Case Studies

How to go from total crop failure to overcoming weed resistance A growing problem with herbicide resistant ryegrass, which culminated in the total failure of a lupin crop 10 years ago, forced Murray and Emma Scholz to tackle the problem head on. Today, after implementing a range of measures, the couple has reduced the threat to their profitability and sustainability and have their weeds firmly under control. Mr Scholz said getting on top of herbicide resistance was an ongoing battle and meant taking daily steps to reduce the impact. “You have got to be constantly planning two or three years out what you are going to do and you need to have strategies. It is not as simple as selecting herbicides, where you can just drive to town and buy a solution,” Mr Scholz said. The Scholzs grow wheat, canola, lupins and some barley on 1670ha mostly red soils with 600mm annual rainfall at Culcairn, NSW, along with beef cattle on their non-arable country. As a result of tackling resistant weeds, Mr Scholz has been chosen as a WeedSmart Champion. WeedSmart is an industry-led initiative managed by the Australian Herbicide Resistance Initiative (AHRI) aimed at enhancing on-farm practices and promoting the long term sustainability of herbicide use in Australian agriculture. The results for Mr Scholz speak for themselves. He has completely eradicated herbicide resistant weeds in the paddock that suffered a total crop failure 10 years ago, simply by not allowing seed set for two years in a row. “It means taking a paddock out of production for two years, and that’s very expensive,” he said. “But we did that 10 years ago on that paddock and it is still free of ryegrass.” Across the rest of his farm he has adopted other less drastic measures to keep the problem at bay, including wide scale windrow burning. By fitting a low-cost chute on the back of his harvester he concentrates all of the straw and chaff into narrow rows, about 18 inches wide and 12 inches high, for slow burning. “We are aiming to get those high 400C to 500C temperatures that you get when a windrow burns for about 10 seconds making any seeds in that row unviable. “We are not getting every seed but even if we remove 80 or 90 per cent these are populations of plants that I do not need to hit with herbicide, so it is a very cost-effective method.” Mr Scholz also cuts silage and said he was happy to go into a paddock and cut the ryegrass patches to get either silage or hay from it. “That has been a very good technique when you have only got a small area in a paddock. It stops the harvester picking up those ryegrass seeds and spreading them across the paddock.” In addition, he does “brown manuring”, a process involving planting a crop of lupins without any inputs and then in the spring spraying it out with glyphosate before a double knock with paraquat. “We let that rot down. It’s a great way of taking weeds out in the spring time and it has the added bonus that although there is no income that year, you get a lot of nitrogen which means a fertiliser bonus in the following year.” Crop competition through high sowing rates and strategic fertiliser application, where he places urea beneath the plant at sowing to make sure the crop gets the boost and not the weeds, further add to his armoury of weed management tactics. Mr Scholz also does variable rate pH mapping to ensure the right application of lime is spread across the whole paddock, often finding some areas only need half a tonne of lime while other areas need two or three tonnes. “By putting that three tonne of lime in the soil it lifts the crop’s ability to compete as ryegrass appears to be a lot more tolerant of acid soils than wheat is,” he said. Mr Scholz said herbicides were a wonderful resource that had been undervalued through an assumption that there would “always be a new one around the corner”. “We have to farm as if there will never be another new herbicide.” While each strategy had its own cost, either in additional time, labour or spending, it was vital to constantly keep chipping away at the problem, he said. “Where we fell down the first time was that we knew there was a problem, we knew it was building and we just kept hoping it would go away.” He said the WeedSmart initiative was a wonderful idea because it helped keep farmers motivated and focussed in their fight against weeds. “This is not a one or two year battle, it is a 20 or 30 year ongoing guerrilla war,” he said.

