
Macadamia
Resource by Plusfarm
Macadamia trees
are evergreen and grow slowly up to 12-15 m after 10-15 years. Most cultivars
are partly or completely self-incompatible so insects, especially bees, have an
important role in pollination.
The fruit
has a pericarp (husk), a hard testa (seed coat or shell), and an embryo (kernel
or nutmeat). The thick husk and the extremely hard shell may provide greater
protection of the kernel against microbiological contamination.
Macadamia
nuts have a subtle, buttery flavor, and velvety-soft crunch
Varieties
Variety |
Description |
EMB-1 |
Smooth surface texture |
KRG-15 |
Smooth surface texture |
MRG-20 |
moderately rough texture |
KMB-3 |
Moderately rough surface texture |
(KMB–3, MRG–20, EMB-1, KRG-1,
KRG-3, KRG-4, and KRG15) were tentatively recommended for cultivation in the
eastern, central and western highlands of Kenya) Three M. Integrifolia
varieties (MRG-20, KRG-15 and EMB-1) and one hybrid (KMB-3) are recommended for
commercial growing |
Cultivation
Soils The
optimum soil pH should be 5-6. Seedlings should be planted in deep,
well-drained, fertile soils; Waterlogged conditions or soils with high salt
concentrations should be avoided. |
Seeding methods and procedures To
ensure uniform and rapid germination of macadamia seed-nuts, it is recommended
to treat the seed as follows before seeding. - Seed-nuts are placed in
buckets or barrels and soaked for 72 hours or 3 days in cold/normal
temperature water. Change and water daily to avoid fermentation. After
removing the water on the 3rd day, plant the seed-nuts immediately. Soaking
seed-nuts in water enhances rapid and uniform germination. - Pre-treat the
sand beds with Nimbecidine to control soil borne pathogens (optional). -
Prepare rows in the sand-beds with spacing of 8 cm within the rows and 3cm
deep. Place the seed-nuts 1 cm apart within the row. - Count the number of
seed-nuts planted and record this to enable the calculation of germination
percentage. - Label the beds with variety, date of planting and the number of
seed-nuts planted. - Cover the seed-nuts with thin layer of sand then water
thoroughly using fine nozzle watering can or hose pipe |
Spacing The
recommended spacing is 7.5 x 7.5m or 10 x 10m depending on topography.
Transplanting The planting holes should be 60 x 60 x 60 cm and should be dug
during the dry spell or two months before planting. The topsoil and the
subsoil should be kept separately. Fill the hole with the topsoil mixed with
two debes of well-decomposed farm yard manure and a handful of compound
fertilizer such as NPK 20 10 10 or DAP (150g). Carefully remove the potting
bag without disturbing the roots. Open the seedling containers carefully
making sure that the soil covering the roots remains intact. Place the
seedling in the Centre of the hole and cover firmly with the topsoil. Ensure
that the seedling is at the same soil level as that of the soil when the
seedling was in the potting bag i.e. avoid burying the graft union |
Pruning Pruning
is done to remove unwanted plant parts. It is best done immediately after
harvesting the last nuts and before flowering to give an allowance for wounds
to heal. - Remove all the dead branches - Remove intermingling branches that
prevent light penetration - Remove branches that have been attacked by pests
and diseases - Remove all branches that are below 1 m from the ground level -
Protect the wound with insecticidal paint - Tools used: Pruning saws and
secateurs Formative pruning Formative
pruning is the training done on the grafted plants to make the tree grow
upright to a height of 1.0-1.5 m. This work should be done within the first 5
years after establishment of the macadamia nut tree and is important for
continuous development of the tree. Selective thinning This is
removal of unwanted trees from the orchard. - Remove trees that are too
closely spaced - Remove diseased trees - Remove unproductive trees - Remove
undesired varieties - Remove volunteer trees |
Pests and Diseases / Commonly Used Agrochemicals
DISEASE/PEST |
SYMPTOMS |
MANAGEMENT |
Phytophthora
root rot and trunk canker |
Reduces
vigour and productivity of macadamia nut Trunk
canker causes discolouration of the bark at the base of the tree, often with
gum exudation. |
