Sunscald in Corn and Soybean

Key Points

• Extreme heat and moisture stress can lead to tissue damage on the leaf surface of corn and soybeans.
• Sunscald can occur in irrigated as well as non-irrigated fields.
• Sunscald causes tissue damage that generally is not yield limiting unless foliar diseases infect and spread from the damaged tissue.

Sunscald in Corn

Sunscald injury on a corn leaf.

• Sunscald occurs when the rate of water movement up to and through the leaf cells cannot keep up with the rate of evapotranspiration from these leaf cells.
• Younger leaves and leaves with direct orientation to the sun are most affected.
• Tissue can have a silver/gray cast initially and then turn brown and necrotic in a few days.
• If no additional disease is present, stalk tissue will look normal.
• Sunscald damage will not progress on the leaves.
• Injury can occur while leaves are still in the whorl.
• Water in the form of dew or from irrigation can injure tissue as high temperatures heat water on the leaf surface.
• Injury to the tassel can occur, but typically will not decrease pollination as damage is usually isolated within the field.
• Susceptibility to sunscald differs by hybrid genetics.

Closeup of sunscald injury on a corn leaf, showing injured tissue between the leaf veins.

Sunscald injury to a corn leaf tip.

Severe sunscald injury throughout the corn canopy.

Sunscald in Soybeans

• Sunscald in soybeans occurs in the same manner as corn with water heating on the leaf surface.
• Typical sunscald injury is usually found on the underside of the leaf, since soybean leaves flip upside down during the warmer part of the day.
• Sunscald in soybeans may be mistaken for herbicide injury, disease, or spider mite damage.
• If no additional disease is present, stem tissue will look normal.
• Spider mite damage may accompany sunscald; be sure to check the underside of the leaf for insect feeding.

Sunscald injury visible on the underside of a soybean leaf.

Comparison of sunscald injury and spider mite damage. Injury caused by spider mite feeding can be distinguished by the stippling pattern on the leaves.