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Other Names: Smooth-Shell Macadamia Nut, Queensland Nut

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This summary was prepared from publications by
Bittenbender, H. C. and H. H. Hirae and
Yokoyama, K. M., et. al.

FAMILY: Proteaceae SCIENTIFIC NAME: Macadamia integrifolia Maiden and Betche ORIGIN: Subtropical Eastern Australia

Neal (1965) describes the macadamia nut tree as a fast growing, regular-shaped, medium-sized tree with heavy, dark green foliage. Leaves develop in whorls of three, paired, or in fours. The leaves are rarely solitary. The leaves are blunt tipped, oblong, 1 foot in length or more, edged with fine teeth, and the petioles are about half an inch in length. The flowers are small, whitish, tasseled, and grow on long spikes. The nuts ripen in the fall, both the spring and fall, or through the year. The nut is encased in a leathery two valved case that is 1 inch in diameter. The case encloses one spherical nut or two hemispherical nuts. The nuts have a smooth hard shell that encases a white kernel.
The highest quality macadamia kernels are free of defects and insect and fungal damage, and they contain at least 72% oil. Kernels with less than 72% oil are usually immature and harder, and they become over brown when roasted.

VARIETIES Back To: Menu Bar
Considerable research has gone into selection and breeding of the best cultivars for Hawaii. The College of Tropical Agriculture and Human Resources (CTAHR) recommends the following cultivars: Purvis (294), Kau (344), Kakea (508), Keaau (660), Mauka (741), Pahala (788), and Makai (800). Donnison (790) performs well at elevations below 500 feet.

USES Back To: Menu Bar
The kernel is the main product from the macadamia nut tree. After harvesting, the husks covering the nuts are removed. The nuts are fried, the shells are cracked, and the kernels are removed to be oil-roasted or dry-roasted. Kernels are commonly sold as snack nuts and chocolate-covered candy. Ice cream manufacturers and the baking industry also use macadamia kernels as an ingredient.
The shell and husk also have uses. Shells can be used as a mulch, fuel for processing macadamia nuts, planting medium for anthurium culture, plastic manufacture and as a substitute for sand in the sand-blasting process. Husks are used as mulch or composted for fertilizer.
Oil can be extracted from culled nuts. The cosmetic industry, especially in Japan, uses the oil in soaps, sunscreens and shampoos. The remaining press cake might be used for animal feed.
A one ounce oil-roasted macadamia nut (approximately 10-12 whole kernels) has 204,000 calories, 21.73 grams of fat, 2.06 grams of protein, 3.66 grams of carbohydrates, 13 milligrams of calcium, 33 milligrams of magnesium, 57 milligrams of phosphorus, 94 milligrams of potassium, and 2 milligrams of sodium.

In Hawaii, commercial orchards are planted with grafted seedlings. Macadamia nut trees can start bearing a small crop in the fifth year after planting, and full production is reached in 12 to 15 years.

Macadamia nut trees can be grown on deep, well-drained soils with a pH of 5.0-6.5 or on well-drained a'a lava land that is sufficiently weathered to support natural vegetation. The trees require 60-120 inches of rainfall a year and can be grown from sea level to an elevation of 2500 feet.
A major concern is strong wind, which can cause severe tree loss. Narrow-profile cultivars, such as Kau and Pahala, are more wind resistant than others.

Interplanting with two cultivars, such as 344 and 660, improves yield through cross-pollination. Beehives near the orchard can generate additional revenue through honey production. Another possibility is the integration of animals. MacFarms of Hawaii and CTAHR are experimenting with sheep as natural lawn mowers to reduce herbicide use and weeding costs. Sheep products also provide an income.
Intercropping macadamia nuts with quicker bearing crops is one way to generate early returns. In Kona on the Big Island, coffee is sometimes grown between macadamia nut trees. An alternative is to increase the initial planting density to get higher total production in the early years. In Australia, for example, some yields peaked at 8000 lb/ac in high-density plantings before competition for light caused a decline. Tree removal or radical pruning to improve light penetration is necessary.

Semiannual leaf tissue analysis is recommended to determine the best fertilizer practice for your orchard and to prevent nutritional problems. If you have never taken a leaf or soil sample, consult with an extension agent or fertilizer representative before beginning. If your orchard appears normal, a sample from one tree per acre is adequate. Collect a leaf sample before trees produce new leaves, generally during February and March or before fertilizing in September or October. Pick three to four branches where the bud at the tip of the branch is just opening and beginning to grow. Do not choose branches with buds with long, hard red scales called false flushes. These will not open for months. At the proper stage, buds will have three small pale green leaves and look like a claw. Pick one healthy leaf from the second node (whorl) of leaves below the bud. Fifteen leaves from four to five trees are needed for each sample submitted for analysis. The samples should be placed in plastic bags and labeled with your name, date of sampling, and sample number.

