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OMAFRA field crop report for the week of May 4: so far, so good

May 13, 2020  By OMAFRA Field Crop Team

Air temperatures for the week of May 4 were below the seasonal average. This has slowed soil warming and, while not hindering planting, has delayed germination and emergence of seeded crops. But – so far – the 2020 season has offered better planting conditions than the past few springs.


Most of the winter wheat crop looks excellent, although the prolonged cool conditions have slowed growth. Some of the later planted winter wheat fields are struggling, but many want to keep these because of the current market pricing. Growth of annual weeds continues to be slow but is starting to get to the stage when herbicides should be applied. However, forecasted cold air temperatures (lower than 5 C) can increase the potential for crop injury from herbicide applications and therefore will be delayed until air temperatures increase in the latter part of the week of May 11.

There is more interest in plant growth regulators (PGRs) this year; producers wanting to optimize the already excellent crop. When considering application of PGRs, tank mixes with herbicides and fungicides should be avoided during these cold conditions. Timing of application relative to crop and pest growth stage is the most important consideration. Even if no PGRs are planned, delaying the herbicide application until overnight temperature forecasts are warmer is recommended. Weeds will not grow rapidly under these cool conditions.


Disease pressure is low across the province, with Septoria being the only disease reported in the lower part of the canopy in some fields. Scout to determine if a fungicide is warranted. In general, disease pressure is well below threshold for triggering application.

Spring cereals are all planted with increased acres across the province, especially oats. Cereals are taking seven to 10 days to emerge under these temperatures, but seed was planted into “fit” soils and everything should be fine.


Corn planting has progressed steadily during the week of May 4 and planting conditions have been excellent. While corn seed planted three weeks ago has not emerged, the ground is not overly wet, which is when the problems of slow germination are of concern. With relatively low temperatures predicted, it is fine that the corn has not yet emerged.

The rate of planting varies widely within and between areas. Some people are completely done and have moved on to soybeans, while others have just started or are yet to start. On average, we predict that around 50 per cent of the corn has been planted across Ontario, with higher levels in the west and east compared to the mid-west and central regions. Areas with heavier soils continue to wait on suitable field conditions.

Where corn is still to be planted, ensure uniform seeding depth of 1.5 to 2.0 inches. Uniform depth is key to ensuring uniform emergence, which will provide an excellent start to corn achieving its yield potential.


Soybeans, like other crops, do best when planted under ideal soil conditions and, for the most part, the 2020 planting season has offered this. Some have expressed concern over the cold temperatures predicted for May 7-11. Once into May, the expectation is that temperatures will only improve, so if soil conditions are good, growers should continue to plant. The recommendation is to plant 1.5 inch or deeper if you need to find moist soil. The emergence of soybeans planted this week will be a bit delayed, which is fine under current soil conditions; low temperatures should have passed by the time emergence occurs. The goal with any crop is uniform emergence of equally vigorous plants, and the 2020 planting season is allowing that to occur so far.


Much of the spring canola planting in the traditional southern Ontario locales is completed. Seeding has started in northeastern Ontario. Seeding should be completed by May 15 for optimal potential and to avoid damage from swede midge during early growth stages.


Cool conditions have kept growth slow in hay fields and pastures. Flowering in grasses is linked to day length rather than heat, so this may reduce yield at first cut, especially for growers prioritizing quality. Scouting should focus on stem counts to assess alfalfa yield potential. Fifty-five or more stems per square foot (ft2) provides full yield potential; stands with fewer than 40 stems/ft2 have less than 70 per cent yield potential and may need to be terminated after first cut. True armyworm scouting in grassy fields should start in the next couple of weeks where fields were green in April.


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