Diseases
Anita Brûlé-Babel discusses the economic losses associated with Fusarium, how resistance ratings are developed for seed guides and utilizing risk maps. 

Click here for the full summary of Brûlé-Babel's presentation.

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Published in Corporate News
Wheat is an important crop in Canada, representing nine per cent of total farm cash receipts in 2015, and averaging 16 per cent of crop receipts in Canada from 2011 to 2015, according to Statistics Canada. And Fusarium head blight caused by Fusarium graminearum is the most important wheat disease. Fusarium head blight also infects barley and is a problem in malt barley production. With increasing corn acreage in Manitoba, there is a greater incidence of ear rot caused by F. graminearum as well.

The first and worst epidemic in Manitoba was in 1993. Since then, Fusarium has slowly spread to new areas across the Prairies, and by 2008, it was commonly found in the Dark Brown and Black soil zones in all three Prairie provinces.

There has been an emergence of new Fusarium populations and shifts in existing populations since 2000. A possible cause is the accidental introduction of isolates from one area to another, or one country to another.

Fusarium head blight is a concern because of the mycotoxins that can be produced by the pathogens. Fusarium graminearum produces two toxicologically relevant groups of mycotoxins. These mycotoxins have major impacts on swine feeding, resulting in poor feed intake and poor growth. Swine feed intake is reduced 7.5 per cent for every one part per million (ppm) of deoxynivalenol (DON) found in the diet.

The first mycotoxin group is the Trichothercens, which includes DON and the acetylated derivatives such as 15-ADON and 3-ADON. The DON mycotoxin is very stable during storage, milling, processing and cooking and doesn’t degrade at high temperatures. The other mycotoxin group in the Trichothercens is Nivalenol (NIV) caused by F. cerealis. It is not a virulent but is 10 times more toxic than DON. This group could become a concern and we don’t have a good monitoring system for NIV.

The second major mycotoxin group is Zearalenone and its derivatives.

The current issues with Fusarium mycotoxins in the Canadian feed supply is that Fusarium pressure in Canada is widespread and may be increasing because of wet seasons that promote the disease. There is also the additional risk of mycotoxin exposure from new feed ingredients such as distiller’s dried grains with solubles (DDGS) that are corn or wheat based. There is an increased risk in livestock feed with DDGS, since DON concentrates in in DDGS by approximately three times.

There appears to be a shift in the pathogen population with 3-ADON becoming more prevalent. This is a concern since 3-ADON makes significantly more toxin that is also more toxic. The LD50 for swine with 15-ADON is 113 milligrams per kilogram (mg/kg) while it is 49 mg/kg for 3-ADON. Analysis conducted by Ward et al in 2008 found that 3-ADON was found in six per cent of Alberta samples tested, 11 per cent of Saskatchewan samples, and 39 per cent of Manitoba samples.

We have looked at genetic chemotyping of DON isolates. On winter wheat, we found 3-ADON accounted for 82.4 per cent of F. graminearum isolates in Winnipeg and 84.6 per cent in Carman, Man. At Melfort, Sask., 3-ADON accounted for 100 per cent of the DON population. Canadian Grain Commission samples of CWRS wheat in 2015 indicated a shift to 3-ADON in the Black and Dark Brown soils zones.

This shift to a greater prevalence of 3-ADON brings new issues in managing the disease because of the increased virulence of 3-ADON. And because of the higher toxin production, there will be new issues at the elevator, in DDGS feeding and at the trade level because of potential downgrading.

The accidental discovery of NIV producing isolates in winter wheat at Carman by Chami Amarasinghe at the University of Manitoba is also a concern. Five of 132 Fusarium isolates were found to be NIV. In these isolates, 65 per cent were identified as 3-ADON, 31 per cent 15-ADON, and four per cent NIV. The presence of NIV is a concern, since it is 10 times more toxic to livestock than DON.

The identification of NIV is a concern because F. cerealis and F. graminearum are very similar and difficult to distinguish from each other. Until 2012, NIV had only been detected in a few barley samples in Canadian grain. However, testing for NIV in Canada is not routinely conducted at grain mills or elevators.

Amarasinghe also investigated the possibility of masked mycotoxins in our grains. These mycotoxins are masked because their structure has been changed in the plant. This process occurs when plants detoxify DON by converting it to DON-3-Glucosides (D3G). Masked mycotoxins are also known as modified mycotoxins and can’t be detected by conventional chemical analysis. However the danger is that gut microbes in livestock digestive systems may be able to convert D3G back to DON.

Findings from Amarasinghe’s research showed Canadian spring wheat cultivars produced D3G upon Fusarium infection, and there were significant differences among wheat cultivars. The susceptible cultivars showed a lower D3G to DON ratio (less D3G content) compared to the moderately resistant/intermediate cultivars. She found the level of resistance might have an effect on the production of D3G during the infection.

