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Driving down problem weed seed banks!

A 1-day workshop for grain advisers and leading growers that will change how you manage weeds for the better.
Share knowledge, discuss experience and develop strategy for problem paddocks and weeds with industry experts and your peers.
These workshops are at the cutting edge of what’s new in weed management. What’s working; what’s not and why. The focus is on driving down the weed seedbank to improve crop options and profits.
All agendas and focus weeds are modified to meet regional needs. Topics include:

Update of new regional weed issues / problems
Strategies for management of problem weeds – glyphosate resistant grasses and broadleaved weeds, multiple resistant wild oats, phenoxy and other MOA resistant radish
Harvest weed seed management – WA and local experience – process and practical tips to make it work effectively
Understanding where and how key pre-emergent herbicides fit
Using multiple weed management tactics in a farming system – whats the economic and weed impact? How to tell if it’s all worth the effort?
The economics of fallow weed management (Wagga and Forbes only)

Discussion leaders at all workshops:
Peter Newman (AHRI), John Cameron (ICAN), Tony Cook (NSW DPI), WA Grower (TBA)
Additional presenters:
Moree: Michael Widderick (DAFF Qld), Tom Murphy (Grower North Star)
Gulargambone & Dubbo: Maurie Street (GOA), Greg Brooke (TBC) (NSWDPI)
Forbes: Murray Scholtz (Grower Culcairn)
Wagga Wagga: Murray Scholtz (Grower Culcairn), Hanwen Wu (NSW DPI), John Broster (CSU)
Dates, locations and times:
Start time is 8:15 registration for an 8:30 start. Finish by ~ 3:30.
Follow the links below for the relevant flyer and registration form:
Mon 10th March, 2014 Moree NSW (RSL)
Tue 11th March, 2014 Gulargambone NSW (2828 Hall)
Wed 12th March, 2014 Dubbo (Bowling Club Newell Hwy)
Thu 13th March, 2014 Forbes (Forbes Services Memorial Club)
Fri 14th March, 2014 Wagga Wagga (Wine & Food Training Ctr – CSU Campus)

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Sowthistle showing signs of resistance

Sowthistle is the newest problem weed to show signs of glyphosate resistance in the north.
Trials currently underway to determine if the resistance exists and if so, at what level, have returned worrying results, according to NSW Department of Primary Industries technical specialist weeds officer Tony Cook.
“Individual plants within the suspect populations survived the glyphosate much better than they should have and within two or three weeks some plants were starting to regenerate again,” Mr Cook said.
The trials investigated five different populations, all treated with two robust rates of glyphosate and applied to two different sowthistle growth stages.
“More work is being done to determine whether it is in fact resistance, and if so what level, but it is a timely reminder to maintain diversity when undertaking weed control and to closely monitor weeds after sprays to detect and control survivors,” Mr Cook said.
Department of Agriculture, Fisheries and Forestry Queensland (DAFFQ) research scientist Michael Widderick recently conducted trials into the best ways of tackling the weed and found the double knock treatment to be the most effective.
“The double knock achieved 100 per cent control of sowthistle regardless of the weed’s size at the time of spraying, while many stand-alone treatments had a limited impact,” Dr Widderick said.
The trials, conducted on the eastern Darling Downs near Cecil Plains in April this year, consisted of 27 different applications of either herbicides applied alone, in glyphosate mixture or as part of a double knock applied seven days after the first treatment.
Dr Widderick said stand-alone treatments had limited impact, with the exception of glyphosate alone on small weeds which was effective, however could give rise to a whole new raft of problems.
“An over-reliance on stand-alone glyphosate treatment may result in widespread cases of glyphosate-resistance in this weed, especially in light of the current testing taking place,” Dr Widderick said.
The Grains Research and Development Corporation (GRDC) is supporting the adoption of integrated weed management strategies to combat herbicide resistance and is encouraging farmers to test suspect weed populations.
Dr Widderick said sowthistle had always been considered relatively easy to control, yet it was still widespread because survivors could set large numbers of viable seed.
“Our weed control efforts are just not effective enough. If weeds, even at low density, are allowed to set seed, the efforts and expense in controlling the majority of the population are undone,” Dr Widderick said.

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Watch out for residuals

Summer weed control is essential and widely used, but the use of residual herbicides can compromise your options for broadleaf crops in winter.
Residual herbicides, while good at knocking down troublesome summer weeds, can damage broadleaf crops such as faba beans, lentils, chickpeas and other pulses or canola, in the winter.
If you are planning a pulse or canola crop in winter, or are at least leaving the option open, make sure you only apply non-residual summer weed herbicides in those paddocks.
Group B herbicides, such as metsulfuron-methyl (Ally), and Group I herbicides, such as Dicamba and Lontrel, have extensive plant back restrictions.
These herbicides need between six and 12 months to breakdown, along with suitable amounts of rainfall.
Crop failure is likely if susceptible crops are sown before the plant back period is complete.
These herbicides will effect the germination and vigour of all grain legume crops including field peas, faba beans, chickpea and lentils, along with canola.
While extensive summer rain can hasten the breakdown of these herbicides, the risk for susceptible crops remains very high.
Non-residual herbicides such as glyphosate, 2,4-D LV ester or 2,4-D Ester 800 and Garlon, are all preferred herbicides for the summer weed spraying program.
All can be used very close to the break of the season.

