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Crop topping, using Sharpen & getting ready for harvest

In the podcast this week, we focus on crop topping and the relatively new herbicide, Sharpen. In our last podcast, Andrew Messina talked to us about Case IH harvester set-up. This week farmer Lance Turner gives us the rundown on John Deere gear. AHRI and WeedSmart Agronomist Greg Condon talks to us about the benefits of crop topping and what to do if you suspect you’ve got herbicide resistance. We also hear from BASF Technical Services Manager, Phil Hoult, about the herbicide Sharpen. It’s now registered as a harvest aid in winter pulses, for winter cleaning of Lucerne and for wild radish seed-set control in winter cereals, so we’ll find out in more detail about its applications for broadacre croppers.
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Spray drift & crop competition

Join your hosts Jessica Strauss and Peter Newman in the first podcast for March! Spraying weeds and choosing seeds are the hot topics this podcast. We chat with Nufarm Australia Spray Application Specialist Bill Gordon, who gives some great tips and insights on correct set-up. Rohan Brill also joins us for insight on choosing canola seeds and the benefits of crop competition! Our webinar series is also kicking off for 2017 next week! If you’d like to register for the March 7 webinar with Rohan Brill, who will be going into more detail on crop competition, click here!
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Post emergent herbicides

Part 1: Spray small radish twice Western Australian research reveals that careful timing, effective application and using different herbicide groups are more important than product choice for controlling wild radish. A range of herbicide combinations can provide effective control of herbicide-resistant wild radish if small plants were sprayed twice and attention is given to achieving good herbicide coverage. Peter Newman (Australian Herbicide Resistance Initiative) and agronomist Grant Thompson (Crop Circle Consulting) discuss the results of their wild radish research. Resources Spray resistant radish early for best efficacy and yield (Grant Thompson, Crop Updates paper 2014) Herbicide resistant wild radish (Peter Newman) Controlling herbicide resistant Wild Radish in wheat in the Northern Agricultural Region of WA with a two spray strategy (Peter Newman) Diverse weed control: Left jab, right hook (AHRI insight) Part 2: When is it worth rotating from clethodim (Select®) to butroxydim (Factor®)? Is there any value in rotating the post-emergent herbicides clethodim (Select®) and butroxydim (Factor®)? The research suggests that Factor® will sometimes kill plants that are moderately-resistant to Select® that could help in driving down the weed seed bank. Dr Peter Boutsalis from the University of Adelaide discusses his latest research and observations using both products with AHRI’s Peter Newman.
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Increase pre-em efficacy through a mix and rotate strategy

Have you got the best and most cost efficient strategy to nuke your weeds before seeding? The case is clear: summer weed control is essential! Controlling weeds through summer and prior to seeding is key to securing moisture and nitrogen for the following crop. Part 1: Control summer weeds for yield and profit Every $1 spent on summer weed control can potentially return up to $8/ha through moisture and nitrogen conservation. The impact on grain yield as a result of various summer weed control treatments is what Colin McMaster (NSW DPI R&D) refers to as “buying a spring”. Listen to Colin and Pete Newman (AHRI) as they investigate the $$ benefits of controlling summer weeds. Part 2: Increase pre-em efficacy through a mix and rotate strategy We’ve done a good job of promoting herbicide rotation over the years. And whilst this advice still stands, recent research shows the benefits of mixing herbicides as well. As American weeds researcher, Pat Tranel, puts it, “rotating buys you time, mixing buys you shots (of herbicide)”. Listen to Pat and Pete as they explore the benefits of the mix and rotate strategy.
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Alternative second knock herbicides for broadleaf weeds in fallow

The sequential application of two separate herbicide treatments has become the most common ‘double knock’ approach used in weed management. Unfortunately, these approaches have added cost, complexity and scheduling issues to weed management programs but have been required for two main reasons: 1. To control herbicide-resistant weed populations, that may have been selected by prolonged use of a similar mode of action chemistry; and 2. Control of weed species or stages that are unsuccessfully controlled with single herbicide applications. Paraquat has been the key active ingredient used in the second knock situation and can provide effective management of a wide range of grass and broadleaf weeds. However, it is clear we require other options to use in this management window to: 1. Avoid the more rapid selection of paraquat resistance; and 2. Provide options that may improve weed control in situations where paraquat efficacy is not adequate. Since winter 2016, NGA has been screening a range of herbicides, to identify options that have the potential for this usage pattern. The two key broadleaf weeds being targeted are common sowthistle (Sonchus oleraceus) and flaxleaf fleabane (Conyza bonariensis). DOWNLOAD FACTSHEET
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Rising significance of resistant barley grass