Looking into the future, Canadian wheat production may be at greater risk of Fusarium infections. An increase of 3-ADON, the potential for NIV to establish, and masked mycotoxins in our grain may be food safety issues. Additionally, with climate change, there is a possible threat of an increase in mycotoxins or having new mycotoxins such as the new NX-2 population establish.

Historically, in Canada we have seen shifts in the past. In the Great Lakes area, we saw a shift from ZEN to DON in the mid-70s, similar to the shift from 15-ADON to 3-ADON on the Prairies in the 2000s.

There are now some wheat varieties that have resistance to Fusarium in winter wheat and Canadian Spring wheat. Other classes also have varieties that are moderately resistant to Fusarium as well. These are important and should be considered as management tools.

This article is a summary of the presentation "War of the titans: The battle for supremacy in wheat-fusarium interactions," delivered by Dr. Dilantha Fernando, University of Manitoba, at the Field Crop Disease Summit, Feb. 21-22 in Saskatoon. Click here to download the full presentation.

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Published in Diseases
I work in Manitoba and we’ve been dealing with Fusarium head blight (FHB) for the last 25 years. In the 1990s, Manitoba started seeing severe infections. Those of you who are from Saskatchewan and Alberta, over the last two to three years, have definitely seen what it can be like when conditions are correct for Fusarium head blight infection.
Published in Diseases
In Ontario, soybean seedling diseases and root rots are the second most important yield limiting diseases, and this year is no different. Cool soil temperatures along with early rains in parts of Essex and Niagara resulted in a large number of soybean fields needing to be replanted and recent significant rainfall has had a negative impact on soybeans in many areas.
Published in Agronomy
In 2016, we conducted field surveys for root rot of pea and lentil in Alberta and Saskatchewan. In Alberta we surveyed 27 lentil and 89 pea fields during flowering, and 67 lentil and 68 pea fields in Saskatchewan.
Published in Diseases
Alberta’s wheat farmers can now add a Fusarium Head Blight (FHB) risk tool to their agronomy toolbox, improving their ability to make well-informed decisions related to FHB disease management. The risk tool was developed in a partnership between the Alberta Wheat Commission and Alberta Climate Information Service (ACIS) with expert support from researchers based at Agriculture and Forestry (AF) and Agriculture and Agri-Food Canada (AAFC).
Published in Corporate News
Most soybean and canola acres have been planted across the province, the majority of corn acres are in the V3 to V5 range, and much of the winter wheat crop has progressed beyond the post-flowering stage, according to the latest field report from the Ontario Ministry of Agriculture, Food and Rural Affairs. Here's the breakdown by crop, below. 

Cereals

A large majority of the winter wheat crop has progressed beyond the post-flowering stage, and spraying for Fusarium head blight protection has been completed in many regions. Stripe rust is reported to be advancing in some areas in fields that did not receive a fungicide application. Significant yield loss can occur in cases where disease pressure is very high. Fields that received a T1 or T2 herbicide application are reported to be still holding disease pressure back well. True armyworm has been observed in some fields, but not at levels that have required control. Growers are encouraged to watch for head clipping feeding. Clover stands in winter wheat look excellent.

Corn
A large majority of the crop ranges from the V3-V5 stages. In general, growers and agronomists in many areas report that plant stands and crops look great. The exception is some localized, heavier textured soil regions where planting conditions of earlier planted corn may have been pushed, and replanting is occurring. Sidedressing has started or is well underway in many areas. OMAFRA recently completed it’s annual PSNT measurement survey from June 5-6. Average soil nitrate concentrations were 8.0 ppm which is lower than the 11-12 ppm range that has been observed over the past 5 years, suggesting N mineralization may be delayed from the cooler spring. The last year when PSNT survey values were in this range was 2011. With the recent warm weather, growers and applicators are reminded to check corn herbicide labels for maximum temperature restrictions. Of particular note, spraying of hormonal herbicides (ie. dicamba) should be avoided when temperatures are expected to be above 25 C during or after application.

Soybeans
With the exception of a few localized pockets where wet conditions have prevailed and planting continues, the majority of the soybean crop has been planted. The majority of the crop is in the 1-2 trifoliate stage. While stands look reasonable in many cases, some replanting continues in areas which received heavy rainfalls after planting where crusting was evident (particularly on fine textured soils), as well as areas where seedcorn maggot pressure was high and reduced populations. A uniform population as low as 100,000 plants per acre is still considered to provide good yield potential. Planting conditions have been reported to be good for late planted or replanted soybeans. Bean leaf beetles and soybean aphids have been observed in some fields, but at very low populations where control is not warranted. If soybeans are to be rolled after planting, rolling should occur at the 1st to 2nd trifoliate stage where plants are no longer brittle and susceptible to snapping, and ideally in the heat of the day when plants are flaccid. High stand losses can occur when plants are crisp and susceptible to snapping between the emergence and the 1st trifoliate stage. When in doubt, check plants after starting to roll and evaluate the stand for snapped plants which will no longer be viable.

