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Ontario Grain Farmer Magazine is the flagship publication of Grain Farmers of Ontario and a source of information for our province’s grain farmers. 

Field Observations


July 11, 2024

This week, the winter wheat harvest continues. Corn is well over waist high in some areas, with tassels beginning to emerge on early planted corn. Note that the first report of tar spot was reported in Ontario this past week. Soybeans are steadily growing vegetatively, with many moving into reproductive stages. Scattered showers have kept fields well-saturated in a number of regions.



Early planted corn is nearing the end of the vegetative stage, and the number of potential kernels is finalizing. Under severe stress, kernel numbers will be reduced. We will start seeing  tassel emergence in the earlier planted fields shortly. When the last branch of the tassel emerges from the whorl, we will reach the VT stage. (VT is for the vegetative tassel stage.)

Tar spot was confirmed in Ontario on July 5 in Elgin County. This is similar to other years, with ideal canopy and environmental conditions for this time of year. Current Tar Spot infections will occur in fields with a history of tar spot and those with a larger canopy, like the earlier planted crop, as the conditions of the larger canopy are ideal for disease development. Late planted corn that has not canopied yet or wide rows and small corn would not be a concern until the crop reaches the V8 to VT timing as the canopy is large enough to be conducive to infection. These late fields may miss the early calendar date but may still be impacted as the disease develops this summer. Scouting fields is the only sure way to confirm disease infection, but apps like Tarspotter can aid in identifying risk levels based on weather forecasts. This disease is now endemic in western Ontario as we have had several years of infection, and the disease overwinters in soils. The disease infection will start lower in the canopy if the disease infection is from spores within the field.

Adjacent U.S. states, Michigan and Indiana, are also reporting tar spot infections. This indicates that more spore development is occurring sooner this year, which can lead to future infections in our fields as the spores are released and wind patterns move spores into unaffected areas. The airborne spores will infect the top of the canopy.

Scouting and identifying the location of the disease in the canopy helps to indicate if the field was self-infected or if the infection was airborne. Either way, you have the disease, and the earlier you can treat the crop, the more leaf tissue and plant health you can preserve to maintain your yield potential. Timing is important as most fungicides are good only for +/- 14 days. The sooner you spray, and if the growth stage is early, the more likely you will need a second spray if conditions are favourable for the disease. Select fungicides that control tar spot, as not all fungicide products control tar spot. If you are spraying when the silks are still green, consider your risk of gibberella ear rot, as it will produce DON mycotoxin. A tank mix with a product that also controls gibberella ear rot should be considered if your spray timing is at the green silk stage (R1). There will be more about that in the coming weeks.


Soybean stages range from still in vegetative growth to R2 (full bloom). At R2, plants have an open flower at one of the two uppermost nodes on the main stem. From R2 to R4, the soybeans are rapidly uptaking water and nutrients (with uptake peaking at R4). It is important to keep soybeans healthy for optimum yield.

Watch for diseases like white mould and insects like aphids (see further info in last week’s field observations).

The Ontario Crop Protection Hub is a great reference for herbicides, fungicides, and insecticides registered in Ontario. Always wear PPE and follow the label.

Double-crop soybeans are being planted after winter wheat when possible. More information on double cropping soybeans and things to consider when double cropping can be found in last week’s field observations.


Winter wheat harvest has continued, as weather allows. Harvest was wrapping up in the deep southwest region before tropical storm Beryl hit, while the rest of the province is gearing up to make a major move on harvest after we dry up from Beryl. Harvest in the province would be approximately 10 to 20 per cent complete province-wide. So far, wheat is coming off close to dry in the 16 to 13 percent range , with average yields and good quality

As the harvest progresses and moves across the province, keeping an eye out for Fusarium is imperative. Using a visual scale to estimate the severity of Fusarium across fields can help target which fields to harvest first. The aim would be to harvest the fields with the highest severity first, as DON levels can almost double each time a storm rolls through. When harvesting, aim to set the combine to blow out Fusarium-damaged kernels (if the moisture is higher, this may be more challenging). Some key tips to do this are in the link above. Note that lodged wheat has an increased potential for Fusarium infection and DON production. More can be found here.

