The March 2018 planting intentions report by Statistics Canada estimated Ontario farmers intended to plant 2.2 million acres of grain corn, comparing to a 5-year (2013-2017) average of 2.1 million acres (OMAFRA Crop Statistics).

A cool April coupled with snow and freezing rain events through to the middle of the month limited early field work. A warm dry period during the last week of April allowed a small amount of early planting on the lighter soils of the deep southwest and well drained soils in other pockets of the province.

Apart from a few locales, rainfall was limited during early May allowing planting to start in earnest on lighter, drier soils of the province by the first week of May. Areas which had received significant April snow, such as parts of mid-western Ontario, remained wet. A large amount of corn was planted the second week of May. By the end of that week, planting was nearly complete in areas which started early and 50% or more in areas that started later. Much of the provincial planting was completed by the third week of May, except for heavier textured soils in Essex, Lambton, western Middlesex/Elgin counties and Niagara where many growers were yet to start planting. Frequent rains in these areas pushed corn planting to the last week of May and beginning of June. Many of these remaining acres were switched to shorter maturity hybrids while some were switched to soybeans. Heavy May rainfall events in the deep southwest, Essex and Chatham-Kent in particular, resulted in some replanting where significant water ponding occurred.

Final grain corn planting estimates for the province were 2.16 million acres (OMAFRA Crop Statistics), close to the 2.2 million acres estimated in the March Statistics Canada planting intentions report.

Early Season

OMAFRA completed its annual Pre Sidedress-Nitrate Test (PSNT) survey June 6th at the V3-V4 corn stage. The survey measures background soil nitrogen supply by sampling fields which haven’t received preplant nitrogen. The purpose of the survey is to gauge soil nitrate levels just prior to sidedress time. In 2018, the average PSNT value was 12.7 ppm, slightly higher than the longterm (2011-2017) survey average of 12.0 ppm, and higher than 8 ppm from the 2017 survey. This suggests natural soil nitrate supply in the 2018 survey was normal to a little higher than normal. Each 5-ppm change in PSNT generally changes N recommendations by around 30 lb-N/ac, though the actual number depends on soil nitrate level and yield goal. See PSNT recommendation at The warm, dry conditions up to early June would have been conducive for nitrogen mineralization from soil, and limited potential for losses. With limited rainfall, the month of June was co-operative for in-crop management practices such as sidedressing.

Thrips were observed in many corn fields across the province in June. Thrips are rarely a corn pest in Ontario, and corn management information is limited. No common threads were evident for their prevalence in 2018 (crop rotation, manure history, planting date, seed treatment etc.). While most fields grew out of injury with little expected yield loss, control was applied in some fields which remained very dry and appeared to be held back by thrip pressure.

With limited rainfall in many areas by the end of June, moisture stress was showing up on soils with poor water holding capacity which had not received significant rainfall.

Pollination and Grain Fill

Earlier corn fields were starting to tassel by the second week of July, with a large majority of the crop pollinated or undergoing pollination by the end of the following week. Given the hot, dry conditions at the start of pollination, there were some concerns as reproductive stages in corn are the most sensitive time for moisture stress. Moisture stress and field variability was becoming evident in pockets of the province which remained particularly dry.

Given the increasing range and ear feeding damage in past years, Western Bean Cutworm (WBC) activity was closely monitored by many producers and agronomists. The Canadian Corn Pest Coalition trap network ( moth counts were still elevated in 2018, but lower than some previous years. Peak moth flight was slightly later than normal and occurred after a large majority of corn tasseled. This is important as WBC moths generally avoid laying eggs in fields which have already tasseled, preferring to look for later planted fields or edible bean fields. Many scouts reported difficulty finding eggs or larvae in fields in 2018. Scouting fields for the 5% threshold of plants with egg masses or larvae was still recommended. Many growers reported not spraying in 2018 due to apparent lower populations and lack of larvae or eggs.

By the end of the third week of July, widespread rainfall events were welcomed across large parts of the province. Persistent rainfall continued through to the end of August in many areas. While wet conditions can be conducive to plant disease, foliar disease pressure remained relatively low, disease progress was likely delayed by the dry conditions during the first half of the growing season.