Listen to the article being read above! Barley grass has a number of tactics up its sleeve to help evade both herbicide and non-herbicide weed control methods. This has made it a weed of interest for the University of Adelaide’s Weed Science Group, led by Associate Professor Gurjeet Gill, who are investigating the ecology of emerging weeds in the low rainfall zones of southern Australia University of Adelaide researchers Dr Gurjeet Gill and Ben Fleet say that understanding weed ecology and undertaking herbicide screening will help find ways to manage increasing resistance in barley grass. With investment from the GRDC, Dr Gill and his team analysed the dormancy traits and herbicide resistance status of 146 random samples of barley grass collected by agronomists in WA, SA, Victoria and NSW in 2018. Of the 146 random samples collected, five per cent of populations showed resistance to Group A herbicides and 21 per cent showed resistance to Group B herbicides. There was no evidence of resistance to glyphosate or paraquat. There were also large differences between the populations in the level of seed dormancy as seen by the timing of seedling emergence in autumn. Barley grass populations from the Eyre Peninsula in particular were much slower to establish than those from other low rainfall regions. Late emerging weeds can escape weed control with knockdown herbicides. In a later study, growers from the Eyre Peninsula Agricultural Research Foundation (EPARF) collected samples of barley grass seed in 2019 from paddocks where growers had experienced difficulty in controlling barley grass with herbicides. These samples were tested for resistance screening in 2020. Resistance screening of barley grass from suspect paddocks on the Eyre Peninsula, SA. “The expectation was that most populations from the targeted survey in 2019 would be resistant to Group A herbicides,” says Dr Gill. “Resistance to the Group A herbicides was confirmed in 17 of the 22 populations from EP, or 77 per cent. Within this Group, resistance to quizalofop was 100 per cent for the suspect populations while there remains some useful activity from clethodim and butroxydim, which will help the growers in the short term.” Herbicide resistant barley grass shows no response to a high rate of the commonly-used Group A herbicide, quizalofop (right) compared to a plant from a susceptible population (left). The same populations were also tested with Group B imidazolinone chemistry, which offers some activity against Group A resistant barley grass, although one of the EP populations was completely resistant to the IMI herbicide. The good news is all of these populations remain susceptible to glyphosate and paraquat. Dr Gill says that research and field observation confirm there is significant variability in barley grass populations’ ecology and herbicide resistance status. “Understanding how different barley grass populations behave is key to their management,” he says. “The seed dormancy and seed shedding traits of a population have important implications in terms of management options. Barley grass often evades pre-emergent herbicides through delayed emergence and at the other end of the season barley grass often sheds its seed before crop maturity, so harvest weed seed control is rendered ineffective in many circumstances.” Barley grass is susceptible to strong crop competition, and on mixed farms Dr Gill says some farmers have had success using pyroxasulfone herbicide in wheat ahead of a pasture phase, where good grazing management can limit seed production in barley grass. Applying the WeedSmart Big 6 integrated weed management strategy to barley grass will keep herbicides working for longer and maximise the impact of cultural control tactics.
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Long-time advocate joins the WeedSmart team