Ensure
good drainage. Pytopthora is greater in soils with poor drainage, low-lying
areas where water pools Chemical
control: The lower trunk of the tree should be sprayed with Aliette
(FosetylAluminium) or Ridomil (Metalaxyl) before the rainy season and young
infected trees should be removed and replanted with healthy stock. |
Botrytis
blight |
Leads to
reduced nut-set - Necrotic flower parts may remain attached to the flower
stalk, and become covered by a matt of fuzzy, grey hyphae. - Can
cause severe fruit drop when prolonged periods of moist weather occur |
Ensure
that the canopy is open allowing light penetration |
Husk spot |
the fungal
disease is restricted to the husk (pericarp) of the nut - Lesions
turn dark brown and fungal spores become visible as a grey discoloration made
up of a thin layer of external hyphae cover the necrotic area. |
Practice
good orchard hygiene, early harvesting and removal of past or out of season
nuts
Strobilurin
based fungicides have shown high levels of efficacy for husk spot
control |
Stick
tight nuts |
nuts remain
on the tree instead of dropping to the orchard floor - This condition tends
to prevail in dry seasons. |
-Practice
good orchard hygiene, early harvesting and removal of past or out of season
nuts that have failed to abscise -
Irrigation: Where the condition is prevalent, irrigate the trees in the dry
season |
Macadamia
stink bug |
The first
nymphal instar sucks sap from young developing nuts before shell hardening. -
The infested kernels become spongy with or without brown pit-like
depressions. Such kernels shrivel, become soft, distasteful and become
translucent |
- Nut
clusters are bagged immediately after nut set -Smoke
from green foliage of Mexican Marigold, Tagetes minuta and others is released
in the orchard to manage the bug Chemical
control: Several insecticides including Decis, Karate, Malathion, Pyerin, and
Bulldock |
Flower
thrips |
feed on
the surface of the green husk and deposit their excreta giving the nut a pale
brown/bronze colouration - Thrip damage is sporadic and does not affect yield
- Thrips are not visible to the naked eye |
Splash
with ash on flower buds Use of
blue sticky traps. Trap
crops: Plant sorghum, Spot-treat
clusters with mild pesticides such as coragen, karate, duduthrin |
Mites |
Feed on
flower buds causing abortion or premature nut drop - These insects are
vectors for diseases |
Field
sanitation Use Actara
and Karate to manage the pest |
termites |
feeds on
the bark of macadamia trees at the base of the plant destroying vascular
tissue, thus hampering the uptake of nutrients and water causing death of the
tree. |
Termites
can also be controlled by brushing them off the tree or by irrigation during
the dry season. Bamako 700
WG Emerald
200 SL |
Mealybugs |
can be
located by tracing the path of feeder ants on the nut stalk |
Use
Karate, Thunder and Duduthrin |
aphids |
Aphids
cause leaves and shoots malformation. |
Use
duduthrin, actara and karate |
Post Harvest
Nuts drop
from the tree when fully mature and should be collected within 2-3 days to
prevent deterioration (physiological) or damage by rodents. Picking or forcing
nuts to fall is discouraged because it is not possible to distinguish mature
from immature ones. Physiologically mature nuts contain 30% moisture in the husk
and 25% moisture in the kernel. The nuts should be spread in layers of about 15
cm on mats or meshed trays under a shade until they are dehusked. For efficient
collection, the area underneath the canopy should be free of weeds and dry
leaves so that the nuts are clearly visible. The yield ranges from 3-5 kg of
nuts for the first harvest after 3 years and 40-75 kg of nuts after 15
years.
Postharvest
handling Dehusking. Dehusking is the removal of the green cover of nuts which
is usually slightly open when nuts drop. Dehusking should be done within 2 days
after harvesting or spread on trays or floor sheltered from the rains in layers
of 6-7 cm to avoid mould infection. The nuts should not be heaped or stored in
sacks. The husks can be removed by cutting with knives, secateurs, or by
carefully pounding in specially designed containers to avoid cracking the nuts.
Although machines may be used to dehusk, large nuts are predisposed to cracking.