Northern Vietnam is part of the original area of distribution of lychee. Current production is 6000 tonnes from 1500 hectares of bearing trees and is expected to rise to 42 000 tonnes from 10 000 hectares in the year 2000. Expansion of lychee is most likely in areas radiating from Hanoi in lowland and upland areas up to an elevation of 150 m (Lat. 20-22°N), where winters are cool and dry enough to provide the necessary growth check for good flowering.
While evaporation is not high in most areas (1000 mm/year), lack of irrigation will have a major effect on production. Other constraints to production include limited range of cultivars, inadequate nutrition (especially nitrogen) and lack of sprays, spray application and technology for integrated pest management of erinose mite (Eriophes litchi), lychee stink bug (Tessaratoma papillosa) and lychee moth (Acrocerops crameralla).
It is proposed to export 60% of the crop to Singapore and Hong Kong. However, Vietnam will need to adopt post-harvest and marketing technologies being developed in Australia, Thailand, Israel and South Africa if it is to compete successfully in world lychee trade.
This article describes the production and marketing of lychee in Vietnam. It follows a UNDP consultancy during May and June 1991 to assist the people of Vietnam increase their production of tropical fruits. The annual consumption of fruit is very low in Vietnam, about 5-10% of that of developed countries. Lychees have a high priority in new plantings, along with citrus. Increased production wil not only increase fruit consumption, but also earn much needed foreign exchange.
The lychee or litchi (Litchi chinensis Sonn.) is native to southern China and northern Vietnam, and wild trees can still be seen growing in rainforest up to about 300-500 m in many areas. For example, in parts of southern China, including Hainan Island, lychee is the dominant species in many rainforests.
The lychee has a long history in southern China, with unofficial records going back 1766 BC. Production is well-developed with some 60-70 000 tonnes a year from 6 provinces, especially Guangdong, Fujian and Guangxi. Lychee is also popular in Vietnam, but the industry is less developed. References in medical text books indicate that commercial production in Vietnam goes back about 500 years. Production in 1990 was estimated to be about 6 000 tonnes from 1 500 ha of bearing trees. There was also 1 000 ha of non-bearing trees and 500 ha of new plantings.
Lychee trees can be found throughout much of northern Vietnam. The major area of production is in a radius of 50-150km from Hanoi (Lat. 21°N) especially in Nam Thanh District in Hai Hung Province, Luc Ngan district in Ha Bac Province, and to a lesser degree in Dong Trien District in Quang Nihn Province and Ao Chau district in Vinh Phu Province. There are also some lychees near Hanoi and further south in Ha Nam Nihn and Nghe Tinh Province (19°N latitude). However, generally, lychee crops well over a narrow area (Lat. 20-22°N), at an elevation of 100 m above sea level. Within a district, the lychee farms are also concentrated in a small area of each other.
Currently most lychee production appears to come from small farms and co-operatives with many plantings of perhaps 50-100 trees (1-2 ha), although larger state farm plantings dominate in Dong Trien District in Quang Ninh Province.
Vietnam lies in the South East Asian intertropical monsoonal zone. A dry winter monsoon mainly affecting Vietnam north of Danang (16°N) comes from the NE between October-March. From April to September, a SW monsoon brings warm wet weather to the whole country except those areas sheltered by mountains (Central Coastal Lowlands and Red River Delta).
Lychee production at present is mainly in the north near Hanoi where winters are cool and dry (daily minimum in January of 8.9°C and total rainfall of 43.4 mm) to provide the necessary growth check for reliable flowering. Further south at Phu Quy (19.5°N), flowering is less reliable where minimum temperatures in January are slightly higher (12.5°C). This area is considered the southern limit of lychee production in Vietnam. The lowland tropical areas such as Ho Chi Minh City are too warm and wet for good flowering (daily minimum temperatures in January at 21.0°C and rainfall of 195 mm).
However, upland areas in the south such as Dalat (12°5) could provide good flowering in some cultivars (daily minimum temperatures in January of 10.2°C and rainfall of 8mm).
