Strategies for regulation of seed borne diseases in organic farming

Summary

Common bunt caused by the fungus Tilletia tritici (syn. T.caries) is one of the most devastating plant diseases in wheat. In conventional agriculture the disease is controlled exclusively by fungicide seed treatment, but in organic farming these fungicides are not accepted. Previous studies in India have shown that seed treatment with plant extracts of Canabis sativa, Eucalyptus globulus, Thuja sinensis and Datura stramonium was fully effective against the disease under field conditions. Later, in vitro studies have shown that also germination of spores of the Karnal bunt pathogen (Neovossia indica) could be prevented by these plant extracts. The experiment was repeated in Denmark with extracts from the same species grown in Denmark, which has climate conditions very different from India. In this experiment the same seed treatments had no or very limited effect on the frequency of the disease. The treatments were compared with indigenous methods from Europe including salty brine, Thuja leaves and lime. These methods had a significant but insufficient effect on disease suppression.