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New Zealand Plant Protection 63 (2010): 281

Testing calcium in a commercial apple orchard for control of bitter rots caused by Colletotrichum acutatum

I.P.S. Pushparajah, J.T. Taylor, M. Walter, K.S.H. Boyd-Wilson and K.R. Everett

ABSTRACT

Previous laboratory and field tests have indicated that calcium shows promise for control of bitter rots on apple caused by Colletotrichum acutatum. This year, a replicated fungicide spray trial was conducted on a commercial orchard in Rukuhia, Waikato, on a block planted with 'Royal Gala' apples. Chemicals were applied at 10-14 day intervals from October to February. Calcium chloride applications were as effective as fungicides for control of bitter rots on fruit at both high and low rates, but high rates damaged apple leaves. Calcium chloride is already applied to some apple cultivars, but not often to 'Royal Gala'. It is a generally regarded as safe (GRAS) chemical, and residues are not tested. Calcium chloride at low rates is suitable as an alternative to fungicides for use in residue-free growing programmes to control bitter rots in the orchard.

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