Karnal Bunt of Wheat Control

Symptoms

Only part of some grains in the ear are affected, so it is also called partial bunt. The infected grain is partly converted into a black powdery mass of spores, usually starting from the germ end, while the rest of the grain looks normal. Affected grains give off a fishy or rotten smell due to a substance called trimethylamine. Damage is often noticed only at threshing.

Damage

Karnal bunt rarely causes large yield loss but it seriously lowers grain quality and market value because the bunted grains smell bad and make the flour unfit. It is a quarantine disease, so even low infection can lead to rejection of grain lots and problems for seed and export. It is favoured by cool humid weather with light rain at the time of ear emergence and flowering.

Organic & cultural control

Always sow certified disease free seed and never save seed from an infected field. Grow tolerant varieties where recommended and sow at the proper time so flowering does not coincide with cool wet weather. Avoid excess nitrogen and frequent light irrigation around ear emergence which keeps the canopy humid. Follow a crop rotation away from wheat in badly affected fields to reduce soil spore load.

Chemical control

Treat seed with a registered fungicide such as carboxin plus thiram or tebuconazole based seed treatment before sowing, and where the disease is established a foliar spray of propiconazole 25 EC at ear emergence and flowering can reduce infection. Always follow the product label dose, observe the pre harvest interval and consult your KVK or agronomist for the correct seed treatment and spray schedule.

Always follow the product label, the recommended pre-harvest interval, and your local KVK or agronomist. Pesticide approvals change, so verify before use.

Prevention

The most important step is to use certified, treated, disease free seed every year. Sow on time, use balanced fertiliser, avoid late evening irrigation during ear emergence, and follow crop rotation. Do not move seed or grain from infected fields to clean areas because spores survive long in soil and on seed.