Alternative means to reduce storage decay in organic apple production; time of harvest and calcium applications

Abstract: In Norway, organic apple growers only have sulphur available as a fungicide. When organically grown apples are stored, growers must thus rely entirely on alternative means to reduce the amount of storage decay. It is known that harvest time and calcium content may affect fruit rots in apple. The effect of harvest time on storage decay was assessed during three years. After storage there was a clear increase in fruit decay from the earliest to the latest picking times, both recorded as total decay and for the important storage diseases bitter rot (caused by Colletotrichum acutatum) and lenticell rot (caused by either Phlyctaena vagabunda or Cryptosporiopsis curvispora). In mean of three years apples of cv. Aroma harvested 2 or 1 week prior to normal harvest time, at normal harvest or 1 or 2 weeks afterwards and stored for three months in a ventilated cold store, had 6, 14, 35, 33, and 35% bitter rot, respectively. Similar numbers for lenticell rot (in mean of two years) were 6, 10, 11, 16 and 24%, respectively. Applications of calcium at different times prior to harvest reduced the amount of storage decay in some trials, but not consistently.