Avocado Production in China - Liu Kangde and Zhou Jiannan*

* Chinese Academy of Tropical Agricultural Sciences, Danzhou, Hainan 571737, China.

China has some 80 years history of avocado introduction and trial planting. Avocado was first introduced into Taiwan in 1918 and then into Guangdong in 1925. Nowadays, avocado is reported to be successfully planted on a trial basis in Guangdong, Guangxi, Hainan, Fujian, Sichuan, Yunnan, Zhejiang, Guizhou, etc. (Cai, Liu, et al., 1998).

The avocados cultivated in China were generally the progenies of some unselected poor-quality seedlings of unknown origin. It was not until 1985 that high yielding varieties of avocado such as Hass were introduced for trial planting by the Guangxi Bureau of State Farms, etc. Collection, introduction and selection of avocado has been conducted by the College of Agronomy, South China University of Tropical Agriculture, since 1986 and more than 80 varieties have been selected. Huang Wenzhen and Liu Kangde established a 33.3 ha experimental plot of avocado and a nursery in Baisa County, Hainan, in 1989, to determine commercial cultural techniques (Liu, Zhang, et al., 1993).

2. PRESENT SITUATION OF AVOCADO CULTIVATION

Avocado is grown in Guangxi, Hainan, Yunnan, Guangdong, Guizhou, Fujian, Zhejiang (Wenzhou city) and Sichuan (Panzhihua city) in China. There has been no sizeable commercial production up to now due to various reasons. The largest tract of cultivation in China is the avocado base in Baisa County, Hainan, covering 33.3 ha. Guangxi has the largest area with scattered avocados. Prof. He Guoqiang, Guangxi Staff University of State Farms, reported that Guangxi used to grow 133 ha of avocado in more than 50 counties/cities, of which 66 ha were under commercial production; the largest avocado orchard was in the Shanyu State Farm, covering 20 ha.

Commercial production of avocado is just at the early stage and the planting area is very limited. No data on avocado is available in the local statistical yearbooks. Avocado sets flowers after 2-3 years of planting and yields 35-103.5 kg/tree at the age of 7-8 years, according to the reports of trials in different locations. The total area under avocado cultivation in China was estimated to be 133 ha in 1998 with a production of around 1,000 tonnes.

Most avocados planted before 1985 were seedlings, and budded and grafted plants of desired varieties have been used only in the last ten years. To date, China has selected more than 70 avocado varieties and more than 10 elite lines. Some of the commercial varieties such as Lula, Pollock, Booth 7, Booth 8, and the local variety ST₃, have good performance in Hainan and other provinces. The varieties used in trials, at present, are indicated in Table 1.

Table 1. Major Avocado Varieties Used in Trials

Race	Varieties	Remarks
Mexican race	Bacon, Zutano, Duke, Mexicola	Trial in Hainan
Guatemalan race	Hass, Nabal, Reed, Taylor, Linda	>>
West Indian race	Pollock, Sharwil, Murashige	>>
Hybrids	Fuerte, Lula, Booth 7, Booth 8, Hall	>>
Local selections	ST3, ST6, ST9, S10	>>

3. PRODUCTION OF PLANTING MATERIALS - NURSERIES

There were no state-owned commercial nurseries in China until recent years. Generally, nursery plants were raised privately by the farmers in state farms. It is since the late 1980s that commercial nurseries have been established separately by the South China University of Tropical Agriculture and the Guangxi Staff University of State Farms, and provide high-quality planting material, mainly in Hainan, Guangdong and Guangxi.

Planting materials used in China are generally polyethylene bag-raised seedlings and budded and grafted plants. Polyethylene bag seedlings were the major planting material before 1985, and polyethylene bag budded and grafted plants have been commonly used since the 1980s. Bare-rooted nursery seedlings have a low success rate of survival and, basically, are not used for planting commercially.

The commonly used vegetative propagation methods include patch-budding, cleft-grafting and side-grafting. Thirty-day-old seedlings are used as stocks for cleft-grafting and satisfactory results are obtained. The grafted plants are ready for planting out after 6-9 months of seed germination, when they grow 50-60 cm high. This mini stock-grafting method shortens the propagation duration by one year as compared to the patch-budding of polybag older stocks.

4. ESTABLISHMENT OF ORCHARDS

Orchards are usually established on gently sloping land with loose soil and good drainage. In areas with strong wind, orchards should be set up against the wind, and windbreaks are necessary. In areas prone to cold injury, orchards are set up on gently-sloping land towards the sun but against wind. Mechanical cultivation is generally practised after slashing and clearing on the gently sloping waste land. Terracing or benching is necessary on the sloping land.

Planting season

Avocado is planted out all the year round in Hainan if irrigation is available. In the cold areas of the mainland the plants are planted between the warm spring and the autumn, prior to the end of the wet season.

