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Yellow wheat

Wheat and barley can handle some flooding but it’s not without cost. When the water recedes and soils drain, you’ll likely notice that the wheat crop (and barley for that matter) has turned pale green or even yellow.

Common reasons for early-season yellowing include:

  • Temporary nitrogen deficiency.
  • Temporary herbicide injury.
  • Early tan spot infection.

Other possible causes include Barley Yellow Dwarf virus or temporary micronutrient deficiencies.

Nitrogen deficiencies

Nitrogen (N) deficiencies with readily identifiable symptoms are most noticeable on the oldest leaves. Symptoms start at the tip of the leaves, progressing toward the base as the deficiency gets worse. 

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Micronutrient deficiencies

Cool and wet conditions make some of the micronutrients less available to the plant. These symptoms are often first noticed in crops grown on coarse-textured soils.

Researchers have chased this problem in the past and found no single culprit to blame. As soon as growing conditions improved, the symptoms also disappeared.

Herbicide injuries

Cool growing conditions make many common small grain herbicides more likely to cause temporary injury. The ACCase class of grass herbicides is especially more active with cooler growing conditions.

This temporary yellowing will dissipate in one to two weeks after application with no effect on grain yield.

Tan spot infection

Early season tan spot infection can also cause the young wheat crop to turn a bright yellow. In particular, young seedlings up to the 3- to 4-leaf stage are very sensitive to a toxin that’s produced by the fungus. This yellowing affects the whole seedling.

If you identify a tan spot as the cause of the yellowing, an early season fungicide treatment is warranted. Use half the labeled rate of any of the labeled fungicides – such as Tilt, Quilt, Stratego and Headline – to halt the development of the tan spot and allow the crop to recover.

Jochum Wiersma, Extension agronomist; Doug Holen, former Extension educator and Dan Kaiser, Extension nutrient management specialist

Reviewed in 2018

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