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The need to diversify farming activities is becoming increasingly important. The hot, wet, tropical coast of far north Queensland is an area that has traditionally had sugar cane as the major and almost only crop. Within the last 10 years, planting of crops such as bananas and papaws and lesser-known tropical tree fruits have increased dramatically.

Interest in a wide range of tropical tree fruits has increased to a level where dozens of different fruit types are being grown in the hope that the trend of a wider interest in ones own diet will create markets. One of the most widely-planted tropical tree fruit is the RAMBUTAN. Although it is a relative new comer to the Australian fruit market, RAMBUTAN has been planted in areas around Cairns for over 50 years.

Native to the tropical jungles of Malaya and Sumatra, Rambutan appears to fruit well in selected areas of the north Queensland coast down to Ingham. Below this, trees may grow, but production and quality is low. Areas in Northern Territory and Western Australia are also suitable, with good growth rates recorded for trees around Darwin.

The Rambutan, a plant of the Sapindaceae family, is a close relative to the Lychee, Longan and Pulasan. The tree is an evergreen with compound leaves. Seedling trees have a distinct trunk and reach a height of over 12 metres while grafted plants branch much lower to the ground. Trees for commercial production should be of a known variety. Of the 50 or more named varieties introduced, only 9 are currently recommended for commercial planting by Queensland Department of Primary Industries. These recommendations are tentative, and are based on trial work at Kamerunga Research Station and observations made by Queensland Department of Primary Industries staff and a number of growers.

Current Rambutan plantings (1988) in Queensland are summarised as:

Not fruiting (0-3 years)	17 000
Fruiting (over 3 years)	3 000
Total	20 000

There are approximately 100 trees per ha.

Only seven growers have produced the bulk of Queensland Rambutans over the last two seasons, but almost 200 more have plantings of between 10 to over 1,000 trees.

Under the best conditions, Rambutan start producing in their 3rd or 4th year, with yields of 3 to 5 kg in their first season increasing to possibly over 200 kg for mature trees.

SOIL
Rambutan trees require deep, well-drained soils. If the soil is poorly drained to the point that pawpaws will not grow, the Rambutan will not thrive.

Acid soils (pH 5.5 to 6.5) with high organic matter are very suitable, but most important is a good supply of suitable water and protection from wind.

IRRIGATION
The water requirement of Rambutan is high and supply should be constant throughout the year. Irrigation systems designed to supply 2,000 litre/tree/week are needed for mature trees in the hot dry period of spring to mid-summer. The irrigated area should extend beyond the drip circle of the tree.

WIND PROTECTION
Wind above 10 k.p.h. will reduce the tree growth. Temporary wind breaks are necessary in most areas while more permanent ones are being established. Our trees have bana grass as a temporary windbreak around each 1 ha block and also up every second row. Permanent wind breaks must be kept more than 6 metres from the Rambutans. The roots of the wind break species, bana grass in particular, will compete with the crop tree.

PROPAGATION
Seedling Rambutans produce an average 1 in 2 plants that will not set fruit (called male trees). Of the fruiting trees few will be found to be as good as the selected varieties available. Propagating trees is not difficult but requires care. Three useful methods are:

1. Approach grafting good success rate but slow, some plants appear weak and may need added root systems.

2. Modified bud graft. Most widely used it produces a good shaped vigorous tree if root stocks are grown well and not root bound.

3. Marcotting - success has been achieved by some but generally there is a higher death rate than with lychee marcots.

Whichever method is used, added root systems will have a number of benefits, including greater ability for the tree to withstand cyclonic winds. Multiple root systems by planting one or two seedling trees approximately 0.5 metre from the crop tree and later approach grafting the seedling rootstock to the crop tree.

PLANTING
Soils should be thoroughly prepared before planting. Deep rip previously cultivated soils to break through any plough pan. It is best to cross rip with the trees planted on the intersecting points. Ensure wind breaks are well established and irrigation is installed prior to tree planting. A suitable planting hole must allow the young roots to spread out. A tree planting auger on a post hole digger is a fast and reliable method of preparing the holes.

MULCH
The addition of mulch such as aged bagasse or spoilt hay applied to the area round the tree will benefit the trees. Mulching helps control weeds, supplies organic matter, conserves water, reduces soil erosion, alters soil pH, increases water spread, increases humidity and insulates the trees' surface roots. All this is most important in young trees. Mulch is applied in a blanket 100 mm thick, 200 mm from the trunk to 1 metre outside the tree canopy. It is applied two or three times a year.

FERTILIZER
Fertilizer programmes should be aimed at regularly applying small amounts. Young trees usually require four applications of 125g of 10:3:6 spaced throughout the year. This amount increases by 125g for each year of age up to fruiting.

