12. LYCHEE PRODUCTION IN VIET NAM

Vu Manh Hai ^[13] and Nguyen Van Dung ^[14]

1. INTRODUCTION

Lychee is a native of South China and is also considered to have existed in Viet Nam for a long time. At the foot of Bavi Mountain, wild lychee trees were found by a French scientist in 1942. In 1970 Professor Vu Cong Hau (late director of the Industrial and Fruit Crop Institute) and his colleagues discovered lots of wild lychee trees in Tamdao (Vinhphuc province) and Tuyenhoa (Quangbinh province) forests.

A Vietnamese legend also recounts that one of Vietnamese Kings of the Mai Dynasty once offered lychee fruits, which were regarded as precious fruit of Viet Nam, to the Emperor of China. This evidence partly shows that lychee can be considered as a native of Viet Nam lychee and that the climate of northern Viet Nam, where winter is short, dry and a little bit cold and summer is long and hot with high rainfall and humidity, is quite suitable for the growth of lychee.

2. PRESENT SITUATION OF LYCHEE CULTIVATION IN VIET NAM

Area and production

Lychee can be considered to have originated from Haiduong province (Thanhha district) where the most important variety has been commercially developed and over time it has spread to other locations in the northern Viet Nam and even to some places in the central part. At present lychee is commercially cultivated in Lucngan, Lucnam and Yenthe districts of Bacgiang province (about 100 km North of Hanoi); Thanhha, Chilinh and Tuky districts of Haiduong province (approximately 60 km east of Hanoi); Dongtrieu, Yenhung and Hoanhbo districts of Quangninh province (nearly 200 km east of Hanoi); and Quocoai, Chuongmy and Unghoa districts of Hatay province (About 40 km northwest of Hanoi).

Data in Table 1 was collected directly from the Provincial Departments of the Agricultural and Rural Development Ministry in the year 2000. Small cultivated areas are not taken into account.

Table 1. Area and production of lychee in Viet Nam

Varieties of lychee grown in Viet Nam

Up to now, the varieties of lychee grown in Viet Nam have not been scientifically classified, particularly local varieties.

Because of this, existing varieties of lychee are mainly named by local people and based significantly on appearance and morphology of the ripe fruits including the colour. It is obvious that the exact number of lychee varieties is much less than those named and recognized since the same varieties can be named differently from location to location.

In this paper, we try to describe the differences between varieties grown by some main characteristics and group them by harvesting time.

To date, the Research Institute of Fruits and Vegetables (RIFAV) has collected and characterized 33 accessions that can be identified as 33 cultivars of lychee grown in different locations in home gardens and consolidated farms. The names of cultivars collected and their areas of origin are presented in Table 2.

Of the 33 cultivars studied, 8 cultivars namely: Duong phen (as sweet as sugar), Hoahong (rose-like coloured fruits), Hunglong, Phudien, Phuchoa, Yenhung, and Thanhha (names of locations of origin) are considered to be promising and have been commercially developed in the main areas of lychee production. Main characteristics in terms of morphology and fruit quality are presented in Tables 3 and table 4.

Table 2. List of lychee cultivars cultivated in Viet Nam

Table 3. Morphological characteristics of promising cultivars of lychee grown in Viet Nam

Table 4. Characteristics of fruits of promising lychee cultivars.

3. PRODUCTION OF PLANTING MATERIALS

Three methods of propagation i.e. seedling (sexual multiplication), marcotting and grafting have existed historically, but the first is now rarely implemented. Up to 1997, the general practice for lychee multiplication in Viet Nam was marcotting (air-layering). The advantage of this method is it retains the characteristics of the mother tree and is quite simple. The disadvantages are that the marcot does not have a strong root system as it lacks a taproot and is easily removed by strong wind. Also the shallow root system is easily affected by long periods of drought more than plants grown from seedling and grafted ones.

Though grafting was done by the Industrial and Fruit crops Institute in the 1970s, application on a large scale was not disseminated until 1997 when RIFAV had achieved significant success in collaboration with Quangxi Agricultural High School. The rootstock varieties of healthy and straight stem were selected from local varieties named ‘vaichua’ (sour taste). The scions were taken from healthy mother trees of well selected individuals, which have been properly managed and pruned to produce as many new branches as possible.

The total area of lychee nurseries in the north is estimated at about 7.6 ha that can produce one million grafted and marcotted trees from which RIFAV and satellite centres have begun to establish a network for lychee production by grafting.

4. ESTABLISHMENT OF ORCHARDS

Generally, new plantation of lychee is done in two main seasons, namely spring (end of February to the first half of May) and autumn (second half of August to October). In some orchards where conditions for planting are favourable (water resource, labour availability, etc.) the planting season can be longer.