Spacing

The spacing varies with climate, soil regime, vigour and growth habit of the varieties. For tall varieties or those with spreading growth habit a wider spacing is given, such as for Fuerte, Linda, etc. For varieties having compact crown (for example Lula) closer spacing is given. The plants are usually planted at a spacing of 4-5 metres to 5-6 metres with 333 - 500 plants/hectare in Hainan. Pruning or thinning is practised when the tree canopy shades the rows, after several years of planting.

Opening of pits and planting

Pits of 80×70×60 centimetres are opened about one month before planting out. Generally, they are opened manually though mechanical pitting has been conducted occasionally in recent years. Surface soil and organic manures then fill the pits after full exposure to the sun. The plants are planted when the weather is cloudy, cool and humid but without rain. The polyethylene bag is removed and the compact root ball is not disturbed. The plants are watered and mulched after refilling and compressing the pits. Interplanting of A and B type varieties should be considered when establishing an orchard.

5. CARE AND MANAGEMENT OF ORCHARDS

Training and pruning

Avocado is trained and pruned based on the characteristics of the varieties. Generally, avocado trees are headed back at an early stage when they are 80 to 100 centimetres high to encourage lateral growth, and the branches are then cut back when they are 50 to 60 centimetres long to form a good framework. The avocado is pruned mainly by removing the dead, weak, crossed and thick branches. The bigger cut ends are sealed to prevent rot and other diseases.

Application of manures and fertilizers

The application dose and proportion of manures and fertilizers are generally based on the soil fertility, tree age, growth and yield. For the young orchards where manures are applied in the pits before planting, fertilizers (mainly liquid N) are applied in frequent low doses. For the mature orchards, mainly N and K fertilizers are applied 3-4 times annually, separately in February to April, April to May, and July to September. P fertilizer and organic manures are mixed and applied before and after avocado fruits are harvested.

Weeding and mulching

Weeds should be controlled in the young orchards. Generally, manual weeding is conducted 3-4 times per annum, together with shallow soil cultivation and fertilizer application. The area around the trunk of the tree is mulched with dead grass or the like to inhibit weed growth, and at the same time to slow down the evaporation of soil moisture, maintaining soil humidity and reducing soil temperature. Legume cover crops such as stylosanthes are intercropped in some young orchards. Glyphosate is used for controlling weeds in the rows of trees not intercropped with cover crops in some young orchards.

Irrigation

Avocado is very sensitive to dry soil. Soil moisture should be maintained in the root zone. Moisture stress gives rise to physiological hindrance, resulting in weak vigour and even defoliation and fruit drop. Avocado sets flowers and bears fruit during December to May, the dry season in most of the southern part of China, hence irrigation is very important. Avocado orchards give a high and stable yield when irrigation is available. Improved irrigation systems such as sprinkle and drip are not used at present. For the orchards with easy access to water, flooding is achieved by water pumping. For the orchards far away from water source, irrigation is carried out using tractors with water tanks.

Control of pests and diseases

Diseases

There are more than ten diseases, such as root rot, collar rot, phytophthora canker, anthracnose (Colletotrichum gloeosporioides), stem-end rot (Dothiorella aromatica), scab (Sphaceloma perseae), etc. Of the diseases, root rot and collar rot are the most serious.

Root rot is the most serious disease of avocado in mature orchards, caused by a fungus, Phytophthora cinnamomi. It attacks small roots, thereby causing leaf fall, dieback of branches and tree collapse. The trees infected show symptoms of weak vigour with withered and sagged leaves, yellowish-green leaves, dead twigs and branches, small fruit and seriously scalded branches. The cortex of the infected roots turns black, rots and dies. Some seriously infected trees wither and die. Root rot is aggravated by waterlogged and poorly drained soils. Chemicals such as Alliette, Ridomil, etc. are used as a soil drench, or Alliette as a trunk injection at 0.3 grams/square metre. Phytophthora-resistant rootstocks are also being selected, such as Thomas, Duke 7, etc, but they are not yet used commercially.

Collar rot, caused by Phytophthora citricola, is another serious disease of avocado in young orchards in Hainan. It attacks the collar, resulting in retarded growth without flushing and then tree decline or collapse. The affected trees show a symptom of shallow honeycombed rot at the early stage, which then spreads, resulting in exudation of white foam-like or pasty sticky liquid (attracting a mass of ants) and, finally, a ringlike rot and death. The disease occurs after heavy rain caused by typhoon. A survey carried out on 4 hectares of affected plantations in 1989 indicated that the incidence was as high as 22 percent.

