Is fungicide actually effective on Sclerotinia head rot in sunflower?

Morgan Cott on August 5, 2026

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By Morgan Cott, Agronomy Extension Specialist – Special Crops, Manitoba Crop Alliance

This is one of the most difficult questions to answer because there are many things to consider. I also don’t want to be outright negative because we do still have options for sclerotinia management in sunflowers. However, management is the operative word.

First of all, sclerotinia head rot infections have an interesting pathway. Spores use dead sunflower florets, plus pollen, as the base to infect a sunflower plant. The spores grow into the receptacle, infecting and decaying the entire head after a period of time. Sclerotinia wilt (basal stalk rot) and mid-stalk rot are also infected by the same sclerotinia species, but it will be via the mycelia that grow from the sclerotia bodies in the soil for basal stalk rot. Mid-stalk rot is also infected by ascospores, but this can be earlier in the season than head rot or at the same time.

Sclerotinia sclerotiorum Diseases of Sunflower​ (White mold) – The American Phytopathology Society (APS)

So, management of sclerotinia does not start at flowering. Crop rotation is the most obvious management tool that we are familiar with in sunflowers, but it is not reliable. Yes, always put at least three years between sunflower crops and any other oilseed that is a host to sclerotinia, but sclerotia bodies have a long life in the soil and it feels impossible to get rid of them.

Here are some additional management tools that, if layered, will definitely help manage the potential of sclerotinia infections of any kind, in any crop:

Nitrogen – avoid excess nitrogen rates, as this will encourage dense vegetative growth and prime conditions in the lower canopy for sclerotia development.

Weed control – many broadleaf weeds and volunteers can be host to sclerotinia, which can multiply sclerotia in the soil after a season of successful weed infections.

Tillage – tillage will move sclerotia bodies around in the soil, burying them and then also bringing them to the surface in a cycle. No-till simply leaves the sclerotia on the soil surface, ready for germination at any moment. The best practice may be to rotate multiple years of no-till with non-host crops so the sclerotia germinate but do not have a proper host to multiply, thereby decreasing in population.

Genetics – unfortunately, this still does not seem like it will be an option in sunflowers as it cannot be perfected or reliable enough to build resistance, or even tolerance, to sclerotinia. It has been found in the past that some hybrids did appear to have partial resistance, though that degree of resistance is easily exhausted in high sclerotinia incidence.

Fungicides – let’s get into this and I will summarize some recent work done in the Dakotas.

 

Sunflower susceptibility to head rot increases as bloom stage progresses and then decreases at R6 staging, where conditions have to be ideal for infection. At R7 and beyond, infection will not occur. Interestingly, at early bloom if temperatures are high, that is when risk is lowest during all susceptible stages.

In 2017-18, North Dakota State University (NDSU) researchers conducted fungicide efficacy trials using Proline and Endura (Lance WDG equivalent) and different application methods on head rot (boom-mounted nozzles and drop nozzles). Summarizing a large project, these are the key takeaways from NDSU plant pathologist Michael Wunsch:

  • Proline displayed moderate reductions in Sclerotinia head rot when disease pressure was low to moderate (<30 per cent incidence) with both standard boom-mounted nozzles and drop nozzles
  • Residual activity may be limited to the first 1 – 3 days after bloom
  • Coverage to the front of the head is optimized in the first half of bloom using standard boom-mounted nozzles
  • Endura (Lance WDG equivalent) showed little or no efficacy against head rot irrespective of application method
  • A significant part of the yield gain associated with fungicide applications targeting Sclerotinia head rot was presented by management of other diseases (rust, Phoma, Phomopsis, etc.)

See full presentation document on “Are fungicides useful for managing Sclerotinia head rot in sunflowers?” by Michael Wunsch. Or Michael Wunsch explains it in this YouTube video.

Essentially, if relying on fungicide, application has to hit the front of every sunflower head and within one day of infection, which is next to impossible to predict. The direct application to the front of the sunflower head may be improved with drone applications, but that is just speculation at this point.

MCA is in the third year of a field-scale trial in our Research on the Farm program, allowing sunflower farmers to test their product(s) of choice and method of choice for the control of Sclerotinia head rot. In 2026, we have two participants that conducted the trial using their spray drones, so we are looking forward to those results and subsequent data collection. See full results from 2024 and 2025 trial years here.

