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How can I estimate the rate of drydown for my mature grain corn?

Morgan Cott on October 7, 2026

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

I was hearing rumours of some grain corn being harvested last week with ranges of 25-33% moisture, which is pretty darn accurate for the last week of September. Considering a few days of fog have passed and some beautiful, mild temperatures are ahead, let’s talk about drydown rates to expect in October.

Prior to physiological maturity (black or brown layer), grain fill occurs during the reproductive stages of corn development. As grain fill progresses, dry matter replaces water content in each kernel. Water is removed from the kernel via the pedicel (point where the kernel is attached to its cob) and via evaporation during the grain fill period. As physiological maturity is reached and those cells that connect each kernel to the plant die, water is no longer lost at that point of contact and can only occur via evaporation, which is much slower.

So, black layer will occur consistently when the grain reaches about 30% moisture and from that point, we rely mainly on weather for evaporation and, to a lesser degree, kernel characteristics of different hybrids. Unfortunately, September 2026 was quite humid and damp, overall, which is the opposite of what farmers require for grain drydown. Aside from environmental factors, hybrid traits also play a major role in the plant and grain’s ability to dry down in the field. Here are some noted characteristics:

Husk leaf number – the fewer, the better for drydown;
Husk leaf thickness – the thinner, the better for drydown;
Husk leaf senescence – the quicker, the better for drydown;
Husk coverage of the ear – the poorer the coverage, the better for drydown;
Husk tightness – the looser, the better for drydown;
Ear declination – the earlier the ears “drop”, the better for drydown;
Cob diameter – the narrower, the better for drydown; and finally,
Kernel type – flint-dent kernels dry down more slowly than dent types because they have a harder kernel.

Moving on to the actual question, how to estimate drydown in the field. October is starting out beautiful with sunshine and warm temperatures from mid-teens to 20^oC. The only things that would make this better drying conditions would be even warmer temperatures and stronger breezes, that are also warm. The general estimation is that during these warm temperatures, you can assume up to 1% moisture loss per day, but I wouldn’t bet the farm on that information!

According to Ohio State University, when the grain is between 30 – 25% moisture, it takes approximately 30 GDD’s to lower moisture by one point. So, 150 GDD’s to lower moisture from 30 – 25%. After that, 45 GDD’s are required to lower the moisture from 25 – 20% (225 GDD total). This is the easy answer and calculation, but there are other factors at play, of course. These drydown rates won’t be the same for every hybrid and will very much depend on weather conditions. I took a quick look at Carman’s Growing Season Report and see that from Oct 4 – 5^th (24 hours), we only accumulated 3 GDD in that period. However, on October 6^th, as I write this, the air temperature is 21^oC and the sun is warm with a gentle breeze, so I assume we are accumulating more GDD today than yesterday. I will also assume that we could be expecting drydown on days like this to be about 0.5 – 0.75% daily, if we are being conservative. As the temperatures cool a bit next week, calculate roughly 0.25 – 0.5% per day, as long as the sun is shining and there is a breeze. Using that information and the Weather Network’s 14 day forecast, my very rough estimate would be that we could lose about 6 – 10% moisture over the next two weeks, depending on potential rains and cloud cover, plus overnight low temperatures.

The only thing we can do is make a best-educated guess on how long it will take the crop to drop “x” points in moisture given the information above and what you know about the hybrids you grow. Maybe you have experience with a certain hybrid and that it took seemingly forever to drop those last 3% in the past, or maybe you have experienced the opposite. Keep detailed notes so you have a record for the future, so when you’re planting early (or late) in spring 2027, you have more decision-making tools on what to plant, and where.

Wishing you all a very safe and productive corn (and sunflower) harvest!

Other resources

Manitoba Agriculture – Harvesting Grain Corn in Late Fall
Manitoba Agriculture – The Facts of Corn Drydown
OSU Extension, Agronomic Crops Network – Cool Weather and Corn Dry Down

Is fungicide actually effective on Sclerotinia head rot in sunflower?

Morgan Cott on August 5, 2026

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

Manitoba Crop Alliance – Sclerotinia ID Card
Manitoba Agriculture – Sclerotinia in Sunflowers
National Sunflower Association – White Mold

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

Morgan Cott on July 2, 2026

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.

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.

Helpful Resources:

The Impact of Mid-Season Excess Moisture
Purdue University: Effects of Flooding or Ponding on Corn Prior to Tasseling

Does applying a fungicide at herbicide timing to control cereal leaf spot diseases in wheat and barley provide a yield boost?

Coles Ag on June 2, 2026

By Andrew Hector, Agronomy Extension Specialist – Cereal Crops, Manitoba Crop Alliance

This question comes up regularly which makes sense. Early season outbreaks of fungal leaf spot diseases like Tan Spot do occur in Manitoba, such as in 2024. To answer this question, we need to dig into the research.

There have been a few studies done in Western Canada over the last 15 years investigating this very practice in both wheat and barley.

