Spraying
The U.S. environmental agency is considering banning sprayings of the agricultural herbicide dicamba after a set deadline next year, according to state officials advising the agency on its response to crop damage linked to the weed killer.

Setting a cut-off date, possibly sometime in the first half of 2018, would aim to protect plants vulnerable to dicamba, after growers across the U.S. farm belt reported the chemical drifted from where it was sprayed this summer, damaging millions of acres of soybeans and other crops.

A ban could hurt sales by Monsanto Co (MON.N) and DuPont which sell dicamba weed killers and soybean seeds with Monsanto’s dicamba-tolerant Xtend trait. BASF (BASFn.DE) also sells a dicamba herbicide.

It is not yet known how damage attributed to the herbicides, used on Xtend soybeans and cotton, will affect yields of soybeans unable to withstand dicamba because the crops have not been harvested.

The Environmental Protection Agency (EPA) discussed a deadline for next year’s sprayings on a call with state officials last month that addressed steps the agency could take to prevent a repeat of the damage, four participants on the call told Reuters.

It was the latest of at least three conference calls the EPA has held with state regulators and experts since late July dedicated to dicamba-related crop damage and the first to focus on how to respond to the problem, participants said.

A cut-off date for usage in spring or early summer could protect vulnerable plants by only allowing farmers to spray fields before soybeans emerge from the ground, according to weed and pesticide specialists.

Monsanto spokeswoman Christi Dixon told Reuters on Aug. 23, the day of the last EPA call, that the agency had not indicated it planned to prohibit sprayings of dicamba herbicides on soybeans that had emerged. That action “would not be warranted,” she said.

The EPA had no immediate comment.

EPA officials on the last call made clear that it would be unacceptable to see the same extent of crop damage again next year, according to Andrew Thostenson, a pesticide specialist for North Dakota State University who participated in the call.

They said “there needed to be some significant changes for the use rules if we’re going to maintain it in 2018,” he said about dicamba usage.

State regulators and university specialists from Arkansas, Missouri, Illinois, Iowa and North Dakota are pressuring the EPA to decide soon on rules guiding usage because farmers will make planting decisions for next spring over the next several months.

Tighter usage limits could discourage cash-strapped growers from buying Monsanto’s more expensive dicamba-resistant Xtend soybean seeds. Dicamba-tolerant soybeans cost about $64 a bag, compared with about $28 a bag for Monsanto’s Roundup Ready soybeans and about $50 a bag for soybeans resistant to Bayer’s Liberty herbicide.

Already, a task force in Arkansas has advised the state to bar dicamba sprayings after April 15 next year, which would prevent most farmers there from using dicamba on Xtend soybeans after they emerge.

Arkansas previously blocked sales of Monsanto’s dicamba herbicide, XtendiMax with VaporGrip, in the state.

“If the EPA imposed a April 15 cut-off date for dicamba spraying, that would be catastrophic for Xtend - it invalidates the entire point of planting it,” said Jonas Oxgaard, analyst for investment management firm Bernstein.

Monsanto has projected its Xtend crop system would return a $5 to $10 premium per acre over soybeans with glyphosate resistance alone, creating a $400-$800 million opportunity for the company once the seeds are planted on an expected 80 million acres in the United States, according to Oxgaard.

By 2019, Monsanto predicts U.S. farmers will plant Xtend soybeans on 55 million acres, or more than 60 percent of the total planted this year. READ MORE 
Published in Herbicides
Though often abused and neglected, mixed forage stands can respond to fertilization. Still, some growers are hesitant to apply fertilizer to meet fertility needs, perhaps because forage yields tend to decline over time or because lack of spring rainfall can limit yield responses.
Published in Other Crops
Farmers in Alberta are being given the tools to take charge against climate change by adopting on-farm best management practices that are scientifically proven to limit the impacts of agriculture on natural resources like air, water and soil.

Fertilizer Canada is proud to announce the signing of a Memorandum of Understanding with the Agricultural Research & Extension Council of Alberta (ARECA) that includes integration of 4R Nutrient Stewardship (Right Source @ Right Rate, Right Time, Right Place®) into the province's Environmental Farm Plan (EFP). This agreement marks a significant milestone on Fertilizer Canada's journey to create truly sustainable and climate-smart agriculture in Canada.

"We are pleased that ARECA has officially recognized 4R Nutrient Stewardship as a best practice for nutrient management on Alberta farms," said Garth Whyte, President and CEO of Fertilizer Canada. "By encouraging farmers across the province to use fertilizer effectively, Alberta is joining the front lines in the fight against climate change and ensuring their place among the world's leaders in sustainable agriculture."

"ARECA is a long-time supporter and promoter of 4R Nutrient Stewardship," said Janette McDonald, Executive Director. "There is no doubt this formalized partnership with Fertilizer Canada will aid us in expanding awareness of the program as a best practice for nutrient management planning."

4R Nutrient Stewardship is a science-based nutrient management system that is universally applicable yet locally focused. By applying the right source of fertilizer at the right rate, the right time and the right place, farmers can ensure nutrients are efficiently taken up by their crops and are not lost to air, water or soil. This increases crop productivity and reduces unwanted environmental impacts.

Managed by ARECA, the province's EFP self-assessment process encourages producers to assess and identify environmental risks on their farms and take action to improve their practices.

"While Alberta's EFPs already include a section on nutrient risks, adding information about the positive long-term benefits of 4R Nutrient Stewardship will expand awareness among the province's farmers," said Paul Watson, EFP Director at ARECA.

As growers in Alberta adopt 4R Nutrient Stewardship under the Alberta EFP, the acres they manage will be counted under Fertilizer Canada's 4R Designation program, which tracks the amount of Canadian farmland using 4R Nutrient Stewardship to boost productivity and conserve resources. Fertilizer Canada aims to capture 20 million 4R acres by 2020 – representing 25 per cent of Canadian farmland – to demonstrate to the world the commitment Canada's agriculture sector has made to adopt climate-smart and sustainable farm practices.

To learn more about 4R Nutrient Stewardship and the benefits it offers, visit www.fertilizercanada.ca

Learn more about the Alberta Environmental Farm Plan and the benefits it offers by visiting www.AlbertaEFP.com
Published in Corporate News
Building off several research studies over the last decade, research scientist Cecil Vera at Agriculture and Agri-Food Canada (AAFC) in Melfort, Sask., wanted to narrow down the fungicide application window for control of pasmo disease in flax and investigate the effectiveness of fungicides in reducing the impacts of the disease. Graduate student Tonima (Trisha) Islam summarized the results of the three-year study that ran from 2014 through 2016 under the supervision of Randy Kutcher, an associate professor in the department of plant sciences at the University of Saskatchewan.