For the control of collar rot it is very important to drain the water after heavy rain, prune regularly the drooping branches and maintain good ventilation of the plantations. Alliette (1%) is applied at a solution rate of some 2.5 kg to the base of the trees in the orchards of high incidence, or to those affected by typhoon. For the affected trees, the soil around the tree base is removed in clear day, and the affected parts are washed by spraying with tap water and, when dry, painted with Alliette paste 2% and refilled with soil. Satisfactory results were obtained by using this method (Shang, Liu, et al., 1996).

Pests

The insect pests include scale insects, mealy bugs and mites, Mexican leaf rollers, aphids, fruit flies, burrowing nematodes, etc. Serica sp. is the most important insect attacking young trees in Hainan. It damages mainly the young leaves and breaks out in April and May. A survey made in May, 1990, indicated that there were 2,853 trees infested with this insect (53.7% of the 5,316 trees surveyed). Dichlorvos (50%, e.c) is used for spraying or as a soil drench at the tree base, and good results are obtained.

6. HARVESTING AND YIELD

Avocado tends to set flowers in February and March in Hainan. The maturity period of avocado varies with varieties. The fruits of local varieties and those of the Pollock variety mature in July and August. Other introduced varieties, such as Lula, Booth 7, Booth 8, etc., mature their fruits at the end of September and mid-October, while Hass matures its fruits in November and December.

Yellow or purple skin (differing with varieties), dark brown wrinkled dry seed coat, and certain minimum oil content reached are considered as indexes for fruit maturity. Fruit maturity may also be estimated by using specific gravity or growth time of the fruit.

Mature fruits are picked manually and carefully to avoid being wounded, and the stalks, some 0.6 centimetres long, are retained, attached to the fruit. Picking is carried out in cloudy cool or clear morning.

The average commercial yield in Hainan is 7.5-15 t/ha. Some varieties, such as Lula, Pollock and the local variety ST₃, give a yield of 15 t/ha and their quality is good, whereas some other varieties such as Hass give a rather low yield of 3-4 t/ha (Table 2). This is probably due to difference in adaptation to climatic conditions. Hass is not suitable for commercial cultivation in Hainan, where temperature and humidity are high.

7. MARKETING

Avocado is in the stage of trial planting and extension. Most of the fruits are sold at low prices in the local markets. Very few fruits are seen for sale in towns away from the orchards. No data on import and export is available.

The fruits for local sale are not treated after harvest. Fruits shipped to the northern parts of China for marketing are handled in two ways: either they are washed with hot water (50°C), packed when cool, and shipped and marketed at ambient temperature, or the harvested fruits are cleaned and stored at low temperature. The recommended temperature for cold storage is 10 to 13°C for the West Indian race varieties, 7 to 8°C for varieties of the Guatemalan race, and 4 to 4.5°C for varieties of the Mexican race. The relative humidity is 80 to 90%. The fruits can be stored for one month at low temperature. The recommended temperature for ripening of the stored fruits is 15 to 21°C.

Table 2. Fruit Characteristics

Variety	Fruit		Pulp			Seed
	Weight (g)	Appearance	Colour	Fibres	Fat (g/100g pulp)	Weight (g)	Seed/pulp weight (%)
Lula	589	Good	Pale yellow	Few	13.70	84.0	18.0
Pollock	741	Good	Pale yellow	Rather few	6.87	106.0	15.5
ST3	420	Good	Yellow	Few	9.82	67.5	14.4
Booth 7	530	Good	Dark yellow	Few	15.50	95.0	22.0
Booth 8	410	Good	Pale yellow	Few	17.70	65.0	17.8
Hass	144	Poor	Pale yellow	Few	17.50	30.0	20.8
Bacon	322	Fair	Creamy	Few	15.30	80.0	27.8
Zutano	264	Poor	Creamy	Few	14.40	56.0	21.2

Note: The figures obtained in 1994 by Liu Kangde, Cai Shengzhong, etc. are the mean value of 10 fruits randomly sampled.

China has a great potential for avocado production development. It is estimated that China will have a population of 1.6 billion by the year 2030. It has called the attention of the Chinese government to securing food for the increasing population. Avocado fruit is very nutritious and can be eaten fresh. Avocado products will have a large market when accepted by the Chinese people.

There is a stretch of hilly land suited for avocado planting in the south of China. The tropical and subtropical land covers some 48 million ha in China, distributed in Guangdong, Guangxi, Hainan, Fujian, Yunnan, Guizhou and Sichuan; the land under tropical and subtropical economic crops covers only 6.385 million ha at present. There is also a vast tract of hilly land in the southwest of China, a large part of which is suited to developing tropical and subtropical economic crops such as avocado.

China has good varieties available for the development of avocado production. Research work carried out has resulted in the selection of over 80 avocado varieties; also, appropriate production techniques, including propagation, transplanting, manuring and fertilizer application, control of pests and diseases, harvesting, storage and shipment, have been determined. This can ensure availability of nursery plants and production technology for the development of avocado production in China.

