University of Nebraska-Lincoln Extension, Institute of Agriculture and Natural Resources

(Left) Tucked midway between healthy lower and upper leaves of a sunflower plant is a pocket of dying leaves. Similar symptoms appeared on most of the plants across an entire field in southwest Box Butte County. (Above) Leaf damage was significant, but limited only to leaves at a particular stage.

(IANR photos by Bill Booker)

July 21, 2006

Sleuthing in sunflowers

Recently a mystery unfolded in an irrigated sunflower field in southwest Box Butte County.

Sunflower leaves curled and turned brown, a sign of sunscald.
The query: The sunflower plants looked great until you looked a little closer – leaves at a particular height among almost all the plants were dying. Older and newer leaves looked good and did not appear to be stressed, but leaves at a consistent level across the field were dying. What had caused the problem and how might it affect yields?

The setting: This field had received lots of sunshine and extreme heat at various points in the summer. It hadn’t been irrigated recently and was normally dry, although there may have been a dew some mornings.

The culprit: Sunscald. Sunscald is caused by exposure to intense sunlight and/or high temperatures and tends to be most severe following periods of high humidity and overcast skies. It first appears as small water-soaked spots on upper surfaces of leaves, stems, or pods that are exposed to the sun. These spots are generally close together, turn reddish brown, and form large spots on affected plant parts. In this field some injuries were severe.

The prognosis: The leaf injury should have little effect on yield. Sunflower can lose 50% of its leaf area and still produce 85% of its yield. The injuries were significant to the impacted leaves but not to the plant.

Bill Booker
Extension Educator in Box Butte County

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Copyright 2006 by the University of Nebraska Board of Regents. All rights reserved.
Published by University of Nebraska-Lincoln Extension in the Institute of Agriculture and Natural Resources Cooperating with the counties and the U.S. Department of Agriculture.
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