“Not much research has been done on the effect of fungicides on the pasmo disease in Saskatchewan and Alberta,” Islam says. “I think these new findings will help flax growers understand how to control the disease.”

The research compared three fungicides and three application timings to measure the effect of pasmo disease severity, crop maturity, seed yield, thousand seed weight and test weight of CDC Bethune flax. Trial locations were at Vegreville, Alta., Melfort and Saskatoon, Sask., and Brandon, Man. The fungicides Headline EC (pyraclostrobin), Priaxor (pyraclostrobin + fluxapyroxad) and Xemium (fluxapyroxad) were applied; currently only Headline and Priaxor are registered on flax for control of pasmo.

Fungicide application timing was at early flower (BBCH 61) and mid-flower (BBCH 65), and a dual application was made at both early and mid-flower. Applications were compared to a control without fungicide application.

Islam found all fungicides reduced disease severity, but Xemium was the least effective. With respect to timing, fungicide application at the early stage was the least effective. There was no difference in disease severity between the mid-flower application stage and the dual fungicide application.

Priaxor had significantly higher yield compared to the control and other fungicides. Priaxor increased seed yield approximately 25 per cent (2,295 kilograms per hectare, or kg/ha) compared to the control (1,822 kg/ha), followed by Headline at 19 per cent (2,172 kg/ha) and Xemium at 18 per cent (2,159 kg/ha). No significant difference was observed between Headline and Xemium.

Effect of the Xemium (fluxapyroxad), Headline (pyraclostrobin) and Priaxor (pyraclostrobin + fluxapyroxad) on seed yield of flax at Brandon, Melfort, Saskatoon and Vegreville in 2014, 2015 and 2016
Pasmo chartSource: Islam et al., University of Saskatchewan.

However, the Priaxor treatment delayed maturity by five days, which could present a risk to seed quality in some years. The dual fungicide application also delayed maturity by five days. This delay in maturity may be a result of the effectiveness of the fungicide treatment – pasmo often results in premature ripening and earlier harvests. Earlier seeding may help to offset the delayed maturity.

wtcm25.4 plotsPriaxor increased seed yield approximately 25 per cent compare to the control.

Timing of application and the impact on seed yield was also significant compared to the control. Applying fungicide at both the early and mid-flower stages increased seed yield approximately 25 per cent (2,273 kg/ha) compared to the control (1,822 kg/ha), followed by mid-flower timing at 21 per cent (2,210 kg/ha) and early flower timing at 17 per cent (2,143 kg/ha). Yield at the mid-flower application timing was not significantly different from either the dual application or the early flower application, but there was a significant difference between early and dual timings.

Effects of fungicide application timings (early, mid and both stages) on seed yield of flax at Brandon, Melfort, Saskatoon and Vegreville in 2014, 2015 and 2016Pasmo chart 2Source: Islam et al., University of Saskatchewan.

In terms of thousand seed weight and test weight – proxies for seed quality – the mid-flower and dual treatment increased TKW and test weight.

Even though the dual application provided the highest yield, economically, the net return on a second application may not make sense. “With the yield increases we have seen in Trisha’s trial and my previous experience in Melfort in the 2000s, I think two applications would rarely, if ever, be economically beneficial, based on current yields and prices for the fungicide and flax,” Kutcher says.

Making the application decision
Basing a fungicide application on the presence of the disease is difficult. Vera says that while there are cases in which pasmo may appear early in the season, in most instances the evidence of pasmo symptoms appear later in the season, and by then, it would be too late to spray.

“Usually, conditions for pasmo infection differ from year to year and from location to location, which was quite evident in this study. I think the best strategy would be to protect the crop with the best and most economical recommendations and hope for good results,” Vera says.

This means a farmer should base their decision to spray a fungicide on environmental conditions coupled with previous experience with pasmo, flax frequency in the rotation and proximity to adjacent flax stubble.

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Published in Fungicides

Tractors delivered participants to more than 10 sites at the 23rd annual Southwest Crop Diagnostic Day. The event, which took place July 5 and 6, saw agronomists, producers and industry professionals visiting stations across the University of Guelph’s Ridgetown campus to learn about new research and the implications for crops in Ontario.

Here’s a sampling of some of the topics covered.

Albert Tenuta [Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA)] and Dave Hooker [University of Guelph – Ridgetown (UGR)] took producers through a few different plot sites and discussed planting corn and soybeans in a cover crop. Although cover crops help with soil organic matter, erosion and moisture control, it’s often best to terminate a cover crop in a dry year.

Peter Sikkema and Darren Robinson (both from UGR) tested participants on herbicide injury in both corn and soybean, respectively. Producers saw first-hand the symptoms caused by new and common herbicides.
IMG 1390Peter Sikkema holding a corn plant injured by herbicides.

Chris Brown (OMAFRA) and Doug Young (UGR) did a smoke bomb demo to highlight soil pores and offered tips for managing water movement through soil. Producers were reminded that soil pores (which include macropores, mesopores and micropores) are impacted by different issues such as soil properties (texture, pH), cultivation (tile drainage, crop rotations), external loads (tillage and compaction) and natural processes (biological activity, frost).

Joanna Follings and Anne Verhallen (both from OMAFRA) talked cover crop seeding rates and options for growers. They highlighted research that indicates underseeding red clover into winter wheat leads to an increase of 10 bushels per acre (bu/ac) for corn and five bu/ac in soybean.
Best clover density plotOne of the plots of red clover planted at UGR.

There’s also a nitrogen credit of 85 pounds per acre. Follings offered tips for seeding, since the biggest challenge with red clover is establishment. (A uniform stand of three to four plants per square foot is the minimum number to be considered a good stand.)

Another session offered an overview of trapping technology, scouting tips and management strategies for Western bean cutworm presented by Christina DiFonzo (Michigan State University), Tracey Baute (OMAFRA) and Art Schaafsma (UGR).
IMG 1521The Z Trap is one of the newest Western bean cutworm traps on the market. 

When scouting, DiFonzo says to look at 100 plants (10 plants in 10 different areas, or 20 plants in five areas) every five days when crop is in the pre- to full tassel stages. The threshold to spray is an accumulation of five per cent of plants with Western bean cutworm egg masses or small larvae over a two to three week period.