Chris Davey has been advocating planned and sustainable weed control programs with growers on the Yorke Peninsula for many years and has been a great supporter of the WeedSmart message in his patch and beyond. In August Chris accepted an offer to join the WeedSmart team as the new Southern Extension Agronomist. He joins Peter Newman in the Western region, Greg and Kirrily Condon in the East and Paul McIntosh in the North. Chris Davey, YP-AG has joined the WeedSmart team of extension agronomists and played a key role in coordinating the 2020 WeedSmart Week in Clare, SA. Chris has hit the ground running with his first responsibility being to coordinate the 2020 WeedSmart Week event in extraordinary circumstances. The annual 3-day event went off without a hitch around Clare in early September, with growers and agronomists from across South Australia hearing from experts in herbicide resistance management and visiting farms where growers have implemented a range of strategies to keep weed numbers low. “WeedSmart Week is a terrific way to share ideas and information surrounding integrated weed management,” says Chris. “We are all challenged with the task of using herbicides strategically within a management program that also includes many non-chemical tactics. There is solid science behind the recommendations and experience in the field shows that WeedSmart’s Big 6 approach is practical and effective.” Justin Harris, Davon Pastoral Co, Thomas Plain (second from left) was one of the six host farmers for WeedSmart Week 2020, Clare SA. In welcoming Chris to the WeedSmart team, program manager Lisa Mayer says having an extension agronomist of Chris’ calibre dedicated to sharing the WeedSmart message with growers in southern Australia offers many opportunities to ramp up the pressure on herbicide resistant weeds in the region. “Southern growers are facing some serious issues with herbicide resistance impacting on their farming decisions,” she says. “Chris and the other extension agronomists in the WeedSmart team have a wealth of experience and knowledge, particularly in their own regions, and this underpins their work in adapting the Big 6 principles to suit the conditions in each farming system.” “We are thrilled to have been able to successfully deliver WeedSmart Week in South Australia this year amid great uncertainty,” says Ms Mayer. “The forum and field tours came together very successfully due to the local support from Chris and the YP-AG team, along with our collaborators – Pinion Advisory agronomist, Jana Dixon, and the Hart Field Site Group.” WeedSmart program manager Lisa Mayer and GRDC Manager Weeds, Jason Emms at the 2019 WeedSmart Week in Emerald, Qld. 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. WeedSmart Southern Extenion agronomist Chris Davey discussing the pros and cons of different harvest weed seed control systems with growers Gary Bruce (left) and Jarrad Cock (right) at the WeedSmart Week machinery site.
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Taking a single shot at weeds