Another concern on farmers’ minds is the chance of sprouting with the continuation of scattered rain showers.

The winter barley harvest is wrapping up.

Spring cereals are closing in on the boot-to-head stages.

Northern Ontario has also been experiencing high volumes of rain, which has crops developing well, although there have been excessive moisture challenges like most of the province.

July 4, 2024

Plenty of moisture over the past week (up to 4 inches in some areas) has, again, caused saturated soils. Crops continue to progress well in most areas (corn staging up to V11 and soybeans up to R1) with somewhat limited disease or insect pressure (crop area dependent) as of yet. With increased moisture in soils and from the sky, there is an increased chance of disease. The winter wheat harvest has begun and will continue until complete, as weather allows.


The corn crop is developing nicely as we move into the summer months. Corn is staging between V5- V11 (six to 12 leaves). Around V5, the growing point is now above the soil surface. At V9, the tassel is rapidly developing but is not yet visible at the top of the plant. New leaves appear every 2 to 3 days, and ear shoots are also developing.

Some Nitrogen is still being side-dressed.

Tar spot has been identified this summer in the southern part of Michigan. Should conditions warrant, be prepared to apply a fungicide that controls tar spot when the forecasted risk level is high (favourable weather) and where disease has been identified in the local area in previous years. The Tarspotter app can give a good indication of risk, with the optimum time to run the app between V10 to R3. It is best to manage tar spot during corn growth stages V8 to R4; always read and follow labels and speak to a local agronomist to make a spray decision.


With the soybean planting date being extended by Agricorp to July 2, some soybeans were still going into the ground this past weekend (where weather permitted). With that, stages for soybeans are anywhere between VE (emergence) and R1 (beginning bloom – at least one flower appears on the plant on any node on the main stem). Staging is important as the season progresses to be able to apply herbicides, fungicides, and insecticides safely and effectively as required.

Fields are looking a bit stressed in some areas from saturated soils. In some fields, nodulation is not occurring yet, and soils are denitrified from prolonged ponding. Symptoms of yellow and stunted plants can be seen between tile runs or in lower areas with heavier soils. As the plant reaches the V2 to V3 stage, nitrogen fixation begins; however, saturated soils have an impact on nitrogen fixation due to the processes (and the associated bacteria) needing gas exchange for the activity.

Root and stem rots can also be common in soils that have excess moisture.

Keep an eye out for Soybean Cyst Nematode damage as the season progresses. At high populations nematodes can cause yellowing of leaves, stunting and early maturity, often in circular shaped patterns. SCN can be tested for and should be monitored for every three to six years; more info can be found here.

Fungicide timing is occurring or approaching for white mould control (find out more about white mould). The key to getting the most benefit out of fungicide applications is timing. Risks for white mould include the field history. If there is a known history of white mould, then the chance of it reoccurring is high. Variety, row spacing, plant density, and how quickly the field will canopy all factor into the likelihood of infection. Weather patterns will also help determine the risk. When it is foggy/humid, and moisture is on the plant most of the day, there will be a higher risk of white mould. The Sporecaster App can help you determine your field’s risk level. Fungicides can lower the severity of infection; however, timing is critical. The application timing ranges from R1 (single flower on the main stem) to R3 (pod on the main stem). Be sure to speak with your agronomist for optimum timing and product selection, and always follow label recommendations.

There have been some reports of aphids. When scouting for aphids, a threshold that should be looked for before spraying is that 80 per cent of the plants in the field have at least 250 aphids per plant with an increasing population. Scouting should occur multiple times over a period of time before an insecticide application is warranted to ensure an increasing population. The Aphid Advisor App is a great resource to help make decisions.

A reminder as the season progresses that Grain Farmers has supported the development with OMAFRA of the Pest Manager app, which allows you to identify, map, and find integrated management options for common weeds, insects, and diseases in corn, soybeans, and cereal crops. The pesticide use information in the app is specific to Ontario, and users should always read the product label before use.