Forages
Growers are reporting excellent yields for first cut hay. First cut hay timed for higher quality has neared completion in many regions. In general, there has been a good weather window for first cut in most parts of the province for both haylage/silage and dry hay, and harvest progressed quickly as a result.

Canola
While a small amount of canola planting was still being reported in some areas up until the end of last week, most planting is complete and the majority of crop across most growing regions is in the 3-4 leaf stage. Swede midge emergence was being reported as early as late May, and was occurring prior to Canola emergence in some fields. Growers are encouraged to place and monitor Swede Midge traps. The control threshold is 20 adults across all traps in a field, and has been met in some fields this spring. Flea beetle pressure has been apparent in some fields, with some control being warranted. As the crop progresses beyond the 3-4 leaf stage, Canola is generally able to keep ahead of feeding. While Cabbage Seed Pod weevil has been observed in some fields, it is not typically an issue until pod set starts.

Edible Beans
Edible bean planting is reported to be nearly complete with an estimated 95 per cent of intended acres planted. Planting progressed very quickly once started, with a large amount of crop planted in a relatively narrow window. Planting conditions have been reported to be good.
Published in Corporate News
Cereals
Current weather conditions are ideal for fusarium head blight development in winter wheat. Many wheat fields in Southwestern Ontario have applied a T3 fungicide to reduce their risk particularly if they are growing a FHB susceptible variety. T3 fungicide applications further east will begin this week and continuing into next week for Eastern Ontario. A number of fields saw increased stripe rust pressure over the weekend. Growers with fields that were a few days away from a T3 application opted to wait and spray for both stripe rust and fusarium at the T3 timing. Some fields received an early heading fungicide application if they were a week or more away from a T3 fungicide application and growing a stripe rust susceptible variety to reduce the impact from stripe rust. Those fields will then receive a second fungicide application at pollination for protection against fusarium if needed. There have been reports of leaf tip necrosis starting on the flag leaf and moving down in fields. This leaf tip necrosis is likely associated with a specific or group of disease resistant genes and is the plant’s response to the presence of disease such as stripe rust. The yield impact from this is minimal.

Early spring cereal fields are at tillering and continue to look good. All weed control applications should be wrapping up shortly.

Corn
Corn planting is essentially now complete. With the exception of corn silage or some growers in long season regions, most unplanted fields will now likely be switched to soybeans. If corn herbicides have been applied but corn could not be planted, work with your herbicide provider to determine next best cropping steps. Overall corn is progressing well with a large amount of crop at the 2-3 leaf growth stage, with early planted corn beyond that. Minimal corn replants have been reported to date. Some sidedressing is now underway. There have been reports of black cutworm and slug feeding in a number of fields as a result of delayed crop planting and emergence and cool, wet weather conditions. There have also been reports of corn turning purple or white as a result of stress but those fields are expected to grow out of this.

OMAFRA Field Crop staff began tracking soil nitrate levels at a number of sites across the province the first week of May. Initial results suggest that soil nitrate levels are lower this year compared to previous years. Conventional PSNT timing sampling is being completed this week. Results will be posted at Weathercentral.ca under “Corn – GFO Nitrogen Research” as they are made available.

Soybeans
Soybean planting is 80 per cent completed across the province with some areas further behind compared to previous years due to significant rainfall this spring. The crop ranges from the hook stage to unifoliate growth stage. There continues to be weed challenges in a number of fields that did not receive a pre-plant burndown. Weed control during the early stages of soybean growth is critical. When making herbicide spray decisions pay attention to the growth stage of the weed as well as the growth stage of the soybeans.

There have been damage reports and replants particularly in Lambton, Essex, Niagara and Haldimand counties where they have received large amounts of rainfall and crusting became an issue. When doing plant population assessments a stand with 100,000 uniform plants per acre should not be considered for replanting. Research has shown that 100,000 plants per acre has a 98 per cent yield potential on most soil types.

On heavy clay soils 110,000-120,000 plants per acre are necessary for maximum yield potential. Rolling fields after the soybeans have fully emerged compared to rolling immediately after seeding helps alleviate stand losses due to crusting. Rolling can be up done up to the 1st trifoliate stage. There have been reports of seed corn maggot feeding in a number of regions due to the cool, wet weather. Fields planted without Class 12 insecticides that have sufficient stand loss due to certain soil insects including seedcorn maggot may warrant the completion of Inspection of Crop Pest Assessment by a professional pest advisor. If stand loss thresholds for the Class 12 regulations are reached, Class 12 insecticides can be purchased for that farm property. Contact a Professional Pest Advisor and refer here for more information. Bean leaf beetle feeding has also been reported in Essex County. Fields planted with fungicide-only seed should be scouted during the early seedling stages. Spray is warranted if 16 adult beetles per 30 cm of row are found on VC to V2 stage soybeans. If plants are clipped off at the stem, control is warranted if adults are still present and actively feeding.