Dave Bilyea (UGR) covered some lesser-known but potentially problematic weeds for Ontario agriculture. Some of the weeds highlighted include annual bluegrass (which competes with young plants and is tolerant to glyphosate) and dog strangling vine. There aren’t many reports of this vine yet, but it’s very competitive and is toxic to insects and animals, affecting ecology. Another weed to watch is wild parsnip, which makes skin UV-sensitive and results in burns similar to those caused by giant hogweed. With scouring rush (also known as snakegrass), part of the challenge is that the plant has no leaves for contact with any herbicides producers might spray.
IMG 1488Dave Bilyea explains the similarities between Northern willowherb and goldenrod.

Bilyea reminded growers that they can send in weeds for herbicide-resistance testing free of charge. 

Jake Munroe and Horst Bohner (both of OMAFRA) focused on fertilizing soybeans: deficiency symptoms, strategies and new research demonstrating the importance of phosphorus in soybean. 4R nutrient stewardship was also highlighted using the Phosphorus Loss Assessment Tool for Ontario (PLATO).

Ben Rosser (OMAFRA) and Peter Johnson from Real Agriculture had participants digging up corn plants from a variety of plots to discuss the effects of planting dates, depth and staging.
Screen Shot 2017 07 06 at 3.43.48 PMPeter Johnson from Real Agriculture discussing the stages of corn development. 

Hail damage in corn was also discussed using the example of a corn plant damaged just a couple of weeks ago. Although the farmer growing the corn in question thought he should plant something else, there was still new growth in the corn and so he was advised to leave the crop; he would likely only suffer a five per cent yield loss from the hail damage.

Jason Deveau and Mike Cowbrough (both of OMAFRA) highlighted the importance of sprayer clean out and compared two different systems: triple rinsing and continuous rinsing.
IMG 1497Deveau and Cowbrough explaining how a continuous rinse system works.

Growers walked through soybean and tomato plots and saw the level of injury caused when equipment isn’t properly rinsed between spray applications. Although triple rinsing is effective, it takes three times longer to do; the continuous rinse system is not only faster, but also limits operator exposure. The current challenge is adding the pump on the sprayer equipment due to challenges with the computer operating systems.

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Published in Corporate News
What I’d like to give you is a view from my previous careers working in Europe, New Zealand, and now Australia with regards to disease management. I’d like to give you a flavour of some of my impressions of disease management over the last 35 years with reference to getting the balance right with regard to the disease triangle and integrated disease management. 

Where are we in terms of integrated disease management (IDM)? What is IDM all about? Principally it’s about trying to make sure we use all the tools in the toolbox, integrating genetic resistance with chemical fungicides, cultural control and overall crop agronomy. When we sow the crop and how we look after it with nitrogen can profoundly affect how much disease pressure we’re under.

Getting it just right is never going to be easy. What’s happened in Australia? Before 2002, there wasn’t a huge amount of fungicide usage because it’s a much less responsive environment. Then we had an “exotic incursion.” Stripe rust came in from North America, probably on a grower’s boots. That changed the pendulum, from a dependence on genetic resistance to a reliance on fungicides, because, overnight, a huge proportion of all of the germplasm in Australia became susceptible to stripe rust.

Meanwhile in Europe, there was a totally different swing of the pendulum. It was inspired by a new set of varieties, in this case semi-dwarf varieties. With the new cultivars and more nitrogen, crops stayed greener for longer. Suddenly yields increased enormously in the ’70s. Higher yields and longer growing seasons in Europe drove growers to apply more and more fungicide. If you go to Europe now, it’s all about T1, T2 and T3 – Timing 1, Timing 2, Timing 3 with fungicides as a fixed part of crop agronomy. Up until 2005 in Europe, the pendulum had swung very much to the fungicide side of the IDM pendulum.

Slide 6
However, that’s all changed. In Europe, the profound driver for change has been fungicide resistance. Fungicide resistance influences everything that a European grower now does with fungicides. If there’s one thing that I think is really important to take on, it is that fungicide resistance – if it’s not affecting you now, it will be shortly unless you can moderate your use of fungicides.

What’s gradually happened over time is that we’ve got better products with greater activity, but at the same time fewer products based on limited modes of action. There are fewer products that are more and more environmentally benign, but at the same time at greater risk of resistance development. In other words, we’ve moved from multi-site fungicides that killed the fungus in many different ways to single-site fungicides that do less damage in the environment but actually are much more vulnerable to resistance.

Fungicide insensitivity and resistance
Fungicide insensitivity and resistance has occurred principally in two ways. In Europe in the late 1990s and early 2000s, strobilurins, such as pyraclostrobin and azoxystrobin, came along with the biggest media hype since glyphosate. However, after only three to four years, the pathogen causing powdery mildew and then Septoria tritici (now Zymoseptoria tritici) in wheat developed resistance to stobilurins, and that’s been a real challenge ever since. In two to three years, the strobilurins went from being the best products to control foliar diseases in broad acre cereals to products that wouldn’t work against Septoria, a disease that is widespread in northwest Europe. I think that’s when attitudes really changed and people started asking the question, “Is there a different way to control disease?”

Slide 16
We’re in our infancy with fungicide resistance issues in Australia. We can see it in the field with powdery mildew in barley. Our triazole fungicides such as Tilt (propiconazole), Folicur (tebuconazole), Proline (prothioconazole), Prosaro (prothioconazole and tebuconazole co-formulated) don’t work as effectively to control powdery mildew. With Septoria, we’re not yet seeing reduced activity in the field, but the samples are showing insensitivity in the laboratory, so there is increasing threat that we will see resistance to fungicides in the field. 

Europe and triazole use
What has happened in Europe with the triazoles over the last 20 years is that triazole fungicides have gradually become less effective against key diseases, firstly not working as effectively in the lab and then gradually being noted to be less effective in the field. That’s why with triazoles I think it’s important to talk about “fungicide insensitivity” and not “fungicide resistance.”

For example, it’s taken 20 years of exposing the Septoria pathogen population to the triazoles for them to become less effective. They still have activity but are now only 60 to 70 per cent effective when it used to be 90 to 100 per cent. So in Europe the triazoles and the strobilurins become less effective and ineffective for key diseases in a similar time period, but the triazoles had been gradually degrading in their effectiveness over time. 

Therefore with the terminology we use, I think it’s important to recognize we really have three basic modes of action that we use in broad acre cereal disease control – triazoles, strobilurins, and the new SDHIs [succinate dehydrogenase inhibitors].

With the triazoles I think it is probably more appropriate to call it “insensitivity” rather than resistance, since if you say to a grower, “It’s resistant,” the tendency is to think that it won’t work when in reality it is still partially effective.

