Karnal bunt

Karnal bunt, caused by the fungus Neovossia indica, is a devastating disease affecting cereal crops worldwide. It is a strictly regulated quarantine pest due to its potential to reduce crop quality and trigger trade restrictions on agricultural products.

The fungus primarily targets wheat, but can also infect triticale and rye. Unlike other types of smut, the infection caused by Neovossia indica is often partial, meaning the fungus does not replace the entire grain but develops within the pericarp, consuming the endosperm and leaving the embryo intact.

Symptoms become apparent only during the threshing of the crop. Infected grains are partially or fully converted into a black, powdery mass of teliospores. A characteristic symptom is a distinct, unpleasant fishy odor caused by the presence of trimethylamine, which taints the grain and renders it unsuitable for consumption or industrial processing.

The development of the disease is highly dependent on environmental conditions during the flowering stage (anthesis). Periods of high humidity, rainfall, and moderate temperatures (ranging from 15°C to 25°C) are ideal for the germination of teliospores and the subsequent spread of secondary sporidia via wind and water splashes.

Management strategies focus on prevention and containment. Key practices include:

• Strict quarantine enforcement on international grain trade.
• Usage of certified, disease-free seed stocks.
• Crop rotation to reduce soil-borne spore inoculum.
• Application of preventative fungicides during the flag leaf to flowering stage.