Forages
First-cut alfalfa has begun in many areas with excellent yields being reported to date. Growers who applied some early season N to forage stands are reporting significant yield boosts. Alfalfa weevil and potato leafhoppers have been present in some areas. 

Canola
Canola emergence has been good to date; however, crop advancement has been slow particularly in northern Ontario. The earliest planted fields are at the 4 leaf stage. Growers in the Timiskaming area are already catching swede midge at this time and are likely going to have to spray sooner than anticipated. Swede midge has also been caught in the Shelburne area but has not yet reached thresholds. Due to the later planted crop and swede midge emergence this year it is anticipated that swede midge feeding will be a significant challenge. There have also been reports of high flea beetle pressure in some fields. 

Edible Beans
Due to the excessive moisture in many areas, edible bean planting is approximately 15 per cent complete. It is expected that the remaining acres will be planted later this week once conditions dry up.
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
Dr. Gary Peng discusses the key management strategies for blackleg in canola and how farmers will benefit from the new resistant gene labelling. 

Click here for the full summary of Dr. Peng's presentation. 

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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
Management strategies
The Canola Council of Canada is proposing a risk assessment chart. If you have a four-year rotation, likely your risk of having blackleg is very low. We know it’s effective, but I realize it isn’t always easy to implement. [Miss part one? Click here]

Scouting is important because it gives you a sense of your risk situation. There is an easy procedure that can be used to assess risk. After swathing, pull 50 plants, cut the stems at the base of the plant where blackleg develops and assess the damage to the stem. Use the pictorial guide I developed to assess the level of disease. If you don’t have any disease or very light disease, your variety might still be holding fairly well as long as you continue with longer crop rotation. But if you have an R-rated variety with a much higher disease level than you expected, your variety may not be holding up.

If you do want to switch varieties, try to rotate to another major resistance gene. We currently don’t have enough public information from seed companies to know what their resistance sources are. The Canola Council of Canada has proposed a new resistance labelling system to show the resistance gene labelling. It is voluntary and may start in 2018.   
Slide 25
Photo courtesy of Gary Peng.

If you don’t have any issues or major blackleg damage, there’s no urgency for you to switch between resistance groups right away, but it’s always a good practice to rotate them if you know the R genes. We understand 90 per cent of growers would rotate among the different varieties today mostly for weed management options. There is a similar principle in rotating varieties for disease management.

I want to also stress that we have quite a diverse pathogen population on the Prairies. In reality, over 90 races have been detected. That means with every known resistance gene, there is a different virulent isolate out there that would be able to overcome the resistance right away. We really need to consider, if we have different R genes available, rotation of those R genes. And we also need to maintain the non-race-specific resistance, which has been serving us relatively well.

What about fungicides?
Research on various fungicide products and application timings has been conducted. One involved 17 station years across the Prairies. We used four fungicide products, mostly the strobilurins and a triazole, and a combination of both active ingredients. We looked at applications at the two- to four-leaf stage, the bolting stage, and an application at both stages.  We also compared a susceptible variety with a resistant and a moderately resistant variety.

When we put all the data from 17 station years together, the early application of a strobilurin fungicide reduced the disease severity and also increased yield quite significantly compared to the non-treated check. The average disease severity was around about 1.5. The later application did not work, which makes sense because the key stage of infection is the cotyledon. 

We further looked at the data and divided it into two scenarios: those fields with much lower disease levels of around a 0.5 severity rating, and those with a disease severity of about 2.5. In the fields with low disease severity, the fungicide application did not provide any yield benefit. Where disease severity was about 2.5, a fungicide application at the two- to four-leaf stage reduced the disease severity significantly and also increased yield by seven bushels per acre compared to the non-treated check. 

However, these results were on Westar – a susceptible variety that was used to show the worst case when an R/MR variety is losing resistance. We looked at R/MR canola varieties at the 17 site years and found none of the fungicide applications were effective in providing a yield advantage (also indicating that the R/MR varieties have stronger tolerance to blackleg impact). That means if you have a certain level of resistance in your variety, in most cases the fungicide application would not provide a substantial yield benefit.