In conclusion, manage your sunflowers very well! Shift focus from sclerotinia control to managing other sunflower diseases, such as rust and Phomopsis, and keeping the full plant healthy to better fight infection. Other management practices to follow are appropriate nitrogen fertilization to prevent excessive vegetative growth, crop rotation of at least four years, control of broadleaf weeds that may also be a host and no-till management where sclerotia bodies on the soil surface form apothecia and then ascospores but have no host to reproduce.

Other resources

What exactly are corn, sunflowers and flax dealing with in this standing water and saturated soils?

Morgan Cott on July 2, 2026

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By Morgan Cott, Agronomy Extension Specialist – Special Crops, Manitoba Crop Alliance

The crops we grow and work with in Manitoba do not generally do well in extended periods of flooding or saturated soils. Roots and growing points need oxygen to develop, so plant growth is delayed in these conditions. Disease development is also escalated in wet, hot, humid conditions, so that is another impending threat down the road.

Timing has not been ideal for corn. If you have puddling or any degree of flooding or standing water, corn at V5 or smaller is at vulnerable staging for survival. The growing point remains below ground until V6 and I think most corn crops were moving into the V6 at the time of the June 23 heavy rainfalls. It can be very stressful for a crop to have excessive moisture arrive as the growing point emerges from underground. No matter where the growing point is in the plant, if it is below the waterline, conditions become anaerobic and it cannot “breathe.” While photosynthesis can still be occurring in parts of the plant above the waterline, root growth is restricted below the waterline and all nutrient and water intake is hindered.

At this point in the season, I want any standing water to recede quickly and I also want the air temperature to stay mild during that period so there is no rapid growth or additional stress. Already, a week after the heavy rains, there is very visible rapid growth in corn fields across southern Manitoba.

Partially flooded corn field. Photo by Eric Tyschinski, MCA summer student.
Partially flooded corn field. Photo by Eric Tyschinski, MCA summer student.

Sunflowers are equally stressed in anaerobic conditions. Even though their water use is very high, if the plant cannot breathe, it cannot grow. In these times of excess moisture, we don’t want the crop to be in standing water for longer than three days, and cloudy, mild temperatures are best to keep other stresses to a minimum. Unfortunately, sclerotinia development is a significant threat in these conditions, and as the fields dry out, humidity will be high and conditions will be favourable to development, so basal and stalk infections could become severe this year. Keep an eye on stressed sunflower fields to ensure new growth is still coming and plants are still photosynthesizing. 

Effects of excess moisture in flax are exactly what we would guess: it has a low tolerance to severe stresses and will not survive long. The estimate for flax in standing water is about three days before the crop really starts to struggle and yield will be affected. Fortunately, stem root diseases are only a minor issue in flax crops and the wet soil conditions won’t affect this crop as much as it would others with regards to disease intolerance.

With all crops, check for new growth regularly to determine how efficiently the crop is still working and developing. Dig up a few plants to assess root growth. In saturated soils, roots don’t need to grow downward to find moisture, so the benefits of a strong root system later in the season might be diminished. Root health may suffer, which will be identifiable by the colour of the root. These are all good assessments to continue until the soil water subsides, the field starts to dry out and the crop can grow as intended.

Partially flooded flax field. Photo by Eric Tyschinski, MCA summer student.
Partially flooded flax field. Photo by Eric Tyschinski, MCA summer student.

Helpful Resources:

What is the difference between GDD, CHU and RM? Why and when are they each important?

Morgan Cott on June 1, 2026

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By Morgan Cott, Agronomy Extension Specialist – Special Crops, Manitoba Crop Alliance

This is such a great question and I understand the reasons for asking. First of all, I think it is understood that GDD & CHU both basically measure how efficiently a day’s heat will benefit a growing or developing crop. One main difference between the two measurements is that CHU does account for extremely high temperatures (>30oC) that negatively affect crop development. CHU also looks at both the nighttime low temperatures (4.4oC as the base) and daytime temperatures between only 10oC (base) and 30oC (optimum ceiling).