With regard to the SDHIs, they’re not actually that new since the family of chemistry has been around for 40 years. But a new branch of SDHI chemistry is now taking Europe by storm, as the strobilurins now have less application because of resistance in key pathogens. But after only three years of commercial use with these new SDHIs, resistance is developing quickly in the net blotch and Septoria pathogens.

It’s really important to recognize that fungicide resistance is changing the way in which growers and advisors elsewhere in the world manage their cereal crops. In Australia, growers and advisors are just beginning on that resistance journey. You’ve already had some exposure in Canada to the fact that the strobilurins are at high risk of resistance development in the pathogen.  It begs the question, “What can you do about it?”

Click here for part two: The importance of multiple modes of action and linking pathology with crop physiology.
Published in Diseases
[Miss part one? Click here]
Importance of multiple modes of action

I’m horrified to hear that you can apply straight strobilurin fungicide to your crops, since there’s no other mode of action in the application to protect you from pathogen mutants that might be strobilurin resistant. If you went back to when the strobilurins were breaking down to Ascochyta in some of your pulse crops, it’s worth asking yourself, wouldn’t it have been better to have been using them in combination with other older multi-site fungicides in order to give the strobilurins a degree of protection? 

What’s now happening in Europe is that there’s a lot of dependence on the triazole fungicides since there is widespread resistance amongst a number of pathogens to strobilurins and increasingly to SDHIs. However it’s not the same with all pathogens. For example, the rusts – stripe rust, leaf rust – seem particularly stable. But with the necrotrophic diseases such as Septoria, such as net blotch, such as scald, populations are shifting. That stated, the triazoles remain the backbone of disease management programs all over the world.

It’s actually becoming more complicated for advisors in Europe. What’s happening is that different regions in Europe have different pathogen populations that are differentially susceptible to triazoles. What researchers are finding is that the triazole that works best in one area of Europe might not be the triazole that works best in another.

Now I know what you’re thinking: aren’t triazoles all from the same family of chemistry with the same mode of action? That’s where the resistance to these molecules is more complicated. For example, in one region, Folicur might not work very well on the Septoria pathogen, but a Tilt still does a reasonable job, depending on the history of fungicide use. Somewhere else in Europe, the exact reverse might be happening.

In Europe, they’ve set up a project called EuroWheat with 26 trials all across Europe examining triazole fungicides and their activity against key diseases, looking at not only what’s happening in the field in terms of foliar control, but then taking samples for lab analysis. It’s revealing that the pathogen is adapting in different regions differently, depending on what fungicides have been used, particularly the Septoria population. 

We are now beginning to see the same thing with Septoria in Australia. Some products that are effective on the mainland of Australia don’t work well in Tasmania. 

What can we do to protect fungicides going forward? We can minimize our use of them. Pick the best adapted, highest yielding, and most resistant varieties we can use. Such a choice might enable you to use just one fungicide application instead of two applications. In some parts of the world, there are guidelines advising using that active ingredient just once in a growing season. But probably the strongest message that comes out around the different regions of the world is the one about mixing different modes of action in cereal crops. 

So think about fungicides as part of that integrated disease management package – use them, but don’t overuse them. 

Across Europe at the moment, the new SDHIs are entering the market already mixed and formulated with a triazole in order to ensure the use of two modes of action in a fungicide application. “Make sure that you’re mixing different modes of action” is the strongest message that comes out of the scientific studies on fungicide resistance and it’s the one key take-home that I can give you. If you’re not mixing, ask why not.

There is one area that is important to clarify and that is with regard to fungicide rate and resistance. I don’t believe that there’s a lot of scientific evidence in the literature that suggests keeping fungicide rates high is a good anti-resistance strategy. Generally it is with herbicides, but I’m not sure that evidence exists for fungicides. Frank van den Bosch from Rothamsted in the U.K. did a literature search on 46 different fungicide studies and found there were more studies showing that increasing fungicide rate increased resistance selection pressure than the reverse. I think it’s more appropriate that we consider fungicide rate as an efficacy message, not a resistance message: i.e. what rate of fungicide is appropriate to obtain the best economic outcome. There are other things, like mixing our active ingredients with different modes of action, which are far more important in resistance management than considering fungicide rates.

Linking pathology with crop physiology
The other factor that is really important is linking our knowledge of pathology with crop physiology. Fungicides don’t only kill a disease, they keep plant leaves greener for longer, providing soil water is available to express the benefit of the disease free leaves. The upper leaves of the cereal crop canopy, particularly the top four, affect the ability of a plant to produce yield. In Australia, disease management strategies based on fungicides are particularly dependent on the presence of soil water to express the benefit of a fungicide both in terms of yield response and economic return. 

One of the things from Europe that I think they have right is that they talk all the time about “What are the key parts of the plant to protect from disease?” If you’re growing a cereal crop, what do the individual leaves on that cereal crop contribute to yield? That’s an incredibly important part of any strategy using a fungicide. We use fungicides to make money, not just control disease, and what’s been really good in Europe is actually characterizing which parts of the plant are best to protect from disease.

When it comes to thinking about fungicides, don’t only think about the disease. The time of disease onset in the crop will determine to which leaves fungicides are applied. In Europe, set development timings trigger the questions. “Do we have the disease? Are the conditions conducive for the disease? What’s this crop going to yield?” These are key questions that link the effect of the disease with the physiology of the crop.

Slide 29
slide 30
I think the key message when it comes to thinking about using fungicides as part of an integrated disease management package is to recognize that they’re not very effective at protecting tissue that’s not emerged at the time of application. Other than reducing overall inoculum in the crop, fungicides only directly protect the leaves and plant structures that are emerged at the time of application, so you need to target the most important leaves that contribute to yield.

The interaction of crop disease development and crop physiology is now a target for an Australian modelling team. In summary, it’s important to look at disease development and crop development together. 

I’d like to finish off with a reference to future developments. The Magnetic Induction Cycler (MIC) is about the size of a four-litre pail. From leaf samples using MIC, you can determine the genetic makeup of the pathogen population, determining not only the presence of genetic mutations that might affect fungicide performance but also the frequency of the population with that mutation. In the future this technology will assist the advisor in making the right product choice for individual paddocks. That technology moving forward could be linked with automated spore traps informing us when pathogen spores are moving into the paddock, their genetic makeup and how that’s going to affect product choice.

Lastly, I believe RNA interference technology has the potential to produce the next phase of environmentally-friendly fungicides. The technology is based on short segments of nucleotide that are absorbed into the plant and pathogen, and which can switch off the RNA messenger before it can synthesize the proteins for fungal development in that plant. It is very specific technology and offers some great potential for disease management in the future.
Published in Diseases
Blackleg is caused by two species of the pathogen. The major one is called Leptosphaeria maculans. The other one is a much less virulent species called Leptosphaeria biglobosa. For control of the disease, pathologists look at some of the weak links where we can apply most of the impact on the disease. The pathogen only survives on residues. If you don’t have a residue, it doesn’t survive well in the soil. That’s why rotation is important.

