Overcoming barewood in apple trees - prevention and reinvigoration treatments.

摘要

The new apple 'Scifresh' (JazzTM) shows a propensity for excessive flowering on one-year-old wood, particularly on young trees on dwarfing rootstocks. Weak flower clusters develop towards the base of the shoots, which do not set fruit and drop off leaving blind buds. This results in the development of barewood in the young tree with a resultant limitation on the early cropping on spur sites. Although fruit can be grown on one-year-old wood, this results in a reduction in fruit size. Work over several years has focused on the use of sprays of gibberellins (GA) to reduce flowering and local application of thidiazuron (TDZ) to encourage bud break on bare sections of wood. Two applications of 400 mg L-1 GA₃ in early and late January to trees in their final year in the nursery, reduced flowering by over 40% assessed after the trees were planted in the orchard. Twelve months later, these trees showed an increased density of spur flower clusters on the original feathers. Applications of GA₇ have been more effective at reducing flowering than GA₃. Sprays of GA₃ and GA₄₊₇ have also been used in the orchard to reduce flowering on one-year-old wood with some success. Aqueous solutions (up to 2500 mg L-1) of TDZ applied by brush, before, during and after budbreak, to sections of barewood on 2 or 3 year-old wood on main branches of 'Scifresh'/M.9 trees resulted in growth of dormant and trace buds. This treatment also proved successful in promoting bud break along the whole length of feathers on newly planted trees.