Where a fungicide treatment might come in is if the varieties you have been using are starting to show signs of an increased amount of blackleg. You should scout crops and assess the level of disease development over time. Also consider the length of the crop rotation and other risk factors outlined by the Canola Council of Canada. If you feel you are at high risk, an early application at the two- to four-leaf stage may be warranted.
Risk chart


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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Top Crop Manager's Herbicide Resistance Summit has been announced! Sign up today for early-bird pricing: https://www.weedsummit.ca/event/registration
Published in Diseases

Small planes have been flying over local farms and taking aerial photos for decades. Now, individual farmers are able to get an aerial view of a field using a small remote-controlled drone equipped with a camera.

But Agriculture and Agri-Food Canada (AAFC) has been receiving information from a far more sophisticated data collection network for at least the past 30 years, according to Leander Campbell.

Campbell, a geographer who specializes in geomatics, works as a remote sensing specialist with the Earth Observation team at AAFC. He says most of his work is on the AAFC Annual Space-Based Crop Inventory. He gets his data in the form of imagery from satellites and uses it to produce an accurate national crop map.

“The crop map, the one I work on, is at a 30 metre resolution so each pixel is a 30 metre by 30 metre square. It covers all of Canada,” he explains. Campbell adds one of the crops mapped in year one of the crop inventory in 2009 was soybeans. Since then, the data has shown how the crop is spreading west and north on the Prairies.
WTCM30.1 MB soybean 2009 2012
Campbell extracted only the soybean fields (in yellow) from Manitoba crop maps for the years 2009 and 2012.
Photo courtesy of Leander Campbell, AAFC.

The network Campbell gets his data from consists of several international satellites. The American satellite Landsat-8 provides optical data to create crop maps anyone can download. In addition to these data, Campbell’s team also uses microwave data from the Canadian RADARSAT-2 satellite.

The combination of optical and microwave data has been shown to produce more accurate maps than maps created from either single source. These maps are created and validated using data collected by people in the field. For the Prairies, “we have agreements with the provincial crop insurance companies,” Campbell says. “It’s not a perfect system but we’re about 85 per cent and 90 per cent accurate and working to improve that.”

Satellites don’t stay in orbit forever and Campbell says a backup is always an asset. Canada has plans to launch a constellation of three microwave satellites in 2018, the RADARSAT Constellation Mission (RCM), to gather data that’s even more detailed and precise than what’s available now.

“There are more uses than I ever thought of,” Campbell says. For instance, crop placements, crop monitoring, research, commodity marketing, land use management and even flood forecasting in Manitoba.

Microwave data collected by the European SMOS (Soil Moisture and Ocean Salinity) satellite allows Campbell’s team to operationally measure soil moisture in the top five centimetres of soil. He says most people don’t realize the Earth naturally radiates very low-level microwave energy and a satellite in space can pick up the variations in waves. Water absorbs microwave energy. When the microwaves radiate out from the Earth and pass through the soil, some of them are captured by moisture in the soil. 

According to Campbell, in September 2015, Statistics Canada did not do a farmer survey, opting to use AAFC climate data to complete their crop yield forecast. Satellite data can describe how agriculture land is changing or evolving over the years, whether it’s farmland expanding by eliminating small woodlots or urban expansion covering agricultural land. These phenomena can be monitored year over year using the AAFC crop maps.

Campbell has compiled maps that helped document the areas where clubroot is developing in canola. Scott Keller, a farmer from Camrose County in Alberta, contacted AAFC, asking Campbell if he could map Camrose County to determine how often canola was grown in particular fields. Keller wanted to determine which fields grew canola most often, either in a tight rotation over multiple years or in succession, in order to determine if there was a correlation between the escalation of clubroot and the rotation schedule.
Canola crop
Map created by Campbell to monitor canola crop frequency in Camrose County, Alta. 
Photo courtesy of Leander Campbell, AAFC.

That’s just one way satellite data can support crop management. Campbell says he’s confident that as computer technology and Internet costs come down, AAFC will be able to create more products from data because they can monitor specific areas once or several times over a growing season, or over years.

Campbell and his six colleagues who create the crop maps, soil moisture reports and the normalized difference vegetation index (NDVI) reports have an international presence as well. “I know some of our maps are incorporated into more global crop assessments for global market information, especially the NDVI maps,” Campbell says.

He explains that several nations around the world use satellite imagery to monitor their own crops. They meet on a monthly basis and compare data on major crops like corn, wheat, rice and soybeans through an organization called GEOGLAM. The group’s website states its vision is to “use coordinated, comprehensive and sustained Earth observations to inform decisions and actions in agriculture through a system of agricultural monitoring.” https://cropmonitor.org

Canadian farmers can access existing maps and data products online from the AAFC website. Because these maps are highly detailed, producers may experience difficulty downloading them on devices while in the field, but they can still view them online. According to Campbell, that’s the sort feedback he needs to hear from farmers.

“In our little world we have all these high-end computers and that works fine for us, but it may not be the most practical thing for others,” Campbell says. And, he’s looking forward to finding more ways to help farmers and make the website more user-friendly.

