Fruit of the abiu (Pouteria caimito) (photo courtesy of R.Goebel).

On this page:

• Soils and climate
• Windbreaks
• Cultivars
• Propagation and land preparation
• Fertilising
• Maintenance
• Pests and diseases
• Harvesting and postharvest storage.

Soils and climate

Abiu is a lowland humid tropical or subtropical tree that thrives well in an environment with a high even temperature and high humidity. A temperature range from 20°C to 35°C is desirable. The northern Queensland environment is suitable for abiu production. However, the unusually cool temperatures (less than -2°C) experienced during the July/August months in northern Queensland can limit the areas where abiu is grown. An evenly distributed rainfall of between 1000-3000 mm per annum is also desirable. Abiu can be grown at altitudes up to 500 m and have a latitudinal limit of 20°S.

Abiu will grow on a wide range of soils provided it has reasonable water holding capacity and very good drainage. It will not tolerate waterlogged areas or saline soils. It can grow on sandy to clay loams. A slightly acid to alkaline soil in the range of pH 5.5-7.5 with high organic matter is preferred.

Abiu need full sun from an early stage. Providing abundant soil moisture is available, the above ground conditions do not significantly impact on abiu growth. Supplementary irrigation will be necessary during the dry season for good growth and high yields to be obtained. The abiu plant will tolerate very short periods of moisture stress and moisture stressed trees may still crop well initially, but the size of the fruit will decrease and subsequent cropping will be reduced until the trees recover. Constant water is required during fruit filling otherwise fruit splitting will occur during this period of rapid maturation.

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Windbreaks

Flowering, pollination and subsequent fruit set can be severely limited by exposure to wind and low humidity. Planting of windbreaks is necessary in the wet tropics because of the cold south-easterlies during the cool dry period. However, the windbreaks will provide little protection from strong cyclonic winds.

Cultivars

There are several identified varieties of abiu.

Queensland developed varieties:

• Gray
• Inca Gold
• Cape Oasis
• Gray
• Z1
• Z2
• Z3
• Z4.

Northern Territory developed varieties:

• T25
• T31.

The varieties Z2, Z4, T25 and T31 produce large and good quality fruit. Z1, Z2 and Z3 are good to heavy producers with good fruit flavour. Both Z2 and Z3 have excellent flesh to fruit recovery. Z3 produces small fruit. Planting material of new varieties is becoming available.

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Propagation and land preparation

Agronomic practices for this species are largely based on field observations and growers' experience and should only act as a guide.

Plant seeds as soon as possible after extraction as seed viability lasts only 1-2 days in dry conditions. Plant seeds near the soil surface. Seeds will germinate readily within 10 days. Germinate in pots or polybags. Seedlings will need regular fertilising, probably with a complete foliar nutrient spray. Field plant when the seedlings are 30-40 cm high and about 9 months old. Field planting can be done at any time in the wet tropical coast of northern Queensland as long as irrigation is available.

Deep ripping is recommended if the soil is compacted, and also to improve soil drainage and root penetration. In areas where waterlogging or ponding may occur, mounding or installation of undersurface drainage, such as agricultural pipes, is recommended. Bird manure, compost or straw may be incorporated into the planting sites 6-9 months prior to planting.

Tree density depends on the soil depth and quality, and irrigation system. Planting distances of 4-8 m in a row and 10 m between rows are used. Full sun is required for healthy growth and development of abiu.

Seedling trees are mainly used for commercial plantings. Grafted trees are not generally used in northern Queensland; however, earlier production can be achieved from grafted trees. Grafting has been shown in other tree species to provide precocity, desirable dwarfness, and economy for picking and pruning.

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Fertilising

There is little information on fertilising abiu. The Rare Fruits Council of Austrlia recommends a preplant application of 15 g in and around the planting hole followed by split (August, December and April) annual dressings (per tree per year of age, up to 10 years) of:

• 10 g N
• 2 g P
• 17 g K.

The department in the Northern Territory recommend a preplant application of:

• 200 g single superphosphate
• 200 g dolomite
• 2-3 kg well cured animal manure.

For non-bearing trees split applications of a 10N:10P:10K fertiliser is given in the following amounts:

• Year 1: 500 g
• Year 2: 1 250 g
• Year 3: 2 000 g.

Bearing trees need Mg and other trace elements. A fertiliser comprising 12N:12P:17K:2Mg+TE is recommended. Four year old trees require a total application of 2.75 kg per annum and an extra 750 g is needed per year of age, up to 11 years. The applications generally coincide with developmental stages (i.e. following each harvest).

However, annual leaf tissue analysis and soil analysis will allow more accurate recommendations to be given. Deficiencies in the trace elements zinc, iron and boron can be corrected. These trace elements are generally applied during flushing as follows:

• zinc at 1-2 g/L
• iron at 1 g/L
• solubor at 1 g/L.

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Maintenance

A general maintenance program such as slashing and/or the use of contact herbicides to remove competition from surrounding weeds is recommended. During early growth, weeds around the tree trunk should also be controlled, taking care not to damage the young trees.

Pruning is undertaken when the tree is young to develop a good tree shape. Pruning of growing trees is necessary to remove dead, diseased, broken or misshapen limbs. Strong pruning is essential and results in fewer, but stronger branches to hold the fruit crop. A single trunk to at least 3 m height and branches not lower than 1 m from ground level is desirable as this will make harvesting easier. Following harvesting of fruit, any suckers and dry panicles are removed to promote healthy and vigorous regeneration.

Pests and diseases

The tree and fruits are relatively free from pests and diseases. The main insect pests are:

• fruit spotting bugs
• fruit piercing moths
• peach moth larvae
• thrips
• fruit flies.

Apart from the damage to young foliage, flowers and fruit by these insects, thrips can cause russet scarring of fruit. Scale insects are minor, but sooty mould can be present where they occur.

The flesh of the fruit is also susceptible to a brown discolouration and produces a watery, bland taste that is unsuitable for market.

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Harvesting and postharvest storage

When the colour of the fruit changes from green to light green and then to bright yellow, it is an indication that the fruit is ready to be picked. The fruit is also quite edible at this stage, but will continue to colour after harvesting. Fully coloured, deep gold yellow fruit is over ripe and undesirable as they will damage during packing and transport. Fruit is hand picked. In northern Queensland harvesting begins in December and ends in June, with the main pick occurring between January and March.

Pick at the bright yellow stage. Always handle the fruit carefully as the skin is susceptible to mechanical damage during handling. Full ripeness occurs 1-5 days after harvest.

Generally fruit can be harvested just 3 months after fruit set. Annual yields are variable, from 10 kg for young (under 3 years) trees to 200 kg of fruit from mature and large fruited varieties. Fruit picked at the appropriate stage and stored at 10°C have a shelf life of 7-14 days.

Fruits are often cleaned following picking and graded according to the size of each fruit. Pack only uniform quality yellow fruit. Fruit is often packed in a single layer in polystyrene or cardboard trays lined with shredded paper to prevent movement during transport, which causes bruising. Coloured tissue wrapping may also be used to improve general appearance.

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