In both these studies fungicide application timings were evaluated on their impact on leaf spot disease severity, overall crop yield, and economic returns of the practice. In both studies, it was found that a foliar fungicide application at herbicide timing (2-3 leaf) did not lower upper canopy disease incidence and severity compared to the check (no treatment or herbicide only).

For barley, the western Canadian study found that the half rate foliar fungicide treatment at herbicide timing provided only a small increase in crop yield compared to the herbicide only check. The study examining spring wheat’s response to early season fungicide found that fungicide application at herbicide did not significantly improve crop yield compared to the untreated check. Across both studies, researchers concluded that fungicide timing for leaf diseases should focus on protecting the upper canopy, particularly the leaves that contribute most to yield.

There has also been some research on this topic out of North Dakota. Andrew Friskop from North Dakota State University recently compiled replicated foliar fungicide timing trial data from 2008-2024. He evaluated the yield response based on “disease risk” scenarios determined by previous crop, variety resistance, tillage, environmental conditions and disease onset.

Figure 1. NDSU disease risk categories for development of residue-borne foliar diseases.

His finding suggests that under moderate and high-risk scenarios, (where wheat was grown on wheat stubble, a susceptible variety was planted and the disease [tan spot] was established early and firmly in the crop), a fungicide application at tillering could provide a small benefit of 2.2 – 3.7 bu/ac. In basically all other production scenarios he found that a foliar fungicide application at tillering would provide very little yield response.

Figure 2. Summary of yield response by disease risk level for early season fungicide application.

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

Morgan Cott on June 1, 2026

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 (>30^oC) that negatively affect crop development. CHU also looks at both the nighttime low temperatures (4.4^oC as the base) and daytime temperatures between only 10^oC (base) and 30^oC (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.

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.

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.

New, promising flax varieties for Manitobans

Morgan Cott on March 4, 2025

Manitoba flax farmers (and upcoming flax farmers) will soon have full access to a new flax variety, CDC Esme. As of spring 2025, CDC Esme is available to seed producers across the province, as long as they have been able to access it from seed dealers.

As stated in the Secan Technical Bulletin for the variety, CDC Esme is a large seeded, high yielding brown seeded flax variety with good lodging resistance and late maturity. Esme proves to be a strong yielder in MCVET trials across several site years, with oil content similar to check varieties. Statistics show an average of 2 cm shorter than CDC Glas, which is a beneficial trend in Manitoba, where farmers are trying to reduce flax straw and residue.

Dr. Bunyamin Tar’an and his team at the Crop Development Centre in Saskatoon developed CDC Esme and have several more flax lines that have strong potential for registration on the Canadian Prairies. Most recently, Tar’an had an experimental flax line that has been recommended for registration via Canadian Food Inspection Agency. This line, currently named FP 2608, will undergo a registration process and could likely be available for seed production in the next two years.

FP 2608 has been a promising yielder in the Flax Co-op trials performed in Manitoba and is a consistently strong yielder. It appears to be quite tolerant of pasmo infections in past reports, and oil content and yield has been ranked very high amongst other varieties and lines. Tar’an has noted that FP 2608 had considerably strong performance in the more northern Co-op trials in Manitoba, which perhaps displays its ability to thrive in less diverse rotations.

MCA is very proud of our relationship with Dr. Tar’an and are very excited about his future work in flax breeding. Some new work that he is working on includes “Accelerated Breeding Strategy for Flax Improvement” which looks at developing inbred populations in a shorter term than is current reality. This would mean that future varieties could potentially be brought to the market more quickly and readily than they have in the past. Another highlight of Dr. Tar’an’s work is that he is committed to reducing straw content while increasing seed production in future varieties. He has had to delve back in time and use flax’s wild ancestor, Linum bienne. By using historial genetics, Tar’an can benefit by breeding their old, shorter varieties with new modern varieties that have bushier plant structure, therefore, higher yielding qualities and improved harvestability.

Flax can have a strong future on the Prairies and Manitoba Crop Alliance is supporting that possibility for our farmers. It is a crop that requires patience and consideration, which we believe Manitoba farmers are great at and can help us solidify the flax industry on the Prairies. Discussions with farmers that have been growing flax successfully for several years tell us that it is one of the top most profitable crops on their farms because they are willing to put an extra effort in to the crop. In this case, it doesn’t mean inputs, directly. These farmers are treating flax like the special crop that it is; slowing down and using precision and sustainable practices to support the germination of a tiny seed into a beautiful and profitable crop.

Please contact the MCA’s Agronomy Extension Specialist for Special Crops if you are considering growing flax or currently work with flax and are interested in more agronomic information.

Research on the Farm: Flax Plant Population Trials Summarized (2022 – 2024)

Morgan Cott on February 5, 2025

Manitoba Crop Alliance’s Research on the Farm program looks at common agronomic, crop-specific concerns on field-scale, replicated trials in commercial fields. 2024 saw the flax plant population trials completed with 19 site-years of data.