As farmers get their hands on fast and accurate weed mapping technology, the frequency of blanket herbicide spraying can be greatly reduced. With an accurate digital map that shows where the weeds are right now, most boomspray rigs can become low-cost spot sprayers. For the past two years John Single and his son Tony have been using the air-borne weed sensor, Single Shot, developed by John’s other son Ben, to rapidly detect and map weeds on their dryland cropping property, Narratigah, near Coonamble, NSW.   John Single with a drone carrying the Single Shot weed sensor. By separating the weed mapping and weed spraying tasks the Singles can take a planned approach to their weed management throughout the year. Ben saw the benefits of separating the weed detection and weed spraying tasks and set about building the platform and working with Robotic Systems to bring the idea to reality. “The main aim is to stay ahead of herbicide resistance,” says John. “Ten years ago we started work on developing drone-mounted sensors that could take over the task of detecting weeds in a green-on-brown situation. Many sprayers, particularly later models, do not require any modifications and there are many benefits in having the weed mapping done separately rather than on-the-go.” Weed maps enable growers to take a planned approach to their weed management throughout the year and to build a historical record of weeds in a paddock. The Single Shot sensor maps green-on-brown but are not limited to fallow situations. The sensors can be used in newly sown crops to map weeds that emerged on the planting rain or were missed in a previous application. These patches, or individual weeds, can be treated in-crop or a pre-emergent can be applied to the patches at the end of the season. The sensor can also be used in-crop to identify high biomass areas within a paddock where high weed density requires more drastic action, such as cutting for hay, and in wide-row crops where the canopy does not fully close and weeds can be detected between the rows. Screen shot of the Trimble guidance screen in operation with a Single Shot spray map. The Singles have used the Single Shot technology in several different management scenarios already and the possibilities seem endless. John says they have used the sensor to identify survivor marshmallow and milk thistle plants in fallow and then spot spray them with a high rate of Starane to prevent seed set. They have mapped feathertop Rhodes grass in wheat to generate a map for applying pre-emergent herbicide post-harvest and have filtered data to segregate weeds based on size, giving them the option to apply a blanket spray on smaller weeds and a herbicide spike to treat larger weeds, or to use a second boom to apply two different products or rates. Where pre-emergent herbicides are used, a perimeter determined by the user can be added to cover the seed distribution area of the mother plant. Another important role for Single Shot at Narratigah is to scout for survivor weeds after herbicide applications. The Singles crop 4500 ha and can map the farm at a rate of up to 300 ha per hour. This is one of the most important tasks in a herbicide program and yet it is generally not done effectively due to the time required. Having ‘eyes in the sky’ makes routine and accurate scouting practical after every spray treatment. The sensor is capable of covering 300 ha/hr under continuous flight or targeting weeds greater than 5 cm diameter. Under normal operating conditions, and including battery changes, the Singles achieve a work rate of around 200 ha/hour. Critically, data processing can be done in the field, if the internet is available at the site, and is done at a speed 1.7 times faster than flight time. Once a weed map has been created, the drone can be sent out again to take high resolution imagery of plants in specific locations in the paddock for identification purposes, allowing John and Tony to plan a herbicide program with their agronomist, based on exactly what’s in the paddock. When it comes to spraying, having the weeds mapped before the spray operator gets in the cab means that the job can be done when conditions are suitable, including at night. The real power of the Single Shot system is the ability to run simulations and to re-process the data to fine-tune a herbicide program based on weed size or density. The sensor requires just a 1 cm ‘brown’ perimeter around a weed to be able to detect the weed size. The weed maps are built from images that are ten thousand times higher resolution than satellite images, giving a 1 cm sampling size. Every part of the paddock is photographed twice so obstacles such as stubble occlusion can be significantly reduced. The drone flies at a height of 75 m, following a pre-determined path, and can also be flown lower and or slower if necessary to collect specific data. The sensor also accurately identifies stressed weeds. “Information is power and this has really put us back in control of our weed management,” says John. “We know how much chemical to buy to do the job at hand, we know the costs and can alter the chemistry to suit a budget if necessary, we can choose to blanket spray or spot spray, and our ability to apply the double knock tactic is greatly improved.” Ready for unmanned aerial vehicle (UAV) spraying In a bid to be one step ahead of the game, the Single Shot software will also calculate the shortest path for the sprayer, which is most useful when doing spot spraying on an ATV, or in the future, to deliver herbicide via a drone-mounted sprayer (UAV) or autonomous vehicles. “We ran a scenario for treating about two thousand survivor weeds in a 125 ha paddock using a spray drone,” says Ben. “To apply a blanket spray to the paddock, the spray drone would need to travel about 310 km. Using the Single Shot software we determined the shortest path to reach all the weeds, which cut down the time required to do the job to just two and a half hours. The sprayer would only be applying herbicide for 16 km of the 54 km flight, and just 5 per cent of the paddock would have herbicide applied.” Left: Actual weed coverage in a 125 ha paddock (blue line is the boundary, and purple is weed). Right: The path that the UAV would travel using the shortest route computation. Weed mapping using tools and systems like Single Shot are putting growers back in the driving seat to cost-effectively and consistently implement the WeedSmart Big 6 tactics that underpin sustainable herbicide use and maintain productivity gains through no-till farming systems.
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Throwing the Big 6 at weeds in South Australia

