9. INTEGRATED PRODUCTION PRACTICES OF CASHEW IN THAILAND - Suwit Chaikiattiyos[9]

1. INTRODUCTION

Cashew was introduced to Southern Thailand in 1901 from adjacent areas of Malaysia from where it spread all over the country. The crop began to be considered as having economic importance to the country by 1984 following the government policy to reduce cassava production by substituting with cashew, particularly for the growers in the North East. The Cashew Research and Development in the North East Thailand project, partly supported by the EC, was later formulated for the replacement of cassava production. Although cashew shares only a small portion of the national economy, it is increasingly becoming important to growers in the East, in terms of regional economy at present.

2. CURRENT STATUS OF PRODUCTION

2.1 Area of Production

Thailand ranks as the third most important cashew producing country in Asia, while India remains the main producer. Initially, major commercial planting areas were scattered in the South, which were predominantly small-scale enterprises. However, in 1984 a rapid expansion of area took place in the Northeast following the government policy, in agreement with the EC, to reduce cassava production due to an international surplus of the commodity. In addition, a number of extension projects were initiated by the government. Eventually, the area under cashew substantially increased from 22,022 ha in 1983 to 61,748 ha in 1989, with major areas in the Northeast such as Nakhonratchasima, Burirum and Si Sa Ket provinces, and in the South in areas such as Ranong, Songkhla and Pattani provinces.

In 1991 however, cashew production greatly decreased, mainly due to poor fruit setting. Either insect infestation or environmental stress may have been responsible for reduced productivity. Consequently, a number of cashew trees, particularly in the North and Northeast have been cut down and many orchards were neglected in 1991-92. Thailand had only 55,407 ha in 1994 with a total production of 58,359 t. Although planting areas in the North and Northeast have declined since 1991, those in the East, particularly in Chon Buri province, continued to increase leading to an expansion of small to medium-sized shelling factories for processing of nuts.

2.2 Varieties

Popular cashew varieties grown in Thailand include Si Sa Ket 60-1 and Si Sa Ket 60-2, which are officially recommended by the Department of Agriculture (DOA), and Sirichai 25 which has been commercially released by a private company. In addition, at the beginning of the national promotion project of cashew, seedlings of the composite variety Si Sa Ket A and seedlings of Maboonkrong from the private sector were also recommended to growers due to insufficient supply of grafted plants to satisfy growers’ requirements.

Si Sa Ket 60-1 and Si Sa Ket 60-2 were developed following clonal selection. They were recommended after results from yield comparison and regional yield trials indicated that they are of good quality in terms of nut and kernel size, and 40 % higher yield than unselected local varieties. The average nut yields of Si Sa Ket 60-1 and Si Sa Ket 60-2 at year 11 are about 33.4 and 25.0 kg per tree and the nut weights are 6.29 and 7.20 g, respectively. Both selected clones have on average about 320 kernels per pound which is the international market standard grade. Si Sa Ket composite A was derived from 10 selected clones including Si Sa Ket 60-1 and Si Sa Ket 60-2. Sirichai 25 had not been tried in the Northeast before widespread planting began in this region. Early yields of young trees were good but the Si Sa Ket varieties may well have yielded better under the same conditions. Among the improved cashew varieties of Thailand, only the composite Si Sa Ket A has genetic variation so that there is little likelihood of all trees becoming susceptible to a new strain of a disease or pest. The potential yield for selected clones Si Sa Ket 60-1 and Si Sa Ket 60-2 is shown in Table 1. Yield potential and quality of different cashew varieties were investigated in 1987 at four different locations. Results showed that the Si Sa Ket varieties were the most promising (Table 2).