The pathogen produces a fruiting body in the spring called a pseudothecium or another type called a pycnidium. They produce spores that land on the cotyledons of canola. If you have insect damage from pests like flea beetles, the infection can be worse. With wounding, the pathogen can get into the cotyledon tissue even without moisture. From there the infection develops and you see the cankers at the base of the stem later on in the growing season.
Slide 4
Photo courtesy of Gary Peng.

There are three important things that can lead to an infection:
·      there’s residue to harbour the pathogen inoculum
·      you need to have early infection to get into the stem
·      insect damage may help the infection to occur more severely. 

The disease was very prevalent in the late ’80s, early ’90s. Then we introduced some resistant varieties in the early ’90s, which brought down the occurrence for many years. Partially that was resistance bred into varieties, but we also had three- or four-year rotations. That was a big part of the whole management effectiveness.

In the last five to six years, the disease incidence has been creeping back up to 20 to 25 per cent in Alberta and Manitoba, and about 10 per cent in Saskatchewan. However, the average severity remained below level 1 (light). Research by Sheau-Fang Hwang in Alberta indicates that in most years, this level of severity could result in a yield loss of about two to eight per cent on a susceptible variety. But from a trade perspective, our trading partners want to see the disease level trend going down.

Why the upward trend?
The first reason for an increase in blackleg incidence is likely the change of the pathogen population, which is adapting to the resistant varieties. The pathogen population may be becoming more virulent or with a greater proportion of virulent isolates in it. 

Plant breeders have used major gene resistance to control the disease. The resistant gene blocks the infection by the pathogen carrying the corresponding avirulence gene. For example, an Rlm3 resistant gene would block the pathogen with avirulence AvrLm3 gene (abbreviated to Av3). It might be like a lock-and-key, but for some reason, over time, the Av gene may change and the resistant gene may not be able to recognize it.

My colleague, Randy Kutcher, looked at the change in pathogen populations in 2007 when he looked at the avirulent gene prevalence on the Prairies. In his work looking at 800 isolates of L. maculans, the percentage of Av2 and Av6 genes were very high in the population, and the others at more moderate to low levels. Further work in 2010 and 2011 with Dilantha Fernando at the University of Manitoba found the picture had changed quite a bit. The presence of the Av3 and Av9 genes had decreased quite a bit, but at the same time Av7 seemed to be increasing quite a bit. That means the Rlm3 gene would be less likely to be effective across the Prairies because the Av3 gene had changed mostly to the virulent type. The Rlm3 gene was first introduced back in early 1990s and has been used for over 20 years.

Other research in Fernando’s lab also looked at what resistant genes are present in 206 varieties/breeding lines in Western Canada. The resistance gene that was predominantly found was Rlm3 in around 70 per cent of the varieties/breeding lines. There was also a bit of Rlm1 detected as well. Overall, the diversity of R genes is still quite limited in the germplasm tested. The important message is that Rlm3 is not going to remain effective on the Prairies because the corresponding Av3 gene is already fairly low in the pathogen population. 

However, when we looked at field data in Alberta and Manitoba, while the occurrence of other Av genes was high, disease levels ranged widely. This told us there was something else going on, which we called non-specific resistance in our varieties, although the effect was definitely less than the major gene resistance.

We further investigated this non-specific resistance in our varieties. We tested commercial varieties with a pathogen without a corresponding Av gene so any resistance observed would be due to non-specific gene resistance. Almost all the varieties had a slightly smaller amount of the disease on inoculated cotyledons than the susceptible Westar. At the same time, it’s a totally different kind of resistance reaction as opposed to the major gene resistance. It would not stop the infection completely – it just slowed it down a little bit, and on some varieties, substantially.

A further look at three of those varieties found the progress of plant mortality originated from cotyledon or petiole inoculation was somehow reduced, but varied between the varieties. Using a fluorescent protein gene labeled isolate, photography was able to show the reduced spread of the pathogen in the cotyledon compared to the susceptible Westar variety.

If you can slow down the movement from the cotyledon via the petiole into the stem, there may not be enough of the pathogen getting into the stem before the cotyledons drop off. This is one of the reasons that non-race-specific resistance works in some of those varieties we have.
SLIDE 22
Photo courtesy of Gary Peng.
Click here for part two: management strategies

This article is a summary of the presentation “Managing blackleg of canola in Western Canada,” delivered by Dr. Gary Peng, Agriculture and Agri-Food Canada, Saskatoon, at the Field Crop Disease Summit, Feb. 21-22, 2017. Click here to download the full presentation.

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Published in Diseases
Scientists with the University of Tennessee Institute of Agriculture have found that the overall health of honeybee hives actually improves in the presence of agricultural production.

The study, “Agricultural Landscape and Pesticide Effects on Honey Bee Biological Traits,” which was published in a recent issue of the Journal of Economic Entomology, evaluated the impacts of row-crop agriculture, including the traditional use of pesticides, on honeybee health. Results indicated that hive health was positively correlated to the presence of agriculture. According to the study, colonies in a non-agricultural area struggled to find adequate food resources and produced fewer offspring.

“We’re not saying that pesticides are not a factor in honeybee health. There were a few events during the season where insecticide applications caused the death of some foraging bees,” says Mohamed Alburaki, lead author and post-doctoral fellow with the University of Tennessee Department of Entomology and Plant Pathology (EPP). “However, our study suggests that the benefits of better nutrition sources and nectar yields found in agricultural areas outweigh the risks of exposure to agricultural pesticides.”

A​ccording to the study, hives located in areas with high to moderate agricultural vegetation grew faster and larger than those in low or non-agricultural areas. Researchers suggest the greater population sizes enabled better colony thermoregulation in these hives, as well.

Meanwhile, bees located in a non-agricultural environment were challenged to find food. Although fewer pesticide contaminants were reported in these areas, the landscape did not provide sustainable forage. In fact, during the observations, two colonies in the non-agricultural areas collapsed due to starvation.

Disruptions and fluctuations in brood rearing were also more notable in a non-agricultural environment. Interestingly, brood production was highest in the location that exhibited a more evenly distributed mix of agricultural production, forests and urban activity.

“One possible explanation for this finding could be the elevated urban activity in this location,” says Alburaki. “Ornamental plantings around homes or businesses, or backyard gardens are examples of urban activity that increase the diversity of pollen in an area. Greater pollen diversity has been credited with enhancing colony development.”

