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Ontario field crops: heat helps emergence, soil crusting reported

June 5, 2020  By OMAFRA Field Crop Team


While planting has largely been completed over the last few weeks, corn is still being planted on heavier soils that have just recently been fit for planting (e.g. Niagara/Haldimand, southern Lambton, southwest Kent). If rainfall further delays planting, more remaining acreage may be switched to soybeans.

Despite great planting conditions, there are reports of soil setting hard, clodding and crusting, which have caused emergence issues, particularly in the southwest. Some stand issues may also be related to cool temperatures, hybrid vigour and time in ground prior to emergence. Where emergence is an issue, most growers report stands are sufficient to keep, though some replanting has occurred. The Replant Decision Aid at may assist replant decisions by estimating yield potential of existing stands, yield potential of replanting, and the costs associated with stand removal and replanting.

Corn planted in early May is generally in the early vegetative stages (V2-V3). Corn planted after the cold weather period has emerged very quickly thanks to very warm temperatures last week. Side-dressing has started on more advanced, early planted corn reaching the 5-6 leaf stages in the southwest. The Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA) conducts an annual soil nitrate survey to help gauge soil nitrogen mineralization around the V3-V4 stages and is planned to start at the beginning of next week.



Soybean planting has wrapped up in many areas but continues on heavier textured soils. There have been some reports of difficulties with residue, particularly late-harvested 2019 corn fields where residue is tough and keeping soil conditions damp. Soybeans planted prior to the cold weather in early May are reported to have pulled through with good stands. Like corn, some emergence issues have been reported due to crusting or hard soils.

Seeding rate suggestions in soybeans have a margin of error for stand loss, and soybeans have a strong ability to compensate, so some stand loss is tolerable. General guidelines are for at least 100,000 plants per acre, or 120,000 plants per acre on clay or other soils where plants may not fill out as much. Further considerations for soybean replanting are available in the “Soybean Replant Consideration” article on

Dry Beans

Dry bean planting is in full swing, with adzuki planting nearing completion and other classes of dry beans about half-finished. Some growers were waiting to avoid the cool temperatures of this past weekend as well as the heavy rains and thunderstorms in the forecast for this week.


Winter wheat generally ranges from close to flag leaf emergence to heads fully emerged for early planted wheat in the far southwest. T3 fungicide applications for Fusarium head blight have started in fields reaching anthesis and will continue as other fields reach this stage. Nutrient deficiencies (nitrogen, sulphur) are reported to be more apparent than normal this time of year, likely due to delays in mineralization from soils due to cool soil temperatures early in the growing season. Very little foliar disease pressure has been reported.

Cereal aphid populations appear higher than normal this spring. The threshold prior to heading is 12-15 aphids per stem and after heading is 50 aphids per stem. Few fields at this point have been over threshold. The Cereal Aphid Manager App can help guide decisions, taking into account weather forecasts and beneficial insect populations.


Rain and warm temperatures have spurred forage growth. Cereal rye harvest has been underway or completed this past week, with yields reported to be average to above average. First cut alfalfa has started this past week on some dairy farms. Insect pests have been found in fields across the province, and producers need to scout to protect forage yields.  Alfalfa weevil has been found in the southwest, while alfalfa snout beetle is feeding on new seedings in the east. Producers in counties on the northern shores of Lakes Erie and Ontario should start scouting for potato leafhopper, as these pests blow in from the southern U.S. on storm fronts. True armyworm was detected in grassy fields earlier this year in NY state, and populations may be building in pastures and grass or mixed hay fields. More details on scouting for forage pests can be found in OMAFRA Publication 811: Agronomy Guide for Field Crops.


Winter canola fields are in the bloom to pod fill stage. Flea beetle-feeding has been a common report in spring canola. Early planted fields which were slow to emerge and grow through the cool conditions of early May are most affected. Quicker growth of later planted canola has kept the crop ahead of feeding injury. Growers should scout fields, particularly those with thin stands (less than five plants per foot squared) most at risk from feeding. The action threshold for flea beetles is 25 per cent defoliation. Details for managing flea beetles in canola are available in “Flea Beetle in Spring Canola: Monitor, Identify Fields at Risk & Consider the Weather.” Swede midge have not been reported yet but typically emerge at the end of May or in early June. Canola fields with slow growth from cold temperatures or flea beetle feeding may be at greater risk of swede midge injury.


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