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Updated : 21/9/2014

Avocados

How to Grow Avocados

Avocados are rich in protein, carbohydrates, vitamins and minerals while the oil content consists of polyunsaturated fatty acids.

Climatic requirements

The optimum temperature for growth is 25 to 28 °C. The humidity should preferably be above 60 %. The Mexican races originated in the cool, subtropical highland forests of Mexico and mature trees can withstand temperatures of –4 to –5 °C.

Soil requirements

A healthy avocado tree has a root system that can penetrate the soil to a depth of 1 m. Root rot (Phytophthora cinnamomi) can develop fairly quickly in poorly-drained soils. It is therefore essential to determine in advance the suitability of the soil for avocado production.

Cultivars

Avocado growers should produce high yields of good-quality fruit, acceptable to the consumer. There is, however, no single cultivar that can fulfil all the requirements of the grower, the packer, the retailer and the consumer at the same time.

Fuerte
CHARACTERISTICS : "Pear" shaped sometimes has a long thinner neck
SKIN : Smooth thin skin that stays green coloured when ripe. Flesh bruises easily.
FRUIT SIZE : Medium sized.
SEED : Medium sized
SEASON : Mid to late February from the Limpopo Province until (early) August from Kwazulu-Natal. 'Out of season' fruit is available year round
STORAGE : Ripens quickly out of cold storage - approximately 7 days from picking. Store at +5 degrees C - NOT COLDER - when green. Fruit will develop big brown and black cold damage marks if stored at colder temperatures
TASTE : Best known variety.
Hass
CHARACTERISTICS : Round / egg shaped fruit
SKIN : Thick, green, pebbly skin changes colour to purple/black when ripe/ready to eat. Skin does not yield to pressure easily - once soft or shriveled, fruit is overripe.
FRUIT SIZE : Small to medium (140 - 350g) - large fruit an exception.
SEED : In proportion to fruit size - small fruit, small seed.
SEASON : Mid / late May from the Limpopo Province until October from Kwazulu-Natal. 'Out of Season' fruit is available year round.
STORAGE : Excellent shelf life with very few port harvest problems. Store at +5 degrees C - NOT COLDER.
TASTE : Rich and nutty, as opposed to the stringy/watery "Natal" seedling varieties
Pinkerton
CHARACTERISTICS : This variety has a definite "neck" compared to the other varieties.
SKIN : Thick rough green coloured skin that stays green coloured when ripe. The thick skin does not yield to pressure easily.
FRUIT SIZE : Medium to large (230- 550g)
SEED : Medium to small
SEASON : Short season. June from the Limpopo Province, July from Kwazulu-Natal. Out of season fruit not easily available
STORAGE : Store at +7 degrees C - NOT COLDER
TASTE : Sometimes slightly sweet.
Ryan
CHARACTERISTICS : Late season egg shaped fruit
SKIN : Slightly rough dark green skin that stays green coloured when ripe
FRUIT SIZE :Large (300 - 500g)
SEED : Large
SEASON : August / September from the Limpopo Province. October from Kwazulu-Natal. Late season fruit readily available
STORAGE : Store at +5 degrees C - NOT COLDER
TASTE : Good.

Layout of orchard

An avocado orchard should be profitable within 7 to 10 years.

There are 3 patterns according to which trees can be arranged in an orchard:

• Rectangular (which leads to hedge-type tree rows)

• Square (which leads to a change of direction when thinning diagonally)

• Diamond-shaped (which also results in a change of direction of tree rows with every

thinning).

Planting distance and planting pattern

The choice of a planting pattern (rectangular pattern discussed here) depends on the management practices followed.

  • Early yields are maximised by planting trees close together in the row.
  • Hedge-type tree rows are more suitable for installing a permanent irrigation system.
  • Where implements are constantly used in orchards, the hedge-type layout is more suitable because access to the orchard is possible for a longer period of time than it is in a square layout. Traffic is also always moving in the same direction in such an orchard—an important point in orchards planted on a slope.
  • The hedge-type tree-row layout minimises the effects of the loss of branches and trees in a row.

Leaf analysis

Leaf analysis indicates the nutrient status of an orchard. The trees can be fertilised accordingly. Soil analysis, in addition to leaf analysis, increases the reliability of the recommendations made.

Fertilisation

  • Do not fertilise young, transplanted avocado trees too soon, preferably only after one year. The trees must first become well established and grow vigorously.
  • Never apply fertiliser against the stems of young trees. It must be spread evenly about 0,2 m from the stem to approximately 0,5 m outside the drip area of the tree.
  • Each fertiliser application must be followed by a light, controlled irrigation.
  • Fertilisers must not be worked into the soil.

Pests

Avocado producers must be familiar with the insects that occur in orchards as pests. Most of these are controlled by natural enemies. The injudicious use of agrochemicals on avocado trees could, however, allow minor pests to develop into major economic risks.

Fruitflies

This pest has only recently gained economic importance in avocados. When the fruit is picked before it is ripe, the larvaenever reach maturity. However, if the fruit remains on the tree for extended periods, as in the home garden, fruitflies may occasionally develop to maturity.

Diseases

Phytophthora root rot

Root rot, caused by Phytophthora cinnamomi occurs worldwide. Locally it is one of the most important avocado diseases and is found in all production areas, as well as home gardens. The severity of infection varies, but the potential loss is very big if no control measures are taken.

Stem canker

This is another form of Phytophthora infection, but it may be caused by P. citricola, P. cactorum and P. cinnamomi.

Anthracnose

This is a pre as well as a post-harvest problem and can cause serious losses. It is present in most, if not all, production areas of the world.

Cercospora spot

This is a fruit-spotting disease, caused by the fungus Pseudocercospora purpurea.

Handling

Picking

  • While the fruit is on the tree, it remains hard.
  • It becomes soft and edible only after picking.
  • A mature fruit ripens evenly. The edible part acquires a smooth, buttery texture and the peel shows no sign of shrivelling.
  • Immature fruit, that is fruit picked too early, will not ripen properly and the skin will eventually become shrivelled.

Picking maturity

The maturity of the fruit is closely related to moisture content. The fruit is normally ready to be picked when it has a moisture content of about 80 % or less. The following procedure may be applied to determine maturity:

  • To test if the fruit is ready, pick a few of the big ones and leave them. If they start to feel soft after 8 to 10 days without shrivelling, you can pick the other big ones. If they shrivel, they are not ripe yet.
     

Harvesting

Always handle fruit carefully during harvesting and packing because avocados are bruised and scratched easily.

Handling

  • Fruit should be taken one by one from the picking bag, by hand, and placed in the trays.
  • Take special care when transporting fruit to the pack house.
  • Trays containing fruit and awaiting transport should be kept in the shade under the trees. If there is not enough shade, the fruit should be covered with empty trays, placed upside down.
  • Do not spread a tarpaulin over the trays, because it will hamper ventilation and cause the temperature underneath it to rise.
  • Harvested fruit should be removed from the orchard as soon as possible.
  • It is important to pack and dispatch the fruit to the market, or to place it in cold storage, on the day it is harvested.

Cold storage

To delay ripening, fruit must be stored at a low temperature as soon as possible. The lower the temperature, the longer the fruit will take to ripen. However, storage temperatures that are too low will cause cold damage of fruit. A temperature of 5,5 °C is generally best. Early maturing avocados may be kept at a slightly higher temperature while late-season fruit may be kept at a slightly lower temperature.

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