Fungal Disease Management in Organic Apple Orchards: Epidemiological Aspects and Management Approaches

Abstract

Environmental considerations are becoming increasingly important and, as a consequence, interest has turned from conventional to organic fruit production, including apple. In this production system, synthetic products are banned e.g. in plant protection and nutrient supply, only natural products are permitted according to organic production standards. As a result, disease control is less effective in organic apple orchards than in conventional ones with the consequence that epidemics of key diseases are likely to be more serious in such a system. The majority of sprays in organic apple production are consumed for apple scab control. Therefore, improvement of fungal disease management in organic apple production is largely dependent on apple scab control. This review will provide novel epidemiological aspects and season-long management options against apple scab in organic orchards. This will include several topics (i) risks of early scab epidemics in organic apple orchards initiated by sexual and asexual forms of fungi, (ii) specific features of apple scab epidemics in organic orchards, (iii) possible control strategies to reduce primary inoculum sources, (iv) appropriateness of various sanitation practices against scab in organic production, and (v) some aspects of efficacy and phytotoxicity of approved fungicidal products against scab in organic orchards. Based on the above examples, a theoretical and practical decision-making approach for apple scab and future trends for organic disease management will be provided for organic orchards based on mechanical, agro-technical and chemical control options.