Cultivation technology influences the occurrence of potato early blight (Alternaria solani) in an organic farming system

Summary

Nowadays, organically produced products have become more popular than ever and interest in them is still
growing fast. The early blight causal pathogen Alternaria solani has not been considered a great threat to potato in
northern climate conditions in the past and has not been routinely sprayed against. During our study early blight
was evaluated in 2010 and 2011 on the plants of a potato cultivar ‘Reet’ in an organic farming experiment. In our
study, both growing seasons were very favourable for early blight development. Significant differences between
the two cultivation technologies were found (F1,12 = 4.84, p = 0.048). In 2010, the area under disease progress curve
(AUDPC) value was 303 on cover crop (CC) plots and 990 on CC + M (manure) plots that is three times higher,
whereas in 2011, the AUDPC value was 967 on CC plots and 1195 on CC + M plots. Our results confirm that potato
early blight has become a serious problem in North-East European organic potato fields and thus susceptible potato
cultivars cannot be recommended for growing in an organic farming system. However, it is possible to influence
the development severity of early blight by selecting the proper growing technology. Since, in the changing climate
conditions and in susceptible cultivars, early blight is a potato disease that can cause early defoliation of plants and crop death, there is a need for resistant potato cultivars.