Abstract
In South Tyrol the first symptoms of Marssonina blotch on apple leaves caused by Marssonina coronaria were observed in the year 2011. The disease with origin in Asia leads to a premature defoliation of infected trees only a few weeks after its outbreak. In order to find a reasonable way to control the pathogen in organic farming and to know more about the vulnerability of Marssonina coronaria in future plant protection strategies, the efficacy of different plant protection products was evaluated in laboratory and in a field trial. The efficacy of different plant protection products allowed in organic farming against the described pathogen was analysed in laboratory with spore germination tests. In addition to a calculated dosage of the respective product, dilutions of 30 %, 10 %, 3 %, 1 %, 0.3 % and 0.1 % of the applied dosage were tested. With generated dose-effect curves the fungicide potential of the tested products was calculated. The evaluation of the efficacy of eight organic plant protection products was conducted in a field trial in 2013. In both studies the best results were obtained with the acid clay-based product Ulmasud. But also lime sulfur and copper in different formulations provided an interesting effect on the pathogenicity of Marssonina coronaria.