Seasonal Dynamics of Alternaria during the Potato Growing Cycle and the Influence of Weather on the Early Blight Disease in North-West Spain.

Early blight caused mainly by Alternaria solani Soraeur and Alternaria alternata (Fr.) Keissl is one of the main diseases of potato. To improve forecasting of disease risk and to provide useful tools for a good decision support system, knowledge about the influence of environmental conditions on the Alternaria species, is necessary. The pattern distribution of the Alternaria spores during eight potato growing cycles in "A Limia" (north-west Spain), and the relationships between Alternaria levels and meteorological parameters were analyzed. Also, the phenology of the potato plants and the meteorological conditions during the study were monitored. Higher Alternaria peaks were found during plant senescence. Nevertheless, extremely high levels can appear starting the plant flowering, when the disease is more destructive. Statistical analysis showed a close relationship between temperature and relative humidity with the concentration of Alternaria in the air. Higher Alternaria levels were observed with a mean temperature above 20 °C and a mean relative humidity below 70%. It is also important to highlight that lower temperature and higher relative humidity during the night, favours the formation of Alternaria spores during the day. The present study showed how differences in weather can be related with the presence of Alternaria spores in the atmosphere of potato crop, and how climate change could affect the development of this agricultural crop. If Spain continues to experience increases in temperature events, longer duration and increasing intensity of early blight epidemics in potato crops are expected in future years. [ABSTRACT FROM AUTHOR]