GDD has historically been used to help estimate certain agronomic events like insect emergence, weed emergence, frost-free days and specific crop staging. My understanding is that CHU is used more for maturity than for the ability to accurately predict these different timelines throughout the season. This might be why certain seed companies use CHU and RM for maturity ranking and GDD for staging references.

Pride Seeds is an example of this, because they break down maturity with both CHU and RM, in addition to two key reproductive stages in GDD accumulation.

PRIDE hybrid

When calculating GDD or CHU, you will start from the day after corn was planted. It takes from 100 – 120 GDD for corn to emerge following planting, which is in ideal conditions, including soil moisture and soil temperature, which were variable this spring (and every spring). Start your calculations from day 1 until the day of emergence and see if that fits the above. Now that corn has emerged and is actively growing in your current conditions, continue to monitor accumulating GDD with the following formula. This will give you a head start on expectations during the growing season. When to expect pollination, for example. Note that this GDD accumulation in relation to corn staging is all in relation to each individual hybrid. A shorter season hybrid will need fewer GDD or CHU to reach black layer than a longer season hybrid, of course.

GDD formula
CHU formula

 

Helpful Resources:

How much 10-34-0 can be applied with my corn seed?

Morgan Cott on May 5, 2026

Oddly, I have had this conversation more this winter/spring than ever before. On paper, there is a finite answer. Anecdotally, there are a few different options and it is all dependent on soil type and soil conditions, moisture, etc.

First of all, side-banding any type of fertilizer is much safer than placing it with the seed. Some fertilizers are safe in certain quantities with the seed, but very few. Side-banding is much safer and provides quick access to the roots. Midrow banding is the safest method, but roots take that much longer to access the fertilizer row, which negates the “starter” effect. The other factor that indicates the level of safety is soil moisture; the drier the soil, the more risky it is to place any fertilizer with or near the seed.

I’m guilty of thinking that fertilizer toxicity to the seed is mainly due to the nitrogen content and a result of ammonia burn. Salt injury is actually more common and affects germination and early season growth, so applying fertilizers that have a low salt index in closer proximity to the seed is best, if any has to be close to the seed at all. Bonus points if there is good soil moisture at the time of fertilization.

As I mentioned, on paper there are defined rates of 10-34-0 that can safely be applied in-furrow with corn on 30” rows. This table shows those rates and placement that will help to avoid salt injury to the corn crop.

Table: Amount of 10-34-0 (gal/acre) to help avoid salt injury to corn grown in 30” rows.

After having some discussions with Manitoba corn farmers on various soil types, I did get some reasonable responses explaining increasing rates in heavier, wetter soils. But more importantly, decreasing the above rates in dry and/or lighter soils. These were purely anecdotal and not research-based.

I recommend being very conservative in 10-34-0 rates if you are new to trying this method of application, and especially if you are planting in dry conditions and/or coarse soil textures. Start small and have many conversations with your peers on their experiences with various rates of 10-34-0 in-furrow. Use that information to make a conservative decision of your own.

Remember, start your season with success and make smart choices. Do not make decisions that could get your crop off to a bad start. We live in Manitoba – Mother Nature is hard enough on us in spring.

CDC Triffid Testing Protocols Terminated

Morgan Cott on May 4, 2026

Manitoba Crop Alliance (MCA) works closely with industry partners to build relationships and collaborative opportunities. Through these industry relationships and discussions with farmer members, MCA has prioritized the importance of eliminating the CDC Triffid testing protocol on Canadian flax being exported into the EU, which has been in place since 2009. It has been over 13 years since CDC Triffid has been identified in any Canadian shipments destined for the EU. The termination of the testing protocol is great news for Canadian flax farmers and exporters and will hopefully lead to improved international trade of Canadian flax.

Read Agriculture and Agri-Food Canada’s full news release here: Removal of non-tariff trade barrier for flaxseed to the EU reflects confidence in Canada’s agricultural exports.

Making Every Pound Count: Nutrient Management in Corn

Morgan Cott on April 8, 2026

Fertility starts with the soil and the variables that make nutrients available to a growing crop.