Researchers also evaluated trapped pollen from each colony for pesticide residues. Low concentrations of fungicides, herbicides and insecticides were identified, but at levels well below the lethal dose for honey bees. Imidacloprid was the only neonicotinoid detected, also at sub-lethal levels.

Agricultural pesticides, particularly neonicotinoids, are considered by some to be a key factor in declining honeybee populations. The UTIA study found that higher exposure to pesticides in agricultural environments did not result in measurable impacts on colony productivity.

This study was supported in part by the U.S. Department of Agriculture’s Agricultural Research Service Pest Management Program.
Published in Corporate News
Surveys of sunflower rust in Manitoba show variations in the predominance of different races from year to year, but the overall trend is towards races with greater virulence.
Published in Diseases
Set out a free smorgasbord and see who shows up. In the case of fababean, as acreage has risen, pea leaf weevil and lygus bug have been coming to dinner. For producers, the main concern with pea leaf weevil is feeding on nitrogen-fixing nodules, while for lygus bug, the economic impact is related to seed quality.
Published in Insect Pests
In wheat, in canola or in pea, the message is the same: control weeds early for highest yields. Those messages have been repeated in the past and now new research highlights the need to repeat that same message with respect to wheat crops.
Published in Weeds
When farmers spray their fields with pesticides or other treatments, only two per cent of the spray sticks to the plants. A significant portion of it typically bounces right off the plants, lands on the ground, and becomes part of the runoff that flows to streams and rivers, often causing serious pollution. But a team of MIT researchers aims to fix that.

By using a clever combination of two inexpensive additives to the spray, the researchers found they can drastically cut down on the amount of liquid that bounces off. The findings appear in the journal Nature Communications, in a paper by associate professor of mechanical engineering Kripa Varanasi, graduate student Maher Damak, research scientist Seyed Reza Mahmoudi, and former postdoc Md Nasim Hyder.

Previous attempts to reduce this droplet bounce rate have relied on additives such as surfactants, soaplike chemicals that reduce the surface tension of the droplets and cause them to spread more. But tests have shown that this provides only a small improvement; the speedy droplets bounce off while the surface tension is still changing, and the surfactants cause the spray to form smaller droplets that are more easily blown away. | READ MORE
Published in Corporate News
Full registration of the imidazolinone-tolerant (IMI-tolerant) chickpea system with recommended chickpea varieties and registered Solo herbicide is imminent. Two IMI-tolerant chickpea varieties – CDC Alma (Kabuli-type) and CDC Cory (Desi-type) – have already been developed. The Prairie Pesticide Minor Use Consortium has submitted the application for Solo herbicide use on IMI-tolerant chickpea to the Pesticide Management Regulatory Agency (PMRA) and registration could be received in early 2017.  
Published in Pulses
Our enemy’s enemy is our friend. That’s the idea behind a calculator being developed to help Prairie cereal growers make decisions on whether to apply insecticides. In this case, our enemies are the various aphid species that infest cereal crops. If aphid populations are high during a sensitive crop stage, these delicate little insects can make a big dent in cereal yields. The aphids’ enemies include an array of insects that are able to chomp down, suck dry or otherwise destroy impressive numbers of aphids.
Published in Insect Pests

June 15, 2016 - Salford Group unveiled what it says is the largest pull-type pneumatic boom applicator on the planet. The whopping prototype is being shown for the first time in public at Canada's Farm Progress Show this week in Regina.

Published in Sprayers

Mar. 16, 2016 - According to the Canadian Agricultural Injury Reporting (CAIR) program, 13 per cent of farm-related fatalities across Canada are traffic-related, and most involved tractors.

During the busy spring season, farmers often travel long distances between fields, and this requires transporting equipment on public roads throughout rural Alberta. Farm equipment is oversized and slow compared to other vehicles using the roads and when certain procedures are not met, this can lead to collisions and other incidents.

"Maintenance is a contributing factor to the safety of transporting farm equipment," says Kenda Lubeck, farm safety coordinator, Alberta Agriculture and Forestry (AF). "Poor maintenance of equipment such as brakes or tires can lead to loss of control of the vehicle."

Check all tires for air pressure, cuts, bumps and tread wear. Always lock brake pedals together for highway travel as sudden braking at high speeds on only one wheel could put the tractor into a dangerous skid. Equip heavy wagons with their own independent brakes.

The number one cause of farm-related fatalities in Canada is machinery roll overs. To minimize the risk of severe injury or death to the operator, all tractors need roll-over protective structures (ROPS)," says Lubeck. "In addition, operators should always wear a seatbelt as ROPS are ineffective in a roll over without this restraining device."

To avoid traffic collisions between motorists and farm equipment, farmers should ensure their equipment is clearly visible and follows all regulated requirements for lighting and signage. This will ensure approaching traffic has time to react to a slow-moving vehicle. Use reflective tape and reflectors in the event that large equipment is required to travel in dim lighting conditions. In Canada, reflective material should be red and orange strips. You can purchase tape in kits or by the foot at local farm or hardware stores.

Dust-covered signage and lights make farm machinery less visible to motorists and dust-covered machinery causes poor visibility for the operator, who may not see oncoming traffic. Be sure to clean farm equipment prior to transportation to minimize the risk of collision due to poor visibility.

"It's important to note that regulated requirements for lighting and signage on public roadways include the use of a slow-moving vehicle (SMV) sign," explains Lubeck. "The SMV sign must be properly mounted, clean and not faded. It must be positioned on the rear of the tractor or towed implement and clearly visible. SMV signs must only be used on equipment travelling less than 40 km/hr."

For more information on the safe transportation of farm equipment on public roads, see AF's Make it Safe, Make it Visible or go to www.agriculture.alberta.ca for more information on farm safety.

 

Published in Maintenance

Mar. 31, 2016 - Much of the tracks-versus-wheels debate on farms has focused on compaction and the ability to drive in wet conditions, but what about differences in fuel consumption?

Testing done in southern Manitoba in 2015 confirmed long-standing research showing tracks require less energy to move in field conditions, dispelling a lingering misconception that implements on tracks require more horsepower to pull than wheeled units.

Research conducted near Altona — the home of track-maker Elmer's Manufacturing — found fuel savings of 11 to 15 percent when pulling a grain cart on tracks instead of wheels.

"We used a grain cart and compared wheels to tracks at the same weights. We tested on fresh tilled ground, tilled and then dried for a few days, untilled canola ground, and concrete for a reference." explains Mike Friesen, general manager and lead engineer at Elmer's.