Plan your summer spraying program carefully to ensure that herbicide residues do not affect your broadleaf crop options.
Also, keep in mind your spraying program from winter 2013.
Some herbicides used for in-crop weed control in cereals have residual properties that present a significant risk to susceptible crops 12 months later.
Each pulse crop differs in its sensitivity to residual herbicides.
Check each herbicide label and assess the rainfall received since the herbicide was applied.
There is a significant risk to grain legumes and canola in paddocks if you applied some of the following herbicides to cereals.
Lentils and chickpeas are most susceptible to group B residues (e.g. Glean, Logran), with field peas and faba beans the least sensitive.
However, the risk for field pea and faba bean is still high.
Faba bean is more sensitive to Monza residues at low soil pH (< 6.5) than chickpea, lentil, lupin and field pea.
All pulse crops are sensitive at higher soil pH (> 6.5).
Chickpea, faba bean and field pea are least sensitive to the group B imidazolinones (e.g. Spinnaker, Raptor, Midas), with lentil extremely sensitive. Lupin and vetch are intermediate.
Raptor has no minimum re-cropping interval if field pea is being sown.
All pulses are vulnerable to Group I pyridine residues (e.g. Lontrel), but faba bean appears to be more susceptible than lupin.
This article was published online at Farm Weekly. More information is available from Pulse Australia.

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Advice from weed resistance expert: try diversity

Renowned weed scientist Steve Powles, having had to find solutions and work-arounds in resistant weed-infested crops in his native Australia, has tried to prepare American producers for their own burgeoning resistance problems.
In 2005, just as glyphosate-resistant pigweeds began to tighten their grip on fields in the American South, Powles cautioned U.S. producers against continuing practices that would only spread resistance.
“There is something Australia is No. 1 in the world at: herbicide resistance. We know about this problem and have the dubious distinction of being tops. However, the United States is about to take the top spot away from us. My prediction is you will be crowned king of herbicide resistance within the next few years.” (Read more here)
In summer 2013, Powles again visited the United States and his message took on a more urgent tone. Agronomic diversity is a must, he told Farm Press, if American producers are to head off massive cropland problems.
Here are comments from the Q&A:
It’s been several years since you were in the States. What have you been doing on this trip?
“I’m participating in seminars and the like. I began with a tour through the Texas High Plains, checked out the Arkansas pigweed situation and then headed to Illinois. That was a great opportunity to speak with many farmers, agronomists, crop consultants and university people.
I’ve spent a few days at the University of Illinois Champaign-Urbana and a day at a weed resistance symposium in Indianapolis.
“Looking at the situation in the field, talking with farmers — which is always great, because I have my own farm in Australia —and all the rest has made for a fantastic trip.”
A few weeks back, University of Illinois Weed Scientist Aaron Hager was saying Illinois’ biggest problem is still waterhemp but pigweeds are becoming a larger issue (read here). Have you noticed that shift?
“Yes. Two years ago, pigweed had become a real problem in the South. That has only spread farther afield.
“When I was visiting the Texas High Plains, they told me resistant pigweed wasn’t a problem in 2012. This year, though, it’s in as much as 50 percent of the fields.
“That’s just the exponential part of the curve, which states like Arkansas, Mississippi and Georgia have been through. Whereas, in the Midwest, the Corn Belt, the producers have had a different set of issues.
“I don’t want to overstate the situation, but on a bus ride from Chicago to Indianapolis — with many stops — you can really see a sprinkling of marestail and waterhemp through some 50 percent of the soybean crops. I’m prepared to claim that those weeds are glyphosate-resistant. Those aren’t just misses. I don’t remember seeing that several years ago.”
What about new soybean technologies?
“I’ve seen some of that. The 2, 4-D-tolerant soybeans are most impressive, actually.
“I hope none of the new technologies are clear ‘winners.’ I say that because if I was a U.S. farmer and could use Monsanto’s glyphosate and dicamba-tolerant soybeans, I’d use them. And then, I’d leave them alone for a few years. Same with Dow’s glyphosate/2,4-D-tolerant technology. Same with Bayer’s LibertyLink crops.
“Get the picture?
“These things offer diversity to the farmer. And they must be protected. Which producer wants to be in Delta Farm Press for being the first one with glufosinate/LibertyLink-resistant weeds or dicamba-resistant weeds or HPPD-resistant weeds?
Well, if they want that, if they want a photo in your publication, they can just keep planting the same thing over and over. The resistance will happen.
“Anyone who wants these technologies to keep going, if they want to keep a good thing, then they must change things up regularly.”
On resistance in Australia…
“We’ve learned the hard way that you cannot simply rely on the next jug. It’s simply unsustainable — you waste the chemicals’ efficacy.
“I love herbicides. I reckon they’re the best way to control weeds in cropping. But they aren’t much good if they don’t work.
“And the only way to keep them working is diversity. That means employing non-chemical techniques as well as smart rotation of chemicals and crops.
“We’ve learned that we must do ‘harvest weed seed control.’ That involves non-chemical, mechanical techniques at harvest.
“When I suggest that in the United States, everyone looks at me and thinks, ‘I’m not doing that.’ I can see it in their eyes, I can see them working it over in the minds: ‘We won’t do that.’
“But you know what? They’re already doing that when they march the hand-hoeing teams across the cotton fields. What they’re doing is practicing very, very expensive harvest weed seed control!”
On the objective of his trip…
“I’m here to help convince everyone involved in agriculture that they should think about harvest weed seed control. But it’s tough because people simply aren’t psychologically ready for that. All the creativity is still aimed at reaching for the next product.
“I hope everyone doesn’t have to learn hard lessons before considering these other techniques.
“But let’s not get depressed about this. It doesn’t have to be this way. We can manage the problems if we’d just be more diverse and pay more attention to agronomy and rotation.
“We wouldn’t be farming in Australia if what I’m saying wasn’t true.
“Fortune favors the prepared mind. You must actually do something more creative than reaching for the next jug.”
Is that a uniquely American mindset?
“No. It’s simply due to the fact that, until recently, there have always been new herbicide solutions.
“You know, ‘There’s a problem? Well, let’s just move on to the next product.’
“That’s been the experience of nearly everyone in our industry. Well, those days are coming to an end and change will come because it will be forced. Multiple herbicide resistance in waterhemp, pigweeds, marestail and johnsongrass is no joke. Control is not easy.
“However, control can be achieved with real attention and effort. I’m afraid without that focus, farmers will go bankrupt.”
On the ‘zero tolerance’ efforts (more here) in the Mid-South…
“I’ve been following that. That’s exactly the sort of thing that’s needed.
“I met with an excellent farmer, David Wildy, of Manila, Ark. On his land, he has very low pigweed numbers. That’s due to zero tolerance, doing what he must. He’s demonstrating success.
“And I’m willing to bet that if you talk to him, he’ll say zero tolerance is a pain in the neck. But he’s done it and made a success of it.
“I was speaking to another Arkansas farmer and said, ‘You can get on top of those Palmer pigweeds.’ He said, ‘Steve, at the moment, pigweed is like my mistress. I think of her when I wake in the morning, throughout the day, and then just before I go to sleep.’
“I thought that was pretty good. But that’s the focus you need to control a formidable opponent.”
On the importance of dealing with the soil’s seed bank…
“Say you’ve got a big cotton field, a Roundup Ready variety, and you’ve got a grown-up mess of glyphosate-resistant weeds. In that situation, simply switching to an alternative technology is a bad idea.
“What you must do is get your seed bank of those resistant weeds low. It seems that many people don’t understand the concept of a seed bank. Get the numbers low enough and your precious herbicides are much more sustainable.
“If farmers would understand that and practice it, they’d be much better off.”
This article was published online at Delta Farm Press.