In all areas, the relative humidity is high, although the northern area (Hanoi) is on average 10-15% higher than the central areas (Phu Quy). While evaporation in the region is not high at 1 000 mm/year, when combined with a long dry season (and irregular wet season in some districts), lack of irrigation will have a major impact on productivity of lychee orchards.
The other factor affecting lychee yields will be extended cloudy weather during fruit set in spring, or short periods of hot dry winds. A range of cultivars of different flowering times should be planted to reduce the impact of these conditions.
Many fruit trees are damaged by strong winds. There can also be a loss of productivity. Lychee is no exception in this regard. All of the coastal Vietnam which includes some of the lychee areas come under the influence of typhoons during the September-October period. Tree crops in these areas need very good wind protection to avoid damage.
Most soils to be developed for lychee production in the north are well-drained to at least 1.0 m. Most of these areas are less than 150 m above sea level. Soils range from silty loams to clay loams with a wide range in colours from red-browns, yellows and greys. Physically, most of these soils are good, provided organic matter levels are maintained. However, the chemical and pH status are vary variable.
Lychee has undergone a long period of selection in China and each district has its own cultivar. Many of the cultivars in Vietnam have been selected under Chinese conditions, although there has been some local selection. The varietal situation in Vietnam is very confusing. The one cultivar may be known under several different names depending on the district. Also, some of the cultivars do not match their description in China or Australia.
Cultivars in order of maturity are described below.
Tu hû (Sour Lychee). Fruit mature very early in the season, normally from early May. The name refers to a small bird which appears at that time of year. Fruit are large and attractive bright-red, but have a large seed and thin sour flesh. It resembles wild lychees. This cultivar often fetches a high price because there are no other lychees available, but is usually only eaten by children or used for offerings in temples. It is mainly grown in the Hong Ha River Delta of Vinh Phu Province.
Vai Trung (Vai Nho or Hybrid Lychee). This cultivar is grown in Dong Trien District of Quang Ninh Province and is thought to be a hybrid between the Sour and Thieu lychee produced about 50 years ago. Fruit mature from late May to early June. Fruit are medium in size (larger than Thieu) with a large seed and sweet/sour flesh. Fruit are only suitable for fresh market.
Tau Lai (Chinese Hybrid Lychee). There are a few trees of this cultivar growing in Tranh Ha District in Hai Hung Province. It reported to be a hybrid of Chinese cultivars. It is similar morphologically to the cultivar Phu Ho which was sent from Reunion Island in the Indian Ocean in 1905 by Mr. Remon, owner of Phu Ho plantation in Phong Chaû District in Vinh Phu Province. Fruit mature in early June and receive very high prices. Fruit are large with a large seed and firm sweet flesh. Fruit have strong market appeal. The proposed expansion of lychee plantings in Vietnam will include this cultivar.
Thieu (Vai Thieu). This cultivar was introduced from China about 100-300 years ago, possibly as a seedling, and is now found growing in Thanh Ha District in Hai Hung Province (Thieu-A), Luc Ngan District in Ha Sac Province (Thieu-B) and Dong Trieu District in Quang Ninh Province. It is the most widely-grown cultivar in Vietnam. Fruit quality is reported to be superior in the Thanh Ha District (Hai Hung Province) where the tree was first discovered (Thuy Lam Village). Fruit mature from mid to late June.
Fruit are small and blotchy yellow red with the segments swollen at maturity. The seeds are small or abortive and flesh moist. Fruit are suitable for fresh market but are reported to discolour in the can. Expansion of lychee in Vietnam is dependent on this cultivar.
Other cultivars held at Phu Ho Institute introduced from China include Que Vi (Kwai May?), Nhu Me Tu (No Mai Chee?), Nguyen Hong or Yuan Hong (Souey Tung), Hac Diêp (Haak Yip) and Thuong Thu Soi (?). Descriptions of the fruit do not match those in Australia or China.
Cultivars imported recently from Australia include the Chinese cultivars Sum Yee Hong (San Yue Hong), Souey Tung (Yuan Zhi), Tai So (Da Zao), Fay Zee Siu (Fei Zi Xiao) and Wai Chee (Huai Zhi). Australian sections include Kwai May Pink and Salathiel.
