Sunscald in Corn and Soybean
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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 injury on a corn leaf
Sunscald in Corn
- 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.
Sunscald (left). Spider mites (right).
Comparison of sunscald injury and spider mite damage. Injury caused by spider mite feeding can be distinguished by the stippling pattern on the leaves.