Avocado Production in Thailand - Chalongchai Babpraserth and Suranant Subhadrabandhu*

* Department of Horticulture, Kasetsart University, Bangkok, Thailand.

Avocado (Persea americana Miller) is an indigenous plant of South America. It is widely grown in Mexico, Guatemala and the islands of the West Indies (Whiley, 1991). In Thailand, avocado plants were introduced by missionaries and were planted initially in Nan province in northern Thailand about 90 years ago. Some seedlings from these introductions are currently found around this area. In 1965, the Department of Horticulture, Kasetsart University, introduced some avocado cultivars which included Kanoe, Ruehle, Kampong and Monk and planted them at Pak Chong Research Station, Nakhon Ratchasima province. Some avocado cultivars were also introduced by interested growers. In 1975, the Department of Horticulture, Kasetsart University, with support from the World Bank introduced 11 cultivars of avocado from Florida, USA, and established them at Pak Chong Research Station. The introduced cultivars were Buccanaer, Booth 7, Booth 8, Catalina, Choquette, Hall, Lula, Peterson, Queen, Taylor and Waldin. The Hass, Bacon and Reed cultivars were introduced also from California in 1993.

The purpose of introducing avocado cultivars into Thailand was to evaluate their suitability under local conditions. Due to their high nutritive value and wide utilization possibilities, avocado fruits are becoming more popular in Thailand. Apart from being consumed as fresh fruits for their palatability, food value with high protein, vitamin E and digestible fat content, their oil is used also in the cosmetic industry.

2. PRESENT STATUS OF AVOCADO CULTIVATION

The production and planted area of avocado in Thailand increases every year. At present, avocado trees are found planted in Nakhon Ratchasima, Chaiyaphum, Nan, Tak, Chiang Mai, Chiang Rai, Rayong, Chanthaburi and Songkhla provinces. However, the big concentration is in the northern and northeastern regions. Total production area in 1998 was 200 hectares in the north, 50 hectares in the northeast, 5 hectares in the east and 5 hectares in the south with a production of 200, 100, 23 and 20 tonnes respectively.

Due to the unavailability of sufficient quantities of planting material, many growers in the Royal Project Foundation areas of northern Thailand have raised avocado from seedlings. These avocado trees have produced fruits of poor quality. The Kasetsart University personnel who voluntarily work for the Royal Project Foundation tried to persuade growers to graft or bud these avocado seedling trees with the recommended cultivars such as Buccanaer, Hass, Peterson, Booth 7 and Ruehle.

About 84 hectares of avocado were planted by hill tribe growers under the extension programme of the Royal Project Foundation with a total production of 45 tonnes in 1997. The future planting area of avocado in the five-year plan of the Royal Project Foundation, from 1998-2003, will be 270 hectares with an estimated production of 1,500 tonnes by the year 2005.

Work for better cultivars continues at Pak Chong Research Station. At present, scions from the recommended cultivars are used for grafting, budding or inarching on Guatemalan and West Indian rootstocks (Pak Chong 6-5 and Pak Chong 1-14). Some selected rootstocks at Tung-roeng Development Centre are also used in some growing areas.

3. PRODUCTION OF PLANTING MATERIAL

The Pak Chong Research Station and the Royal Project Foundation are the two main production sources of grafted and budded avocado plants. These two institutions produce more than 4,000 plants per year for the growers.

Seedlings are raised in the nursery under 50% shade. The seeds are cleaned and soaked in fungicide solution for about 20 minutes. They are germinated in 8 x 15 cm PVC bags. The seedlings can be budded or grafted after 4-6 months.

Patch budding or modified chip budding are commonly used depending on the rootstock. If the bark cannot be peeled easily from the stem of the rootstock, modified chip budding must be used. Patch-budding can be used when the bark can be peeled off easily.

Bark-grafting is used when the bark could be peeled off easily from the stem, and this is commonly seen when the rootstock is over six months old. Modified side-veneer-grafting is used for the rootstock that cannot peel off the bark easily, usually when the rootstock is 4-6 months old. Modified side-veneer-inarching is also used for rootstocks that are 4-6 months old.

4. ESTABLISHMENT OF ORCHARDS

4.1 Land preparation

Where hardpan is evident, a sub-soiler is used for breaking the hardpan. The land is ploughed and holes of 60 x 60 x 60 cm are dug. The planting medium is a mixture of soil, animal manure and organic matter at the ratio of 2:1:1. Generally, land preparation is carried out before the rainy season.

4.2 Spacing

Spacing of avocado is dependent on the cultivars and the soil conditions of each site. In Thailand, a spacing of 8 x 6 metres is used for Ruehle, Peterson, Hass and Buccanaer, whereas wider spacings of 8 x 8 metres, 8 x 10 metres, and 10 x 10 metres are used for Booth 7, Booth 8 and Hall cultivars.