Integrated weed management delivers against herbicide resistance By using a combination of windrow burning, crop and herbicide rotation, increased crop competition and farm hygiene, Dubbo farmer Maurie Street has halted the previously rapid spread of resistant weeds and significantly reduced their impact on his bottom line. Mr Street, a former commercial agronomist in Central West NSW and now a researcher with the Grains Research and Development Corporation (GRDC) funded grower solution group Grain Orana Alliance (GOA), has spent much of his time talking to farmers about herbicide resistance, prompting a decision several years ago to practice what he preaches. “I have spent my entire professional career talking to growers about techniques to manage herbicide resistance but as a small scale cropper I am now trying to put some of that into practice,” Mr Street said. “I use as many tools as I can to proactively combat herbicide resistant ryegrass on my property. “To win a war you must win many smaller battles and that is why an integrated approach is our best chance. No one technique is perfect so the key to success is to use as many of them as you can.” Mr Street only crops 160ha of canola, wheat, barley and lupins on a mixture of sandy loams through to light clay, with an average rainfall of 550mm, but he believes the principles can be applied to farming systems of all sizes. After trialling a variety of techniques he has found that positive results from integrated weed management appeared almost as quickly as the emergence of the resistance problem. “This farm has only been cropped for the last six years with at least 14 years of pasture before my wife Kate and I bought it in 2006, which demonstrates just how quickly resistance can develop,” Mr Street said. “But after a few years of really concentrating on the problem I have gone from having patches of crop suffering about 20-30 per cent yield penalty due to uncontrolled weeds, to almost no impact at all.” Mr Street is now a WeedSmart Champion, an industry-led initiative managed by the Australian Herbicide Resistance Initiative (AHRI) aimed at enhancing on-farm practices and promoting the long term sustainability of herbicide use in Australian agriculture. Mr Street said his main problem weed was annual ryegrass. “But I am also concerned about the development of resistant black oats (wild oats),” he said. “Resistance in summer fallow weeds is the biggest threat, with very few practical alternatives for control. “I am getting ryegrass tested for resistance this year to confirm my suspicions that the weeds are resistant to at least the FOPs and Group B herbicides, and I strongly suspect they are developing resistance to DIMs, so I may have very few herbicide options left available to me. “Even if I only have weak resistance of about 20 per cent, and I continue to rely only on herbicides for control it could go to 100 per cent within a few years. I really needed to do something different.” After hearing of windrow burning at a GRDC integrated weeds management course several years ago, Mr Street trialled the method in one paddock and said the initial success led him to this year expand it across his entire property. “It has certainly stopped the populations increasing and reduced the population spreading,” he said. “Windrow burning may have slowed my harvest down by about 10pc but only in some crops as much of the time we often harvest quite low anyway. “It may also have some impact on fallow efficiency and nutrient dynamics but these are costs I am willing to bear.” Mr Street said the improvements provided by windrow burning had been complemented by other techniques including increasing crop competition. “Research has shown that crop competition can reduce seed set of weeds by up to 80pc, so this year I increased seeding rates from the traditional 45kg/ha to 75kg/ha.” It was easy to see how successful it was just by walking around his property and finding areas of thin crop or missed areas. “In those spots I will find ryegrass with 20 or more tillers, but 20cm either way in thicker crop, the ryegrass plants may have only three tillers, so much less seed is produced and returned to the seedbank.” Mr Street also believes crop rotations are an important tool. “Changing crop types allows for easier herbicide rotations but also allows for staggered sowing dates to better accommodate pre-sowing knock downs,” he said. “To get optimum yields for canola, lupins and long-season cereals the crops are dry sown or sown early, with either no knockdowns applied or knockdowns applied before weeds are fully emerged. “Shorter season wheat and barley crops allow for effective knockdown of weeds and take the pressure off in-crop herbicides.” He is also interested in other alternatives such as hay or silage crops where weeds can be cut off before they seed, or summer crops where weeds could be targeted with different herbicides. “Farm hygiene is important as well – I have enough problems with my own weeds let alone spreading them with seed or machinery,” Mr Street said. “Grading my own seed to a high standard is the first step because if there are weed seeds in my planting seed there is a very good chance they are resistant, so I am also careful where and who I buy from.” Mr Street also sprays his firebreaks and fence lines using “double knocks” and residual herbicides, and has minimised the width of his fence line breaks to minimise the potential for fence line resistance. “I also try to follow the mantra, ‘if I can’t sow it don’t spray it’ particularly for areas such as contour banks and other non-cropped areas.” Other options he has considered are slashing or cultivating the breaks or planting competitive pasture or plants to try and out-compete the weeds. “All these techniques  do come at a cost,  but we have always paid to control weeds so now instead of going to town to buy drums of chemical, we pay for it in a different way,” he said.