Know Your Soil Texture

  • Clay – very fine, soils with >50% clay
  • Silt – rock & mineral particles that are larger than clay and smaller than sand. Soils with >87% silt
  • Sand – very coarse, soils with >70% sand
  • Loam – a balanced mixture of clay, silt and sand (approximately 20-40-40)

 

Soil Texture Triangle
Soil Texture Triangle

Soil texture determines a soil’s water holding capacity. Sand has low capacity to hold water and low water content at permanent wilting point (~10-15% v/v). Clay loam has a higher capacity to hold water, therefore has a higher water content at permanent wilting point (~15-20% v/v).

Relationship Between Soil Texture and Water Availability
Relationship Between Soil Texture and Water Availability

Nutrient Balance

Nutrient balance is vital to soil fertility and crop production. Nitrogen is most commonly the first and most limiting nutrient for non-legume crops, but without an adequate fertility blend with other nutrients, nitrogen use efficiency is not “maxed out” and suffers.

A poorly fertilized corn crop uses just a little less soil water over the season than an adequately fertilized crop, and yet fewer bushels of corn are produced per inch of water used. The properly fertilized crop is able to be much more efficient in water usage to produce more grain per inch of water used.

Nutrient Uptake

 Nutrient movement in the soil and uptake by plant roots is important to understand because it dictates where fertilizer placement best facilitates root uptake. Nitrogen and sulfur are very mobile in the soil and move via mass flow. This essentially means that they move with the soil water. As a plant transpires water, the roots are required to draw in more nutrient-rich soil water and they do this by creating tension that draws the soil water to the roots. The rate of transpiration is related to environmental conditions, so poor soil moisture or cold temperatures,  for example, will decrease the rate of transpiration, therefore decrease uptake of soil water (and nutrients) via mass flow. Phosphorus and potassium move in the soil via diffusion, meaning that with the help of soil moisture, the nutrients move from areas of high P or K concentration to areas of lower P or K concentration. As the nutrients are absorbed by plant roots and moved up into the plant, the roots become an area of low concentration, thereby drawing nutrients towards the roots from a higher concentration zone.

Nutrient Mass Flow & Diffusion
Nutrient Mass Flow & Diffusion

Nitrogen

 Exact nitrogen rates in corn are still hard to identify and perfect. Modern corn hybrids have improved in nitrogen use efficiency, but more than that is required to optimize nitrogen uptake. We have already discussed how nutrient balance in the soil optimizes nutrient uptake, but soil conditions and the environment above and below the ground play major roles in this as well.

In 2016-17, John Heard, former Manitoba Agriculture Soil Fertility Specialist, performed a nitrogen use and uptake project in corn to identify whether nitrogen recommendations needed to be updated. Following this project, Dr. Don Flaten’s graduate student, Lanny Gardiner, then began his Master’s research, in 2018, on a similar study, “Optimum Nitrogen Fertilizer Management Strategies for Modern Corn Hybrids in Manitoba”. The two studies complemented each other with similar findings, which were the following:

Nitrogen requirement to achieve the economically optimum yield for higher and lower potential yields. John Heard, 2022 – Profitable Nitrogen Rates.

 

A site that has a “lower” potential yield would be one that could be considered to have poor productivity. This may include variables like drainage issues, salinity, soil productivity, or poor crop management choices like delayed seeding, compaction issues, or delayed weed control, for example.

Dry sites in 2018-19 needed more nitrogen to achieve similar yields because dry soils have less mineralization of soil organic matter and decreased mass flow movement of nitrate-N to the plant root.

Phosphorus

Phosphorus is required for plant growth and seed development, therefore should be placed at least in a sideband for availability in early growth. It is not very mobile in the soil and will not get leached in spring conditions like we know nitrogen will in high moisture.

The general recommendation for phosphorus requirements in corn is +0.6 lbs of P per bushel of yield. Uptake is equivalent to 0.6 lbs P/bu and removal is 0.36 lbs P/bu, so it is very important to consider what your preferred level of phosphorus in the soil is following a corn crop.

Applying phosphorus at planting is the best practice for availability. The safest placement is in a 2×2 band but proceed with caution if applying P in a sideband with other nutrients. P is used throughout the season and some farmers choose to apply additional P in-crop, which can be a good practice but not studied thoroughly in Manitoba to come to an economical conclusion.