Low weed seed banks underpin all profitable farming enterprises. Keeping weed numbers low and quickly regaining control of blow-outs is the sole purpose of the WeedSmart program. Each year growers and agronomists are invited to attend WeedSmart Week, somewhere in Australia. This year the 3-day event will begin with a 1-day forum at Clare Golf Club on Tuesday 1 September. The following two days will be spent touring farms in the Clare region to see how growers are implementing the WeedSmart Big 6 tactics to minimise the impact of herbicide resistance on their businesses. The WeedSmart Week theme ‘Diversify and Disrupt – Use the BIG 6 to beat crop weeds’ says it all! YP AG senior agronomist Chris Davey (right) is encouraging growers from South Australia and beyond to attend WeedSmart Week in September as a good opportunity to formulate a plan to manage weeds throughout the year and through the rotation using the WeedSmart Big 6. This flagship event of the WeedSmart program is supported by GRDC as the major sponsor and a wide range of herbicide and machinery companies that have skin in the weed control game. This year’s event will be co-hosted by Pinion Advisory, YP AG and the Hart Field Site Group and will be the sixth WeedSmart Week event. WeedSmart program leader, Lisa Mayer says the event in Clare is the first of its kind for South Australia, giving growers and agronomists access to practical research and implementation of tactics that are known to effectively manage the risk of herbicide resistance in weeds. “Weeds have gained the upper hand on some farms and have too much influence over farming system decisions,” she said. “The herbicide and non-herbicide tactics that form the WeedSmart Big 6 have been researched and demonstrated in the field – we know they work! Growers and agronomists in each region and on each farm can adapt the Big 6 principles to bring more diversity to their farming system and bamboozle weeds.” “WeedSmart is committed to exploring and promoting farming systems and technologies that produce ‘more yield, fewer weeds’ every year.” WeedSmart Week brings together a wealth of knowledge and experience from local and inter-state growers, researchers, advisors and technology experts – putting the spotlight on herbicide resistance and weed management. Growers can see what is and isn’t working first-hand and consider how key principles can be applied directly to their own farming operation. At the forum and on the bus trip growers, agronomists and researchers put all the options and ideas on the table for discussion. In August last year, leading agronomist from YP AG, Chris Davey attended the Horsham event along with Pinion Advisory agronomist, Jana Dixon, and growers Jarred Tilley and Adam Cook. Chris says it was a very valuable experience that gave him the opportunity to interact with growers and industry people involved in weed management in a range of environments. The machinery displays and demonstrations at WeedSmart Week events are a great opportunity to see some of the newest weed management technology and grower innovations. “The interaction between attendees was excellent as growers and agronomists swapped experiences and things they had learned about tackling certain weeds or modifying equipment,” said Chris. “Having WeedSmart week in Clare this year is a fantastic opportunity, particularly for South Australian growers, to get together and discuss new ideas and learn how different tactics are working for other growers.” There will be a focus on both herbicide and non-herbicide tools and plenty of chances to see how mechanical tactics like harvest weed seed control can fit into a variety of farming systems to drive down weed numbers. Jarred Tilley, a mixed farmer at Kapunda, will be one of the host farmers for the WeedSmart Week farm tour. Jarred is tackling glyphosate resistant ryegrass and has recently added a chaff cart to their weed management strategy. He has had good success with baling the chaff and using it to improve the profitability of their livestock enterprise. The growers, agronomists and researchers speaking and participating in expert panels at the Day 1 forum will spark important discussions about herbicide resistance and how the Big 6 tactics can be used to target the weed species and farming systems in the southern cropping region. There’s one thing for sure – doing nothing is not an option. Day 2 and 3 will be bus tours to farms in the Northern Yorke Peninsula and the Mid to Lower North regions around Clare. Attendees will have several opportunities to see and discuss cutting-edge technologies such as the latest sprayer technology and a range of harvest weed seed control implements, including impact mills and chaff decks, and will find out how other growers in the region are implementing the Big 6 weed management tactics in a variety of farming systems and environments. Register for this important 3-day event for the ‘early bird’ single ticket price of $165 (GST incl), guaranteeing a seat on both the bus tour days as well as the forum, all fully catered here! WeedSmart is committed to the health, safety and well-being of everyone working in, and in support of, the Australian grains industry. WeedSmart Week may be postponed in response to the current coronavirus outbreak, and in accordance with Australian Government advice in relation to social distancing.
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Crop competition halves weed seed numbers

