Reducing Spread of Spores of Common Bunt Disease (Tilletia tritici) via Combining Equipment

The disease common bunt (Tilletia tritici syn. caries) has become a more frequent problem in winter wheat in Europe during the last 15 years. In organic farming, common bunt causes serious problems for seed producers, and many seed lots are discarded due to contamination with Tilletia tritici. Owing to the biology of Tilletia tritici, with spores loosely attached to the surface of the grain, there is a risk that spores can be disseminated via grain handling equipment, including combine harvesters. Preventive efforts should focus on the role of grain handling equipment and how the fungus life cycle can be broken. The dissemination of spores via the combiner after harvesting infected fields has been investigated. Six trials were conducted over three years, counting the number of spores in up to seven emptyings of the combiner. Up to four emptyings with non- contaminated grains were needed in order to achieve an acceptably low level of contamination. Using Denmark as a case, several important factors influencing disease spread via harvest equipment are discussed. It is concluded that one easy preventive strategy is to avoid using the first four emptyings of the combiner. This method should always be combined with analysis of seeds for spore load.