Potassium

Corn requires 1.28 lbs K per bushel, but will only remove 0.21 lbs K/bu. In a 150 bushel crop, uptake will be about 192 lbs of potassium and removal will be 32 lbs of potassium because so much of the nutrient stays in the vegetative tissues. Manitoba soils are generally high in potassium, but it is important to monitor and fertilize to maintain K supply in the soil. 

To support a corn crop, ensure there is greater than 200 ppm of K in the soil. When levels start appearing in the 100’s, farmers may see benefits from adding K at this time. Livestock farmers may find a significant benefit from applying manure in this situation.

If potassium becomes deficient, the plant will pull the nutrient from older leaves to feed the younger leaves, developing grain, etc., just like nitrogen, and that is when deficiency symptoms appear.

Sulfur

Sulfur is not needed in high quantities like our other three macros, but it is required for corn development and chlorophyll production, therefore photosynthesis. 

Corn does not necessarily respond to additional sulfur fertilizer, unless soils are already deficient, whereby a yield response will occur with fertilization. Farmers should be aware of sulfur levels in the soil and be prepared to apply sulfur when levels decline. Sulphate sources are typically available to the crop immediately, so timing of application can be flexible. If deficiency symptoms appear (interveinal striping), rescue applications can be effectively made. 

Additional Resources on Corn Fertilization:

2025 Sunflower Crop Survey Results

Morgan Cott on March 3, 2026

The Sunflower Crop Survey is led by the National Sunflower Association and carried out by a network of volunteer from universities, government, producers and industry, including Manitoba Crop Alliance (MCA). Participating regions include Manitoba, North Dakota, South Dakota, Minnesota, Nebraska, Kansas, and Colorado, where data is collected on a number of variables and compiled to document sunflower growing conditions, pest challenges and yield. The survey is conducted on alternate years, with fall 2025 being the most recent.

Manitoba and U.S. Survey Overview:

191 Sunflower fields were samples across all participating regions. The following management practices were observed:

  • Sunflower type: 7% confection; 93% oilseed
  • Water Management: 2% irrigated; 98% dryland
  • Tillage: 24% conventional; 21% minimum; 55% no-till

The survey has a large focus on pest pressures. The cumulative pests that were monitored across all locations were as follows:

  • 34% of fields had blackbird damage
  • 11% of fields had seed maggot damage
  • 8% of fields had bud moth damage
  • 8% of fields had sunflower midge damage
  • 14% of fields had long-horned beetle damage. It is important to note that long-horned beetle has not been found in Manitoba during this survey, or in anecdotal scouting events, however there are fields sampled in this survey that are extremely close to the MB-ND border that had long-horned beetle (dectes) damage in both 2025 and 2023.

Manitoba Overview:

12 sunflower fields in 10 municipalities were sampled in Manitoba from the RM of Brokenhead to the RM of Two Borders:

  • Sunflower type: 100% oilseed
  • Water Management: 100% dryland
  • Tillage: 25% conventional; 67% minimum; 8% no-till
  • Row Spacing: 50% had 20” or narrower row spacing, 50% had 22” to 30” row spacing

Each field was surveyed in two locations and a small sample area of two rows by 25 feet was used to gather data in each of the two locations. Pests were recorded, full plants were assessed, and seed samples were taken.

The highest yield in a sampled area was 2,792 lb/ac.

The lowest yield in a sampled area was 983 lb/ac.

The average yield among all 12 fields sampled was 2,000 lb/ac.

Yield-Limiting Factors

  • Seven of the 12 fields were limited mainly by disease, in general.
  • One of the 12 fields was limited mainly by bird presence and feeding.
  • One of the 12 fields was limited mainly by row spacing, as it was a solid-seeded field. This was hard to measure yield on such a small scale with fewer plants per foot of row.
  • Three of the 12 fields were limited mainly by weed pressure, with one of them being specifically limited by kochia infestation. In the 12 fields, weed pressure was generally quite low and not at all a concern in 75% of the fields.
  • Secondary limitations in the 12 fields sampled included wildlife (i.e., elk), lodging, insect, sclerotinia and birds.

