Alternative seed treatments for organic legume production

European law provides that, in organic farming, organically produced seed should be used. Therefore new sanitation treatments need to be developed which do not use classical fungicides but still produce seed free from pathogens which can strongly affect yield of the crop. Greenhouse trials were carried out in order to test the efficacy of different seed treatments alternative to chemicals against Colletotrichum lindemuthianum causing anthracnose on bean and Ascochyta pisi causing Ascochyta blight on pea, respectively. Resistance inducers, commercially formulated micro-organisms, non-formulated selected strains of different micro- organisms (fungi, bacteria and yeasts) and plant extracts were applied as dry or liquid seed treatments on naturally infested seeds. Seedling emergence and disease incidence and/or severity were recorded. Possible suppression of Ascochyta blight in peas was masked by the high rate of infection (around 20%), so almost all seed treatments turned out to be ineffective in controlling infection, with the exception of treatments with thyme oil and a strain of Clonostachys rosea. C. lindemuthianum infection was successfully controlled by all resistance inducers. However, they also caused a significant reduction of plant emergence. Among the micro-organism formulations, Bacillus subtilis-based formulations provided the best protection to anthrachnose. Some bacterial strains, a disease-suppressive saprophytic strain of Fusarium oxysporum and the mustard powder-based product Tillecur™ proved to be effective against bean anthrachnose. Tillecur™ (Schaette AG, Bald Waldsee, Germany) and thyme oil are promising for application in integrated pest management and could possibly be used in organic farming