The Importance of Wheat Seed Treatments

The Importance of Wheat Seed Treatments

Compilation photo of wheat seed diseases
Figure 1. (left)  Bunt balls (spore-filled grain) containing spore masses of the common bunt (stinking smut) fungus.
Figure 2. (center)  Loose smut. Spores of the fungus replace grain on the wheat head.
Figure 3. (right)  Black point. The disease is caused by several fungi during grain maturation. The fungi blacken the embryo end of the grain.

 

Ergot in wheat
Figure 4.  Ergot.  Individual seeds on the wheat head are replaced by black sclerotia or ergots (compact masses of mycelium of the causal fungus).
Fusarium in wheat
Figure 5.  Scabby wheat with kernels infected by the scab (Fusarium head blight) fungus.  Severe seedling blight can result if this grain is used as seed.

Aug. 7, 2014

Fungicide seed treatments help to reduce losses caused by seed transmitted and soilborne fungal diseases of wheat.  Some seed treatment products contain a fungicide and an insecticide and offer additional protection against fall season insects such as aphids.

Seed-Transmitted Diseases

Seed-transmitted fungal diseases of wheat include common bunt, also known as stinking smut (Figure 1); loose smut (Figure 2), black point (Figure 3), ergot (Figure 4) and diseases caused by Fusarium (Figure 5).  These diseases can cause varying levels of yield loss and occasionally total loss. 

Loss results from seedling blights and damping off caused by some fungi and grain loss caused by common bunt and loose smut fungi. In the case of common bunt, total loss is almost certain due to rejection at the elevator, as happened this year in an area covering portions of southwest Nebraska and northeastern Colorado. 

In addition to loss in quantity, these diseases also lower grain quality and therefore value because affected grain is downgraded.

Soilborne Diseases

Soilborne fungal diseases of wheat include common root rot; Pythium root rot; Rhizoctonia root rot; and Fusarium root, crown, and foot rots.  These diseases often go unnoticed because they affect the roots and crowns and are less visible than foliar diseases. However, they cause significant yield loss resulting from poor stand establishment (Figure 6) and weakened plants that are vulnerable to attack by other diseases and insect pests.

Poor stand of wheat
Figure 6. Poor stand establishment due to soilborne and some seed-transmitted diseases of wheat.

Management

Seed-transmitted and soilborne fungal diseases of wheat are effectively controlled by planting certified, fungicide-treated seed. Because some of these diseases are internally seedborne, systemic fungicides are recommended.  Avoid planting farm-saved seed from previous years.

Treating Seed

It is best to buy certified treated seed or use a commercial seed conditioner to clean and treat seed.  Seed treated on-farm should be cleaned before treatment.  Thorough coverage maximizes effectiveness of the seed treatment.  For a list of seed treatment fungicides for control of seed transmitted and soilborne diseases of wheat, see Wheat Seed Treatment Fungicides.

Stephen Wegulo
Extension Plant Pathologist