Disease Presence and Severity

Sclerotinia:

  • Sclerotinia basal stem rot was minor in all fields sampled. Half of the fields had no basal wilt present. One field had up to eight plants with basal wilt symptoms, which would be estimated at about 8% of the sample size in that field.
  • Sclerotinia mid-stalk rot presence was similar to basal stem rot. Eight fields had zero or just one plant infected; one field had six infections and another had seven infections; two fields had 10 or 12 plants infected, respectively.
  • Sclerotinia head rot were higher, in general. Half of the fields had four or less infected heads; three fields had 5-7 infected heads, one field had 10 infected heads, one field had 12 infected heads and one field had 22 infected heads. This last field did report the lowest yield as well, unsurprisingly.

Downy Mildew:

  • Low incidence among all fields, except one that had four affected plants

Phomopsis:

  • Six of the 12 fields had almost negligible one or zero plants with Phomopsis infections.
  • Five of the 12 fields had from six to 15 stalks infected with Phomopsis.
  • One field had 40 plants with Phomopsis infections, which was roughly 80% incidence in that location.

Phoma:

  • Incidence was much higher and present in relatively high numbers in each of the 12 fields, except for two that had zero incidence.
  • The three highest fields of incidence had 32, 42 and 46 plants with Phoma stem infections.

Rhizopus:

Rhizopus has not been a disease of concern in Manitoba, simply because it can largely go undetected. The last time the sunflower survey was conducted, in 2023, three of eight fields had Rhizopus in the sample set.

Rhizopus can be identified on a sunflower head by the presence of gray, fuzzy mycelium, usually viewed on the face and between developed seeds. The disease prefers warm, humid environments and most often originates via wounds on the back of the sunflower head. Infections do affect yield by limiting seed fill and potentially causing head drop in severe cases.

Rhizopus on sunflower head. Photo courtesy of North Dakota State University.

Sunflower Rust:

Sunflower rust was very minimal in 2025 and was found in four of the 12 fields at very minor severity in September. The highest severity was one field that exhibited 0.75% of leaf area on the top four leaves being affected by rust pustules.

Verticillium Wilt:

Verticillium wilt is also uncommon in sunflower fields in Manitoba, though it was found in the 2025 survey. Symptoms can include leaf mottle, or interveinal chlorosis, and a greenish discolouration on the stem, where further inspection is required. By splitting the stem at the base of the plant, discoloured vascular tissue is visible around the pith.

  • Three fields were found to have Verticillium wilt with five, six and 12 plants infected, respectively.

Insect Presence and Severity

Sunflower Midge:

  • Seven of the 12 fields had Sunflower Midge damage.
  • The field with the greatest damage had seven affected heads.

Sunflower Seed Maggot:

  • Three of 12 fields had Sunflower Seed Maggot damage.
  • Each of the three fields had one plant affected.

Sunflower Bud Moth:

  • Nine of 12 fields had Sunflower Bud Moth damage, specifically on the sunflower head.
  • The field with the greatest damage had 14 affected heads, followed by a field that had 10 affected heads.
  • The remaining seven fields had minor damage noted.

Blackbird Presence and Severity

Blackbird feeding was noted in five of the 12 fields sampled. Assessment is based on the area of the sunflower head with missing seed that has recognizably been fed on by birds. Seed is usually completely missing and sunflower seed shells may be found on or near the plant in question.

All four fields with damage noted were quite minor in the sampled areas, the greatest having about 6.35% of the total head area missing seed.

Other Yield Factors

Actual plant populations of sampled fields ranged from 12,200 to 24,400 plants per acre. Strangely enough, the lowest populated field also had the smallest head size, averaging about 5.75” in diameter. The field with largest head size overall was 8.45” diameter. Generally, head size was smaller in the sampled fields than an average year would see, but this may have been a result of dry growing conditions during head development.

Seed size was reported to be good to excellent and seed fill ranged from 70 – 99% across the 12 fields. Centre seed set was reasonable, but there were some fields that did have up to two inches of the head centre undeveloped, which drastically affects yield.

MCA would like to thank all 12 participants of the Sunflower Survey for allowing us to use your fields for this project. Also, thank you to Manitoba Agriculture oilseeds specialist Sonia Wilson and crop production extension specialist Callum Morrison for your help surveying several fields. Finally, thank you to Dr. Ahmed Abdelmagid, research scientist and oilseed pathologist at AAFC Morden, for surveying several fields and collecting various samples of sunflower diseases to understand the scope of disease presence in Manitoba.

