Fruit trees naturally experience fruit drop at different stages of development to prevent overburdening of resources. Mango flowers contain thousands of flowers but only a few fruits are needed for a normal crop. Fruit drop occurs in three stages - first shortly after flowering when unpollinated or defective flowers drop, second around two weeks later when unfertilized and some fertilized flowers drop, and third when fruits reach a marble size. Fruit drop can be caused by mechanical, climatic, physiological, nutritional, cultural, pathological, and varietal factors. Proper cultural practices and plant growth regulators can help reduce fruit drop.

2.  Fruit trees usually bear a large number of
flowers and only small percentage of which
are enough to give a normal yield.
 Single inflorescence of mango contains 5000
flowers but an average of 5 fruits per
inflorescence would provide a good to heavy
crop.
 The actual percentage of fruitset will be
much lesser.

3.  Fruit drop is natural and beneficial to the
trees and it will prevent exhaustion of
resources and breaking of branches by over
bearing.
 This drop occurs at three stages as indicated
below:
1) First drop
2) Second drop
3) Third drop

4.  It occurs shortly after flower opening.
 Usually flowers with aborted pistils drop off
at this stage.
 Lack of pollination, low stigmatic receptivity,
defective flowers, poor pollen transference
and occurrence of incompatibility are some
of the causes attributed for this drop

5.  It occurs a fortnight later than the first drop.
 This drop includes unfertilized flowers and
some fertilized flowers.
 Fertilized flowers also drop off at this stage
as a result of adjustment in the trees
between nutritional factors and fruitset.

6.  This drop occurs when the fruits are ‘marble
size’ due to the formation of abscission
layers in the young fruit stalks.
 This is common in most deciduous fruits and
as it coincides with the June month, (June
drop).
 This natural thinning of fruit helps the trees
to produce remaining fruits with good size.

7.  Dropping or shedding of fruit takes place
before harvest.
 Half and three-forth developed fruits are
shed due to many causes.
 This is a loss to the growers and is a serious
problem confronted by them especially in
apple, mango and citrus fruits.

8.  Mechanical
 Climatic factors
 Physiological factors
 Nutritional factors
 Cultural practices
 Pathological factors
 Varietal factors

9.  Mechanical factors
Wind and hailstorms cause fruit drop
 Climatic factors
High temperature, low humidity and very low
temperature hasten the formation of
abscission layers.
Eg: high temp + low humidity -> fruit drop in
mango.
 Physiological factors
Abnormal fluctuations of soil moisture favour
heavy fruit drop

10.  Nutritional factors
lack of available nitrogen and similar other
nutritional factors may cause fruit drop.
it is more in weak shoot than in the strong
ones and also more in young trees than in
medium or old trees.
 Cultural factors
deep digging or deep ploughing during fruit
development phase will injure the roots and
cause the fruit drop.
Drought or lack of irrigation -> fruit drop in
mango (3rd stage)

11.  Pathological causes
incidence of pest and diseases will cause
more shedding of fruits.
eg: high incidence of diseases like powdery
mildew and anthracnose and pest like
hopper and mealy bugs in mango favours
more fruit drop.
 Varietal factors
within a kind of fruit, the varieties differ
among themselves in the extent of fruit drop.

12.  Proper and timely culture such as irrigation,
manuring, plant protection, provision of
pollinizers and wind breaks will help to
prevent the amount of fruit drop.
 NAA @ 10-20 ppm -> reducing drop fruits in
pome fruit such as apple and pears.
 2,4-D @ very lower concentrations (<20
ppm) -> controls pre-harvest fruit drop.

13.  2,4-D and 2,4,5-T at 5 to 10 ppm when
sprayed on kadai orange decreased fruit
drop and increased fruit retention.
 NAA @ 10 ppm -> reducing fruit drop in litchi
 GA @ 60 ppm -> reduces fruit drop in
jamuns