9. CONSTRAINTS IN AVOCADO PRODUCTION DEVELOPMENT

Little awareness of avocado

Avocado is a very nutritious fruit, containing fat, protein, vitamins, minerals and other elements. Most Chinese are not aware of the nutritional value of avocado. Avocado fruits are consumed fresh as are other fruits at present in China. They are neither sweet nor sour and hence less favoured compared to other tropical and subtropical fruits such as litchi, longan, mango, etc. It is hard to popularize a cold dish, sandwich and salad made with avocado. It will take time for the Chinese people to accept avocado, and publicity is necessary.

Difficulty in marketing

The avocado market has yet to be developed since very few people know the nutritional value of this fruit. In the early 1990s, avocados were shipped and marketed in big cities such as Beijing, Shanghai and Guangzhou; however, only some large hotels with foreign cooks showed interest in this fruit. Difficult marketing has given adverse impact to the expansion of the planting area for commercial production.

Avocado has a short storage life under normal temperature. Cold storage and shipment increase cost and farmers will not take the risk of selling their avocado far away in small markets. The industrial demand is very limited and it is hard to stimulate expansion although avocado facecream and soap are produced to some extent. Avocado fruits are marketed locally at low price, discouraging farmers from planting avocado trees.

Natural calamities

Natural calamities include typhoon, hot temperature and cold injury. Typhoon is the major calamity in Hainan, Guangdong and Fujian. Strong wind results in damaging the branches and trunks of the trees, causing poor bearing and low yield. High temperature in the south of Hainan also shows adverse influence on the growth of avocado. Cold injury of avocado occurs in the north of Guizhou, Yunnan and Guangxi. For the development of avocado production, careful selection of varieties for various climatic conditions should be considered.

Weak extension service and dissemination of technology

Avocado orchards were privately owned in the past, and the trees planted were progenies of unknown source without selection. The farmers had very little technical knowledge. The needed production technology for commercial cultivation has been developed by the South China University of Tropical Agriculture and the Guangxi Staff University of State Farms since the late 1980s when good varieties were introduced and trials were instigated. Nursery plants of selected varieties have been distributed for trial planting in some provinces of South China. There are, however, very few people engaged in avocado research. The orchards are widely scattered, and there are very few large-scale commercial plantations, leading to difficulties in extension work and dissemination of technology.

10. GOVERNMENT POLICIES AND PLANS FOR RESEARCH AND DEVELOPMENT OF AVOCADO

Research work on avocado was included in key programmes of the Ministry of Agriculture of China between 1986 and 1995. The Guangxi Bureau of State Farms and the South China University of Tropical Agriculture were entrusted to embark on avocado research work. Scientists were sent to the USA and Mexico for training on aspects of avocado production development. Demonstration plots for commercial cultivation have been established in Hainan, Guangdong and Guangxi. However, very limited financial contribution is made at present by the government to commercial expansion of avocado due to poor marketing. In spite of this, the government encourages companies and farmers to plant avocado for strengthening its publicity.

11. CONCLUSIONS

China has an 80-year history of avocado. The climate and soil in several provinces of south and southwest China are suitable for avocado production. However, there is no large-scale commercial production of avocado in China at present due to various reasons. Also, there are no import and export markets for avocado.

Avocado is planted at present mainly in Hainan, Guangdong, Guangxi, Yunnan and Fujian provinces. However, there is a larger tract of hilly land in south and southwest China suitable for avocado development.

China has a large population with limited cultivated land. To secure food for the increasing population, avocado has a role to play as a source of food and nutrition. Avocado will have a great potential market when substantially more Chinese people become aware of its nutritional value, and accept it. The major constraints to the development of avocado production are little awareness of its nutritional value and difficulties in marketing.

REFERENCES

Chinese Academy of Tropical Agricultural Sciences and South China University of Tropical Agriculture. 1998. Cultivation of Tropical Crops in China, pp. 621-654. China Agriculture Publishing House, Beijing.

Cai Shengzhong, Liu Kangde, et al. 1998. Major Characteristics of Avocado Germplasm. Research of Tropical Crops, (2): 22-28.

Office of Development of South Subtropical Crops, Ministry of Agriculture. 1998. Tropical and Subtropical Fruits in South China, pp. 211-217. China Agriculture Publishing House, Beijing.

Zhang Shaoruo, Liu Kangde, et al. 1996. Conditions for Onset of Collar Rot in Young Avocado Orchards and Its Control. Research of Tropical Crops, (2): 46-53.

Liu Kangde, Zhang Shaoruo, et al. 1993. Introduction of Avocado for Large-Scale Trial Planting. Research of Tropical Crops, (4): 38-47.