CROP LOADING STUDIES WITH ROYAL GALA AND BRAEBURN APPLES - EFFECT OF TIME AND LEVEL OF HAND THINNING

The effects of time and level (fruit number/tree) of hand thinning on fruit size were investigated for 'Royal Gala' and 'Braeburn' apple (Ma lus domestica (Borkh.)) trees growing on dwarfing rootstocks. Early th inning resulted in larger fruit at harvest in three separate experimen ts whereas the number of fruit per tree had a significant influence on mean fruit weight in only one experiment. Compared to thinning at ful l bloom (FB), mean fruit weight of 'Royal Gala' at harvest was reduced by 16% when thinning was delayed by 3-4 weeks after full bloom (WAFB) , with a much smaller decrease in weight with further delay. 'Braeburn ' gave the opposite pattern, with the greatest loss in mean fruit size at harvest being recorded when thinning was delayed by 8 WAFB. Thinni ng 4 or 8 WAFB resulted in a 17% decrease in leaf area per tree of 'Ro yal Gala' compared to thinning at FB, whereas later thinning of 'Braeb urn' reduced leaf area per tree by 6% per 4 weeks delay in thinning. R emoval of fruit from 'Braeburn' spurs at FB reduced spur leaf size, ki ng Bower receptacle diameter/dry weight, and bourse shoot length on th at spur in the year after treatment compared to removal at a later tim e.