4.3 Planting

Planting is carried out at the beginning of the rainy season (May-June). The plants should have no sign of insect pests and diseases on the stems and leaves and they should be subjected to hardening under full sunlight before transferring to the field. The plants are brought to the prepared holes and are removed from bags or containers. They are then placed in the hole, with soil mixture filled and firmed to ensure good contact with roots. They are then watered regularly to ensure availability of sufficient moisture until establishment. Insecticides are sometimes applied to protect from termite damage every three months and also fungicide, often by using 100 grams of metalexyl (Ridomil 50 g) granules around each plant. The plants are protected from wind by planting windbreak trees as well as by using bamboo stakes for supporting newly planted trees.

4.4 Mulching

Plastic sheets can be used as mulching material but this is not seen commonly in Thailand. Often, organic materials such as straw, rice husk and wood chips are commonly used as mulching material because these materials can later decay and become available to plants as organic fertilizer.

5. CARE AND MANAGEMENT OF ORCHARDS

5.1 Training and pruning

Avocado trees are normally trained under a modified leader or open centre system. When plant height of newly established plants is about 70 cm, the growing tips are pinched off to allow development of more side shoots to form a round-shaped tree. After harvesting, the trees should be pruned. The upright branches, water sprouts, dead wood, infected branches, and the branches that are not exposed to the sun should be pruned off.

5.2 Fertilizer application

A mixed fertilizer of 46-0-0 and 15-15-15 at 250 grams/tree is applied two months after planting and the same rate is repeated again three months later. The same formula with a slightly higher rate of 300 grams/tree is applied in the second year at the beginning of the rainy season with repeated applications every three months. From the third year onwards, as well as for bearing trees, the amount of applied fertilizer depends on the radius of the tree canopy, i.e. at every one-meter radius, one kilogram of mixed fertilizer of 46-0-0 and 15-15-15 is applied.

5.3 Weeding

The weeds are often cut, as ploughing to control weeds is not recommended because of the shallow root system of the trees. Some growers use contact or systemic herbicides for chemical weed control.

5.4 Mulching

In Thailand, where the climate is very warm, organic materials are rapidly decayed, so more organic mulching materials are recommended to be applied to the trees.

5.5 Irrigation

Supplementary irrigation during the dry periods appears to be needed for young as well as mature avocado trees.

5.6 Diseases

Avocado root rot is the most serious disease that affects avocado trees in Thailand. The disease is caused by the fungus Phytophthora cinnamomi. This soil borne disease is commonly found in acid soils with poor drainage. It is recommended to use resistant rootstocks such as Duke-7 in the areas where the disease is prevalent. A well-drained soil is needed to prevent the spread of the disease. No ploughing underneath the tree canopy is advised. For avocado seedlings in the nursery, 20 ppm Dexon, applied as soil drench, is recommended to control Phytophthora in the nursery.

Other diseases that have been recorded are anthracnose on leaves and fruits which is controlled by spraying with mancozeb or carbendazim fungicides. Algal spot was found on leaves also, and can be controlled effectively by spraying with copper oxychloride or, alternatively, by pruning the trees to provide good ventilation.

5.7 Insect pests

The insects that are occasionally found to cause some damage in avocado are termites, twig-cutting bee, leaf-eating caterpillar, thrips and hemiptera species. Usually, the damage from these insects is not up to economic injury levels. In case of serious damage, however, spraying with insecticides such as Sevin can give satisfactory control.

6. HARVESTING AND YIELD

The harvesting time of avocado cultivars in Thailand extends from July to December. Harvesting time of the same cultivar grown under different climatic conditions may vary from one to three weeks. The fruit characteristics of some avocado cultivars are shown in Table 1.

Table 1. Fruit Characteristics of Some Avocado Cultivars in Thailand

Cultivars	Flower type	Shape	Weight gm	Skin Surface	% Fat	Pulp Colour	Taste
Buccanaer	B	pear	250-300	rough	12-18	yellow	excellent
Booth 7	B	round	300-400	green, nearly smooth	12	dark yellow	good
Booth 8	B	pear	300-400	green, nearly smooth	6-12	bright yellow	good
Fuerte	B	pear	150-250	green, smooth	18	yellow	excellent
Hass	A	oval	150-250	rough, black	18-25	yellow	excellent
Peterson	A	round	200-350	smooth	12	dark yellow	good
Ruehle	B	pear	200-350	smooth	10	yellow	good

6.1 Maturity index for avocado in Thailand

a) Skin colour change

Variety
Peterson	from green to greenish yellow.
Ruehle	from green to greenish yellow.
Hass	from green to black
Booth 7	skin colour is still green at maturity
Booth 8	but stalk colour changes from
Buccanaer	green to yellow

b) Age from fruit-set to maturity

Ruehle	4.5 months
Peterson	6 months
Booth 7	8-9 months
Buccanaer	8-9 months

c) Percentage of fat

As the fruit approaches maturity, the percentage of fat in the pulp increases to reach the standard level, characteristic of each cultivar.

d) Seed coat peels off easily.

e) Percentage of dry matter of the fruit comes to a constant level.

6.2 Yield

The yields of avocado per tree recorded at Pak Chong Research Station are indicated in Table 2. Due to the productivity and eating quality of their fruits, Booth7 and Buccanaer are the two cultivars that have been recommended to growers in Thailand. However, the fruits of the Buccanaer cultivar were found to be of better quality and receive good market acceptance.