While wheels pulled easier than tracks on concrete, there was less resistance pulling tracks in all three field scenarios.

That's because tracks "float" or stay higher on top of the soil, reducing what engineers describe as "rolling resistance." Since tires generally create deeper ruts, they have a greater rolling resistance than tracks on soft soil, as explained by researchers AJ Koolen and H Kuipers in Agricultural Soil Mechanics back in 1983.

"In plain English, the tracks don't have to continuously try to get out of the rut they are digging like the wheel does," explains Friesen.

Hartney, Manitoba farmer Tim Morden's experience pulling large capacity Bourgault cart on Elmer's TransferTracks supports the findings.

"When we had duals on the back of the cart, dirt would build up in front of the wheels and slow it down, making it hard to pull," he says. "This didn't happen with tracks."

Morden explains the biggest difference he's noticed with switching to tracks is the reduced compaction and rutting, especially in wet conditions.

"The number one fact is it doesn't really leave a rut at any time, unless it's really wet, but it's significantly less than tires," he says. "We have much more confidence on the field with the track."

The study also compared energy required to pull Elmer's large tracks versus Elmer's smaller TransferTracks, which concluded that, while both tracks pulled easier than wheels, the TransferTracks required less horsepower at weights below 35,000 lbs per wheel making it the ideal candidate for use with an air-seeder cart, small grain cart or a rolling water/fertilizer tank.

The reduced energy requirement not only results in improved fuel efficiency, but it could also allow a grower to optimize their existing horsepower in other ways, such as driving faster or pulling a wider drill with the same tractor during seeding.

 

Published in Tractors

With foliar fungicide applications, timing is a key factor in soybean yield response. A soybean specialist gives his take on the best timing options.

Based on his research results so far, “the long and the short of it is that fungicide timing is highly dependent on the year and what disease you are going after,” says Horst Bohner, provincial soybean specialist with the Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA).

Bohner’s research interest in fungicide applications began about 10 years ago. “In 2004, soybean rust was found in Ontario for the first time. It was just on one leaf so it wasn’t an economic issue. But it did stir the industry to register fungicides to help control that disease if an outbreak occurred,” he explains. “Prior to that we really only used foliar fungicides in soybeans very sparingly and mostly for white mould. Unfortunately fungicides didn’t really work well for white mould control because soybeans flower for such a long time.” (For white mould, the aim of a fungicide application is to protect the flowers because infected petals are the main way the disease starts in the plant.)

“So in 2005, we started a number of trials – as did many people – to assess the different foliar fungicides available at that time. We found that there was a real yield benefit even in the absence of soybean rust; often there are other minor diseases present or, in some cases, there are no visible disease symptoms at all.”

Once they knew there was a definite yield benefit from a foliar fungicide, the next question to answer was timing-related: which soybean growth stage would be the best time for spraying? Given that soybeans flower for a long time, what timing would be the most effective for white mould? And what timing would be best for controlling other foliar soybean diseases?

Fungicide companies had been recommending that foliar fungicides be applied between the R3 (beginning pod) stage and the R4 (full pod) stage, based on research conducted mainly in the United States. However, results in some initial Ontario trials by BASF and by David Hooker from the University of Guelph’s Ridgetown campus indicated that an earlier timing, between the R2 (full flower) stage and the R3 stage, provided a greater yield benefit. So Hooker conducted trials in 2013 and found that an R2 to R3 timing increased soybean yields by about one to 1.5 bushels per acre compared to the R3 to R4 timing.

Generally in Ontario soybean trials, the yield response to a single foliar fungicide application averages about two bushels per acre, so the possibility of an extra bushel per acre is exciting. As a result, Hooker continued his fungicide timing trials in 2014 and 2015.

Hooker’s 2013 results sparked Bohner’s interest in fungicide timing. So Bohner has been conducting field-scale, replicated
trials to compare various application timings for the past two years, with funding assistance through the Grain Farmers of Ontario.

Bohner’s 2014 trials involved Priaxor and Acapela, and took place at Bornholm, Lucan and St. Thomas, with two soybean varieties at each site. The fungicide timings were: untreated control; in-furrow; V6; R2; R4; in-furrow + R2; and in-furrow + R2 + R4.

The 2015 trials involved Priaxor, Stratego Pro, Allegro and Acapela, and were conducted at Bornholm and Lucan, with two soybean varieties at each site. The timings were: untreated control; in-furrow; V6; R2; R4; and R2 + R3.

The in-furrow treatment was included in the trials because interest in liquid in-furrow applications in soybeans has been increasing in Ontario. “The idea of applying a foliar fungicide in-furrow is to help protect the roots and early seedlings, similar to putting a fungicide on the seed, which is what we often do now; most certified soybean seed has a fungicide on it,” Bohner explains. He notes that in-furrow foliar fungicide applications are being tried in the United States with mixed results.

The tables on the right show the yield results of the different treatments in 2014 and 2015. So far in the trials, the in-furrow and V6 fungicide timings have not resulted in statistically significant yield gains.

In 2014, the wet, cool weather conditions favoured white mould at two of the sites. The results showed that if white mould is present at moderate levels, then using a foliar fungicide can produce large yield gains. The greatest yield benefit occurred with the most intensive treatment (in-furrow + R2 + R4); the in-furrow portion of this intensive treatment likely did not affect the yield.

In 2015, there was no statistically significant difference between any of the yields, likely because there was no disease pressure present.

Timing tips
Bohner’s results show that the choice between R1, R2, R3 and R4 timing depends on which disease is the major concern and on the weather conditions.

“If you are trying to suppress white mould – white mould is a really hard disease to control so we talk about suppression – you need to think about spraying two times in the growing season. Because you are trying to protect the flowers, consider spraying at R1 [first flower] and then following up with another application 10 to 14 days later, which is around R3. The timing of the first application is not the early part of R1, because R1 can happen quite early in the season. Often R2 is fine for the first spray; if you do that, then you would follow with another application at R4,” Bohner says.

“[The choice between a late R1 timing and an R2 timing] depends on the growing season, how big the plants are, how much moisture there is and how much it looks like there is going to be a disease problem. One of the main considerations is coverage. If the plants are quite small and good coverage can be achieved at R2, then this timing is likely all right.

 “For the other foliar diseases, when most growers will only need to spray once, the earliest you should spray is at R2,” he adds. “In 2015, we showed that you could spray right up to the R4 stage and get the same [yield] response as at the R2 stage. So the window for the correct timing is wider than we thought it was. It probably ranges from mid-R2 to R4 in most years, depending on the growing conditions that season.”