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Desiccation timing critical to sorghum crop success

Maximising the profitability of this season’s sorghum crops could be as simple as a well-timed desiccation.
That’s the opinion of Landmark senior agronomist Paul McIntosh who said the timing of spray-out was critical to preserving yield and grain quality and avoiding lodging issues.

“There are some basic rules I adhere to when it comes to desiccation timing of all sorghum varieties,” Mr McIntosh said.
“Don’t judge physiological maturity by the colour of grain; get out into the crop and look at black point percentage numbers on the sorghum seed; and look on the bottom of the sorghum head on the southern side to determine if physiological maturity has reached this last area of grain turning.
“If grain moisture is less than 25 percent with over 90-odd percent physiological maturity then spray-out results are going to be far more positive and much quicker.”
Grains Research and Development Corporation (GRDC) supported research suggests that black layer (abscission layer) formation in the field is the best tool to safely schedule spray-out timing as it can help growers determine their risk approach and modify it as needed on a paddock and variety basis.
When spraying, Mr McIntosh said growers needed to ensure that application was carried out in the prime time of day, usually early morning when stomates are open; ensure water quality was good, water volume adequate and adhere to seven days withholding period.
“It is also important to remember that healthy green leaves will always accept glyphosate into the plants’ system more effectively and that spraying post first frost is a usually a no-no for continuing the spray out programme.”

The current dry conditions will impact on the speed of the dry-down process according to Pacific Seeds summer grains agronomist Trevor Philp and growers should have their harvest preparations finalised before undertaking desiccation.
“Due to the dry hot growing environment, stalk rot pathogens such as charcoal rot and fusarium stalk rot may well be present and desiccation could aid in their rapid development. This type of situation will further reduce the timeframe from spray-out to harvest and may pre-depose the crop to lodging,” he said.
“In badly drought-affected crops growers may find some of the plants have already dried off. These plants won’t die from a glyphosate application prior to harvest and some regrowth will occur after the next rain.
“In severely drought-affected crops, it may pay to do an initial harvest, wait for rain and then desiccate the field. This will reduce the risk of lodging and improve the effectiveness of the spray out.”
When accessing the crop for physiological maturity, Mr Philp said the crop should also be checked for lodging potential with tell-tale signs being early matured heads and plants that are fully senesced.
“When the leaves are stripped back on these plants the stem will be discoloured and soft when squashed at the base. When the stem is split, the base of the stem will discoloured,” he said.
“If a crop is showing early symptoms of these stalk rots, earlier harvest should be considered especially at the current price.”

