Effect of timing of hand thinning on productivity of Moorpark apricots destined for drying

Thinning at full bloom was compared with thinning at 3 stages of fruit deve lopment and the effects on size, total soluble solids level (TSS) and yield of apricots are reported. In 2 seasons separate branches of 9-year-old Moo rpark apricot trees were hand-thinned to a density of 1 blossom or fruit pe r 50 mm of fruiting wood. Times of thinning were at full bloom, 5-15 mm siz e fruit, stone tip hardening and 21 days post stone tip hardening. These tr eatments were compared with an unthinned control. Experimentation was carri ed out at Loxton, South Australia. All thinning treatments reduced the yiel d of fresh fruit. Thinning reduced yield of dried fruit irrespective of tim ing in the first season but only at the 5-15 mm diameter fruit timing in th e second season. Total soluble solids level of the fruit was increased by t hinning which tended to improve drying ratio. Compared to the unthinned con trol all thinning treatments increased the size of fresh fruit. Mean fruit weight and diameter progressively decreased as thinning was delayed from fu ll bloom till stone tip hardening. Thinning at full bloom produced higher y ields of 35-mm-grade dried fruit than other treatments. To achieve the grea test benefit from thinning it should be carried out at blossoming.