Normal spacing for lychee plantation is 7 x 7 m or 8 x 8 m depending on the fertility of the soil and the topography of the orchard. The dimensions of holes is recommended at 70 x 70 x 70 cm and in some case bigger dimensions up to 1 x 1 x 1 m are applied. Planting holes are filled with organic matter such as farmyard manure and compost, and phosphate fertilizer applied at least one month before planting. The young tree does not require watering since it normally obtains water from the rain during March to May (for spring planting) and September to early November (for autumn planting). However, it should be emphasized that watering of young litchi is definitely needed in areas where the rainfall is quite limited and irregular.

Since grafted young tree have been largely used as the main source of planting material and great attention paid to intensive production, the density of lychee has increased from 150-200 trees/ha to 300-400 trees/hectare.

The over-all design of lychee orchards should be established according to topography. The raised-bed model in the lowlands and contour making in steep land are the two main designs. Intercropping with annual crops such as legumes and vegetables is also applied in some lychee plantations at the first stage of the biological cycle, when land space is available between lychee trees.

5. CARE AND MANAGEMENT OF ORCHARDS

In the past, training and pruning were rarely applied in lychee orchards and only pest affected shoots were removed. The situation changed when lychee growers became aware of the importance of these technologies through training courses and guidance given by extensionists. Most farmers now have sufficient knowledge for taking care of lychee plantations, particularly growers in traditionally concentrated areas of lychee production such as Thanhha district (Haiduong province), and Lucngan and Lucnam districts (Bacgiang province). In various orchards, weeding and mulching seems not to be necessary since healthy lychee plants are properly intercropped with annual crops such as soybean, groundnut, pea, etc.

On the other hand, supplementary irrigation is not a regular activity because of two main reasons:

• As mentioned above, lychee is often grown in spring and autumn in the north, the rainfall during these periods is considered to be sufficient for young trees.

• Lychee is largely grown in hilly areas where water resources are not easily exploited.

On the issue of pests and diseases, no serious problem is observed in lychee orchards. However, in certain conditions the brown bug, which sucks the sap of young shoots and fruit causing them to fall off, and the spider, which sucks leaf sap, are the main problems to be mentioned. In fact, both pests can be controlled easily by using insecticides. In 1998, lots of adult lychee trees in Lucngan district declined and died rapidly. Some fungus and nematodes were observed in the affected trees and fungicides were then applied in combination with proper cultivating technologies, i.e. making the soil aerobic, pruning, fertilizer application, etc., and the problem was solved.

6. HARVESTING AND MARKETING

In northern Viet Nam the most popular variety namely ‘vaithieu’ ripens in May to June. Early varieties and accessions can be harvested in late-April and well-selected individuals of these varieties have been paid great attention to prolong the duration of harvesting.

Concerning the problem of consumption, it is estimated that about 70-75 percent of the total production of lychee fruit is consumed in local markets, the rest is exported to China, Hong Kong, ASEAN countries and some European countries such as France and Russia.

Lychee fruits are also processed as syrup and dried fruit. The juice of the latter is mainly exported to China or used for local consumption.

7. CONSTRAINTS AND POTENTIAL FOR LYCHEE PRODUCTION

Because of irregular bearing resulting mainly from the cold temperature requirement for flower initiation, production of lychee may be quite low in some years. One of the disadvantages of lychee is that its harvesting period is rather short (about one or one and a half months). This makes it difficult for growers to sell all their harvest as most fruit ripens during a short period.

Some other problems are as follows:

• Lack of elite varieties: Though some varieties have been studied and selected, there is one main variety of lychee that is extensively grown. This is likely to be wiped out by epidemic diseases or pests as the result of its narrow genetic base. It also makes the harvesting period short.

• Lack of post-harvest technologies involving equipment needed for conservation and packaging.

  Though the above mentioned constraints are not easily solved in one or two years, the prospect for lychee production in Viet Nam is quite good due to the following advantages:

• Suitable climatic conditions for the growth of lychee. Even with rather poor hilly soil, lychee is growing well.

• High market demand: apart from local consumption that is quite high (in central and southern parts), lychee fruits can be exported to southern China, a country which also loves to consume lychee but cannot produce enough.

• High potential for processing: Lychee is a fruit with pleasing aroma and taste, either fresh or after processing. The latter includes canning of the flesh (seed removed) or by extracting its juice, both of which are on high global demand as few countries in the world can produce them.

• The authorities (Government and Ministry of Agriculture and Rural Development) consider lychee as one of the specially promising fruit crops and policies for encouraging the study and production of lychee have recently been formulated.

8. CONCLUSIONS

Viet Nam in general and northern Viet Nam in particular has high potential for lychee development. In fact this fruit has an important role to play in improving the national economy and living standard of local farmers.

Although, some successes in research and development have been already obtained recently, constraints need to be solved accordingly.

In order to overcome the problems and improve the situation, the following issues should be mentioned.

• Strengthen International Cooperation in the fields of biological genetic exchange and cultivation technologies for application on a large scale.

• Encourage and improve the study of post-harvest treatment of lychee that includes increasing the investment for construction of cold storage and packaging.