Wheat and canola crops offer growers some really practical options to improve crop competition against weeds, particularly grasses, and vastly reduce weed seed set. Researchers at the University of Adelaide, led by Dr Chris Preston and with GRDC investment, conducted an extensive study to identify the agronomic factors that promote strong early crop growth. They found that simple strategies of growing hybrid canola and sowing wheat early, can couple with pre-emergent herbicides to achieve a very effective double-knock. The result is more yield, less weed seed produced and less selection pressure on the herbicides. “In the canola trial we used a range of pre-emergent herbicides and compared open pollinated and hybrid canola,” says Chris. “The bottom line of our trial is that if you grow a hybrid canola with pre-emergent herbicides and do nothing else different, you’re going to reduce your grass weed seed set by 50 per cent.” If you grow a hybrid canola with pre-emergent herbicides (left) and do nothing else different, you’re going to reduce your grass weed seed set by 50 per cent (right, conventional canola and no pre-emergent herbicide). This level of non-herbicide weed control was also measured in an Australian-first study that looked at the competitive ability of 16 canola genotypes against annual ryegrass and volunteer wheat over two contrasting seasons, led by Professor Deirdre Lemerle at Charles Sturt University. In a separate trial conducted by Rohan Brill, former research and development agronomist, NSW DPI based in Wagga Wagga, and colleagues at Trangie and Tamworth, a rule of thumb was established that seed size had a greater effect on early biomass production in canola than did cultivar type (hybrid vs OP). This gave rise to the recommendation that all farmer-retained OP canola seed be cleaned and graded to collect planting seed that is 2 mm in diameter or larger. Their study showed that sowing large canola seed, regardless of the cultivar, is key to strong early crop growth and the crop’s ability to compete with weeds. Having observed that later planted wheat often hosts more weeds, the Adelaide University team looked at the effect of planting wheat as early as possible. “Our previous idea for managing weedy paddocks was to delay sowing, apply another knockdown treatment to control more weeds and then put the crop in,” says Chris. “In this trial we found that even in weedy paddocks you can put the wheat in early with a robust pre-emergent herbicide package, and the result is more wheat yield and less ryegrass seed at the end of the season.” Dr Chris Preston, University of Adelaide, says if you sow the right wheat variety early and apply the right pre-emergent herbicide package, you can halve your grass weed numbers, just from competition in the middle part of the season, and you don’t have to change anything else. “If you sow the right variety early and apply the right pre-emergent herbicide package, again you can halve your grass weed numbers, just from competition in the middle part of the season and you don’t have to change anything else.” There are a few practicalities to consider when looking to sow wheat earlier. Firstly, you need to choose a variety that will still flower in the right flowering window for your location. If you are sowing several weeks earlier than normal you need a longer season variety to manage frost and heat risk at the end of the season. Crop competition trial site at Roseworthy, SA. Secondly, if you are sowing completely dry, then most of the pre-emergent herbicide options are open to you. If there is some soil moisture, but not enough for crop germination, some of the pre-emergent herbicides will not perform well. You need to give careful consideration to your choice of herbicide to suit the environmental conditions of each season. These findings underpin WeedSmart’s aim, to promote farming systems that produce ‘more yield and less weeds’. More resources: Best seed, best establishment and fewer weeds Choose highly competitive canola
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Understanding weed competitive traits in barley