Characteristics of some of the cultivars are shown in Table 1.
|Percentage of fresh weight||Brix (%)||Skin Colour|
|Theiu (A) - Thieu Thanh Ha|
Thieu (B) - Thieu Lue Ngan
PROPAGATION, PLANTING AND EARLY TREE MANAGEMENT
Lychees in Vietnam are normally propagated by air-layering (marcottage), with grafting and cuttings less popular. The branches are air-layered after harvest during the rainy season in late June to early July. Root development normally takes 2- 3 months and the air-layers are cut off in September-October. The air-layers are potted up and planted within 1-2 months.
October is considered the best month for planting since it is still rainy and warm. If air-layering is slow, planting can be delayed until March or April.
A great detail of attention is placed on the selection of the mother tree and branch for air-layers. The tree should be at least 10-20 years of age with stable yields, few pests and diseases and have fruit characteristic of the cultivar. Branches on the outside of the canopy about 1.5-2.0 cm in diameter are preferred. The branch is normally about 50 cm long and has three strong laterals. The length of the cincture is about 3.0-4.0 cm. The cinctures are usually allowed to dry for 2-3 days before the plastic bag filled with soil and organic matter is wrapped around the cut. Success rates are normally greater than 90- 95%. Synthetic auxins such as 2,3-D hasten the rate of root development, but are not essential. The air-layer is detached once the white roots begin to yellow, but before they turn brown.
The air-layers are grown in 10-litre bamboo baskets filled with loamy soil and organic matter and placed in trenches in a shade house. Superphosphate is added to the mix (1. 5kg/m3). Plants are watered regularly. The leaf area is reduced by two-thirds to reduce water loss. A weak nutrient solution of rotted organic matter and 1% urea is applied to the plants twice a month. The trees are planted out in the field once the roots appear at the bottom of the pot.
Tree spacings are 9 x l0 m (110 trees/ha) or 10 x 10 m (100 trees/ha) in good lowland soils and 8 x 8 m (156 trees/ha) or 8 x 10 m (125 trees/ha) in poorer upland soils.
About 30 kg organic matter and 0.5kg each of superphosphate and potash are applied to a 1m planting site once a month before planting and incorporated to a depth of 60 cm. Soil tests including soil pH are not used and lime or dolomite are not routinely applied, although some soils have < pH 6.0. A pH of 5.5-6.0 is considered optimum for lychee.
The trees are normally irrigated (by hand) for a few months after planting. Tree guards and windbreaks are not used.
Many of the young plantings are intercropped with vegetables, cassava, legumes or even other fruits such as pineapples.
Many of the smaller lowland farms irrigate their lychees by flooding. However, much of the upland plantings are not irrigated, with a major effect on the regularity of fruit set and yield, especially when spring and early summer are very dry.
In the areas where irrigation is available, the benefits of withholding water during the dry winter period for good flowering is well recognized.
Fruit browning and splitting before harvest does not appear to be a problem in Vietnam, possibly because of high relative humidity during much of the growing season.
Rates of fertiliser are similar to that in Australia, although older trees in Australia do not normally receive large amounts of organic matter which release nitrogen over a long period. Suggested rates for well-grown trees of various ages are indicated below.
|1-4 yrs||5-10 yrs||>10 yrs|
|Organic matter (kg/tree)*||20||30||50|
|P(as superphosphate) (g/tree)||30-40||50-70||100-150|
|* 1 kg supplies about 5g N, 2g P and 5g K|
Young trees are normally fertilised three times per year (February, April and July). For older trees, the organic matter is applied in July/ August and N, P and K split between February/March, April/May and June/July. These applications are used to encourage flower development, fruit growth and leaf growth, respectively.
The fertilizers are normally mixed together and applied in a drench around the drip line. The fertilizers are then covered with soil during the next rainy period.
