Agriculture Reference
In-Depth Information
ethephon releases these buds. The buds in 'Pink's Mammoth' and 'African
Pride' are more suppressed and may require leaf stripping in the summer.
Adventitious buds can arise at any point on a trunk.
Atemoya produces the fi rst fl owers of a season and the most fl owers on
1-year-old wood. The second and third fl ushes of fl owers occur on new growth
and produce most of the crop (Fig. 6.5). The fl owers of the fi rst fl ush may be
removed, as they show poor fruit set and have greater problems with fruit
splitting upon ripening. In south-east Queensland, each year the 1-year-old
fruiting wood is shortened to about 10-15 cm, with four to six buds (Sanewski,
1991). These pruned laterals are retained after producing fruit and allowed to
become part of the framework, thus extending the canopy by 30-50 cm each
year. However, dense shading within the canopy is a major problem. The open-
goblet system is used to produce an open, spreading tree that will produce fruit
early and avoid dense shading. The strategy is to produce one or two fruits on
each shortened, 1-year-old lateral. These laterals are removed completely after
2-3 years and replaced by new growth closer to the leader. The ideal seasonal
growth of laterals producing fruit is about 60 cm long and about 10 mm in
diameter at the base. Annual lateral growth more than 100 cm is considered
excessive for mature fruiting trees. This system allows the development of
fruiting laterals along all the main limbs, with a moderately open centre,
although trees under this system rapidly grow tall. Pruning is normally
carried out in spring before large amounts of bud growth have occurred, with
a moderate summer pruning. Defoliation during the cool season to allow early
development of the buried buds and more uniform fl owering is sometimes
carried out with an ethephon-urea mixture (Sanewski, 1991). Rejuvenation
by heavy pruning is occasionally needed.
Summer pruning of cherimoya was tried in Chile by removing the shoot
tips, leaving six or ten buds, after artifi cial pollination had been performed. In
some cases, girdling or scoring were used in combination. The best treatment
was to cut the shoots at ten buds combined with girdling the trunk during
fl owering time, with an increase of 22% in fruit yield and 25% in fruit weight
(Razeto and Diaz de Valdes, 2001).
Sweetsop is pruned so that 1-year-old branches are cut back to 10 cm.
The pruning left 120-150 branches per tree, with root pruning not being
recommended. Flower initiation begins at the basal end of the growing branch
(Lo, 1987). In Taiwan, normal pruning occurs in January/February, with
fruit harvest from July to September (Fig. 6.7). A summer pruning with fruit
thinning (June-October) of selected trees can lead to harvesting fruit from
October to the next March (Yang, 1987). Highest winter fruiting occurs when
summer growth is pruned, compared with pruning non-fruiting shoots or
pruning in late May.
