BACKGROUND: Increase in the ratio of small berries in blueberry production decreases the farmers’ profits due to weakening market competitiveness and harvest efficiency. One of the reasons for increased small berries is over fruit-load. To increase productivity and competitiveness of blueberry in Korea, hand-thinning can be applied to increase fruit quality before the developing adequate chemical thinning methods. This study was conducted to investigate the proper timing and methods for floral buds thinning in rabbiteye blueberry.
METHODS AND RESULTS: Fruit size distribution by leaf-to-fruit ratio was investigated by counting the number of leaves and fruits in canes of 127 ‘Brightwell’ plants whose fruit set varied. Fifty percent of flowers/floral buds were removed in four different floral buds stages such as bud swell, late pink bud, full bloom and petal fall, and the consumed time for thinning and fruit characteristics were recorded to investigate the effect and proper timing of floral buds thinning. Fruit weight and soluble solids content tended to increase in proportion to leaf-to-fruit ratio and the production of the number of fruits less than 13mm in diameter decreased when leaf-to-fruit ratio is more than 2.5. Manual floral buds thinning by hands was fastest in full bloom stage and slowest in bud swelling stage. In all cultivars, fruit size was significantly smaller in non-thinning treatment than thinning, however, there was no significant difference in total fruit yield. The number of fruits less than 13 mm in diameter increased in both cultivars as floral buds thinning was delayed. Consumed time for picking 90% berries out of total berries per bush was shortest in full bloom stage thinning in ‘Brightwell’ and bud swelling, full bloom thinning in ‘Powderblue’. These were 25 and 20 days faster than no thinning, respectively.
CONCLUSION: Although the effect of floral buds thinning varies depending on the cultivars, our results confirmed that floral buds thinning was effective in the early intensive harvesting and the increase of the large fruit ratio and the harvesting productivity, in order to increase thinning efficiency, it is recommended to remove the flower buds before the full bloom stage.