Always think about your impact on weeds Damien Sommerville from Spalding, South Australia, makes sure to consider the impact on weeds in every decision he makes Damien has a long association with the land. He has been involved with Sommerville Partners for nearly two decades and has seen a lot of different things in his time. His recommendation to growers is: Think about the impact on weeds with each and every decision you make, all year round. Damien is determined to help people in his area and further afield to understand the issue of herbicide resistance. “The issue affects growers everywhere. It’s obviously more high profile in the west but southern growers need to be aware and managing the issue whenever they can,” Sommerville said. “Growers have to use as many options as they can to prevent weeds setting seed. They can’t afford to lose one year in the battle as things spiral out of control quickly.” “There really is no one answer. What can work, if your conditions are right, is the use of lupins and or hay in your crop rotations. Using varied rotations each year is a great step towards managing weeds and resistance.”

Windrow burning beats wild radish Two key messages have emerged from long-term windrow burning trials in Western Australia’s northern wheatbelt – focus on trash from non-cereal crops and burn in the daytime where possible. Rod Messina, whose family farming business “Spring Park Farms” has hosted windrow trials for more than a decade, says the practice has underpinned their property expansion. “We find that when we buy a new property it always has a lot of weeds but after two or three years of integrated weed management (IWM) practices including burning windrows, it’s amazing how quickly weed numbers come down,” Rod said. “Weeds dictate what we do here, they’re our number one issue. So if a paddock’s dirty, rotation becomes vital and ultimately allows us to continuously crop. “It is quite expensive to leave paddocks out of production so with the rotation and windrow burning it allows our operation to be more profitable in the long run.” Rod farms 12,500 hectares with his father Charlie and brother Andrew on the Eradu sandplain east of Geraldton. They employ a wheat/lupin/wheat/canola rotation and strategically use herbicides to control radish in the cereal phase while windrowing canola and lupin crops to collect and destroy hard-to-kill wild radish seed. “Wild radish is one our most problematic weeds. We do have ryegrass but radish is our biggest concern because the seed is viable for so long,” Rod said. “In our lupin and canola phases we try to make sure we control all the seed set either through windrow burning or crop-topping. “We try to get a germination of wild radish before we sow but in this environment that is not always possible. “There is no doubt through our long-term IWM strategy, including windrow burning, autumn tickles, crop-topping, a double knock and now the mouldboard plough, that our weed numbers are decreasing.” The Messinas aim to stop seed set at every stage of the crop production and weed life cycle. “We deep rip to stimulate a germination of weeds that we can treat with a knockdown herbicide or double knock, then we’ll use one, maybe two post-emergent sprays followed by crop-topping lupins and windrow burning.” The Messinas have trialled a mouldboard plough and spading but chose to go with the mouldboard plough for its weed and non-wetting soil management benefits. Rod says the practice of windrowing as demonstrated by the GRDC-supported work by Department of Agriculture and Food WA (DAFWA) weed researcher Peter Newman has been proven over more than a decade. “The numbers are declining quite rapidly and one of the greatest benefits of windrowing is that it doesn’t slow harvest at all,” he said. “The hotter the fire the better it is and through the GRDC focus paddocks we’ve learnt that you do need a much hotter fire to control wild radish than for ryegrass. “We have to try and get the fire as hot as possible. It’s easy in lupins and canola because there is less chance of the fire spreading than in wheat so you can light the windrows up during the day and make sure you get a really hot burn. GRDC/DAFWA plots across the district are achieving 99% control of weeds using windrow burning. “In an ideal world you wouldn’t windrow your wheat because there is a chance you’ll lose the paddock but in a lighter year like this year we’ve windrowed all the paddocks in order to use that tool.” Rod says a cereal crop of more than two and a half tonne per hectare is too dense for windrowing due to the risk of burning the whole paddock and losing valuable soil cover. “If you’ve got a really dense windrow the fire will run across the top and won’t penetrate the windrow and research shows some of the seed falls to the bottom within about 24 hours.” He advocates burning late in the day rather than at night as the intensity of the fire drops as the temperature falls. “Five to seven years ago we windrowed every acre but now that we’ve got our numbers down we can just do the lupins and canola phases,” he said. “There is more opportunity to control wild radish during the wheat phase using herbicides and other tools and can manage the ryegrass during the non-cereal phases.”