Winter wheat is staging from GS 85 (soft dough) to fields harvested. Harvest for many areas is about one week earlier than normal.

The maturity of wheat can be determined by the peduncle changing from green to yellow. At this point, the crop is fully mature, grain fill, and the translocation of plant sugars has been completed (this stage can be compared to the black layer on corn). It takes roughly 660 growing degree days (GDD) to fill a wheat head. This period of GDD spans approximately 25 to 30 days for grain fill (less if it is extremely warm) – not a very long time.

Winter wheat harvest has begun, as weather has allowed, in the deep southwest region of the province. As harvest continues, scout for fusarium-damaged heads in the field. Infected fields should be harvested first to limit continual toxin build-up in case of rain events or delayed harvest. Set the combine correctly to help blow out the lighter infected kernels. Fusarium is showing up at low levels, sometimes only infecting a few florets on a few plants within a field (this might be due to T3 fungicides being applied at ideal timing for the majority of the field, but some tillers might have pollinated slightly behind the majority of the field). The incidence of fusarium infections has been reduced over the past 20 years due to genetic improvements and the use of fungicides during pollination (T3 timing) to help control fusarium. This spring, a larger amount of the winter wheat crop was exposed to ideal conditions (think of the disease triangle for fusarium infection: susceptible host + pathogen + favourable environment), but farmer practices have helped to manage the incidence of infection.

If winter wheat is harvested and reductions in yield and quality due to high fusarium levels are experienced, be sure to contact Agricorp.

With lots of moisture and lodged wheat, there could also be a concern about sprouting. Keep an eye out for sprouts and harvest early. Review any delivery contracts and look for the specification of the grain required for delivery against the contract. Ship grain that meets the required specifications that are signed off on. The most notorious inclusion on contracts is the base falling number requirement that can be caused by rainy weather and sprouting or caused by high alpha amylase expression in the grain due to cold stress during grain fill.

With the early wheat harvest, double-crop soybeans are a common conversation in some areas. If aiming for double-crop soybeans, seed supply on early-season beans will be needed. The date of wheat harvest and the field location will determine a lot. Aim for seed maturity that is at least one full maturity group shorter, but check with your seed dealer about what they suggest and what is available. The seeding rate should be increased to at least a population of 250,000 seeds per acre. The planting date should be considered, looking at frost dates, as the yield potential will drop considerably if soybeans are planted too late. Early to mid-July planting dates are ideal, be sure that the soybeans are going into good conditions. The ideal planting dates for double-crop soybeans would be before July 10 in southwestern Ontario and before July 20 in the deep southwest, but there is a large risk at any date; the soybeans might yield or not. Managing straw is critical; be sure to spread straw and chaff evenly. If you are considering baling, realize that the time spent baling might keep you out of the field planting for a couple of days. If you plan to double-crop soybeans, plant to moisture – up to 3” in July as they will push through. If there is no moisture at that level, aim for 1” planting depth and hope for rain.

The need for weed control in double-crop soybeans will be less – in theory, one pass would still be needed to control weeds. Most annual weeds emerge during May and June, and if double-crop soybeans are planted in July, weed pressure should be considerably less. Limit the investment in weed control as the chance for good soybeans is less likely, with much relying on the weather cooperating for a good yield and harvest so late in the season.

4R and soil sampling

As winter wheat is harvested, it makes for a great time to get some soil samples complete in an effort to ensure that the right rate of fertilizer is being applied at the right time, in the right form, and in the right place.

Cover Crops

Cover crops have an important role in maintaining soil productivity and quality. After cereal crops are harvested, it can be an ideal time to plant cover crops. The Cover Crop Selector Tool uses Ontario-based research (supported by Grain Farmers of Ontario) to help farmers select the best cover crops and provide management support, like planting population, for their operation.