Table 2. Avocado Yields per Tree at Pak Chong Research Station

Cultivar	5-year old trees		8-year old trees
	No. of fruits/tree	kg/tree	No. of fruits/tree	kg/tree
Pak Chong 3-3	110	40.2	209	75.2
Booth 7	249	87.1	527	179.2
Booth 8	200	63.0	280	86.8
Buccanaer	250	70.0	332	146.2
Catalina	117	44.0	182	67.7
Choquette	102	45.9	194	85.5
Hall	225	108.0	380	170.7
Lula	50	17.5	150	52.0
Peterson	110	27.5	150	40.5
Queen	141	51.0	210	73.5

7. MARKETING

Avocado production in Thailand is still small and all fruits are sold locally as there is still high demand in the domestic market. There is, however, a potential for exporting avocado fruits to Japan, Hong Kong and Singapore. Local consumption of avocado fruits is increasing every year, but local consumers should be taught how to eat fresh avocado. Avocado oil extraction for the cosmetic industry is also increasing and there should be a good possibility for establishing a small factory locally when the fruit supply exceeds the local demand.

8. FUTURE PROSPECTS

The results of studies on avocado indicate that this fruit tree is suitable for the northern and northeastern regions of Thailand. At present, extension work is mainly carried out by the Royal Project Foundation and the Department of Agricultural Extension. It is expected that in the next five-year period the area under avocado will be increased to 500 hectares with a projected production of 2,500 tonnes by the year 2003.

The development of the avocado industry in Thailand can be promoted by forming an avocado society. This society should be supported by government institutions like the Ministry of Agriculture and other educational institutes that will help to improve technologies for better management of the crop through research and development. The society should have the bargaining power in selling and exporting fruits. At present, the Royal Project Foundation helps avocado growers by collecting the fruits from them and selling them to supermarkets and hotels in the cities of Bangkok and Chiang Mai. This marketing system of the Royal Project is only on a small scale and is responsible for growers in the project area in northern Thailand. Therefore, there is a need for another organization to undertake the marketing of avocado for the whole country if avocado production is going to be expanded to other parts of the country.

One important factor to be borne in mind is that the local market for avocado is somewhat slow in expanding as the taste of avocado fruits is not so sweet as compared to other exotic tropical fruits. If the planted area is rapidly increased the price at the farm gate is bound to drop. There is a need to promote the avocado fruit based on its nutritional attributes, especially to make consumers aware of its high nutritional value.

8.1 Future research

The following research studies need to be undertaken in Thailand:

a) Cultivar selection and breeding for better fruit quality and yield.
b) Selection of dwarf rootstocks for developing compact trees.
c) Selection of better rootstocks resistant to Phytophthora disease.
d) Studies on harvesting and post-harvest handling of avocado fruits.
e) Study on export market feasibility of avocado fruits to Japan, Hong Kong etc.

The following activities are planned to be carried out in the Royal Project Foundation area:

a) Top-working of commercial cultivars on existing seedling trees grown by private growers.
b) Short training of growers and extension staff on avocado production.

Although avocado has been grown in Thailand for almost 90 years, the rate of increase in planting area is very slow when compared to other tropical fruit trees. There are some salient reasons for this situation. Firstly, the people do not understand much about commercial marketing of avocado. The early introduced cultivars gave fruits which were too big and unsuitable for the local and export market. This took a long time to be understood by local specialists. It is only now that better commercial cultivars are being introduced and top-working of the existing trees has been undertaken. Secondly, the taste of avocado fruit is not familiar to local consumers, as they are familiar only with sweet-tasting fruits. The promotion on how to eat avocado fruits must be initiated in Thailand if it is to be incorporated as a component in the local diet.

In the next five-year plan, Thailand will have more area under avocado and, hopefully, avocado fruits will be more and more utilized at home level when consumers realize its high nutritive value. Also, the avocado has some export potential in selected Asian markets if the appropriate small-fruited types are promoted for cultivation in the cooler northern and northeastern regions of the country.

REFERENCES

Alexander, D. M. 1978. Some avocado varieties for Australia. Commonwealth Scientific and Industrial Research Organization, Australia. 36 pp.

Babpraserth, C. 1991. Avocado. Extension and Training Center, Kasetsart University, Kamphaengsaen, Nakhon Pathom, Thailand. Extension Bulletin No. 42. 32 pp. (in Thai).

Babpraserth, C. 1997. Plant Propagation in Tropical Fruits. Department of Horticulture, Faculty of Agriculture, Kasetsart University, Bangkok, Thailand. 45 pp.

Banks, A. 1992. Growing avocado in Queensland. Division of Crop Sciences, Department of Primary Industries, Queensland. 36 pp.

Whiley, A.W. 1991. Persea americana Miller. p. 249-254. In: E.W.M. Verheij and R.E. Coronel (eds). Plant Resources of South-East Asia No. 2: Edible fruits and nuts. PROSEA, Pudoc, Wageningen, The Netherlands, pp. 249-254.

California Avocado Society Yearbooks, 1960-1970.