Ontario crops respond to summer heat

Hot weather spurs corn soybeans wheat growth across Ontario

According to the OMAFA Field Crop News team, Ontario field crops are showing rapid development as summer-like temperatures have dominated late June early July. The warm spell has accelerated growth and helped reduce the heat unit deficit from a cool spring. 

Corn fields have seen a burst in growth, especially early-planted varieties now reaching V8 or more advanced stages.  

Side dressing is mostly complete, though late nitrogen applications are beginning. Issues like magnesium, zinc, and manganese deficiencies, along with root stress from compacted soils, have become more visible.  

Some corn on sandy knolls is showing temporary heat or drought stress. Farmers are also on alert for tar spot, recently confirmed in the United States in Indiana.  

Soybeans are progressing, with early plantings starting to flower. Yellowing in fields is commonly linked to delayed nodulation. Stand counts vary, particularly in no-till or residue-heavy fields.  

Soybean aphid populations are building in some regions, though current temperatures over 34°C may slow reproduction. Natural predators remain active, keeping aphid levels below treatment thresholds.  

Wheat continues its grain-fill period but may be impacted by the ongoing heat, which shortens grain development and can reduce yield. Stripe rust has been managed well with fungicides, although susceptible varieties still saw damage where treatments were delayed.  

Wheat harvest is expected to start early in some areas, with a recommendation to begin at 18% moisture to preserve grain quality. 

Farmers are advised to continue scouting for nutrient deficiencies, pests, and weed breakthroughs, especially in fields where pre-emerge herbicides are wearing off. Weather remains a critical factor as crops push through key stages of development across Ontario. 

For more information about the soybean aphid, for more information about weed, pest, or crop diseases, please visit the Farms.com Field Guide pages. 

Photo Credit: gettyimages-oticki