June 27, 2024

The first few days of the summer season were warm, leading to rapid crop development and crop heat unit (CHU) accumulation. From June 17 to June 23, 2024, in Elora, 206 CHUs were accumulated compared to the 54-year average of 176; other areas of the province are also showing greater than average accumulations, as can be expected with temperatures exceeding 35 degrees Celsius.  

Corn and soybean development continues as winter wheat harvest nears for the deep southwest of the province.


With the heat last week, corn motored along, reaching knee-high well before the first of July (with some corn at waist-high), with others close behind. There is still a high degree of variability in crop staging across the province from V1 to V9 (8 leaf). Side dressing is occurring.

At about the V6 stage (six collars, or 8 leaf stage), the growing point emerges above ground level. The critical stage of ear development is from this stage to about a week before pollination. Ear initiation starts, and then the kernel rows per ear are determined. The number of kernels per row is determined as the ear elongates and is determined before pollination. Stress in the upcoming weeks from lack of nutrients or moisture will reduce grain potential through reduced kernel numbers. Stress can be caused by many factors like too high a population, weed pressure, root pruning from machines or insects, lack of fertility, lack of rainfall, standing water, hail damage, disease, etc.

Rapid growth syndrome has been and can be seen in fields with changes from cool to high heat. It occurs when corn leaves do not unfurl properly, and the whorl becomes tightly wrapped and twisted.

As fungicide timing approaches, be aware of the potential for Tar spot and Gibberella ear rot (which can cause DON in corn). The Ontario Corn Committee has posted the 2023 Ontario Corn Hybrid DON Screening Trials. These trials may be helpful in determining how susceptible hybrids are to Gibberella ear rot and DON accumulation—use them as a tool as fungicide spraying approaches.    


Soybean fields are staging from the VE (emergence) up to beginning bloom (R1—plants have at least one flower at any node). Soybean planting is still occurring in areas that struggled to plant earlier this year, and some replants are also occurring.

In the V3 to V5 stages, axillary buds develop into flower clusters near the top of the stem. In the coming days, flowering will begin, starting on the 3rd to 6th nodes and continuing down the stem. At this point, the plant will transition into reproductive stages (R1) while continuing to grow vegetatively.

As resprays occur, be sure to mitigate drift. Both and the recent Grain Farmers of Ontario GrainTalk webinar with Dr. Jason Deveau have valuable tips when spraying to help mitigate drift.

Agricorp planting deadlines and reporting of final acres for soybeans are all due on June 30.


Winter wheat harvest will begin gearing up in the coming days in the deep southwest. As harvest approaches, scout for fusarium-damaged heads in the field. Infected fields should be harvested first to limit continual toxin build-up in case of rain events or delayed harvest. Set the combine correctly to help blow out the lighter infected kernels. Fusarium is showing up at very low levels, sometimes only infecting a few florets on a few plants within a field (this might be due to T3 fungicides being applied at ideal timing for the majority of the field, but some tillers might have pollinated slightly the majority of the field). The incidence of fusarium infections has been reduced over the past 20 years due to genetic improvements and the use of fungicides during pollination (T3 timing) to help control fusarium. This spring, a larger amount of the winter wheat crop was exposed to ideal conditions (think of the disease triangle for fusarium infection: susceptible host + pathogen + favourable environment), but farmer practices have helped to reduce the chance of infection.

Across much of the province, kernel fill is still occurring in the winter wheat crop (GS 73 to GS 87 hard dough/physiological maturity). Prolonged hot, dry weather will limit kernel fill resulting in smaller kernels as the water availability for the crop becomes limited. Kernel abortion and dead heads can be seen as the plant dies rather than matures if moisture becomes too limited during this period (during the hot, dry period of last week this was seen occurring on sandy knolls within fields).

It is imperative to ensure that treated seed does not make its way into grain at harvest. As planting wraps up and harvest nears, ensure that equipment that handled treated seed is ready to handle grain (and cleaned out using proper protocols), with no contamination. Grains or oilseeds contaminated with treated seed or other foreign material put domestic and export markets at risk. Learn more in the Grain Farmers of Ontario Handling treated seed Fact Sheet.