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Brome grass resistance rising

Brome grass is proving to be a headache for grain growers across southern Australia with more plants showing resistance to Group B herbicides.
University of Adelaide reports an increasing number of brome grass plants are showing herbicide resistance across the southern and western grain growing districts of Victoria, South Australia and Western Australia.
Researchers have been collecting brome grass seed samples from fields where farmers were suspicious that herbicide resistance may be the cause of poor herbicide performance.

 
 
 
 
 
 
 
 
Samples collected from across the South Australian Mallee region were tested for resistance to current registered herbicides and the tests revealed a high level of herbicide resistance in these weed populations.
University of Adelaide (UA) Associate Professor—Weed Management, Dr Chris Preston, said herbicide resistance was identified in around 50 per cent of the samples tested.
“Group B sulfonylureas such as Atlantis and Monza are the only cereal-selective herbicides available to growers to control brome in non-Clearfield wheat,” he said.
“We are finding brome grass with low level resistance through to 100pc resistance to Group B products.”
“Some populations are showing resistance to Group A products, especially when there is high pressure in pasture and legume rotations with cereals.”
Brome grass is also turning up in new areas with the wide-spread adoption of no-till farming favouring brome grass, according to Dr Preston.
“Brome grass in continuous cropping paddocks is showing a higher level dormancy compared to plants growing along fencelines,” he says.
“These populations require darkness and/or cold stratification to germinate, meaning they emerge after the crop when fewer herbicide options are available.”
Dr Preston said the pre-emergent herbicides farmers were using were not effectively driving down the weed seed bank and brome grass was gaining the upper hand in some areas.
“Trifluralin is at best variable and at worst is ineffective, especially in the higher rainfall production areas,” he says.
“In drier areas the use of this pre-emergent option can work well if all the brome grass seeds germinate quickly.”
UA reports of the newer pre-emergent herbicides, Boxer Gold offered little control as the later germinating brome escapes.
Sakura has achieved up to 85pc control in optimal conditions but as low as 30pc control in dry conditions and on non-wetting soils, according to UA.
“All these pre-emergent options are only effective against brome grass plants that germinate early,” Dr Preston said.
“And that is the real threat of the shift in the brome grass populations towards longer dormancy that allows more individuals to ‘escape’ control by germinating later in the season.”
He said one option is to use a mixture of Sakura plus Avadex against brome grass, with the mixture having consistently achieved more than 80pc control, but at around $70/ha was expensive and probably not an option in the production areas most affected.
“It seems that growers need to develop new systems that give them more opportunities to get on top of weeds like brome grass that have developed resistance to the available chemistry,” Dr Preston said.
He said better control may be possible in other phases of a farming system.
“A green manure vetch crop is one option that growers might consider to clean fields before planting cereals,” he says.
“The vetch could be grazed or cut for hay then the field sprayed with glyphosate or a paraquat-based product.”
He said another option was to include a pasture phase and to graze the brome grass early while it is still palatable to sheep.
The pasture can then be spraytopped with paraquat to prevent seed set. Hay freezing using glyphosate is another way to conserve the nutrient value of the pasture for up to two months while reducing seed set and is less expensive than hay baling. Sheep will avoid eating brome grass seed so it is important to treat the pasture early, before seed set.
In the cereal crop, stubble burning is an effective way to remove seed from the weed seed bank.
“If seed set can be prevented for two consecutive seasons the effect on the seed bank is likely to be significant,” Dr Preston said.
“At the moment there is very little research into the non-chemical options for managing herbicide resistant brome grass so the suggested options have not been thoroughly investigated.
“Our experience with ryegrass has shown that controlling seed set is the key to regaining control over these resistant annual weeds.
“Brome grass has more dormancy than rye grass, but like ryegrass it is not very persistent. With rye grass we have seen two years of seed set control lead to several years of ongoing control because of better in-crop options being available.”
In the higher rainfall zones Dr Preston says break crops such as canola and pulses also provide an opportunity for the use of another mode of action against brome grass. “A strategy that works well against rye grass in break crops is the use of a pre-emergence herbicide then a post-emergence herbicide and finally croptopping for harvest weed seed management,” he said.
“There is a risk of resistance developing to Group A herbicides used in break crops so it is important to use an effective strategy to prevent seed set.”
As well as the South Australian Mallee, brome grass is a significant weed in the Victorian Mallee, Upper Eyre and in Western Australia.
To read the original article, click here.