The supply of large amounts of nitrogen as organic nitrogen may be one of the factors contributing to vegetative growth in winter before flowering. In Australia, it is recommended that growers do not apply large amounts of organic matter to bearing lychee trees which release nitrogen over a long period. Leaf nitrogen concentrations should be about 1.5-1.8% N in winter for optimum production. The nitrogen status of lychee orchards in Vietnam should be monitored. Nitrogen is the major nutrient affecting productivity of lychee trees.
Trees need to be pruned to provide a strong tree structure, to minimise wind damage and to increase the fruit-bearing area. For dense cultivars such as Thieu, about 10% of the branches within the canopy are removed after harvest. You should be able to see broken sunlight on the ground under the tree. This practice allows wind to move through the tree and reduce the risk of the tree twisting out during heavy winds.
Trees are also skirted by removing all branches and shoots to a height of 0.5m leaving a clean single trunk
The lychee in Vietnam, as in most other countries, seems to be little-affected by serious diseases. The most obvious disease is the parasitic algae, Cephaleuros virescens, which can be readily controlled by copper oxychloride sprays applied to the trunk and limbs before and after the wet season (4g/1itre).
Nematodes, 'Decline and Sudden Death', don't appear to be a problem in Vietnam.
Production and quality of lychee in Vietnam can be seriously reduced by a complex of pests associated with this crop. Damage to non-bearing trees can delay the onset of fruit production, which reduces the rate of return on the grower's investment. In bearing trees, pest activity at flowering and fruit set can dramatically influence the quantity of harvestable fruit, while its quality can be substantially reduced by a number of species present in the orchard before harvest.
There are about 26 species of insects which affect lychee production in Vietnam. However, there are only a few which have a major impact when present. These are described below.
Lychee erinose mite (Eriophyes litchii ). Symptoms are blistering on the leaf surface and brown felting on the underside. Mites migrate from old to new growth, and flowers and young fruit can also be affected. Young trees can be killed if infestations are severe. Fruit production can be substantially reduced in older trees. Infested leaves should be removed and burnt. The new growth should be sprayed every 10-14 days with wettable sulphur (800g/kg) at 3g/1itre or dimethoate (400g/L) at 0.75ml/litre, from just before the flush emerges until it hardens off. Species of predatory phytoselid mites from China are a possible value for biological control.
Lychee stink bug (Tessaratoma papillosa). The nymphs and adults damage the young growth flushes and developing inflorescences in spring, by piercing and sucking the panicle stalks and flower pedicels. They also sting the fruit to suck the juice, causing the fruit to ferment and abscise. It is a very destructive pest and may cause the loss of crops. Trichlorphon (625g/1itre) is the preferred chemical for control, as it has a short residual life and is less disruptive on parasites of the stink bug than dimethoate. One spray before flowering and two sprays (0.75 ml/litre) after fruit set are recommended. Anastatus spp. wasp parasites have proved to be very effective against this pest in China, and technology for rearing these parasites are well-developed and should be introduced into Vietnam.
The lychee moth (Acrocercops cramerella ). The moth lays eggs on the skin of the fruit and the larvae pierce the skin and feed on the flesh, causing the loss of the fruit. The moth can complete several generations per year. The lychee moth may be quite severe in some regions. If left unchecked, this pest can be almost as serious as the lychee stink bug especially after rain. Procedures for monitoring the pest have been worked out in China. Most seasons require at least one application of dichlorvos about one month before harvest.
Leaf-eating beetles (Anomala radicola) often swarm during the evening in summer and damage the soft new growth. Beetles can live for several months, and there are 2-3 generations per year. Swarms can inflict damage quickly and failure to detect them negates the benefits of any control measures. Beetles often appear soon after initial rainfall in summer. Carbaryl (800g/kg) should be applied at 1g/1itre as late in the day as possible to achieve maximum impact when beetles emerge to feed at night.
Stem (Aristobia testudo) and bark borers (Arbela tetraonis) occasionally attack branches causing loss of links. Chemical control is not effective.
Fruit bats, wherever encountered in the world are difficult to control in lychee orchards. Strategic netting and shooting have proved the most effective means of control in Australia.
Birds do not appear to be a major pest of lychee in Vietnam.