June 20, 2024

There are variable-looking crops, both in stage and appearance, across the province as spring rolls into summer this week. Corn planting has wrapped up, while soybean planting is still progressing. Winter wheat is staging from milk to dough stage, and winter barley harvest is beginning. Heavy rains from pop-up storms have caused some temporary ponding in fields (and possible crusting in newly planted fields).


Corn planting is mostly wrapped up as the Agricorp extended deadline for insurance has come to a close; any remaining acres will now almost certainly be transitioned to soybeans. Crop development is occurring rapidly, with heat units accumulating quickly. Lots of corn is between emergence (VE) and V8 stage (9 leaf). V stage refers to the vegetative stage with the counting of collars on the corn stalk. At these early stages, side dressing occurs when field conditions allow in between rains. From V6 to V10, the corn plants will be developing the ear, and at this stage, kernel numbers per row and rows per cob will be determined. Stress in the upcoming weeks from lack of nutrients or moisture will reduce grain potential through reduced kernel numbers.

As corn plants are developing rapidly, plant variability is showing up as evidence of compaction damage from tillage or planting when conditions were too wet. This could be seen as smaller plants, discoloured as purple or yellow as root development is limiting nutrient uptake due to impacted soil.

The province has received consistent rains and rainfall up to this point, along with some ideal temperatures for tar spot development. If it does begin to develop, infection may start showing up in the first couple of weeks of July in fields that have had tar spot in previous years as spores are present locally. Check the bottom of the canopy for these local infections. There are still some variables, but if weather conditions continue with high humidity and leaf wetness, it will encourage the development of the disease. Disease progression will continue depending on the weather received and the spore load coming for infected fields; spores coming from other fields will show infection starting on the top of the canopy. For more info on tar spot and to see what to look for, read our Agronomy Alert. There have already been fields identified with Tar spot in Indiana.

Be on the lookout for black cutworm, as it can cause problems. Fields that do not have insecticide-treated seed or do not have Bt hybrids containing Cry1F or Vip3A should be given priority in scouting. Learn more about what to look for in this Field Crop News article.


Soybean staging is up to the 4th trifoliate in many areas, with some just emerging. Some soybeans are struggling in areas that have had very heavy rains after planting, creating crusting and causing slow emergence; planting is still occurring in some areas.

Be on the lookout for insect pressure, especially on fungicide-only or untreated soybeans.


Winter barley harvest has begun.

Spring cereals are in the stem elongation stage.

For winter wheat, stages range from the milk stage (GS 71- kernel watery ripe) to dough stage (GS 87- hard dough). Standability seems good so far in most areas. However, some are seeing some lodging in fields that had high nitrogen (N) rates, in those that had received manure that is traditionally high in N, or in those that have received heavy rains.

As temperatures increase, crop development speeds up. The average temperature range of 19–22 °C is the optimum for anthesis and grain filling in wheat. The high temperatures occurring and expected will impact grain fill. High temperatures also mean high water needs. In general, much of the province has a good supply of moisture in the soil, but this may be tested in the coming days if timely rains do not occur.

Ideal conditions for DON development are also occurring; some fields that saw timely T3 applications are still showing minimum fusarium infection. This is caused by application timing and the timing difference of anthesis within the canopy. Variable field conditions also lead to different pollination timing within the canopy. Fields that are showing Fusarium infection should have the combine adjusted to blow the Fusarium-damaged kernels out the back of the combine (due to their light weight). This will help improve the grading factor.

Be on the lookout for army worm, province-wide, and be prepared to spray as warranted.

Field Crop News houses tools for corn growers

Field Crop News is now the source for the Ontario Corn Nitrogen Calculator, Ontario Corn Replant Decision Aid Tool, Optimum N-Rate Estimator, Ontario Corn Committee Hybrid Selector Tool, Ontario Manure Nutrient Calculator, and the Ontario Crop Residue Value Estimator. These tools were all previously housed on website (which has been replaced by

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