Macadamia Nuts in Hawaii: History and Production - ctahr ...

Figure 76. Rat-damaged nuts under a tree that was isolated and
poorly maintained. Rats gnaw through the outer hard
shell, creating an opening through which they are able to
reach the nutmeal.
Figure 77. Rat bait stations made of cans with a lip bent up on the
lower opening to reduce rainwater falling on the bait.
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are self- or cross-compatible. Although honeybees
do help in pollination, evidence indica tes tha t bee
population from a given apiary rapidly declines
with distance from the hive (15). However, no
suggestions as to the distance between apiaries in
an orchard or the number of hives necessary per
acre can be given at this time. Until reliable data
on the macadamia nut becomes available, the beehives
in the orchards should be clustered to make
placement easier, at the rate of about one hive per
acre. The density of hives can then be changed as
further information becomes available. Syrphid
flies and other insects also aid in pollination (85).
Consequently, any insecticidal spray program
should be closely monitored during the flowering
season.
Honey from macadamia blossoms is considered
excellent.
Flowering and Nut Set
The macadamia flower cluster is a raceme (16)
with 200 or more perfect flowers, each on its own
pedicel, arranged along the sides of a common
flower stalk. Each raceme extends to its fullest
development before the buds begin to open at
random throughout the cluster. The flowers stay
open for a few days, during which time most of the
pollination takes place. Some flowers have their
own pollen capsules attached to the stigmatic
surface, and are self-pollinated. Although no data
have been collected, visual indications are that
only about 10 percent or fewer of the racemes
formed on the tree will eventually produce harvestable
nuts. Initial fruit set on these racemes is
generally heavy, but for causes not yet determined,
some young fruits up to \4 inch (0.5 centimeter) in
diameter will drop very early, leaving only a few
nuts to mature on a setting raceme. When the nuts
are much larger, "June drop" occurs during the
summer months, further reducing the harvestable
nut set. Experiments on the effect of the growth
regulator succinic acid 2,2-dimethylhydrazide
(SADH) have been conducted (50, 59). Results of
these trials using 1O-ppm solutions have shown a
10 percent nut set increase without affecting nut
quality, growth, or mineral nutrition of leaves.
However, more research in this area is needed.
Flowering normally occurs during the period
from November through February in Hawaii; the
nut harvest period starts about August of the
following year and continues until about February
or March. In older trees, however, flowering can