Disease Pressure Builds in Winter Wheat.
Persistent rainfall across Ontario through late May temporarily stalled fieldwork, but improving weather conditions are now helping farmers regain momentum, according to the latest Ontario Ministry of Agriculture, Food and Agribusiness (OMAFA) Field Crop News report released May 28.
Up until May 26, saturated soils limited planting and field activity across much of the province. However, recent drying conditions combined with a warm and dry forecast are expected to support the completion of remaining acres in the days ahead.
Winter Wheat Advances Amid Rising Disease Pressure
Winter wheat development continues to progress, with the most advanced fields reaching head emergence, while many others are at the flag leaf stage. Alongside this advancement, disease pressure is increasing.
OMAFA reports visible presence of powdery mildew and septoria within lower canopies, while stripe rust has been detected at low levels in parts of southwestern Ontario, including Huron, Oxford and Wellington counties.
Fusarium head blight risk is currently rated moderate to high, prompting strong recommendations for timely fungicide applications from the Field Crop Team.
Agronomists emphasize that precise staging is critical. Once 75 percent of wheat heads reach GS59 (full head emergence), growers enter what is known as “day 0.” The ideal fungicide application timing is “day 2,” when pollination begins and anthers become visible on the wheat head.
The team reminds farmers that this window is crucial because the crop is most vulnerable to infection when the greatest number of florets are exposed. With warm temperatures expected, crop development may advance rapidly, making vigilant monitoring essential.
Producers are also reminded not to apply strobilurin fungicides beyond the boot stage due to potential yield and quality risks.
Insect and viral pressures are also present, albeit at relatively low levels. Reports confirm wheat streak mosaic virus in some fields, along with cereal aphids and cereal leaf beetle activity. True armyworm larvae have been detected in isolated cases, while moth trap counts are increasing, though still below levels observed in neighbouring U.S. regions.
Spring Cereals and Corn Show Mixed Progress
Spring cereal crops are developing at varying rates. The earliest seeded fields are approaching stem elongation, while later-seeded acres are just emerging.
Herbicide and plant growth regulator applications are expected to proceed as conditions allow.
Corn planting is nearing completion on lighter soils, but heavy clay areas remain a challenge due to excess moisture. Provincial planting progress is estimated between 80 and 95 percent complete.
The continued delay is prompting some growers to switch to shorter-season hybrids as the calendar moves into June.
Emergence of planted corn ranges from VE to V3, with generally strong and uniform stands reported. However, uneven emergence is noted in some early-planted fields where conditions were less than ideal.
Soybean Planting Uneven Across Regions
Soybean planting progress remains variable, ranging from approximately 50 to 80 percent complete depending on soil type. Fields with lighter soils are further advanced, while heavy clay areas have seen limited activity.
Early planted soybeans are emerging well, with no significant frost damage reported to date.
Growers are being reminded to carefully verify herbicide tolerance traits before application to avoid costly misapplication errors. This is particularly critical for identity-preserved soybean production, where weed control options are more limited.
Managing resistant weeds such as Canada fleabane continues to pose a challenge, underscoring the importance of timely and effective weed control strategies.
Canola
Spring canola planting is ongoing in northern and eastern Ontario, with strong emergence reported overall. However, some early-seeded fields experienced severe frost damage, and replanting decisions are currently underway.
Producers are encouraged to assess regrowth carefully before terminating damaged stands, as viable recovery may still occur.
Winter canola is progressing through flowering, and planning for the next crop season is already underway, with seed orders due by mid-June.
Forages and Edible Beans Show Progress
Forage crops are responding well to warmer temperatures. Rye and triticale harvest is nearly complete in southwestern Ontario, with yields exceeding expectations in many cases.
Alfalfa harvest has begun in Oxford County and is expected to expand across the region in the coming days, with other areas of the province following within the week.
Edible bean planting remains limited but is expected to accelerate significantly with improved weather conditions.
Weed Pressure Expected to Increase
Earlier cool temperatures slowed both weed emergence and herbicide activity. With temperatures now rising, annual weeds are expected to emerge more aggressively.
The Field Crop Team advises growers to prioritize timely post-emergence herbicide applications to target smaller, actively growing weeds and reduce competition with crops.
Soil-applied herbicides remain an important component of weed management programs, even in the absence of immediate rainfall. While activation may be delayed, these products can still provide partial control and reduce reliance on post-emergence applications.
For information to help producers identify and control common and invasive weeds, destructive pests and crop diseases, visit the Farms.com Field Guide Pages.
Photo: Winter canola approaching the end of flowering in Chatham-Kent on May 25, 2026.
Photo Credit: OMAFA