Warding off herbicide resistance to rescue no-till The unpalatable thought of losing his no-till farming system drives grain grower Geoff O’Neill, “Llano”, Bellata, NSW in his fight against the formidable threat of herbicide resistance. Geoff says moisture retention via no-till farming is the key to crop success in an environment where rainfall is the major limiting production factor. He says weed control is vital for maximising crop yield. “We have a 610 millimetre annual rainfall and work on moisture retention the whole time so resistant weeds are going to be a big problem for us if means a return to cultivation for weed management.” Geoff joined the no-till revolution in 1994 with the purchase of a no-till planter that allowed him to sow into higher levels crop residue on the heavy black clay and sodic grey soils of “Llano”. “We had a few tough years learning the new system but since then it’s done a great job on these soils,” he said. “Our production has become more stable under the no-till system. “We work on a four-crops-in-five-years rotation which includes long fallow durum/chickpeas/short fallow wheat /long fallow to summer crop, either sorghum or cotton.” Geoff is keen to use an integrated approach to herbicide sustainability management and follows WeedSmart strategies including: rotating chemicals and chemical groups, ensuring spray rates are accurate, rotating crops, diligently controlling weeds (including those in summer fallows) to stop seed set, considering alternatives to glyphosate, researching weed biology, and testing for resistant weeds. “If herbicide resistance puts our no-till system under threat it would mean a big shift in thinking for us,” he said “To go back to a conventional tillage system is just not possible. We could not do what we’re doing.” He says rotation underpins his strategy. “Rotation is the key word – we rotate crops, we rotate chemicals, we rotate chemical modes of action and we do use strategic tillage when we have to or we can. “That’s not very often in a no-till system but we use strategic tillage at the end of the cotton cycle which ties in with pupae busting to manage helicoverpa and that’s given us another non-chemical option.” Geoff welcomes Grains Research and Development Corporation (GRDC) funding into strategic tillage practices currently underway across the northern region by Queensland Department of Science, Information Technology, Innovation and the Arts (DSITIA) researcher, Dr Yash Dang. “There’s more we can learn about strategic tillage including when and how and do we need to till the whole paddock?” he says. Rotation is the key word – we rotate crops, we rotate chemical modes of action. Knowing the herbicide resistance status of his paddocks and farm is important to Geoff and he has tested twice for barnyard grass which is the major weed of concern on “Llano”. He says while the tests were negative the weed is notoriously difficult to control and he monitors the threat of developing resistance. “We have trouble killing barnyard grass with glyphosate so timing and stress are obviously factors and we are working on that.” He says the move to a Case self-propelled spray rig two years ago has provided a “tremendous efficiency boost” in weed control and allowed him to cover more hectares per hour. The result has been better execution of the double knock technique for difficult-to-control weeds including fleabane. “We had a trailing spray rig before and we found we couldn’t keep up with the double knock,” Geoff said. “Using the self-propelled spray rig we can cover the ground more quickly if the conditions are right. “We also use a disc planter now which allows us to conserve stubble in that we’re not burying stubble when we sow. “In dry planting times we do miss the tyne planter but we haven’t had too many big issues.”

Glyphosate resistance can be beaten – but it’s better to avoid it in the first place. In late 2008, Chris Reichstein, bought a new property near Esperance knowing that glyphosate resistant ryegrass was widely established. He was confident in his ability to bring the problem under control and set about using every tactic possible to reduce weed seed numbers on the farm. Starting with herbicide resistance testing to find out what still worked, Chris established a rotation plan to make the most of crop and herbicide combinations, including swathing and croptopping, narrow windrow burning, chaff carts, autumn tickle and a triple knock strategy of two chemical applications followed with a competitive crop. Containing the problem is now a permanent part of his farming system. More information: Glyphosate resistant weeds – beat them before they beat you It’s time for a glyphosate intervention AHRI Insight – Don’t waste glyphosate