WW-06967     Reviewed 2009  

Herbicide and Nonherbicide Injury Symptoms on Spring Wheat and Barley

Nutrient Deficiencies

Nutrient deficiency or toxicity stresses small grains and can appear similar to herbicide injury. Nitrogen (N), sulfur (S), iron (Fe), and copper (Cu) are the most common nutrient deficiencies that occur in spring wheat and barley. Nutrient deficiency symptoms are similar for spring wheat and barley.

Copper
Copper deficiency in spring wheat and barley occurs in high organic soils. Although copper is required in minute quantities to activate plant enzymes, the lack of the element in relation to other metal ions can affect yields. Copper deficiency symptoms in small grains develop on the youngest leaves and generally appear on younger plants instead of more mature ones. Leaves appear light green and become dry at the tips. In addition to leaf tips dying, severe copper deficiencies lead to leaves that become shriveled, twisted, and broken and eventually to the death of the plant. Roots of affected plants are stunted and are excessively branched. Copper deficiency in mature small grain plants can cause bleached heads, poor fill, and occasional partial head emergence. See photo 37.

Photo 37 Copper deficiency in small grains is generally seen as a light green color in plants with leaf tips turning brown.

Other factors causing white heads are frost injury, wheat stem maggot, head blight (scab), barley yellow dwarf virus, and common root rot disease.

Nitrogen
Soil nitrogen can become limiting to small grains for a variety of reasons. Intensive cropping, with or without rotation, can deplete the soil nutrients starting with nitrogen. Excessive rain can leach nitrogen from sandy soils or cause denitrification, making nitrogen unavailable for plant uptake. Low levels of nitrogen in the soil can cause reduced tillering, stunting, poor kernel fill, and low grain protein. Nitrogen deficiency causes an overall yellowing of the plant with the lower leaves yellowing and dying from the leaf tips inward. Nitrogen deficiency can mimic injury symptoms caused by propanil (Stampede), imidazolinone, and sulfonylurea herbicides. See photo 38.

Photo 38 Wheat plants lacking in nitrogen first become light green, then yellow.

Phosphorus
Phosphorus deficiency is a common occurrence in spring wheat and barley. The common phosphorus deficiency symptom usually associated with many other crops, purple leaf discoloration, is less common with wheat and barley. The lack of vigor and poor tillering in small grains is the best indicator of phosphorus deficiency. Phosphorus deficiency symptoms are similar to injury caused by aryloxyphenoxypropionate and dinitroaniline herbicides. See photos 39 and 40.

Photo 39 A laboratory demonstration shows the effects of phosphorus deficiency.

Photo 40 Wheat and barley plants without adequate phosphorus levels appear stunted, have reduced tillers and a poor root system.

Sulfur
Sulfur deficiency occurs only in sandy soils where the organic matter content is 2 percent or less. The symptom of sulfur deficiency in spring wheat and barley is an overall yellowing and stunting of the plant. It is difficult to distinguish sulfur from nitrogen deficiency. Sulfur deficiency is similar to injury caused by aryloxyphenoxypropionate, imidazolinone, and sulfonylurea herbicides. See photo 41.

Photo 41 Yellowing of leaves is a characteristic of sulfur or nitrogen deficiency. Yellowing from nitrogen deficiency usually begins with older leaves and moves upward. Sulfur deficiency is usually more pronounced in younger leaves.

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