With these other foliar diseases, you have some time to scout and decide whether the disease problem is serious enough to warrant a fungicide application. For white mould, however, you cannot wait until the disease shows up in the crop. “Typically at that late R1, R2 or R3 stage, when you’ll be spraying the first time for white mould, almost no disease would be present. So you have to base your spray decision on the field’s disease history and the weather. If it is cool and wet, and you have had a lot of disease in that field, in my estimate you should apply that first spray at the late R1 to early R2 stage. And then you see what the weather does. If it is wet and cool and you are starting to see some white mould, then you spray again 14 days later. If it turns hot and dry, you don’t spray again,” Bohner explains.

He emphasizes, “If you wait to see significant white mould in the crop, then it’s too late to spray. The research shows that. If you wait to spray at R5, for instance, there is no response at all to a fungicide. The disease is set in.

“Overall, if you are going to chase control of disease and higher yields with these fungicides, then so far in my work, two applications provide much more consistent results. Of course the problem with that is the cost. And the cost is a pretty big barrier.”

foliargunicidetablesfeb16

 

 

 

Published in Soybeans

 

Spraying herbicides well is both an art and a science. But it’s also mostly a matter of always doing certain things and never doing others, according to Mike Cowbrough, weed management field crops lead at the Ontario Ministry of Agriculture, Food and Rural Affairs  (OMAFRA), and Steven Johns, agronomic sales rep with Syngenta Canada.

So how do farmers improve weed control success through spraying well? Let’s first look at mixing. Cowbrough points out that successful tank mix compatibility is all about starting with a clean tank and making sure products are mixed efficiently. “Some products are easy to foam, like glyphosate and water, and if you add a de-foaming agent prior to adding the glyphosate, that will take care of it,” he says. “Also, always make sure your inductor is full so it’s not drawing air, and minimize agitation.”

More serious issues with gelling and clogging of spray lines seem to occur often with EC herbicides and a dry granular product. “Do a jar test if there is any doubt,” advises Cowbrough. “Mix up a little batch in a pint jar that’s the equivalent measurement to what you’d apply to an acre. I once mixed 2,4-D amine and Sencor DF, for example, in a jar test and didn’t let Sencor dissolve well enough first, so I got a coarse white precipitate in the jar that was hard to flush away. It would be exponentially worse to clean up in a sprayer.”

Johns advises those using a new tank mix to ask the retailer to double-check about things like mixing order. “Surfactants can also be added to make products compatible,” he says. “Many products that contain atrazine don’t ‘like’ to be mixed with glyphosate, but if you add a non-ionic surfactant, you can make them very compatible.” He reminds farmers to pay attention to the general
mixing rules: add wettables, powders, granules, then agitate, then liquids, flowables, and ECs, followed by true solutions.

“All of us are in a hurry at springtime, and we have to slow down and remember that these products were never designed to mix with each other, so we need to mix one thing at a time, and give it time,” he notes. “With dry flowables, put them through the inductor to smash them and then they’ll get suspended well in solution. Temperature and water volume are also very important.”

Cowbrough agrees. He notes that low water volumes can have a very negative influence on how well high-volume dry granular flowable herbicides dissolve. He advises using high water volumes if you want to have complete dissolving, and prevent product sedimentation in the first place. “With any flowables or wettables, you should have valves on your boom sections, and flush your system well,” Johns adds. “I’d also like to stress that you should never leave a partial tank sitting around unapplied, unless you have the spare time to agitate it every hour or two until you want to finish applying it. If you let stuff sit in sprayers for any length of time, sedimentation can occur. So, go ahead and finish spraying even if it’s raining. And also remember, never put products into jugs that aren’t correctly labelled.”

Cowbrough also makes the point that products might not fully dissolve in acidic or alkaline water. He says studies done at Purdue University in the U.S. showed that the efficacy of Eragon was found to be reduced in acidic water, for example. “The price of litmus paper is cheap, so testing your water is worth it,” he notes.

Application advice
Last year, Cowbrough and his colleagues conducted weed surveys across the province in six counties and found that six weed species were predominant. Canada fleabane and giant ragweed are at the top of the list, but so is lamb’s-quarters. “It’s a species that we get asked about in terms of whether it’s herbicide-resistant,” he notes. “But that’s not going on and yet it seems to be resistant. So, what is it?”

Johns notes that to answer that, we need to take a close look at application. “Soil application is different than contact post-emergence application, but with lamb’s-quarters or giant ragweed, we advise using a higher water volume post-emergence,” he says. “You are spending a lot of money on herbicides, so make sure they work. Don’t skimp and you’ll get much better droplet dispersion and much better results.”

Cowbrough’s survey results also revealed the fact that what is being reported as lamb’s-quarters might actually be fig-leaved goosefoot. “So, make sure to do good scouting,” Cowbrough advises. “And make sure you are trying to spray when the lamb’s-quarters are small, at the eight-leaf stage. When you apply herbicides at this stage, control is excellent.” At medium size (three to four inches tall), glyphosate efficacy with lamb’s-quarters is still excellent, but the efficacy of Basagran and Pinnacle falls off. At six to eight inches tall, Basagran and Pinnacle are not effective on lamb’s-quarters at all, Cowbrough notes, and glyphosate cannot do well because there is too much calcium in the leaves. He adds that if weeds are at a high density, they can shade and protect each other; so again, getting them when they are small is very important.

So, size matters, but so does time of day. Cowbrough says different time-of-day herbicide applications on velvetleaf and lamb’s-quarters were recently compared by Peter Sikkema, a crop scientist at the University of Guelph (Ridgetown). Sikkema found that control of velvetleaf is much better if spraying is conducted between 9 a.m. and 6 p.m. Johns points out that earlier than 9 a.m. and later than 6 p.m., dew can interfere with efficacy, so make sure the field is dry. Time of day also affects leaf orientation. For velvetleaf in particular, the leaves drop as the sun goes down, so spraying later in the evening is not recommended. The efficacy of glyphosate and other herbicides can also be reduced by soil and dust on weed surfaces.

“Also keep in mind that a thick crop canopy appears to serve the same function of another residual herbicide application,” Cowbrough notes. “Less sunlight getting through means fewer weed seeds germinate. So, use whatever seeding rates and whatever row space you wish, but don’t ignore fertility.” He says studies have shown that soybean canopy closure is much quicker with the use of both a pre- and post-emergent herbicide program. “But we know that less than 20 per cent of glyphosate-tolerant soybeans receive a pre-emergent herbicide application,” he says. “That’s something to think about.” 

 

Published in Weeds
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