The objective of this specific trial was to quantify the agronomic and economic impacts of various plant populations in flax production in Manitoba. A lack of genetic improvements in flax varieties in recent years raises the question of whether farmers can either increase or decrease their planting populations with improvements in quality and/or yield. Farmers took to the field to make that final decision.

Figure 1: MCA Research on the Farm: Flax Plant Population Trial locations from 2022 – 2024

Tone Ag Consulting performs MCA’s Research on the Farm trials in all 6 of our crop-types. In this specific trial type, they are helping the farmer with planting and harvest of the plots, plus taking some key information during the growing season. This includes soil sampling in the spring followed by growth stage notes and precipitation data during the season.

Table 1: Three-year summary of flax plant population trial for 19 site years. Zero of the 19 site-years contributed statistically significant yield differences which would provide profit for the farm, based only on seed prices.

When looking at this full data set, it doesn’t necessarily give a farmer the details they are looking for. At the end of the day, they want to know the ROI for each treatment, which includes spring seed costs and flax prices off the combine. Simply stated, if the “high” planting rate outyielded the “low” and “check” planting rates, it may have only been marginally, therefore the higher seed cost of planting at a high rate was likely not the economical choice.

Table 2: Three-year economic summary of flax plant population trial for 19 site years. Net profit per acre was calculated using estimated seed cost in spring 2024 and contract pricing in fall 2024.

According to this small data set in Manitoba, farmers appear to seed on the heavier side of what is necessary for their management practices. Experience determines what works best on any given field, in addition to being mindful when it comes to general flax management. It is a special crop and requires a certain amount of care and precision to achieve profitable yield, but it absolutely is realistic in Manitoba.

Planting populations are reasonably simple to set up on-farm and MCA recommends farmers make the effort to periodically do this same testing. 2022 and 2023 were dry years in areas of Manitoba and 2024 had much more precipitation. It is important to continue to collect data in years of varying precipitation to determine planting rates that work better on your farm in all environments.

Tone Ag Consulting carries out MCA’s ROTF trials in all six of our crop-types. They assist the farmer with plot planting and harvesting, then capture key information throughout the growing season. This includes soil sampling in the spring, followed by growth stage notes and precipitation data during the growing season.

Phantom Yield Loss

Morgan Cott on December 4, 2024

Phantom Yield Loss – A phenomenon related to yield loss with little to no explanation why, aside from letting the grain dry naturally, prior to harvest.

Farmers who have to pause harvest, after opening a field, do record decreased yields when they return to continue combining. A few things come to mind when considering what the losses are a result of. Could it be ear drop? Or lodging is a common occurrence, the longer the crop stands in the field and is exposed to wildlife, snow, or wind. Another consideration is that as the grain dries in the field, it does loosen from the cob and can fall to the ground when disturbed. Low moisture grain is also susceptible to cracking or breakage at harvest, resulting in losses.

Speaking to Manitoba farmers, it appears that phantom yield loss is caused by none of the above. All the obvious culprits (ear drop, lodging, kernel shattering) can be accounted for and there are yield penalties beyond these factors, still.

Purdue University performed research on this topic in the early 90’s – before the phenomenon even had a name. The project looked at three hybrids over the course of four years and measured kernel dry weight until physiological maturity and again after maturity until they were ready for harvest. The study found that kernel dry weight increased until reaching physiological maturity, which occurred at about 25% moisture for all three hybrids. Following maturity, during the dry down period, kernel dry weight decreased by an average of 1.1% for every one per cent decrease in grain moisture content. This is an average across three hybrids in the four years of study. There was one year where none of the hybrids experienced any significant changes in kernel dry weight. The “bottom line” of the project is that there is a potential average 1% yield loss per point decrease in grain moisture content. That is to say that if a field is left to naturally dry down 5 moisture points following physiological maturity, there is a potential +/- 5% yield loss.

So, how does this occur and why? We now know that this is part of the drying process, but why is so much dry matter being lost as the grain dries a small amount?

Quite simply, physiological maturity occurs and each kernel develops a “black layer” where it connects to the cob and had gained access to nutrients and water throughout the season. Once black layer is achieved, grain continues to use up the starch and sugar reserves, which decreases kernel dry weight and quality. Grain is typically alive following black layer until it has dried down to around 15% moisture, so it is not surprising that this process results in loss of dry matter.

Unfortunately, it is impossible to predict losses as a result of this phenomenon. Factors affecting losses include harvest timing, soil type, hybrid/genetics, and of course, environmental factors. That being said, it is difficult to predict what genetics are most susceptible to respiration losses following black layer, so that isn’t something that would normally factor into hybrid choices. Earlier harvest timing is the best way to avoid significant losses, in this case. As mentioned, losses are impossible to predict, but measuring drying costs against the alternate potential yield loss is key in finding the best management practice for your farm.