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Brome grass resistance increasing and spreading

An increasing number of brome grass plants are ‘surviving’ treatment with Group B herbicides across the southern and western grain growing districts of Victoria, South Australia and Western Australia.
Researchers have been collecting brome grass seed samples from fields where farmers were suspicious that herbicide resistance may be the cause of poor herbicide performance. Samples collected from across the South Australian Mallee region were tested for resistance to current registered herbicides and the tests revealed a high level of herbicide resistance in these weed populations.
Dr Chris Preston, University of Adelaide (UA) Associate Professor—Weed Management, says resistance to herbicide was identified in around 50 per cent of the samples tested. “Group B sulfonylureas such as Atlantis® and Monza® are the only cereal-selective herbicides available to growers to control brome in non-Clearfield wheat,” he says. “We are finding brome grass with low level resistance through to 100 per cent resistance to Group B products.”
“Some populations are showing resistance to Group A products, especially when there is high pressure in pasture and legume rotations with cereals.”
Brome grass is also turning up in new areas with the wide-spread adoption of no-till farming favouring brome grass. “Brome grass in continuous cropping paddocks is showing a higher level dormancy compared to plants growing along fencelines,” he says. “These populations require darkness and/or cold stratification to germinate, meaning they emerge after the crop when fewer herbicide options are available.”
Dr Preston says the pre-emergent herbicides farmers are currently using are not effectively driving down the weed seed bank and brome grass is gaining the upper hand in some areas. “Trifluralin is at best variable and at worst is ineffective, especially in the higher rainfall production areas,” he says. “In drier areas the use of this pre-emergent option can work well if all the brome grass seeds germinate quickly.”
Of the newer pre-emergent herbicides, Boxer Gold® offers little control as the later germinating brome escapes. Sakura® has achieved up to 85 per cent control in optimal conditions but as low as 30 per cent control in dry conditions and on non-wetting soils.

“All these pre-emergent options are only effective against brome grass plants that germinate early,” says Dr Preston. “And that is the real threat of the shift in the brome grass populations towards longer dormancy that allows more individuals to ‘escape’ control by germinating later in the season.”
One option is to use a mixture of Sakura® plus Avadex against brome grass. This mixture has consistently achieved more than 80 per cent control, but at around $70/ha is very expensive and probably not an option in the production areas most affected.
“It seems that growers need to develop new systems that give them more opportunities to get on top of weeds like brome grass that have developed resistance to the available chemistry,” says Dr Preston. “Better control may be possible in other phases of a farming system, such as in a pasture phase or with legumes. Farming systems must be more robust and have less reliance on herbicides.”
“A green manure vetch crop is one option that growers might consider to clean fields before planting cereals,” he says. “The vetch could be grazed or cut for hay then the field sprayed with glyphosate or a paraquat-based product.”
Another option is to include a pasture phase and to graze the brome grass early while it is still palatable to sheep. The pasture can then be spraytopped with paraquat to prevent seed set. Hay freezing using glyphosate is another way to conserve the nutrient value of the pasture for up to two months while reducing seed set and is less expensive than hay baling. Sheep will avoid eating brome grass seed so it is important to treat the pasture early, before seed set.
In the cereal crop, stubble burning is an effective way to remove seed from the weed seed bank.
“If seed set can be prevented for two consecutive seasons the effect on the seed bank is likely to be significant,” says Dr Preston. “At the moment there is very little research into the non-chemical options for managing herbicide resistant brome grass so the suggested options have not been thoroughly investigated.”
“Our experience with ryegrass has shown that controlling seed set is the key to regaining control over these resistant annual weeds,” he says. “Brome grass has more dormancy than rye grass, but like ryegrass it is not very persistent. With rye grass we have seen two years of seed set control lead to several years of ongoing control because of better in-crop options being available.”
In the higher rainfall zones Dr Preston says break crops such as canola and pulses also provide an opportunity for the use of another mode of action against brome grass. “A strategy that works well against rye grass in break crops is the use of a pre-emergence herbicide then a post-emergence herbicide and finally croptopping for harvest weed seed management,” he says. “There is a risk of resistance developing to Group A herbicides used in break crops so it is important to use an effective strategy to prevent seed set.”
As well as the South Australian Mallee, brome grass is a significant weed in the Victorian Mallee, Upper Eyre and in Western Australia.