HARVESTING Back To: Menu Bar
Macadamia nuts are harvested manually after they have fallen. In Hawaii, the nuts typically drop 8-9 months of the year from July to March. Large-scale producers also employ mechanical sweepers and pickup devices on relatively even land to offset the high cost of agricultural labor in Hawaii. CTAHR developed a tractor-mounted pickup device for smaller orchards. Nuts should be harvested at least every four weeks when the weather is rainy and less often in dry weather. This is to prevent losses from mold, germination, and pig or rat damage.

Never store unhusked nuts more than one day in a bag or box. It is best to husk the nuts immediately and air dry them or take them to the processor the next day. If the nuts were picked and cannot be husked nor delivered to the processor, then the in-husk nuts should be dried. The in-husk nuts should be spread on a wire or slotted rack out of the rain and direct sun.

DISEASES Back To: Menu Bar
Macadamia root rot - Kretzschmaria clavis
Trunk canker - Phytophthora cinnamomi
Dieback or slow decline - disease infection in trunk or root, prolonged drought, anaerobic conditions caused by compaction or poor drainage, poor root structure caused by planting root bound trees, toxic chemicals from herbicides or overapplication or uneven application of fertilizers, or nutritional problems

Macadamia quick decline (MQD) - unknown stress factors (Waterlogged soil, low pH, nutritional problems, and fungal and stem rots are suspected stress factors with ambrosia beetle attacks hastening the tree decline. The fungi Xylaria and Nectria are frequently associated with MQD.)
Flower blights - Phytophtora capsici or Botrytis cinerea with Cladosporium usually secondary or affecting raceme tips
Premature nut drop - most premature drop is normal, environmental stress may cause more premature drop than normal

INSECTS Back To: Menu Bar
Ambrosia beetle (Xyleborus affinis)
Broad mite (Polyphagotarsonemus latus)
Longhorned grasshopper (Conocephalus saltator)
Narrow-winged katydid (Elimaea punctifera)
Southern green stink bug (Nezara viridula)
Koa seed worm (Crytophlebia illepida)
Macadamia shot borer (Hypothenemus obscurus)
Hawaiian flower thrips (Taenothrips hawaiiensis)
Redbanded thrips (Selenothrips rubrocinctus)