2025 Manitoba Corn Disease Survey Results

Morgan Cott on January 30, 2026

Anne Kirk, Manitoba Agriculture
Morgan Cott, Manitoba Crop Alliance
Simon Huang, Manitoba Agriculture

A corn disease survey was conducted across Manitoba in September of 2025.  Crop disease surveys are important for documenting the severity and geographical distribution of various diseases. Results from disease surveys provide warning about new diseases and help to prioritize where future research is needed. 

Methods

A total of 54 fields were surveyed across Manitoba to document the prevalence (% of fields having infection) and incidence (average % of plants showing infection within infected fields) of various corn diseases. Field were surveyed in September around the beginning of crop maturity.  

Plants were visually assessed for the presence of Goss’s wilt (Clavibacter michiganensis subsp. nebraskensis), common rust (Puccinia sorghi), common smut (Ustilago maydis), head smut (Sphacelotheca reiliana), and stalk rot.  Holcus spot (Pseudomonas syringae pv. syringae) was recorded in some but not all fields.  In each field, 50 plants were surveyed in a “W” pattern, where the five points of the “W” were at least 50 paces apart and 100 m from field edges.  The presence or absence of disease was noted for each of the 50 sampled plants per field, except for Goss’s wilt and holcus spot.  Goss’s wilt and holcus spot were simply recorded as present or absent for each field.

Results
At crop maturity Goss’s wilt was found in 54% of the fields sampled, making it the most common disease found in the fall survey.  Holcus spot was found in the majority of fields surveyed in the central region, but prevalence is not reported as all surveyors were not assessing plants for holcus spot. Head smut, common rust, stalk rot, and common smut were found in 33%, 11%, 7% and 6% of fields surveyed, respectively (Table 1). 

 Table 1. Results of the 2025 corn disease survey.  Prevalence (% of fields having infection) and incidence (average % of plant showing infection within infected fields) for each region and for all fields surveyed.

Region

Common Rust

Common Smut

Head Smut

Stalk Rot

Anthracnose Stalk Rot

Goss’s Wilt

Central (35 fields)

      

    % Prevalence

14

9

29

6

0

71

    % Incidence

17

8

3

13

0

n/a

Eastern (9 fields)

      

    % Prevalence

0

0

22

11

0

44

    % Incidence

0

0

8

2

0

n/a

Interlake (2 fields)

      

    % Prevalence

50

0

0

50

0

0

    % Incidence

10

0

0

6

0

n/a

Southwest (8 fields)

      

    % Prevalence

0

0

75

0

0

0

    % Incidence

0

0

5

0

0

n/a

Manitoba (54 fields)

      

    % Prevalence

11

6

33

7

0

54

    % Incidence

16

8

4

9

0

n/a

Acknowledgements
This survey was supported by Manitoba Agriculture and Manitoba Crop Alliance.  Thank you to the grower co-operators who allowed for their fields to be surveyed and provided surveyors with field information. 

Contributed by Anne Kirk, Cereal Crop Specialist with Manitoba Agriculture.

Emergency Use Registration: Avian Control For Use as Blackbird Deterrent in Sunflower

Morgan Cott on September 2, 2025

Manitoba Agriculture, Manitoba Crop Alliance and Avian Enterprises® are pleased to announce that Avian Control® Bird Repellent has been approved for use to deter blackbird feeding in sunflowers in Canada.

The need for a product used to deter blackbirds from feeding on sunflower crops has been identified as a need in Manitoba due to the significant losses recorded by farmers. Sunflower seeds are particularly vulnerable to predation by blackbirds due to the high nutritional value and easy accessibility.

After nesting, blackbirds form large flocks and begin feeding in grain fields nearby. Feeding begins in sunflowers soon after petal drop and most of the damage occurs during the following three weeks. Peak concentrations of blackbirds occur in mid-September, coinciding with the crop reaching physiological maturity.