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Weeds harvest strategy

Growers are being urged to try to control weed seeds during harvest as a key strategy for prolonging the effectiveness of certain herbicides, which is being threatened by resistant weed populations.
Dr Michael Walsh from the Australian Herbicide Resistance Initiative (AHRI) says harvest weed seed control plays an important supporting role to subsequent early season weed control.
“If there is one message we want to deliver, it is to control weed seeds at harvest – whether that is by using the Harrington Seed Destructor or a chaff cart behind your header, baling harvest residues or narrow windrow burning – the key is to capture and destroy seeds from weeds,” Dr Walsh says.
GRDC-supported research shows seedbanks of annual weeds can be rapidly depleted when harvest weed seed control systems are used to capture and destroy weed seeds.
“Our weed control efforts are aimed at driving these seedbanks towards zero,” Dr Walsh says. “The key is: control the seedbank to control the weed.”
Dr Walsh says annual weeds such as ryegrass, wild radish, brome grass and wild oats have adapted to cropping systems, growing to similar heights as cereals and maturing at the same time as annual crops.
“For this reason, some growers may be sceptical about how much seed is captured at harvest, but AHRI research shows a high percentage of total weed seed production is retained on plants at a height that ensures collection during harvesting.”
He says recent research shows that at the start of harvest high proportions of weed seeds are retained at least 15 centimetres above the soil surface for annual ryegrass (88 per cent), wild radish (99 per cent), brome grass (73 per cent), and wild oats (85 per cent). By harvesting at this height these weed seeds are captured by the header and can be dealt with from there.
Dr Walsh urges growers and agronomists to move from the existing global industry paradigm of controlling weed seedlings to also consider harvest weed seed control.
The effectiveness of on-farm methods of weed seed collection at harvest booklet is available here.

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Surprise CTF findings

New survey-based research indicates that adoption of controlled traffic farming (CTF) in Australian grain operations is limited by low understanding of its basic principles and how they work as part of an integrated system.
This was the finding of a CTF survey in 2011 and 2012, which was the first of its kind in Australia. The findings were released in September. Of the 222 grain growers surveyed in Victoria, New South Wales and Queensland, just 33 were matching the widths of their machinery to three-metre permanent wheel tracks for all their operations with harvesters, tractors, sprayers and spreaders.
CTF Solutions chief executive officer Dr Don Yule says permanent wheel tracks are a cornerstone of CTF, so use of this practice by only 15 per cent of growers shows that CTF adoption is lower than previously thought.
National, more general CTF surveys by the GRDC in 2011 and the Australia Bureau of Statistics in 2010 revealed respectively that 19 per cent and 15 per cent of growers had implemented CTF on their properties.
“But permanent wheel tracks are basic to all CTF systems, so their limited use highlights an actual low overall adoption of CTF,” Dr Yule says.
“About 34 per cent of growers reported that they used permanent wheel tracks, but many of these were not matching the widths of all their machinery because they used 2m wheel tracks, in addition to 3m wheel tracks.
“One set of 3m wheel tracks is a fundamental requirement in CTF operations because farm machinery and implements need to be matched to the harvester, which runs on 3m wheel spacings.”
Of the growers who were using permanent wheel tracks, the study indicated that for tractors, 49 per cent were using 2m wheel tracks and 40 per cent used 3m wheel tracks. Meanwhile, for sprayers, 44 per cent of growers surveyed used 2m wheel tracks and 49 per cent used 3m wheel tracks.
Dr Yule says this low rate of permanent wheel track use has implications for the adoption of other CTF principles.
Apart from restricting the load bearing of farm machinery, permanent wheel tracks also provide the framework for coordinating other CTF practices, such as paddock layout, zero-till and inter-row sowing.

For example, good layout designed around one set of 3m wheel tracks can restrict soil compaction to less than 15 per cent of the total paddock area and improve machinery efficiency, potentially reducing fuel use by up to 50 per cent.
In addition to looking at adoption levels, the research also identified key barriers to the uptake of CTF principles.
Dr Yule says a lack of understanding of CTF as a holistic system combining five core principles was the main overall barrier to on-farm adoption.
These CTF principles, which function cooperatively, include:

one set of 3m permanent wheel tracks to separate machinery traffic from crop areas;
whole-farm and paddock layout incorporating permanent wheel tracks to maximise operational and machinery efficiency, plus help manage soil erosion and waterlogging;
use of real-time kinematic (RTK) global navigation satellite systems (GNSS) with two-centimetre accuracy to guide machinery on permanent wheel tracks;
precision farming practices, such as inter-row planting and shielded spraying; and
optimised stubble cover as part of zero-till operations.

“It’s not only farmers who have limited understanding of CTF practices and how they work together; it’s the agronomists and machinery and GPS sellers too,” Dr Yule says. “We’ve got a long way to go, which is a challenge.”
Other major challenges to CTF adoption highlighted by the research were limited access to information and low recognition of the potential for increased farm business profitability.
It also revealed that 22 per cent of growers were not using permanent wheel tracks due to the shape of their paddocks, trees or rocks; and 16 per cent said the cost of implementing CTF was a barrier to adoption.
The surveys were conducted as part of a Spatial Information Applications in Rural Australia (SIARA) project led by the CRC for Spatial Information (CRCSI) in partnership with CTF Solutions, the Victorian Department of Environment and Primary Industries, NSW Land and Property Information and the Fitzroy Basin Association.
Dr Yule says the barriers identified are expected to guide future stages of the SIARA project, which aims to lift the national rate of CTF adoption to 40 per cent by 2020.
“This would see about 17,000 farmers using permanent wheel tracks and RTK GNSS to grow crops across 20 million hectares,” Dr Yule says.
This article was printed in the November/December edition of GRDC Ground Cover. You can access the GRDC Controlled Traffic Farming Fact Sheet here.

