Rural Industries Research & Development Corporation

The New Rural Industries
A handbook for Farmers and Investors

Mangosteen

Introduction

The mangosteen (Garcinia mangostana L.) is a tropical fruit relatively unknown in Australia but which sporadically appears on some of the larger markets here. It is better known in South East Asia, where the crop originated, and the major producing countries are Thailand, Malaysia, Philippines and Indonesia. Most of the fruit in these markets is obtained from backyard trees or from trees planted as a component of mixed fruit orchards. Outside South East Asia mangosteen has proven difficult to cultivate on a broad scale. In Australia, around 10,000-12,000 trees (about 50 ha) have been planted in the Northern Territory and far north Queensland.

Mangosteen, native to the wet tropics, is adapted to heavy and well-distributed rainfall and has been described as the `Queen of Tropical Fruits' because of its instant visual and taste appeal. This fruit could undoubtedly find a significant niche on the Australian domestic market, and export possibilities also exist due to the fruit's good transport characteristics and its relatively long shelf life. A

ustralia enjoys a partial `reverse hemisphere' production advantage over Asia and could become a world focus of mangosteen production. Pioneering research on early establishment requirements has already made considerable progress, particularly with respect to propagation, shading, nutrition and irrigation.

Recommended agronomic practices for mangosteen are often based on field observations in specific locations, rather than on scientific experiments. Successful growers will be those with an intense interest in the crop and a willingness to experiment to further accelerate early plant growth and to induce precocious, reliable flowering.

Markets and marketing issues

Mangosteen fruit is normally consumed fresh and tends to lose its delicate flavour when preserved. Market intelligence on the crop is limited but indicates a potential for market growth. Since there are few suppliers, the fruit sells for relatively high prices outside of South East Asia, e.g. $A3 per fruit on the London retail market and $A2-3 per fruit in Sydney and Adelaide. Wholesale prices in Sydney are $A50-$A60 per tray (20-30 fruit). In Australia, a challenge for market development will be to significantly and reliably increase production of the crop so as to enable it to become more generally known in the domestic market, to reduce the current high prices which are an impediment to consumers and to provide continuity of supply to potential export markets.

Currently, the major producing countries are Thailand (130,000 t from 15,000 ha in 1995), Malaysia (27,000 t from 2,200 ha in 1987), Philippines (2270 t from 1130 ha in 1987) and Indonesia (2500 t in 1975). Thailand is the major exporter of mangosteen fruit to international markets($US5m). Export from Indonesia has increased dramatically during recent years, from 452 t in 1991 to 2235 t in 1994.

Production requirements

Mangosteen is a shade-tolerant, understorey tree adapted to the humid, wet tropical lowlands of South East Asia. In Australia, it is currently grown in the wet tropics of far north Queensland (Cairns, Mossman, Innisfail) and the seasonally wet/dry tropics in Darwin. Irrigation is required during the `dry' period to maintain soil moisture at or near field capacity to a depth of at least 0.5 m. At Darwin, shading is required for at least 10 years after planting to prevent leaf burning, which is caused by high solar radiation levels in combination with low humidity, high temperatures and wind. In far north Queensland, shading is required only during the first two years after field planting.

Trees are transplanted from the nursery to the field in which established banana or other shade trees provide natural shelter. Banana is useful as a short-term cash crop to bridge the long period before mangosteen becomes productive. It also adds large amounts of organic matter to the soil and improves the microclimate around mangosteen trees by increasing the relative humidity and lowering temperature. Leguminous trees such as Inga edulis (ice-cream bean) when planted for permanent shade also add nitrogen to the soil.

Mangosteen grows best in the wet tropics where rainfall is frequent, and supplementary irrigation is available during dry periods. A high water table seems to favour growth, provided the water is free-moving. It has been observed that mangosteen grows best along river banks and near ponds or lakes. Preferred soils are rich in organic matter and slightly acidic. The optimum temperature range for growth is 25-33°C with over 80% relative humidity. The tree makes little growth below 20°C and is killed at 5°C.

