7 months ago

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.