A NOVEL DEVICE FOR PRECISE AND SELECTIVE THINNING IN FRUIT CROPS TO IMPROVE FRUIT QUALITY
A novel device was developed at Bonn University to thin fruit crops at the flowering stage in order to improve fruit quality (fruit size, coloration, sugar viz taste, firmness, and storability) and overcome alternate bearing. The novel device consists of three horizontal rotors. Their brushes remove up to one third of flowers in slender spindle trees. By selecting a range of combinations of brushes, rotor speed, and tractor speeds the amount of removed flowers can be precisely determined from 0 to 33%. Results from three years (2005-2007) on apple varieties including Elstar, Braeburn, Gala, and Golden Delicious showed that the novel device can precisely remove flowers, not only in the tree periphery, but also close to the tree trunk where fruit of lesser quality otherwise develop. Rotor speeds of between 300 to 420 rpm showed the best efficacy of flower thinning using tractor speeds of between 5 to 7 km/h. Damages to branches and leaves were less than 8% at the maximum employed rotor speed of 420 rpm. The device saves labor cost otherwise required for hand thinning in the order of 15 to 30 hours/ha, equivalent to ca. $100-200 US/ha. The cost of the novel device per hectare is estimated at ca. 100 US $/ha/year based on a life span of ten years and an area of 20 ha to thin each year. The novel device may be an alternative for both organic and integrated fruit growers, particularly as chemical thinning agents become less available for environmental reasons. The novel device with its precise thinning mode may also have a market potential not only for apple, but also for certain stone fruit and Mediterranean fruit crops, where thinning and achievement of a high fruit quality is required for successful economic returns.
Damerow, L. and Blanke, M.M. (2009). A NOVEL DEVICE FOR PRECISE AND SELECTIVE THINNING IN FRUIT CROPS TO IMPROVE FRUIT QUALITY. Acta Hortic. 824, 275-280
apple (Malus domestica Borkh.), alternate bearing, fruit firmness, fruit size, precision agriculture, precision horticulture, return bloom, sugar, sustainability, sustainable horticulture, taste