Table 1. Average Yield at Si Sa Ket of Recommended DOA Varieties (Kg/Tree)

Varieties	Year 3	Year 4	Year 7	Year 9	Year 11
Si Sa Ket 60-1	1.2	9.8	13.7	15.7	33.4
Si Sa Ket 60-2	1.7	6.9	9.6	10.1	25.0

Table 2. Yield and Quality of Different Cashew Varieties at Year 4 (Average of 12 Trees from 4 Locations)

Varieties	Yield (kg/tree)	Nut Weight (g)	Kernel Recovery (%)	Number of kernels/lb
Si Sa Ket 60-1	4.4	6.6	26.7	263
Si Sa Ket 60-2	3.0	7.2	26.0	245
Composite SK-A	2.2	5.9	27.5	279
Sirichai 25	2.5	7.0	28.0	238
Maboonkrong	1.4	6.7	27.4	251
Local	1.4	5.4	28.1	302

3. PROPAGATION AND PRODUCTION OF PLANTING MATERIAL

Following the government policy to decrease cassava production by introducing cashew to the farmers, particularly in the Northeast in 1981, the Si Sa Ket Horticultural Research Center of the Horticultural Research Institute (HRI), was responsible for the supply of planting material. Both grafted plants and seedlings were produced. The grafted varieties using a modified inarching method included Si Sa Ket 60-1 and Si Sa Ket 60-2 which were released by government agencies. A private company was also involved in cashew extension by supplying grafted plants, namely Sirichai 25 to growers who obtained bank loans from the Bank of Agriculture and Cooperatives. In most cases, rootstocks were prepared from seeds with high specific gravity since such seeds gave higher percentage of germination.

Propagation by marcotting, budding and from cuttings is also possible, but this is considered to be too expensive, unreliable and more complex. In grafting, the rootstocks should be 2-4 months old and scions should be 8 to 10 cm long and of pencil thickness. The color of the scion should be turning from green to brown and the top 4-5 leaves should be dark green indicating proper maturity. A longitudinal cut of 3-4 cm is made on the scion on either side to make a wedge and is inserted into the split on the rootstock and tied with polythene strips. The grafts are kept in the shade for 3 to 4 weeks and later transferred to an open site to allow new vegetative flushes to grow.

4. ESTABLISHMENT OF CASHEW ORCHARDS

Cashew can be cultivated on a wide variety of soils in Thailand. However, for realizing better yield potential, sandy loam soils without a hard pan are desirable. Although considered drought tolerant, the tree requires a well drained soil with substantial moisture available for the root zone if commercial yields are to be attained. This has been confirmed by the rapid expansion of areas in the East where soil moisture content and relative humidity are relatively higher than the North and Northeast. Furthermore, cultivation of cashew in the South over a long time also substantiates the theory that sufficient moisture content assures high yields.

It is strongly recommended that the crop be raised from grafted plants. Recommended spacing is 6m x 6m except those trees grown from seedlings, particularly in the South. Pits are opened to a size of 50 cm x 50 cm x 50 cm and manure is mixed before planting. It is recommended that planting be started during the early rains in June to ensure maximum tree survival. After year 8, every other tree in the row may be removed to allow the remaining trees to spread their canopies without inter-row competition.

5. CARE AND MANAGEMENT OF CASHEW ORCHARDS

Cashew trees should be trained to one main stem. After branching begins, training may be practiced to achieve a tree with one leader shoot of 0.5 - 1.5m. A major vegetative flush follows the onset of the rainy season in May or June and flowering occurs at the growing tips of terminal shoots within 3-4 months after the period of restricted growth in November and December. Cashew may produce fruit at year 2 or 3 if trees are raised from grafted plants. Light pruning need to be practiced soon after harvesting in April-May in order to allow new vegetative flushes and to get rid of dead wood.

Guidelines for fertilizer application for cashew are presented in Table 3. Irrigation on cashew is not generally practiced in Thailand. However, weeds are controlled at the time of orchard establishment to reduce competition, and to later facilitate harvesting.

In large-scale plantations in the past, inter-cropping was considered fairly important since it provided an income to growers during the initial years. Trials at the Si Sa Ket Horticultural Research Center have indicated that sweet corn, groundnut and vegetables can be profitably grown in the crop avenues during the initial years of orchard establishment.