Varieties

Mangosteen lacks genetic variation since the seeds are formed apomictically (without fertilisation). The flowers on commercial trees are female only; male trees have been reported, but are rare. Some clonal variation may exist based on reports of a larger fruit size in countries such as Malaysia, but this could be related to environment.

Mangosteen is propagated from seeds which, like many other tropical species, do not remain viable for very long. Larger seeds produce stronger seedlings. Successful germination requires prompt importation and quarantine clearance of seed from South East Asia.

Vegetative propagation in mangosteen has been attempted by cleft grafting mature scions to seedlings of G. mangostana and related species such as G. tinctoria, G. cochinchinensis, G. xanthochymus and G. morella. Although precocious bearing has been observed on G. mangostana rootstocks, grafting has not gained favour due to significant problems with suckering below the graft union.

Australian research has shown that early growth can be significantly promoted by improving nursery management.

Fresh seeds are germinated in small pots containing equal parts of peat moss and coarse sand. A few months later, 2-4 leaved seedlings are carefully removed with minimal root disturbance and transplanted into 10 L black polyethylene bags (160 mm diam ¥ 500 mm length) containing a soil mix of peat moss, composted pine bark and coarse sand (1:1:1) mixed with 10 g of a controlled release fertiliser (Osmocote Plus® ). This potting mix has improved growth compared with commercially available potting media, by providing better aeration and an acidic pH of 6.2. Seedlings need fertilising every three months with a repeat application of Osmocote Plus and by fortnightly application of foliar nutrient spray (2 mL concentrate per litre of water; Wuxal Liquid Foliar Nutrient, Schering Pty Ltd, NSW). The seedlings are irrigated by overhead sprinklers for 15 minutes, four times a day.

An aspect critical to growth in the nursery is the level of light provided. Optimal light levels have been shown to shift over the three-year period that plants normally spend in the nursery before transplantation to the field. Initially, seedlings need to be very heavily shaded. Experimental work in shade houses in the Darwin area shows that mangosteen seedlings can develop 9-10 pairs of leaves (flushes) in the first year when grown under 80% shade cloth. After developing these 8-9 primary nodes they commence branching and grow more rapidly through the development of increased leaf area at successive flushes. Shading levels should be reduced to 50% at this stage and further reduced to 20% in the year before field planting. In the wet tropics where frequent cloud cover attenuates sunlight, young seedlings require less shading (e.g. 50% in year 1).

The slow growth of mangosteen is associated with very low photosynthetic rates of leaves. It has been shown that photosynthesis and growth can be greatly increased (60-80%) if supplementary carbon dioxide is provided, but this is unlikely to be practical for non-commercial nurseries.

Field planting and management. In the wet/dry tropics, mangosteen seedlings can be field planted at a density of 200 trees/ha in their third year. They are best transplanted just before the wet season in a non-flushing state. A nurse crop (e.g. banana) should already be present as an overstorey. During the dry season, leaves can be sprayed with kaolin suspension (5-10%) to reflect high solar radiation and heat load. If permanent shade trees are planted (e.g. Inga edulis), they will require annual pruning to ensure that mangosteen shading does not exceed 50%. The field-planted trees require at least 100 L/tree of irrigation water applied by under-tree sprinklers on alternate days. As trees mature, irrigation should be increased to 200 L/tree on alternate days. Fertiliser (N:P:K 15:15:15 + micronutrients) should be applied at three-monthly intervals at 0.5-1.0 kg/year for young trees (1-3 years). Mature trees should receive an N:P:K:Mg mixture (12:12:17:2) at the rate of 2.5 kg/tree. Foliar application of micronutrients may be required to correct deficiencies of zinc and iron which are common in Australian soils. In addition, regular mulching with organic manures is beneficial.

Flowering and fruiting. Although mangosteen is noted for its long juvenile phase
(10-15 years), the provision of improved conditions for early growth has reduced this period to 6-7 years in trees grown in the Cairns and Darwin area. Work now needs to be done on methods to reliably induce flowering in young trees. Manipulation of plant water stress levels is a possible strategy in the wet/dry tropics, but in the wet tropics growth regulators may be required to induce flowering.

