjacent sensitive crops or areas.
Set the boom height to achieve a double overlap of the spray patterns.
Avoid higher spraying speeds.
Leave buffers unsprayed if necessary and come back.
Continue to monitor conditions, particularly wind speed, at the site during the spray operation.

https://www.weedsmart.org.au/webinars/spray-wisely-well-maximise-efficacy-bill-gordon/
Watch what happens in this demonstration of fine particle movement under surface temperature inversion conditions.

Other resources:

‘Spray wisely and well’ Webinar – Bill Gordon
Ask an expert May 2017 – Bill Gordon
Maintaining efficacy with larger droplets – New 2,4-D application requirements
SnapCard App
GRDC Nozzle Selection Guide 2017
Cotton Field Awareness Map (CottonMap)
Nufarm Spray Wise Decisions
Spray Application GrowNotes

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