ASSESSING INTERACTIVE EFFECTS BETWEEN CYTOLIN AND ETHEPHON ON CROPPING RED DELICIOUS

A trial in north-western Tasmania studied the effects of Cytolin and ethephon sprays on the thinning and shape of 'Delicious' apples. Untreated control and hand-thinned treatments and trees sprayed with Cytolin alone were compared with trees treated with a full thinning programme (FP). This consisted of ethephon at full bloom (FB) and seven days after full bloom (AFB) or combinations of the FP missing out either the FB or the seven days AFB ethephon sprays, with or without Cytolin. Cytolin was applied at 25 mg l-1 at the king petal (KP) stage. Ethephon was applied at 100 mg l-1 at FB and/or seven days AFB. Cytolin alone had no effect on thinning. Omitting the FB ethephon spray from the programme resulted in underthinning and lower fruit weights. Adding Cytolin to the programme did not cause extra thinning or changes in fruit weight or pip numbers. There was evidence that ethephon thinning sprays reduce the length/diameter (LD) ratio of fruit but the addition of Cytolin to the successful programmes can restore the shape. Cytolin can safely be used in conjunction with an ethephon spray thinning programme. It is recommended that the preferential ethephon programme, with Cytolin, consists of only the FB application.