Avocado (Persea americana), butter pear or alligator pear, is a tree native to tropical and subtropical regions of Central and South America, classified in the flowering plant family Lauraceae along with cinnamon, camphor and bay laurel. The name “avocado” also refers to the fruit (technically a large berry that contains a large seed) of the tree which may be egg-shaped or spherical. Avocados are a commercially valuable fruit and are cultivated in tropical climates throughout the world. Trees are partially self-pollinating and often are propagated through grafting to maintain a predictable quality and quantity of the fruit.
The skin of an avocado can vary from a bright green to a very dark purple reminiscent of eggplant. Much like a banana, an avocado is usually picked from the tree in an unripened stage. Consumers are urged to select avocados with a dark color and a slight ‘give’ when pressed. An avocado should be stored in the open air or with bananas until fully ripe. The flesh of a ripe avocado should be greenish-yellow to a deep yellow.
Avocado is almost always served raw. In the Philippines, Avocado is one of the popular dessert found in the dining table. Avocados contain an inordinate amount of fat, it also have significantly more potassium than bananas, and avocado oil is an extremely popular skin care ingredient, high in vitamins A, B1, B2, D and E.
The avocado varieties in the country have been developed mainly through introduction and selection. Many varieties have been introduced since 1903 and most of them have been lost. Today, only a few varieties exist. Most of them are selections from local seedling trees, and they are confined to only a few nurseries and backyards. These are:
- Cardinal: The fruit bottlenecked with an average weight of 400 grams. The skin is reddish-purple and thick (1.3 mm). The seed is small (40 g) and is loose to tight in the cavity. The flesh is yellow, moderately fibrous and constitutes 80 per cent of the whole fruit by weight.
- Calma: The fruit ovoid and weighing 600 grams. The skin is reddish-purple and intermediate in thickness (1.0 mm). The seed is small (80 g) and is loose in the cavity. The flesh is yellow and is 80 per cent of the whole fruit by weight.
- Uno: The fruit ovoid and weighing 400 grams. The skin is purple and is rather thick (2.0 mm). The seed is small (80 g) and is loose to tight in the cavity. The flesh is creamy yellow and is 80 per cent of the whole fruit by weight.
- 240: The fruit ovoid and weighing 600 grams. The skin is green and thin (1.26 mm). The seed is intermediate in size (90 g) and is rather loose in the cavity. The flesh is creamy yellow and is 80 per cent of the whole fruit by weight.
- 227: The fruit is bottlenecked and weighing 500 grams. The skin is purple and thick (1.3 mm). The seed is small (50 g) and is loose in the cavity. The flesh is dark yellow and is 80 per cent of the whole fruit by weight.
Recently, three new varieties were approved by the National Seed Industry Council. However, these have not yet been released to the private nurseries. These new varieties are:
- Parker: The fruit ovoid and having an average weight of 600 grams. The skin is purple and thick (1.1 mm). The seed is small in size (70 g) and is tight in the cavity. The flesh is creamy yellow and is 80 per cent of the whole fruit by weight.
- RCF Purple: The fruit ovoid and weighing 400 grams. The skin is reddish-purple and thick (1.2 mm). The seed is small (40 g) and is loose in the cavity. The flesh is creamy yellow and is 80 per cent of the whole fruit by weight.
- Cepillo Green: The fruit pyriform and weighing 700 grams. The skin is green and intermediate in thickness (0.9 mm). The seed is intermediate in size (90 g). The flesh is dark yellow and is 80 per cent of the whole fruit by weight.
No varieties have so far been identified for rootstock use. Available seeds coming from the seasons produce are usually sown and the resulting seedlings are used as rootstocks.
Production of Planting Materials
Since the avocado is not considered a major fruit in the country and is planted mostly in backyards, only a limited amount of planting material is being produced in a few government institutions and private nurseries. Planting materials may come in the form of grafted plants or seedlings for rootstock use. Government agencies such as the Bureau of Plant Industry of the Department of Agriculture and the University of the Philippines Los Baos, particularly the National Seed Foundation and the Department of Horticulture, produce a few hundred grafted plants of locally available varieties. Small private nurseries which also sell sexually propagated avocado plants are a good source of seedling rootstocks for propagation. Seedlings grown in the nurseries are heterogeneous – each seedling different from another, even though the seeds may have come from one variety or only from one parent tree.
The commonly used and preferred method for large-scale propagation is grafting. This method is less labour-requiring, faster and economical in the use of scion materials. In the case of cleft-grafting, 6-12 months old seedlings are used as rootstocks. Budwood sticks are obtained from the seasons mature growth with well-developed terminal buds. New shoots are formed within three to four weeks. Other methods of propagation which are sometimes employed are inarching and shield-budding. Inarching is a slow and laborious process although it can be used during the rainy season when grafting and budding cannot be done successfully. Shield-budding on the other hand is a fast method. However, it requires skill.
Training and Pruning of Plants
Avocado requires very little pruning once the tree has been established. When the trees are still young, especially during the first few years, the plants are trained to a desirable shape by allowing three well-spaced branches to develop and eliminating the rest. Once the trees have attained the desired form, pruning is confined to the removal of diseased, infested and interlacing branches and watersprouts.
