Field and management factors can reduce potato early blight severity - An observational study on farms combined with field trials in southern Sweden

Abstract

Abstract Background and aims The necrotrophic fungal pathogen Alternaria solani is causing early blight and thereby yield reduction in the potato production. The pathogen is today mainly controlled by fungicide applications. The severity of early blight can vary largely among farms and fields. The aim of this study was to improve the understanding of what field and management parameters that are most important for early blight infection to create more farm specific fungicide treatment recommendations. Methods Over three seasons, 2019–2021, more than 50 field plots were observed at farms in southern Sweden. In each field a 24 m x 24 m plot was left untreated against early blight. However, late blight fungicides were applied. The disease rate was scored in the untreated plot and information about various soil/plant parameters and farmer’s management was collected from each field. In addition to the observational study, field trials were performed in 2021 and 2022, evaluating the effect of potassium fertilizer levels on severeness of infection. Results We found that the soil composition was of significant importance for the rate of infection, in particular the sand, clay, and potassium content. Low levels of leaf potassium increased the severity of early blight infection and this observation was confirmed in field trials where different levels of potassium fertilizer were applied. Conclusion With knowledge about field and management factors that influence disease field specific recommendations can be developed supporting an integrated pest management strategy for early blight to reduce and optimize the fungicide usage.