Fruit piercing months including Othresis fullonia and Eudocima spp. are major pests of citrus in Vietnam, but are not considered important in lychee.
HARVESTING, STORAGE AND MARKETING
The season in Vietnam is about 6-8 weeks (May-June). Fruit of a single cultivar in an orchard is usually ripe over about 1-2 weeks. There is no maturity standard and much of the fruit in local and Hanoi markets was only half-coloured. Picking of immature green fruit rather than fruit browning appears to be more of a constraint to increased lychee production in Vietnam. Fruit are picked by hand and sold in clusters of 300-500g in 10-20kg bamboo baskets. Much of the fruit is sold locally. Traders in Hanoi buy the fruit from the growers at a set price ($US0.30-0.40/kg) and they are brought in by lorry without refrigeration. Small vendors purchase the fruit in small quantities, 20- 50kg. Fruit normally sell for $US 0.60-0.80/kg. Prices are generally higher at the start of the season, when small, sour fruit are available. There are small quantities of lychee air-freighted to Ho Chi Minh City.
Browning and fruit deterioration are major problems for lychee marketing in Vietnam if fruit are not consumed soon after harvest. Lychee fruit lose their bright-red skin colour and turn brown within a few days. Browning is delayed by keeping the fruit moist and by covering with banana or other leaves. However, fruit must normally be consumed within 1-2 days after harvest.
Because of the short production season, about 30-40% of the lychee crop is dried. The lychees are normally dried on the farm in small coal-fired ovens. About 5kg of fresh lychee is required to produce 1 kg of dried lychees. Price for dried lychees is about $US3.00-3.50/kg. Small quantities are exported to China.
Hanoi has three canneries which produce canned lychees in syrup. Canned lychees are very expensive (US$0.50/can). Most of the fruit is exported to the Netherlands.
There are currently no export of fresh lychees from Vietnam.
Average yields of trees of various ages for the two main cultivars are indicated below.
|Cultivar||Year 5||Year 6||Year 8||Year 10||Year 30|
|*Yield in t/ha at 100 trees/ha|
Yields are generally higher in private farms, possibly because of better tree management. Yields in 1991 were very low, possibly only about 10-20% of the 1990 crop in most districts. Lychees are considered to be biennial bearers in Vietnam, but there are no production figures for individual trees. The failure of flowering was the reason given for the poor performance of most trees in 1991. Other factors may include extended dry season and inadequate control of lychee stink bug.
Lychee is a popular fruit in Vietnam and prices may exceed $US1.00/kg earlier in the season. A small orchard of 50-100 large trees may return $US1200 year, when average income is less than $US200/year. There is good support from the farmers for lychee production and strong demand for new and improved cultivars. Major nurseries have yet to be established. At the moment State Farms are the only source of nursery plants.
The projected area under lychee cultivation is 5000 ha in 1995 and 10,000 ha in 2000. Similarly, anticipated production is 15,000 tonnes in 1995 and 42,000 tonnes in 2000. The proposed production increase is mainly dependant on the supply of nursery plants from the project of about 105,000 air-layers per year. The yields proposed for reaching these objectives of 4t/ha in 1991, 6t/ha in 1992-96 and 7t/ha in 1997-2000, are realistic in the light of yields achieved in Vietnam to date.
It is proposed that 30% of the crop will be exported to Hong Kong and Singapore in 1991-92. This is anticipated to rise to 50% in 1993/94 and nearly 60% from 1995-2000. Export earnings in the year 2000 would be $US45-90 M. I feel that these objectives are over-ambitious unless the project resolves many of the post-harvest and marketing problems. The supply of nursery plants can also not be guaranteed at this stage. Grade standards for export fruit need to be very high. In Australia, with high inputs, only about 20-30% of the lychee crop would be suitable for export. Vietnam, with low inputs and unirrigated plantings would have difficulty producing high quality export fruit. Also, the performance of cultivar Thieu in export markets is untried. However, the domestic market in Vietnam is very much under-supplied in fruit. The local market could very well handle the increase in supply. Lychee consumption per year would increase from 0.1kg/capita to 0.8kg/capita.
DATE: May 1992
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