PRODUCTION Back To: Menu Bar
The macadamia nut originated and is grown in Australia, but commercial production in concentrated in Hawaii. Some countries in Latin America, Africa and Asia also grow macadamia nuts. In the continental United States, trees are found in California and Florida.
The yield of in-shell nuts on poorer land in Hawaii is about 5200 lb/ac, with at least 7000 lb/ac attainable on better land. In Australia, the yield in good orchards is about 4000-5000 lb/ac.
The shell accounts for most of the macadamia nut's weight. Hawaii's average kernel recovery rate from in-shell nuts was 23.5% during 1989-1990. With an improved cracking system, better shell-kernel separators, and cultivars with a high percentage of kernel, the recovery rate could increase to 35%.
Of the 49 million lb of gross, wet in-shell nuts delivered to processors in 1988-89, 3.5 million lb, or 7.1%, were culled. The primary causes of loss were mold and rot (2.2% of the total crop delivered), followed by immature nuts (2.1%); stink bugs Nezara viridula (1.1%); germinating nuts (0.7%); koa seed worm, Cryptophlebia illepida (0.5%); and the macadamia shot hole borer, Hypothenemus obscurus (0.5%). The figures exclude nuts culled before delivery and losses at the farm caused by rat damage, macadamia quick decline (MQD) and other factors.
Data on worldwide production are scarce and conflicting. An estimate for 1989 indicates that macadamia nut plantings covered 54,600 ac and total production of in-shell nuts was 62 million lb. Hawaii is the major producer, accounting for over 73% of total production, followed by Australia (22%). Other producers include South Africa, Guatemala, Kenya, Costa Rica, Malawi, Brazil, Mexico, New Zealand and China.
About 2000 acres are planted in the San Diego area. Although not all plants have begun bearing, Southern California growers produced about 150,000 lb (in-shell) of rough-shell macadamia nuts in 1988 at a farmgate price of approximately $1.50 lb Rough-shell nuts do not roast well; the price reflects a novelty demand for in-shell or raw nuts.
Hawaii is the world's leader in growing and processing macadamia nuts. In 1989-90, Hawaii harvested a record 50.5 million lb of buts (net, wet in-shell basis) for a record farm value of $44.9 million, up from 18.2 million lb and $5.8 million in 1975-76. The crop covered about 22,300 acres in the state, of which 18,200 acres, or 82%, were bearing acreage.
The price of in-shell nuts has climbed along with production in Hawaii. The net farmgate price has gone from 31.6 cents in 1975-76 to 89 cents in 1989-90.
In Hawaii, macadamia nuts are grown by both small-scale farmers and large corporate producers. Most operations are located on the Big Island. Mauna Loa Macadamia Nut Corp. (a subsidiary of C. Brewer) and MacFarms of Hawaii are the two largest local growers and processors.
A 1989 CTAHR study calculated annual net returns per acre in Hawaii from start-up to maturity (16 years or older) for farms of 25, 50, 100, and 500 acres. Various price and yield scenarios were used for mature orchards, showing substantial economies of scale for the larger farms. A previous study published in 1982 assessed the economic feasibility of 5-, 10- and 20-acre farms in Hawaii. Most growers are multiple-income farm families, and macadamia nuts supply only a fraction of their income.
Australia is the second largest producer of macadamia nuts, with an estimated 15,000 acres planted in 1989. While most of the Hawaii trees are mature, an estimated 20% of the trees in Australia are bearing. As the trees mature Australia will become a more formidable competitor.
US per capita consumption of macadamia nuts increased from 0.04 lb in 1979 to 0.06 lb in 1988. macadamia nut consumption in 1988 was somewhat comparable to that of filberts (0.09 lb) and pistachios (0.19 lb), but considerably lower than that of almonds (0.66 lb), pecans (0.52 lb) and walnuts (0.44 lb).
In 1989-90, US (Hawaii) production of macadamia kernels was about 11.9 million lb (assuming a 23.5% kernel recovery rate). During 1989, the US also imported 5.1 million lb of macadamia nut products, of which 4.2 million lb were shelled nuts at a CIF value (cost, insurance and freight) of $20.4 million. In addition, 673,000 lb of prepared or preserved nuts and 189,000 lb of unshelled nuts were imported at values of $1.2 million and $175,000, respectively.
In 1991, the farm value of macadamia nuts fell to $34.7 million, the lowest since the 1984-1985 crop season, as grower prices slid to a seven year low. Production was estimated at 49.5 million pounds, net wet-in-shell, down 1 percent from the previous season. Weather in the major growing areas was drier than usual, however the effects on yield were varied. Continued dry weather in Kona and South Kona generally had a downward effect on yields, whereas normally wet East Hawaii orchards benefited from the drier conditions. Total acreage, at 22,500 acres, remained at about the same level. An anticipated increase in bearing acreage was postponed pending rejuvenation of major plantings.
US imports of macadamia kernels have increase nearly eight times, from 539,700 lb in 1982 to 4.2 million lb in 1989. Australia was largely responsible for the increase; its exports to the United States rose from 21,800 lb in 1982 to 2.4 million lb in 1989. Imports from Malawi also increased substantially, from nothing in 1982 to 945,800 lb in 1989.
In the 1992-1993 (July 1, 1992 to June 30, 1993) crop year, there were 660 farms with 20,500 acres in crop. There were 17,500 acres bearing a net production of 2,700 pounds per acre. There were 53,000,000 pounds of macadamia nuts delivered wet in-shell to processors. The net production less the total spoilage through cracking was 48,000,000 pounds. The gross farm price (farm value divided by gross production) was 61.6 cents per pound and the net farm price was 68 cents per pound. The farm value (net production multiplied by net farm price) was $32,640,000.
In 1989, Australia supplied 94% of unshelled macadamia nut imports to the US. Australia also was the major supplier of shelled macadamia nuts, accounting for 58% of the total US imports, followed by Malawi (22%) and Guatemala (15%). Other suppliers included Costa Rica, Kenya, Zimbabwe and Brazil.
The average US import price (CIF) of macadamia kernels was $4.81/lb in 1989. The major ports of entry were Honolulu (32.6% of total imports), San Francisco (31.4%) and Los Angeles (28.8%).
Hawaii is the most developed market for macadamia nuts. The estimated value of Hawaii's chocolate-covered macadamia nut wholesaling industry is over $100 million. The snack nut market is another major outlet for macadamia nuts.
Japanese visitors purchase a large quantity of macadamia products in Hawaii to take home. These "suitcase exports" are not included in the US export statistics.
The Hawaii Macadamia nut Association publishes an annual proceedings of research and issues, and a quarterly newsletter, MacFacts.

REFERENCES Back To: Menu Bar
Bittenbender, H. C. and H. H. Hirae. 1990. Common Problems of Macadamia Nut in Hawaii Research Extension Series 112. College of Tropical Agriculture and Human Resources, HITAHR, University of Hawaii.

Neal, Marie C. In Gardens of Hawaii. Hawaii: Bishop Museum Press, 1965.

Yokoyama, Kevin M., Kulavit Wanitprapha, Stuart T. Nakamoto and H.C. Bittenbender. 1990. Macadamia Nut Economic Fact Sheet #9. Department of Agricultural and Resource Economics, CTAHR, University of Hawaii.

Statistic of Hawaiian Agriculture 1991. Prepared by: Hawaii Agricultural Statistics Service, P.O. Box 22159, Honolulu, Hawaii, 96823-2159. December 1992. 105 pages.

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