Effect of different seed treatments against seed borne diseases on corn salad

Seed borne pathogens may cause high yield losses in various crops. It is therefore of vital importance that seed treatments that eliminate seed borne pathogens are available. The aim of this work was to evaluate the effect of selected seed treatments against two seed-borne diseases (Acidovorax valerianellae and Peronospora valerinaellae) on corn salad (Valerianella locusta). Treatments with ethanol, caustic potash and a seed encrustation with compost powder were compared to the reference treatments sodium hypochlorite, a hot water treatment and the aerated steam method as well as to untreated seeds. To test the efficacy of these methods, naturally infected seed lots were used. The detection of P. valerianellae was done with the grow-out test; the detection of A. valerianellae was performed with a combination of a grow-out test and polymerase chain reaction. Additionally, the germination capacity of the treated seeds has been tested. The caustic potash treatment had a very good effect (equal to the reference methods) against A. valerianellae. The effect against P. valerianellae was good, but lower than the reference methods. More experiments are necessary to determine whether the effect of a caustic potash treatment against P. valerianellae is sufficient for economic production. For the ethanol treatment, no effect against A. valerianellae was detected and against P. valerianellae only a partial efficacy was observed. The encrustation technique of the compost treatment is not yet mature and caused a great reduction of germination capacity. In the tested form, this treatment cannot be recommended for practical use. The sodium hypochlorite treatment had a very good effect against P. valerianellae and A. valerianellae and a high germination capacity of the seeds was conserved. However, sodium hypochlorite is not permitted in organic farming because of poor degradability and potential toxicity. The hot water treatment and disinfection with aerated steam have again proven to be very effective against both diseases. With this, previous results of performance tests are confirmed and the relevance of the hot water and the aerated steam method for seed treatments in organic farming was reinforced.