Many avocado trees in the Philippines are grown without the benefit of fertilizer. This may be the reason why fruit yield and quality tend to decline after fruiting for several years.
Under the existing orchard soil conditions in the country, young and nonbearing avocado trees require only nitrogenous fertilizer. Farmers apply 100-200 grams of ammonium sulphate or about 50-100 grams urea/tree, twice a year. As the trees bear fruit, 500 grams of complete fertilizer are applied, twice a year. For full-bearing trees, two kilograms of complete fertilizer are applied per year. A supplemental application of organic fertilizers, e.g. animal and poultry manure, and compost, is also given.
The fertilizer is applied at the onset and towards the end of the rainy season. It is usually applied in a ring around the trunk of the tree or in shallow holes dug beneath the tree canopy.
Weeding and Mulching
Mulching of avocado trees is not practised in the Philippines. Weeding, on the other hand, is confined only to the removal of weeds within a one-metre radius from the trunk especially when the trees are still young; it is usually carried out manually with the use of a scythe or mechanically with the use of a grasscutter.
The practice of irrigating avocado trees in the country is uncommon. The plants are irrigated only when they are newly planted in the field and at certain times of the year when the dry season extends from four to five months. Otherwise, the trees are rainfed. Irrigation is effected manually.
Control of Pests and Diseases
The insect pests attacking the avocado, in order of their importance, are the following:
- Borers: The borers, Niphonoclea albata and Niphonoclea capitoe, attack the trunk, pith and twigs by boring their way and cutting off the plants tissues. Lime wash and lime sulphur are used as repellents. In some instances, the tree is sprayed with insecticide.
- Scale Insects and Mealy Bugs: The scale insect, Asphidiutus destructor, and the mealy bugs suck the sap from the leaves, shoots and fruits, causing premature falling of the fruits. Oil emulsion spray is used in controlling these insects.
- Oriental Fruit Fly: The Oriental fruit fly, Dacus dorsalis, attacks the mature fruits which are about to ripen. They are controlled by spraying with malathion.
The major diseases which affect the avocado are:
- Root rot: This is caused by the fungus Phytophthora cinnamomi. Symptoms include yellowing of leaves, sparse foliage, wilting of leaves and dieback of shoots. Prevention of conditions conducive to the growth of the fungus by providing adequate drainage or avoiding planting in waterlogged areas seems to be the best method at present to control the disease.
- Anthracnose: This is caused by Colletotrichum gloeosporioides and affects the leaves, twigs and fruits. It is controlled by spraying with Bordeaux mixture or copper sulphate.
A minor disease of the avocado is the scab which is caused by Sphaceloma perseae. It attacks the fruit and is controlled by spraying with Bordeaux mixture.
Avocado fruits are harvested when they are fully mature. Indications of maturity are the appearance of reddish-purple streaks on the stem-end of purple-fruited varieties and a change in color from green to light green on green-fruited varieties. In the case of loose-seeded varieties, an indication of fruit maturity is the production of a hollow sound when the fruit is tapped with the fingers.
Avocado fruits on the same tree do not mature at the same time, so selective harvesting is usually practiced. This requires going over the tree several times until all the fruits are harvested. Harvesting is accomplished manually by climbing the tree or by using a ladder. Fruits which cannot be reached by hand are harvested with the use of a long bamboo pole fitted at one end with a wire hook and an attached net to catch the fruits. The fruits are then placed in sacks or in rattan or bamboo baskets lined with banana leaves, for transport to the market.
From the national figures on area and production for the years 1990-1997, a mean annual yield of 9.6 t/ha with 84 kg/tree was estimated. This is quite an improvement from the figures recorded 15 years earlier, when mean yield was only 4.9 t/ ha with 50 kg/tree. Though the total area planted and the number of bearing trees recorded for both periods did not change drastically, the yield almost doubled. This was due to the increased yield reported for the Cagayan Valley, Central Visayas and ARMM. The reason for this could only be surmised. This may be due to improved production practices followed by the farmers in these regions. Otherwise, the yield in the other regions did not change much.
In terms of quality, much is to be desired. Most of the avocado fruits sold in the market are of poor quality. This is due to poor crop management employed by the farmers plus the fact that most of the trees grown come from seeds of unknown origin. Another reason for the low quality of the fruits is the poor accessibility of the production areas of the avocado. In many instances, the farm is situated in areas accessible only by trails and paths making transport of the produce difficult and time-consuming. With proper cultivars and improved production and transport facilities, the yield and quality of avocado are projected to improve substantially.
In the Philippines, the marketing of avocado involves two very simple systems. In the first system, the farmers bring their harvest to the market together with other farm produce i.e. banana, root crops, chicken, and sell these directly to the consumers. In this way they obtain a higher price for the avocado fruits. In the second system, a middleman, locally called ‘comprador’, buys all the avocado fruits from the farmers at a lower price and sells them in the market at a higher price. The middleman generally dictates the farm-gate price since he bears the transportation cost. Under the present nature of small-scale and backyard avocado production, where the volume of production is small, the farmer prefers to sell his produce to the middleman. Avocado production is for the local market.
Source: Avocado Production in the Philippines – Rachel C. Sotto; Photos: hort.purdue.edu and avos4u.co.nz