Don’t Sweat the ‘Corn Sweats’

“Corn sweat,” the colorful shorthand for transpiration in corn, is generally a healthy, natural process. But under the right conditions, it can contribute to negative consequences.

What is Corn Sweat?

This process occurs when sunny days and high temperatures cause the corn plants to release water through their stomata, or pores, on the undersides of leaves. Stomata open to allow the plants to take in carbon dioxide (CO₂), a crucial gas for photosynthesis, and to release oxygen and water vapor to cool them as temperatures rise. The process also delivers nutrients to plants as water rises up the stalks. During dry spells, the stomata close to retain water and protect yield.

Corn Sweat Contributes to Disease Spread

Evapotranspiration is the combination of plant transpiration plus evaporation from the acreage on which the crop grows. The extra moisture adds more heat to the environment, creating muggy days and nights that reduce a plant’s cooling ability. These steamy conditions are especially hospitable to fungal diseases, including Northern corn leaf blight, tar spot and rusts.

For the most part, corn sweat is a regional phenomenon, particularly impacting the Midwest and Ohio.

Preventing Disease Spread From Corn Sweat

To combat this condition, preventive fungicide applications are a good choice, especially when high daytime humidity is followed by cooler nights that bring heavy dew.

When to Start Scouting

Growers should start scouting for signs of disease from the V12 to V14 growth stages, especially if high heat and humidity have already set in. V16 to VT is the most crucial scouting window — earlier if tar spot is suspected. When disease is present, the optimal time for fungicide applications is VT to R1, particularly if lesions are found on 50% of plants. Growers should continue scouting at R2 to R3 for prolific fungi like tar spot and Southern rust. They should also prioritize fields with corn-on-corn, no-till practices or susceptible hybrids.

Preventing Excess Water Loss in Corn

As important as it is for cooling and supplying plant nutrients, transpiration equals water loss in plants — something growers can’t afford, especially in a particularly thirsty crop.

But Midwest growers have found Miravis^® Neo fungicide can help both control diseases in the canopy and lower transpiration rates, conserving more water and nutrients, even in drought. With a three-active-ingredient-formulation — including azoxystrobin, propiconazole and ADEPIDYN^® technology, Miravis Neo can help boost potential yield. Its plant-health benefits support efficiencies in plant photosynthesis, water and nutrient use, and stronger stands for improved harvestability and ROI potential.