As satellite mapping matures, both farmers and scientists will view agriculture in new ways and Campbell is enthusiastic about the possibilities. “It’s a really exciting time to be in our field,” Campbell says.


This article originally appeared in the June 2016 issue of Top Crop Manager West

Published in Emerging Trends
Dr. Kelly Turkington discusses considerations to spray a fungicide, recommendations for Fusarium head blight in cereals and how to get the most out of your cereal fungicide applications. 

Click here for the full summary of Dr. Turkington’s presentation.

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Published in Diseases
Crop rotation is an important tool for our first line of defence in Western Canada. From a pathologist’s perspective, a wheat-canola-wheat-canola rotation – a single year between host crops – is not long enough to realize one of the benefits of rotation and allow decomposition of any infested crop residue. 

Variety resistance is also an excellent tool. When you have a variety with good levels of resistance, you really don’t need to spray a fungicide. The problem is that in your field you’re facing a range of diseases and it’s been very difficult to get varieties that have good levels of resistance to absolutely every disease issue that you might have in that field. If you have a tight rotation, your variety may not have the package of resistance that you need and, as a consequence, you will start to rely on fungicides. 

We like to use the disease triangle to express what a disease is all about. It’s the result of a susceptible host, a favourable environment and sufficient quantities of a virulent pathogen. The key thing to remember is that what you do in terms of crop management practices will impact the interaction of those three factors and ultimately, the risk of disease. 
Disease triangle
The disease triangle. Source: Dr. Kelly Turkington

Interation of fungicides with variety resistance
At a trial in Melfort, Sask., three barley varieties rated susceptible (Sundre), intermediate (Chigwell) and with a good resistance package (Vivar) against net-form net blotch were sprayed with Twinline (metconazole + pyraclostrobin) fungicide at the flag-leaf stage. With no fungicide application, Sundre had just under 20 per cent leaf area diseased on the penultimate leaf, but there was very little disease on Chigwell and Vivar with or without a fungicide. With a fungicide, there was a dramatic reduction in disease with Sundre.

If we look at yield, Sundre went from around 115 bushels per acre (bu/ac) without a fungicide to 145 bu/ac with the fungicide application. Chigwell had a bit of a response to fungicide application, which may be because it has an intermediate level of resistance. Vivar’s response to fungicide was basically flat. So, if you’re using a resistant variety that is giving you the protection you need, you don’t need to worry about putting on a fungicide.

General knowledge on application timing
In terms of fungicide application timing in cereals for leaf disease, it is important to know where yield and grain fill comes from. The literature suggests the wheat ear (head) contributes about 22 per cent to yield, while the flag-leaf contributes about 40 to 45 per cent, and penultimate (leaf below the flag) contributes about 23 per cent. Those are the key plant tissues that you want to protect. 

In barley, the flag-leaf is less important because it tends to be quite small in some varieties. The literature for barley suggests the head contributes around 13 per cent, the flag-leaf stem 25 per cent, the flag-leaf nine per cent and the penultimate about 20 per cent.

Overall, if you’re looking at a target as far as protecting the plant tissues that are key for grain filling and yield, the upper canopy tissues in those cereal crops are going to be your target.

Pathogen characteristics
The characteristics of the pathogen can be very important when trying to improve your ability to manage plant diseases with a fungicide. A monocyclic pathogen has one cycle of spore production, host infection and disease development, so there’s a very specific target there. Fusarium head blight (FHB) is a monocyclic pathogen.

Polycyclic pathogens cycle on the living crop more than once per growing season. These are diseases like stripe rust, tan spot, Septoria, net blotch and scald. This cycle may mean you can’t rely on a single application and may need several applications to get the level of control you desire, especially with highly susceptible varieties and under favourable weather conditions.

Stripe rust is an example of a polycyclic pathogen. It can move from spring wheat onto winter wheat seedlings in the fall. If I were advising a producer, I would note the presence of stripe rust in the fall and then be out in the winter wheat field as soon as the crop started to re-grow in the spring to see if the stripe rust fungus had survived. The stripe rust pathogen can rapidly cycle on the wheat crop: spores released from pustules on infected leaves are carried by the wind to healthy leaf tissue where they germinate, produce hyphae, penetrate plant tissue and within seven to 14 days, you’ll have symptoms – including pustules that produce a new crop of spores. So, every seven to 14 days, stripe rust can cycle on the crop well before head emergence. Thus, later on, on those upper-canopy leaves, you may see symptoms of stripe rust that can cause significant concern, especially if the disease becomes established in the crop before flag-leaf to head emergence.

Fungicide insensitivity
What about pathogen adaptation to the active ingredients in fungicides? Pathogens with a high risk of adapting to the active ingredients in fungicides have the following characteristics: they have mixed reproduction, so they reproduce sexually as well as asexually; and they also have an outcrossing system of reproduction where with they have male and female isolates – or mating types, – so you need a male and female for sexual reproduction to occur.