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Grazing strategies for reducing the weed seedbank

A pasture phase in a crop rotation provides many benefits, including the opportunity to reduce annual grass weed populations and manage herbicide resistance.
Tim Condon, Senior Farm Advisor with Delta Agribusiness says that although livestock have long been an integral part of mixed farming operations there are some well-known strategies for managing annual weeds that need to be brought back into focus and implemented specifically for herbicide resistant weeds.
“The key is to have a weed management strategy that spans the whole pasture phase, not just the year before returning to cropping,” he says.
“For example, during the recent drought years in NSW, weed management in the pasture phase took a back seat on many properties. These farmers now have an opportunity to use their livestock to significantly reduce the seed bank of grass weeds like annual ryegrass, brome grass and barley grass, as well as vulpia and wild oats.”
“In this system, achieving very high levels of weed control is possible using a coordinated strategy involving heavy grazing, herbicides and possibly fodder conservation or slashing.”
During the pasture phase Mr Condon suggests spray topping to reduce weed seed set. When the grass weeds are at the late vegetative stage, livestock, usually sheep, can be grazed heavily at around 30 to 40 DSE/ha to reduce the bulk of the pasture and stimulate even grass seedhead emergence, making it easier to time herbicide application.
“Both Gramoxone and glyphosate are registered to spray top barley grass and ryegrass in pasture,” he says. “Gramoxone has a narrower window at flowering in which it is effective. Having the majority of the weeds flowering together is very important to gain the full benefit of this herbicide. Glyphosate is effective over a slightly wider window either side of flowering.”
Spray topping generally reduces seed set of the targeted grass species by around 80 per cent. Once the grazing withholding period is over livestock can return to feed on the high quality pasture, which is also free of grass seed that would otherwise cause eye, wool or skin problems for sheep.
Winter cleaning is the alternative, again using livestock to remove the bulk of the pasture before applying herbicide. “Winter cleaning relies on very heavy grazing of the whole paddock to reduce the pasture to less than 500 kgDM/ha,” he says. “This must be done around July while the annual grass weeds are still young and palatable.”

Once the sheep are removed an application of Gramoxone, in combination with other herbicides depending on the pasture type, will achieve a very high level of annual grass weed control. Growers should consult product labels or seek advice on suitable options from their advisor.
“After six to eight weeks the pasture will recover and be almost free of annual grass weeds,” he says. “In the last year of the pasture phase the winter cleaning may be followed by a spray fallow over spring and summer to conserve moisture and remove any surviving weeds before planting canola or wheat in autumn.”
A similar level of control is possible using mechanical options such as cutting for hay and silage or slashing. Again, grazing heavily beforehand is still useful to ensure uniform head emergence to maximise the removal of seedheads before the seed has set.
“In different seasons or locations different options will have advantages over others,” says Mr Condon. “Planning to prevent seed set for at least two seasons prior to cropping is very effective in driving down the weed seed bank during the pasture phase.”
“Another excellent option going into cropping is a triple-knock strategy using glyphosate for initial control, then grazing heavily and quickly, at around 50–60 DSE/ha, to reduce the bulk of any survivors, then finishing off with an application of Gramoxone.”
“These are broad strategies to get started but there are several ways to go about grass weed management in the pasture phase,” says Mr Condon. “There are also a number of possible herbicide combinations that are worth investigating with a local agronomist.”
Using livestock to assist with weed control often requires additional management input and may not always line up with the best use of the pasture for grazing. This sacrifice is rewarded through with a significant reduction in the weed population going back into cropping.

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Solubility key to pre-emergent options

Choosing and applying the right pre-emergent herbicide can be difficult, particularly if herbicide resistance is becoming a challenge in a no-till system.
Dr Chris Preston, University of Adelaide (UA) associate professor weed management says the choice is simplified when the chemistry of the available products is understood.
“Most growers are aware of the need to incorporate trifluralin into the soil within 24 hours of application and that this chemical does adhere to stubble, which can render it ineffective if insufficient chemical reaches the soil,” he says.
Another major concern is the increasing populations of weeds that are resistant to trifluralin.
“Because of these two problems we’ve done a lot of work with industry to bring new products to the market,” he says. “Boxer Gold® and Sakura® are now available and it is important to understand the differences between how these new products work and how trifluralin works.”
The main difference between Boxer Gold® and Sakura® and trifluralin is their respective levels of solubility.
Dr Preston says trifluralin has no water solubility to speak of, which means that it won’t move from where it is applied unless there is soil movement or exceptionally heavy rain.
Wheat is not very tolerant of trifluralin but this herbicide can still be used safely in a wheat crop provided adequate chemical-to-soil contact is achieved and the chemical is not applied to soil that will come in contact with the emerging wheat seedlings.
This means planting at the correct depth and making sure that trifluralin-treated soil does not end up above the wheat seed.
Generally disc seeders displace too little soil from the seed row to make trifluralin a safe option for use.
The amount of stubble also needs to be considered because trifluralin will stick to stubble and be rendered ineffective. Dr Preston says using higher rates and bigger droplets can help get the chemical through heavier stubble and onto the soil but if stubble is matted on the ground the trifluralin will not get through to the soil and will not work.
However, if trifluralin-resistant ryegrass is present a grower will need to look at other pre-emergent herbicide options.
“Where ryegrass populations are not big or overly resistant, we’ve found that a mixture of trifluralin and Avadex® can achieve a reasonable level of weed control, particularly in areas where wireweed is a problem,” he says. “But, if the population is large or there is significant resistance to trifluralin then this strategy will not work. This has been demonstrated repeatedly in our trial work.”
This is where the new products, Boxer Gold® and Sakura®, have their place but the different chemistry needs to be understood. Dr Preston says that these new products are more soluble in water than trifluralin, Boxer Gold® more so than Sakura®.

