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Species Page

Karnal bunt of wheat

Tilletia indica
This information is part of a full datasheet available in the Crop Protection Compendium (CPC). Find out more information on how to access the CPC.
©CAB International. Published under a CC-BY-NC-SA 4.0 licence.

Distribution

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Invasive
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Host plants / species affected

Main hosts

show all species affected
Triticale
Triticum (wheat)
Triticum aestivum (wheat)

List of symptoms / signs

Inflorescence - black fungal spores
Inflorescence - twisting and distortion
Seeds - discolorations
Seeds - galls

Symptoms

Symptoms depend on climate and are manifested most clearly when cool/warm humid conditions prevail at heading. The fungus causes a reduction in the length of ears as well as in the number of spikelets of bunted ears. Infected plants may be dwarfed. In general, T. indica rarely infects more than a few spikelets per ear and then the affected grains are not swollen. Oblong or ovoid sori, 1-3 mm diameter, develop, containing dusty, brown to black spore masses. These characteristically smell of decaying fish (trimethylamine) as do those of T. tritici, T. foetida and T. contraversa (EPPO/CABI, 1996). Feeding studies have revealed no adverse health effects, but consumers can begin to taste and smell the fishiness when 3% or more of grain is affected.

The grain is partially destroyed, the attack starting at the hilum and running along the suture, leaving the endosperm intact and covered by the whole or partly ruptured seed coat. In the case of mild infection, only a black point just below the embryo towards the suture is apparent. In advanced attack, tissues along the suture and adjacent endosperm are replaced by spores. The glumes spread apart, exposing the infected grains, and both glumes and grains may fall to the ground.

For more information, see Holton (1949) and Duran and Fischer (1961).

Prevention and control

Cultural Control

High nitrogen applications and excessive irrigation favour the disease (Warham, 1986). Crop rotation may help to control the pathogen, but its value is questionable because T. indica can survive for up to 4 years in the soil. To prevent the spread of T. indica into previously unaffected areas, the use of disease-free seed is essential. The movement of farm machinery and soil from contaminated fields may also be restricted.

Chemical Control

Due to the variable regulations around (de-)registration of pesticides, we are for the moment not including any specific chemical control recommendations. For further information, we recommend you visit the following resources: