Fruit drop occurs on most trees

Press, Volume CXII, Issue 33100, 15 December 1972, Page 13

Fruit drop occurs on most trees

About this time of each year a seemingly inexplicable phenomena occurs with most commonly grown top fruit. It is known as fruit drop. A good percentage of the crop is suddenly shed and the appearance of young fruit scattered beneath the tree often causes anxiety lest there is something wrong with it. Research on this problem has demonstrated that only about 3 per cent of the fruit which sets on a tree need reach maturity to provide a reasonable crop. There are usually two or three separate falls which occur with most of our generally grown top fruits. The first shedding of fruit normally occurs shortly after blossoming. This can be attributable to frost damage but is also caused by a blossom failure associated with insufficient pollination. Again, this can be, in part, due to weather which may have restricted bee activity. It could also mean in some cases that there is a need for better cross-pollination and that a suitable cross-pollina-tor must be located nearer to the existing subject. This applies very much to pears, very many Japanese plums and some European plums and also to cherries. It is not necessary with apricots or all but one (J. H. Hale/million dollar) of the peaches. Apples do not require such safeguards but their fruiting capabilities are improved where suitable varieties are planted in close proximity to one another.

The second drop may occur when the fruit is about the size of a marble. On this occasion the shedding may be due to excessive competition between the developing fruits for a limited supply of nutrients and moisture. Once more the weather can greatly influence this occurrence and it will be particularly noticeable where a heavy crop has set under very dry conditions. Damage to the root system, excessive feeding or insufficient plant food availability, particularly nitrogen, and very poor drainage are other contributory factors. The pre-harvest drop (or

arops) can oe due to a: I variety of reasons, depending j on the kind and even the: i variety of fruit. A major I ! cause is again weather—for! instance a warm period of ! weather followed by cold I nights. Trees which have I been subjected to high amounts of nitrogenous feedjing are more likely to shed fruit at this stage. I When fruit is mature it j drops even more naturally land the cause is due to the formation of an abscision layer which develops between the stem and the stalk of the fruit in much the same way as occurs to the leaves of deciduous trees and shrubs.