In contrast, ear mould pressure was becoming very evident with field scouting from late August into September, particularly in southern Ontario. Several ear moulds in Ontario, including Gibberella Ear Rot, the white-pink ear mould that produces DON mycotoxins, prefer moist conditions. Wet conditions at silking are conducive for ear mould spores initiating infection on fresh silks and establishing on ear tips. Continued wet conditions thereafter allowed the established ear moulds to grow and spread along the ear via the cob.


Corn silage harvest started in earnest around the middle of September in many parts of the province. With average to above average heat unit accumulation, there were a few comments of silage being drier than expected.

The annual Ontario ear mould and DON (vomitoxin) survey was completed September 21 to 28. The purpose of the survey is to measure the relative levels of DON in the grain corn crop just prior to harvest to provide information for growers and industry. A total of 146 samples were collected from across the province. Visual mould symptoms and DON levels were higher than what are typically observed, with 60% of the samples testing at less than 2.00 ppm, 15% at 2 – 5 ppm and 25% above 5.00 ppm. This compares to 6-8% of samples testing above 5.00 ppm in more recent elevated years. While elevated samples could be found in many areas surveyed, the largest concentration of high testing samples was from southern Ontario. The final report is available at

While some Western Bean Cutworm feeding was evident in survey samples, levels were significantly lower than more recent surveys, both in incidence (% of samples with feeding) and severity (amount of feeding damage per ear) which would be consistent with scouting observations at tasseling. The majority of ear mould appeared to be associated with silk-initiated infections, not ear feeding damage.

There are some strategies to reduce ear mould and mycotoxin risks going forwards. The most significant factor is weather, the key contributor to 2018 infections, and naturally beyond our control. Hybrid selection is next. No hybrids are resistant to ear moulds, but there are differences in susceptibility. Selecting more tolerant hybrids should reduce risks. No public ear mould ratings are available, it is important to work with your seed provider or from local experience. Hybrid risk is another reason why it is important to grow at least a couple different hybrids on your corn acres. Some, but not all corn fungicides provide ear mould suppression. The two products registered for ear mould suppression in Publication 812, Field Crop Protection Guide (, are Proline and Caramba. Like tolerant hybrids, fungicides do not provide complete protection against ear moulds, but proper applications have been shown to provide suppression. Timing is critical for efficacy, with silk protection being the key goal. Silk coverage at the fully emerged, fresh silk stage is the recommended target. Spraying before silks have fully emerged will miss silks protected under husks, while spraying later when silks have started to dry may be too late to protect against mould infection.

With reasonable planting dates and above average heat unit accumulation, some grain corn was harvested as early as the end of September and Thanksgiving weekend when soybeans were not ready for harvest. Persistent rainfall, delayed soybean harvest, and snow thereafter resulted in a drawn out, slow harvest in many areas. Progress was variable with a large majority of crop harvested by the middle of November in areas of mid-western and eastern Ontario, while the crop in southern Ontario (Essex to Middlesex to Niagara) was generally 50% harvested or less. Harvest in these areas was generally wrapping up over the first and second week of December.

Despite growing season challenges, and with exception to a few pockets of the province where dry weather prevailed through the latter half of the summer, many growers reported yields above expectations or farm averages.

As of December 19, Agricorp reported that 53% of Agricorp insured acres had been reported with an average yield of 181 bu/ac. This compares to a 10-year average yield of 170 bu/ac for these same growers. The current 10-year average grain corn yield for Ontario as a whole (2008-2017) is 158 bu/ac (OMAFRA Crop Statistics).

Final Ontario Corn Committee (OCC) corn hybrid trial results are available at the homepage of Yield results for some locations were delayed due to wet field conditions, but as of December 19, all data and trials have been finalized. There are several options for viewing data, including printable PDF, sortable spreadsheets (yield index, moisture lodging, company or hybrid name etc.) and yield by moisture graphs demonstrating the trade-off between yield and harvest moisture of hybrids within each OCC table.