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 fr equent problem in winter wheat in Europe during the last 15 years. In organ ic farming, common bunt causes serious problems for seed producers, and man y seed lots are discarded due to contamination with Tilletia tritici. Owing to the biology of Tilletia tritici, with spores loosely attached to the su rface of the grain, there is a risk that spores can be disseminated via gra in handling equipment, including combine harvesters. Preventive efforts sho uld focus on the role of grain handling equipment and how the fungus life c ycle can be broken. The dissemination of spores via the combiner after harv esting infected fields has been investigated. Six trials were conducted ove r three years, counting the number of spores in up to seven emptyings of th e combiner. Up to four emptyings with non-contaminated grains were needed i n 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 sh ould always be combined with analysis of seeds for spore load.