“One of the difficulties with the new chemistry is the management of the herbicide down the seed row,” says Dr Preston. “Boxer Gold® only needs about 5–10 mm of rain to wash it in and activate it, giving really good early weed control. But too much rain after application can wash the herbicide into the seed row and cause crop damage. We have found that wheat is more susceptible to damage than barley.”
He says knife-point application of Boxer Gold® works better than using a disc seeder to apply the herbicide.
“This chemical degrades fairly quickly in Australian soils, generally within a few weeks, so in longer season areas or in years with rainfall through late winter and into early spring it is likely that later flushes of ryegrass will escape,” says Dr Preston.
“The location of the crop and the level of competition needs to be considered as we have seen situations where Boxer Gold® has fallen away very badly at the end of the season, but it does provide very good early control.”
The other new product on the market, Sakura®, is also water soluble, requiring about 10–15 mm to activate it in the soil. Dr Preston says this characteristics means problems can arise if the soil is dry on the surface but there is moist soil underneath.
“What can happen is a small amount of rain might fall that is sufficient to germinate the weeds but not enough to activate the herbicide and the weeds can grow through it,” he explains. “Sakura® is also harder to get through a heavy stubble than Boxer Gold®.”
The advantage with Sakura® lies in its residual action that will continue to control ryegrass late in the season. Dr Preston says sometimes, if there is a dry start to the season after early rain, there is an escape of early ryegrass but these plants become stunted as the season progresses because Sakura® is still present and working on the weeds’ roots.
Registrations and rotations need to be carefully considered as Sakura® is only registered for use in wheat and triticale crops (not durum) and may affect following crops such as oats and durum.
Dr Preston says another important finding of the Grains Research and Development (GRDC) supported research work was that, as with trifluralin, adding Avadex® to Boxer Gold® and Sakura® often gives better control than using these herbicides on their own.
“We have seen this added efficacy consistently with Avadex®.” he says.
Growers can use the GDRC weeds app to identify weeds, and download fact sheets here.

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Wild radish research refines control options

Trials in Western Australia’s northern agricultural region this year have provided further evidence of the importance of spraying wild radish while it is small and following up with a second spray, as part of an integrated management strategy to control the weed.
The ‘Managing stacked resistant wild radish with herbicides’ project was initiated by the Grains Research and Development Corporation (GRDC) Geraldton port zone Regional Cropping Solutions Network (RCSN).
Agronomist Grant Thompson, of Crop Circle Consulting, is conducting the research at Northampton, Casuarinas and Chapman Valley.
“The aim of the trials is to find alternative options to kill wild radish with stacked, or multiple herbicide resistance,” he said.
“Over-reliance on valuable new herbicides such as pyrasulfotole (eg.Velocity® and Precept®) could lead to wild radish developing resistance to them.
“The work that we’ve done has shown that there are other options that can achieve effective wild radish control, particularly if we use an early timing followed by a timely second spray.”
Mr Thompson said the two large-scale trials at Northampton and Casuarinas, where herbicide tolerant wild radish populations are present, tested the efficacy of 56 ‘two-spray’ herbicide treatment combinations and the results supported those from 2012 trials in the region.
“Almost all of the treatments achieved 100 per cent weed control when herbicide was applied early, at the 1.5 to two-leaf stage, followed by a spray four weeks later,” he said.
“There were cases where some herbicides performed more quickly and impressively, but most of the treatments designed by the steering committee associated with the trials provided very sound control.

“On the other hand, unacceptable results occurred when wild radish populations received a later initial spray at the five leaf stage, despite a second herbicide spray being applied.”
Mr Thompson said the ‘timing of application’ trial at Chapman Valley clearly showed that there would be reduced control of wild radish if growers decided to wait and use just one late spray.
“This reduced efficacy occurred even when more robust treatments, with additional tank-mixed products, were applied,” he said.
Mr Thompson said the best performing trial plots would be harvested and analysed for grain quality to assess the effect of the different treatments on grain yield, quality and final grain value returns.
He stressed that chemical control methods should be used in combination with non-herbicide weed control practices.
More information about the trial results is available by contacting Mr Thompson on 0427 652 521 or grant@cropcircleconsulting.com.au
The GRDC RCSN initiative aims to help growers get the information they need, when they need it, so they can make good decisions about farming practices. Details about RCSNs are available here.

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