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Tackling ryegrass in Tasmania’s high rainfall zone

The wettest April in 60 years is likely to cause growers in Tasmania’s high rainfall zone some unique challenges when it comes to controlling annual ryegrass, the Australian grain industry’s #1 weed.

Blow-outs are mostly in wet years and in paddocks with other underlying issues where ryegrass can take advantage of any gaps or areas of lower crop vigour. Many growers are finding that ryegrass is particularly difficult to manage in winter cereal and canola crops where the long cool season allows multiple germinations of ryegrass and the wet conditions reduce the residual benefits of pre-emergent herbicides.

WeedSmart southern agronomist Greg Condon says creative farmers and agronomists are addressing the problem head on and finding ways to implement the WeedSmart Big 6 weed management tools to stop seed set and drive down weed numbers.

“Farmers need to operate in a low-weed environment so they have more options in their crop and livestock decisions,” says Greg. “The principles of crop diversity, crop competition and mixing and rotating herbicide modes of action are central to keeping farming systems profitable.”

Diversity in cropping and livestock operations needs to result in diverse weed control tactics.

“The creativity comes in with the problem-solving process needed to apply these principles in challenging environments. The practices that have been developed in other high rainfall zones do not always apply directly to the Tasmanian farming systems.”

Growers and agronomists can use the WeedSmart Big 6 to keep ryegrass numbers under control while maintaining maximum flexibility in their cropping program. Greg says all the tactics will work in the Tasmanian high rainfall zone, with the exception of harvest weed seed control.

“Growers in the region have a distinct advantage when it comes to diversity in their farming system and this needs to drive the use of different weed control methods to keep the weeds guessing – using both herbicide and non-herbicide tools,” he says.

“Unfortunately, harvest weed seed control is far less effective in the Tasmanian cropping zones than it is in other high rainfall zones,” he says. “This is because a large percentage of the ryegrass that germinates in the crop will shed its seed before harvest. Some growers may still find value in this tactic to collect the seed from the later cohorts of the weed but it just isn’t as cost-effective as it is in other areas.”

Even without harvest weed seed control as a mainstay option, growers can still implement a three or four year ‘war on weeds’ program to drive down the ryegrass seed bank.

“To start with, tactics such as spring cropping, fodder crops and triple break crops can be used to maximise the efficacy of available herbicides and reduce ryegrass germinations,” says Greg.

“When it comes to herbicides it is critical that a plan is put in place to mix and rotate herbicides across the whole crop sequence,” he says. “In-crop herbicides are scarce and products like clethodim are registered for use in many crops so it is easy to keep using it, but we know that quickly leads to resistance problems.”

Having diversity of crops in the system only helps with weed control if it is used as a way to rotate chemistry. Testing the weeds for their susceptibility to single products and mixes of herbicides allows growers to plan ahead with more confidence. Double knocking each herbicide application preserves the available chemistry, particularly glyphosate.

Growers can also take advantage of ryegrass’ poor competitive ability. When placed in a competitive environment, ryegrass sets less seed, reducing the pressure of this weed on farming system decisions.

“Crop agronomy has a major impact on competitiveness,” says Greg. “The choice of crop, solid plant establishment, sowing early with a robust pre-emergent herbicide and attending to any soil constraints all swing the advantage toward the crop and away from the weeds.”

The final tactic that growers can implement is stopping weed seed set using hay and silage, crop-topping in canola or spraying under the cutter bar when swathing, or using camera-guided shielded sprayer technology to target weeds growing in the inter-row.

Cutting weedy areas of the crop for hay is a highly effective tactic that can reduce the impact of a weed blow-out.

Ian Herbert, Southern Farming Systems’ Tasmanian Projects and Trials Manager says fodder crops and livestock play a critical role in managing ryegrass on many Tasmanian farms.

“Growers can plant fodder crops directly after grain harvest, graze these fodder crops through winter, while allowing multiple germinations of ryegrass to occur, and then remove these plants using broad spectrum herbicides and or cultivation prior to planting a grain crop in spring,” he says. “This tactic reduces the pressure on selective herbicides and changes the timing of when ryegrass is controlled, compared to years where the paddock is in a cereal production phase. Cultivation is often needed to remove the deep pugging from livestock, which often occurs during our wet winters.”

Livestock can play an important role in weed management and there are many options available to growers.

Michael Chilvers is one grower who is embracing an integrated approach to managing ryegrass on his 1200 ha farm south of Launceston, where he runs a diverse cropping enterprise of around 300 ha of grain production along with intensive lucerne hay, potato and hybrid seed production.

Michael says the exceptionally wet autumn across much of the high rainfall zone, and particularly in their region, is going to put heavy pressure on the pre-emergent herbicides applied at planting.

“Incorporation of pre-em herbicides is critical and often not easy to achieve,” he says. “Unfortunately, the newly released pre-em products are probably not going to be an option for us in very wet seasons so we need to focus on getting the most out of the existing products.”

Michael is also very aware of the heavy reliance on Group A herbicides such as clethodim across his farming system and is doing what he can to rotate away from this key mode of action at every opportunity.

“Not only do we use it frequently, we also know that its efficacy can be compromised in our environment through a long cool growing season, which means we are running a real risk of losing it if we don’t adopt a more diverse approach to managing ryegrass,” he says.

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What to expect at WeedSmart Week 2021

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

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

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

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WeedSmart agronomist set to tackle high rainfall zone weeds

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

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Never cut the herbicide application rate

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

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

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