WeedSmart Scientific Partner Barley is known as a fairly competitive crop, but not all genotypes are equal when it comes to weed suppression and weed tolerance. To un-pick the complex mechanisms behind competitive ability in barley, QAAFI weed researchers Gulshan Mahajan and Bhagirath Chauhan, and cereal plant breeder Lee Hickey, teamed up to quantify the effect of weed interference on commercial and elite-line barley genotypes. Their two-year field trial compared the competitive ability of eight barley genotypes against a mimic weed (oats) by measuring weed biomass, weed seed production and barley yield. Weeds can cause huge yield losses in barley – between 43 and 78 per cent difference between weedy and weed-free growing conditions for the eight genotypes tested. There is considerable variation in the weed competitive ability of current and elite breeding lines of barley in Australia. The most weed suppressive variety, Westminster, reduced weed seed production by 73%, compared with that of LaTrobe. Similarly, weed biomass of Westminster reduced by 55%, compared with that of LaTrobe. There is scope for the development of high-yielding weed-competitive barley genotypes through additional screening of elite lines in weedy conditions. Higher panicle production in barley appears to be a strong indicator of a genotype’s competitive ability. When it comes to using a crop to compete with weeds there are two discreet mechanisms – weed suppression, where the growth and seed production of weed plants is reduced and weed tolerance, where crop yield is maintained, even in weedy conditions. The most competitive genotypes will use both of these mechanisms and knowing which mechanisms are at play is valuable information when planning an integrated weed control program. Competitive genotypes are a powerful non-herbicide weed control tactic and growers will gain significant benefits if they can plant a strong weed-suppressive crop into a weedy situation, particularly if they do not have to sacrifice yield. While yield and malt quality have driven the barley breeding program to date in Australia, this research suggests that there is great advantage in understanding the response of the variety to weed pressure. Observations on the competitive ability of the four commercial varieties tested: Commander barley is both weed suppressive and weed tolerant. If sown with an effective pre-emergent herbicide, Commander is probably the best choice to maintain low weed numbers. Westminster is the most weed suppressive and might be a better choice if weed numbers are starting to increase, or for use in low input and organic production systems. Westminster is not weed tolerant, so a significant yield penalty should be expected in weedy situations. Although Compass is tall and has a droopy architecture (like Commander and Westminster) it is not weed suppressive or weed tolerant, and should only be chosen for weed-free situations. LaTrobe is the least weed seed suppressive but is weed tolerant, maintaining a reasonable yield in the presence of weeds. The competitive ability of a particular genotype may vary in different locations, seasons and management systems, and in the presence of different weed species. Experimental design features The experiments were conducted in 2017 and 2018 at the University of Queensland research station at Gatton. The crops were sown at a depth of 5 cm in rows 35 cm apart on 17 May 2017 and 23 May 2018. The crops were irrigated to maintain field capacity and were harvested on 4 November 2017 and 28 October 2018. There were eight barley genotypes, weedy and weed-free treatments and three replicates. Four of the barley genotypes are commercial varieties and four are elite breeding lines being assessed prior to commercial release. Like most other plant breeding programs, Australian barley varieties are usually screened in a weed-free environment with a focus on yield and malting qualities. In this experiment, each genotype was sown at the recommended seeding rate (125 kg/ha) in a weedy and weed-free environment. Oats was used as a mimic for wild oats, a serious weed in barley. Wild oats could not be used because it has non-uniform germination and sheds its seed before barley harvest. The plot size was 8 by 1.4 m. The weedy plots were sown with a commercial oat variety at a target density of 40 plants/m2. There was no significant seasonal effects so data from the two seasons could be analysed together. Weed infestation and genotype influenced the number of panicles produced per metre row length of the barley crop and crop yield. Only genotype influenced crop plant height. While genotype had a significant impact on weed biomass, weed seed yield, weed-tolerance ability and weed-suppressive ability, phenotypic traits are not always a reliable indicator of a genotype’s weed suppressive ability or weed tolerance ability.   In this experiment, panicle number was a good indicator of both weed suppressive ability and weed tolerance ability, but plant height and architecture were not reliable indicators. Left: Weed seed yield in weedy treatment for each barley genotype.Right: Effect of barley genotype and weed treatment on barley grain yield. Other factors, such as lodging and harvest index, will also need to be considered in a variety selection process but were not measured in this experiment. Some genotypes possess both mechanisms for competing successfully with weeds while others possess one but not the other, and some have poor suppression and tolerance. Table: Plant attributes and mean values for the weed-tolerance ability and weed-suppressive ability of the eight tested barley genotypes. This research suggests that screening barley varieties in a weedy situation may provide valuable information to growers seeking to choose varieties that will provide the greatest weed suppression and or weed tolerance in weedy paddocks. It is not possible to screen for competitive ability in a weed-free environment and there is clearly scope for the development of high-yielding weed-competitive barley varieties in Australia. In the face of increasing herbicide resistance in key weed species, the value of non-herbicide weed control tactics increases considerably. The real value of crop competition (narrow rows, high seeding rate, weed-competitive genotypes) comes to the fore a few weeks after planting and through the main growing season to suppress late emerging weeds. Herbicides will remain the main tool for weed control in preparation for planting and to provide a weed-free environment for the crop to establish and rapidly achieve canopy closure. This research was conducted and funded by the University of Queensland, a WeedSmart scientific partner. Related resources: Read the published paper QAAFI – a WeedSmart research partner WeedSmart Big 6 – Grow a competitive crop
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Maximising the weed control value of my crop rotation

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

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