Sexual reproduction where different mating types are needed has the potential to create more genetic variability in the fungal pathogen, which can then be selected for when applying a fungicide. The other important thing is high genetic and pathogenic diversity in that pathogen, which increases the risk that a pathogen will adapt.

An example of a pathogen at moderate to high risk of adaptation to either plant disease resistance or fungicide active ingredients is the net blotch pathogen. In a study funded by the Western Grains Research Foundation, Alireza Akhavan, a PhD student working at the University of Alberta, found high levels of genetic/pathogenic diversity in the net blotch pathogen. It also reproduced asexually as well as sexually and with mixed mating types. Using a laboratory assay, Alireza found a few isolates that were insensitive (resistant) to Tilt (propiconazole) and, in some cases, insensitive to Headline (pyraclostrobin).

Randy Kutcher at the University of Saskatchewan is also looking at the tan spot fungus and potential insensitivity in the tan spot population.

Shifts in the fungicide sensitivity of cereal pathogens have been recognized in Europe for some time now and there have also been reports of changes in North America.

For example, in February 2015, Chris Mundt and colleagues at Oregon State University put out a disease update notice (Oregon State University, Disease Update, February 20, 2015, Chris Mundt, Mike Flowers, Nicole Anderson and Clare Sullivan), stating that, based on surveys from 2014, there were indications some fields had Septoria resistance to strobilurin (Group 11) fungicides. They also reported resistance to triazoles (Group 3) was starting to build.

Their recommendation in that part of the Pacific Northwest was to only apply a fungicide for early-season leaf disease control when stripe rust was present, because the fungicides were still effective against stripe rust. They also recommended using a succinate dehydrogenase inhibitor (SDHI) fungicide (Group 7) once per year, and for growers who did so to combine it with either a strobilurin or perhaps a triazole.

Click here to see part two: managing the tools available, including fungicide application timing trials.


This article is a summary of the presentation “Getting the Most Out of Your Cereal Fungicide: A Western Canadian Perspective,” delivered by Dr. Kelly Turkington, Agriculture and Agri-Food Canada, Lacombe, Alta., at the Field Crop Disease Summit, Feb. 21-22, 2017. Click here to download the full presentation.

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Top Crop Manager's Herbicide Resistance Summit has been announced! Sign up today for early-bird pricing: https://www.weedsummit.ca/event/registration
Published in Diseases

Managing the tools available
Given that fungicides are an important component of their leaf disease management programs, farmers need to manage the fungicides we have by using products with more than one active ingredient and/or rotating the products they use. [Miss part one? Click here.]

When a susceptible variety is grown and weather conditions are very favourable, farmers may be concerned about early season leaf disease development. Rather than applying a fungicide with their herbicides, one option might be to look at a seed treatment and use xylem-mobile fungicides that will move from the seed up into the leaf tissue to provide some early season leaf protection.

These fungicides are mixed with other fungicides that give us good activity on some of the root rots, whether it’s Fusarium or Rhizoctonia or Pythium and so on. Ideally, one may want to use a seed treatment with different active ingredients versus foliar fungicides that may be used later on in the season, with one application of a triazole to give us some suppression of FHB and late-season leaf disease management. 

Using a seed treatment for early season leaf disease management is food for thought and may be a strategy to consider.

Nature of a fungicide influences risk of resistance
The nature of the fungicide also plays an important role in effectiveness. Some fungicides do very well in terms of particular plant pathogen groups versus other fungicides, so check the provincial crop protection guides to make sure you are choosing the right fungicide for the disease issues you are targeting. 

The nature of the fungicide also influences the risk of fungicide resistance. Fungicides with a very specific individual target (single site activity) within the pathogen are typically at higher risk versus actives that have multiple targets (multi-site activity).

Mobility within the plant also plays a role, as it influences the efficacy, persistence and period of activity. Mobility also influences application technology, so if the product is not systemic, it will be especially critical to use practices that ensure good coverage of the plant surface you are trying to protect.

Fungicide timing and leaf spot diseases
Fungicide application timing is important for cereal leaf spot management. From 2010 to 2012, we looked at the effect of fungicide timing on leaf spot diseases in barley at 13 sites. Specifically, we compared tank-mixing a fungicide with herbicide versus putting that fungicide on at the flag-leaf stage versus using a split application, a half rate earlier on and then coming in with either a half rate or a full rate of fungicide at flag-leaf emergence.

Overall, our results indicated the best leaf disease control and the highest yields were achieved where we put a fungicide on at the flag-leaf stage and where we did not delay the herbicide application and, thus, had early weed removal. 