Fruit are borne on terminal shoots either singly or, occasionally, in clusters. The period from flower opening to harvest requires about 12-16 weeks and fruit is normally available during March-May in north Queensland and during September-December in the Northern Territory. Yields of 100-1500 fruits/tree have been reported from overseas, with large, but not necessarily biennial, variation between years.

Pest and disease control

Mangosteen is relatively free from pests and disease in Australia, with any outbreak being readily controlled by use of the appropriate pesticide. The major pest observed in Australian plantations is red-banded thrips (Selenothrips rubrocinctus) which infest flowers and damage the fruit skin. Other pests reported from overseas include tussock caterpillar (Eupterote favia), coconut scale (Aspidiotus destructor Sig.), a small ant, mites, rats and bats.

Known diseases include coffee thread blight (Pellicularia koleroga), Helminthosporium leaf spot, Pestalozzia blight and stem canker (Zignoella garcineae). Postharvest diseases include Botryodiplodia theobromae Pat., Diplodia sp., Gloeosporium spp., Pestalotia flagisettula, Phomopsis spp. and Rhizopus spp. These usually result in hardening of the pericarp and the decay of the aril. The physiological disorder, `Gamboge', which causes yellow exudate to infiltrate the aril and cause a bitter taste occurs in all mangosteen growing countries, including Australia.

Harvest, handling and postharvest treatment

Fruits are hand-picked. The optimum harvest time is when 25% of the fruit skin has developed a purple colour. At this stage the skin is resistant to mechanical damage during handling but will develop an appealing purple colour within 1-2 days of harvest and retain a relatively long shelf life. Since the fruits on a tree ripen over a two-month period, frequent harvests are required. A six-stage colour chart is available from the Institute of Industrial Scientific and Technological Research, Thailand to assist growers in determining the correct time for harvest.

After harvest, fruits are cleaned in water and graded according to fruit weight: >100 g, 75-100 g and <75g. For export markets, Thailand growers wrap each fruit in tissue paper and pack them into cardboard cartons (38 ¥ 25 ¥ 7.5 cm). Each box has ventilation holes and contains 24-30 fruit. Storage at 13°C is suitable for maintaining a high standard of quality, and the ideal transit temperature range is 13-25°C. Experiments have shown that mangosteen can be stored for 7 weeks at 4.5°C and 85-90% relative humidity, but hardening of the pericarp under such conditions causes a reduction in fruit quality.

Economics of production

Mangosteen is not grown as a plantation crop in the traditional growing areas of South East Asia; rather it is a component of mixed plantings in homestead gardens. As a consequence, the economics of mangosteen production have not been fully assessed. However, growers in Thailand, the major mangosteen producer in the world, have recently been profitably exporting fruits to Singapore, Japan, Hong Kong and Europe.

In Australia mangosteen is a new crop and the production levels that can be achieved in largescale plantations have not yet been fully evaluated. Land, nursery and infrastructural costs will be similar to other horticultural tree crops. However, extra costs include seed importation and maintenance of seedlings in the nursery for three years (approx. $30/tree over three years). Finally, in considering mangosteen, potential growers should build in a long lead time to full production and ensure the use of high-value nurse crops (e.g. banana) to provide returns in the early years after establishment.

Key contacts

Key References

Yaacob, O., Tindall, H. D., Menini, U.G., and Hodder, A. (1995). Mangosteen cultivation. FAO Plant Production and Protection Paper 129. FAO, Rome.

Chacko, E. K., Wiebel, J., and Downton, W. J. S. (1995). Mangosteens. In `Australian Horticulture', Ed. B. Coombs. Morescope Publishing, Melbourne. pp 447-449.

Mansfield, J. G. (1995). Final Report RIRDC Project DAQ116A. Control of production patterns in tropical fruit. Part 5 - Mangosteen.

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