Effect of scoring and GA3 application during full bloom on fruit set and yield in 'Triumph' persimmon
In South Africa (SA), the industry standard treatment to increase fruit set in 'Triumph' persimmon (Diospyros kaki Thunb.) is 20 mg L-1 gibberellic acid (GA3) applied at 30% and 70% full bloom (FB). However, fruit set is often poor and young orchards are slow to come into production despite application of GA3. GA3 application and scoring during FB were evaluated for their effect on fruit set, yield, return bloom and vegetative growth in a young 'Triumph' orchard during two seasons. GA3 did not increase fruit set or yield. In contrast, scoring increased the average yield over two seasons by 61% compared to the untreated control and by 92% compared to industry standard GA3 application. Scoring decreased average fruit mass by 18% in 2006-07 and also decreased one-year-old shoot growth. In conclusion, our data show that GA3 application is ineffective and does not increase fruit set or yield. We recommend the discontinuation of GA3 application and its replacement by scoring to obtain the early onset of regular high yields in young 'Triumph' orchards. Scoring should be accompanied by appropriate pruning and thinning strategies to obtain sufficient fruit size and enough new fruiting wood.