Farmers have alternative options to applying a deterrent, like Avian Control ®. Alternate practices include planting far away from roosting areas, like cattail marshes and woodlots, or planting at the same time as neighbours to spread feeding damage over more acres during seed maturity. Insect and weed control will reduce the pre-season food source for blackbirds before the crop reaches a susceptible stage for feeding. Delaying cultivation or harrowing of crop stubble in neighbouring fields increases alternate feeding area for hungry birdlife. Desiccation to advance harvest and getting the crop harvested as soon as possible also reduces exposure.

Another effective management practice is to control cattail production areas, which reduces nesting sites for blackbirds. Managing cattails does take a significant amount of time and should be a collective project for local farmers to deter blackbirds from roosting in a large geographic area, to be effective. Scare methods, like bangers or sound devices, to frighten birds away from the area have achieved different levels of success, but birds tend to start tolerating certain tactics after a period and return to host crops.

How does Avian Control work?

The active ingredient in Avian Control is methyl anthranilate. This active irritates a bird’s trigeminal nerves, which are sensitive to smell and taste, and causes a temporary, non-harmful, but unpleasant sensation to the affected bird’s eyes, beak and throat. The first birds to visit the treated field associate this discomfort with that location and communicate this information to the rest of their flock, instructing them not to feed there.

Methyl anthranilate is a food-grade additive, naturally derived from Concord grapes. It is a non-toxic, non-lethal and humane repellent, recognized as safe for humans and other animals. Due to the nature of this product, it does breakdown on surfaces much quicker than pesticides and will likely need to be applied more than once for continued efficacy.

Crop Specific Instructions for Avian Control

  • Apply Avian Control to ripening sunflowers before damage by blackbirds begins to occur
  • Do not apply when crop is wet or rain is expected
  • Repeat treatment at 6 – 8 day intervals if significant crop damage from blackbirds begins to occur
  • Avian Control may be applied up to the day of harvest
  • Use with non-ionic surfactant at 0.06 – 0.25% v/v
  • DO NOT exceed 5 applications per year

For full Avian Control label on sunflowers, click here.

Please contact Avian Enterprises for more information on Avian Control and product orders:

Jon Stone
President, Avian Enterprises
1 (888) 707-4355
https://aviancontrolinc.com/products/avian-control/ 

Sunflower Survey 2025

Morgan Cott on June 30, 2025

In partnership with National Sunflower Association, every other year Manitoba Crop Alliance and Agriculture and Agri-Food Canada participate in a Sunflower Survey. The collaboration includes several states in the U.S. where sunflowers are grown, so participation in Manitoba is beneficial to the dataset. 

Some of the factors included in the survey are:

  • Field analysis: population, head size, seed fill, yield calculations
  • Weed pressure: weed prevalence
  • Insect Pressure: insect incidence and damage severity
  • Disease Pressure: disease incidence and severity
  • Blackbird Presence: percent blackbird damage estimate
  • Other Limiting Factors: environmental, uneven growth, herbicide damage, plant spacing, and more.

Sunflower diseases make up the bulk of the survey since, agronomically, they are the greatest concern to the crop. The requirements are to assess ten diseases in incidence (number of plants) and severity (% damage to affected plants) of sunflower rust, specifically. 

MCA is funding the participation of AAFC’s oilseed and Pulse Crop Pathologist, Dr. Ahmed Abdelmagid, on this project. Dr. Abdelmagid participates in the field survey and also analyzes stalk disease samples from each field to determine various strains present in Manitoba sunflowers.

This survey is important in a “minor” crop for Manitoba in order to help farmers understand the specific pressures they are working against. Together with AAFC and Manitoba Agriculture, we can use the survey data to create extension for farmers and agronomists that will strengthen the crop’s success on the Prairies. Paired with the U.S. data, we are able to make fair comparisons and and identify Manitoba’s successes and areas that need improvement. This leads to more directed research projects in the future and extension work with farmers on specific topics.

The 2025 Sunflower Survey will begin in late August. MCA is looking for several sunflower fields across the province to include. Please contact Morgan Cott at morgan@mbcropalliance.ca or 204-750-2489 if you or someone you know would like to be contact this summer to be involved in the survey. This tends to be a quick visit to collect data on all points mentioned above and the farmer will be kept informed throughout the short process.

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