Table 1: Yield and herbicide/fungicide treatment
slide 33
Turkington et al. 2015. The impact of fungicide and herbicide timing on foliar disease severity, and barley productivity and quality.               Can. J. Plant Sci. 95: 525–537.

Timing also a factor in stripe rust control
Another trial, led by Kutcher and Brian Beres with Agriculture and Agri-Food Canada in Lethbridge, Atla., and conducted in Lacombe, Alta., illustrated the importance of fungicide application timing for stripe rust control in winter wheat. The most effective application for AC Bellatrix, a susceptible variety, was in the spring at the flag-leaf stage. For Radiant, a variety with some resistance, there was no need for a fungicide.

As mentioned previously, seed treatments may be an option for early- to mid-season leaf disease management. Recently, we did a set of experiments – including at Melfort – looking at the interaction of variety, seed treatment and fungicide on net blotch on barley. In 2013, we simply used a seed treatment without a fungicide and reduced the level of disease to less than 10 per cent of the leaf area affected from 30 per cent in the untreated control. If you looked at Twinline foliar fungicide applied with no seed treatment, there was very good control. Where we combined seed treatment with foliar treatment, it really didn’t improve control.

Our best yield response was where we simply put Twinline on at the flag-leaf emergence stage, whether a seed treatment was used or not. Overall, if you look at work done by research groups across Western Canada, if you have the opportunity to choose a variety that has good levels of resistance to the disease spectrum you’re dealing with, that’s an excellent tool to manage disease and will help you to avoid a fungicide application. 

However, the varieties you want grow may not have a complete package of resistance to the diseases of concern. Thus, it will be important to scout fields at or just prior to flag-leaf emergence to assess disease risk and its potential impact to determine if a foliar fungicide application is required to protect key upper plant canopy tissues. 

FHB application timing
Currently the recommendation for FHB fungicide application is to spray when you’ve got 75 per cent of the heads out of the boot – that’s when you can start – to about when you have 50 per cent of the head showing anthers in the middle part of that head. The problem with starting at 75 per cent head emergence is that 25 per cent of the heads are still in the boot. Thus, given the nature of the fungicides that we use for FHB, applications at 75 per cent head emergence will not provide much, if any, benefit for those heads not yet emerged.

Recent research from the United States suggests we may have a wider window for application post head emergence to get the most out of that fungicide application. 

Trials from the U.S. looked at fungicide timing and effect on FHB disease rating and DON content with applications at the start of anthesis (when you first see yellow anthers emerging from the middle part of the wheat head) and then either two, four or six days following the start of anthesis. Overall, results suggested that even at four and six days after anthesis, control was as good as applications at anthesis, and in some cases may actually be slightly better.

The trend was similar with DON content.

I think, in terms of getting the most out of our fungicide application for FHB, we need to look at revising our target. Maybe going a little later is something to consider so you provide protection for all heads within the crop. However, growers are cautioned that they need to follow label recommendations and the pre-harvest intervals for the products they use.

Expectations for fungicides
In terms of expectations for fungicides, it’s important to be realistic. Fungicides can certainly be effective tools for some diseases, but it’s important to use them prudently and to manage those fungicides so they remain effective tools for you over the next 10, 15, 20 years. Timing can have a huge impact. Fungicide application also doesn’t mean a completely disease-free crop and, thus, it is important to leave some check strips so that you can adequately judge fungicide performance.

Overall, farmers are encouraged not to rely exclusively on fungicides as their only defence against plant disease. Try to use the other tools in the toolbox. The more tools you have, the broader your ability to control disease and other pest and crop management issues in your crop.  By using a range of tools, including crop rotations of at least two years between host crops, you’re going to prolong the effectiveness of tools such as disease resistance and fungicides into the future.


This article is a summary of the presentation “Getting the Most Out of Your Cereal Fungicide: A Western Canadian Perspective,” delivered by Dr. Kelly Turkington, Agriculture and Agri-Food Canada, Lacombe, Alta., at the Field Crop Disease Summit, Feb. 21-22, 2017. Click here to download the full presentation.

Don't forget to subscribe to our email newsletters so you're the first to know about current research in crop management.

Top Crop Manager's Herbicide Resistance Summit has been announced! Sign up today for early-bird pricing: https://www.weedsummit.ca/event/registration
Published in Diseases
LET'S START WITH THE PAST...
In the past, disease management in field crops was largely based on major gene resistance and the use of fungicides.
Published in Diseases
Dr. Bruce Gossen discusses some of the results of his long-term cropping study and what that means for growers in Canada looking to manage crop diseases.

Click here for the full summary of Dr. Gossen's presentation.

Don't forget to subscribe to our email newsletters so you're the first to know about current research in crop management.

Top Crop Manager's Herbicide Resistance Summit has been announced! Sign up today for early-bird pricing: https://www.weedsummit.ca/event/registration
Published in Diseases
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