Articles
GROWTH REGULATORS IN PEAR PRODUCTION
CCC has a highly repressive effect on the vegetative growth of all the varieties tried so far.
The volume and height of Comice trees sprayed for eight consecutive years were 43% and 69% respectively of the volume and height of untreated trees.
Several trials showed a slight but significant increase in the number of fruit buds.
These differences were rather attributed to the variations in crop quantity with the different treatments in the preceding years than to the direct influence of CCC.
The effect of CCC on yield, especially of young trees, is considerable.
The yield efficiency (yield/volume of the tree) of Comice trees sprayed for eight consecutive years was almost twice the control value.
In a trial with Spadona di Salerno, sprayed for five consecutive years, CCC induced a cumulative yield 30% over control value.
The major yield efficiency is attributed to a better fruit setting or to a minor june drop.
By utilizing the radio isotope CCC-C14 on young trees grown in pots, it could be observed that the radioactivity persisted especially in the zones of application, whereas only minor quantities were translocated to the other zones.
Chemical analysis of the whole trees in the rest period demonstrated that the dosis applied had not been entirely metabolized.
In fact, unmetabolized CCC was found in the whole tree, with the highest concentrations in the epigeal part.
The repressive effect of Daminozide on the growth of pear trees is notably weaker than that of CCC. It has instead a strong influence on bud differentation, doubling or triplicating the amount of blossoms.
Therefore the application of Daminozide is useful whenever an increased bud differentation is required, e.g. on young trees in training, or when an inhibition of bud differentation due to extreme yield is expected.
Ethrel can be usefully applied to defoliate scions in the nursery, but is effectiveness depends on the time of application, on