What spoils Swedish apples during storage?

Since application of fungicides is totally prohibited in organic orchards and very restrictive for integrated production (IP), fungal decay is the major reason why Swedish apple production is facing serious economic problems. A successful application of fruit protection strategy depends on several factors including the availability of enough knowledge about the pests and diseases present in packing houses. To provide such information, a multi-research project was conducted in the major production area in South Sweden during five seasons, 2011-2015. Analyses of rotten fruits, collected from packing houses, showed that 44.0% of fungal decay was caused by Neofabraea sp., 30.0% by Colletotrichum acutatum, 13.0% by Penicillium expansum and the rest by Monilinia Fructigena, Botrytis cinerea, Phacidiopycnis washingtonesis and Fusarium avenaceum. N. alba was the most serious problem in three packing houses while N. perennans was more frequent in the other two packing houses. Identifications were performed based on the symptoms on fruits as well as on the morphology of colonies in culture and conidia. Only 15% of the storage losses of organic apples and 9% of IP apples were caused by physiological disorders, especially soft scald. No significant differences in the susceptibility of apples to physiological disorders were found between fruit from the two production systems. Organic fruits were more sensitive to fungal decay than fruits from IP-orchards. The investigation of ten apple cultivars from IP orchards showed a strong correlation between cultivar tolerance to fungal decay and its ripening period. Early cultivars had low tolerance compared to late cultivars. Neofabraea sp. and C. acutatum caused most of the fungal decay during storage.