Fruiting trees require 90gN:10gP:60gK per year of age up to year 10. In heavy rainfall areas, the addition of trace elements may be necessary, as organic matter is quickly decomposed and leached. Additional light applications of nitrogen are required regularly when heavy bagasse mulching is used.

FRUITING
Rambutan fruiting for young trees is spread from December to August due to extended flowering patterns. As trees mature they settle into one main fruiting per year. For mature trees the range of recommended varieties give 3-4 months of harvest. Flowers of recommended varieties are mainly hermaphrodite, with most being only female functional. It appears that sufficient pollen is available for good fruit set in most named varieties. Flower pollination is not considered a problem, as the flowers are highly attractive to insects such as honey bees and native bees. Excessive fruit set may lead to the dropping of fruit at an immature green stage, not much larger than 3 cm across.

PESTS
Pests of Rambutan include:

Leaf eating grubs - a number of species of leaf-eating loopers cause rapid damage to tender leaves.

Leaf eating beetles - these may cause damage to all leaf stages and to the bark of young growth flushes.

Fruit spotting bug - young growth shoots and fruit may be attached.

Ants - hosts for scales and mealybugs, ants also loosen the soil around the plants' roots causing excessive drying.

Mealy bugs and scales - these find the large clusters of Rambutan fruit to be well-protected areas. They, along with various mites, cause fruit to be downgraded or not marketable.

With the limited areas suitable to its growing, its highly attractive appearance and its relatively long fruiting season, Rambutan growing has more than a fair chance of being a good investment for those prepared to overcome the problems of pests, cyclones and whatever else.

Like many other crops, the real challenge to being viable in the long term will be marketing attitudes. On-farm quality control and the best of post-harvest handling will be necessary to produce a top-quality product that will maintain a good return for this new and exciting fruit.

TABLE 1
CHARACTERISTICS OF RAMBUTAN CULTIVARS *

Cultivar + Height	Tree Spacing	Mean Fruit Size mm	Pericarp Colour	Spintern Colour 2/	Mean Fruit Weight Range	Mean Aril	Mean Brix Mature	Cling or Freestone	Testa Objectionable	Aril Crisp or Juicy	Skin Thickness
Bin Jai medium-small	10x10	48/40	orange-red	green tips	32-41	41	18-21	cling	not	crisp	thin
Jit Lee (Deli) Medium	10x10	60/40	crimson/red	green tips	30-55	35	20-22	free	slight	both	thick
Rongrien medium-large	12x10	53/36	dark red	green tips	32-37	41	19-21	free	moderately	crisp	thin
R9 medium	12x10	65/40	pink/crimson	red	40-51	36	20-23	free	slight	both	v. thick
R134 Medium-large	10x10	56/40	red/orange	red/green	34-46	45	20-22	free	slight	v. juicy	thick
R156 (red) 3/ Medium-large	12x10	48/40	pink/red	green tips	34-43	43	20-22	medium	slight	v. juicy	thin
R156 (yellow) Medium	10x10	50/45	yellow/orange	sl. green tips	38-47	54	19-22	free	moderately	both	thin
R167	10x10	58/42	crimson	red/green tips	37-46	34	20-23	free	slight	crisp	thick
Silengkang 4/ Medium-large	10x10	65/40	red	green overall	40-48	51	19-21	sl. cling	slight	juicy	thin

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1/	Length/width excluding spinterns (spines).	Other Promising Cultivars
2/	Except where indicated, the colour of base of spintern is same as the pericarp (skin).	R37	- Yellow, clingstone.
3/	This cultivar imported as R156 but incorrect, and true identity not yet received.	Gulah Batu	- Red, slightly clingstone
4/	Description does not fit Indonesian description, may be wrongly named. Also, yield data for this cultivar is not well established.	R3	- Red, slightly clingstone
*	Recommended for North Queensland by officers of the Horticultural Branch of the Queensland Department of Primary Industries.

TABLE 2
PESTICIDES RECOMMENDED FOR USE ON RAMBUTAN

Pest	Pesticide	Withholding period (days)	Rate of commercial preparation per 100L	Rate of Active Constituents	Remarks and Safety Precautions
CASTER OIL LOOPER Achaea janata	carbaryl *	3	125 g of 350 g/L product	0.1%	regular inspection, particularly of young trees is recommended.
FRUIT SPOTTING BUGS Amblypelta spp.	endosulfan	14	150 ml of 800 g/kg product	0.05%	spray fortnightly from just after fruit set.
SWARMING LEAf BEETLES Rhyaparida spp.	carbaryl *	3	125 g of 800 g/kg product	0.1%	spray when beetles or damage are evident.
RED SHOULDERED LEAF BEETLE Monolepta spp.	carbaryl *	3	125 g of 800 g/kg product	0.1%	spray when beetles or damage are evident.
* Do not apply at flowering.

Roger Goebel

DATE: September 1988

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