Table 3. Fertilizer Recommendations for Cashew

Year	Density (trees/ha)	Type of Fertilizer	Fertilizer Rate (kg/ha)
1-2	280	12-24-12	140
3-5	280	15-15-15	280
6-8	280	13-13-21	560
8-12	140*	13-13-21	550
12-20	140	13-13-21	550

* Trees in between rows are removed at year 8.

Thrips (Haplothrips sp.) can suck sap from tender shoots and inflorescence resulting in die-back. The pest can be controlled with Carbosulfan at 30 ml per 20 l of water or carbaryl at 50 g per 20 l of water. Tea mosquito bugs (Helopeltis antonii) cause severe damage to the tender shoots and inflorescence of the cashew tree, often leading to heavy economic loss of the crop. Both adults and nymphs suck the sap from tender shoots, floral parts, cashew apples and even from immature nuts. The pest can be controlled with either carbaryl at 20 g per 20 l of water or with cyhalothrin at 10 ml per 20 l of water. Although insect infestation, particularly thrips and mosquito bugs is reported on both the Maboonkrong and DOA varieties, it is significant that the former types are more prone to attack by these pests than the latter varieties. Stem borers (Plocaederus ferrugineus) cause damage in the form of small holes in the collar region of the tree trunk which results in gummosis, yellowing and shedding of leaves, drying of twigs and ultimately, the death of the tree. The pest can be controlled effectively by mechanical removal of the larval stages in the early stages of the infestation. The pest is also controlled by injecting carbaryl or ichlovos into the tunnels. Severely affected trees beyond recovery should be cut and removed from the plantation. Many other insects have been reported including aphids and mango shoot weevils. Control measures using insecticides are possible, but alternating between different chemicals is advisable in order to prevent the build up of resistance.

Damping off of seedlings can occur under wet conditions or due to poor drainage in the nursery. Different fungi including Fusarium sp., Pythium sp., Phytophthora palmivora and Cylindrocladium scoparium have been reported as causal organisms. The fungi attack either the root or collar region or both, mainly at the tender seedling stage. Control measures include provision of adequate drainage in the nursery and the use of benalaxyl. Anthracnose (Colletotrichum gloeosporioides and Botryodiplodia sp.) can infect the panicles by penetrating through the wounds on panicles caused by sucking insects such as thrips. The anthracnose pathogen penetrates the dead tissue. The fungus enters the fruit through the stigma of flowers at the blooming stage. The disease is severe when rainy weather occurs during flowering. Recommended control measures include removal of affected parts and spraying trees with copper oxychloride or mancozeb at 40-50 gm per 20 l of water.

6. TOPWORKING OF OLD TREES

For rejuvenation of old trees, topworking can be done using scions from superior varieties. This is being practiced in most cashew orchards in the South where trees were established from unselected seeds. A two to three fold increase in yield in the third year after topworking has been reported provided proper fertilizer application, regular chemical sprays and weeding operations were practiced.

7. HARVESTING OF NUTS AND YIELD

Mature nuts are manually harvested and collected over a period of 8-10 weeks in the months of March-April. Fruits are usually allowed to drop during the first 4-6 weeks at the beginning of the harvesting season. Nuts can later be picked from the trees. After separation from the apples, nuts are cleaned in water and sun dried for 2-3 days to reduce the moisture content before disposal.

8. MARKETING

In 1992, Thailand exported 3334 tons of raw nuts at a value of US$2.7 million and 102 tons of kernels valued at US$55 million. Exports have however, greatly decreased since 1993 because of poor productivity, particularly in the North and Northeast. Production now almost equals consumption and there is only a small net export trade. In 1995, export of raw nut and kernel was only 70 and 79 tons, respectively. Any future increases in production may have to find export markets.

The cashew nut shelling industry in Thailand is relatively small. There is only one company (Maboonkrong) operating nut shelling on a large scale. Most cashew nuts produced in the country are sold and sent across to factories in the East for shelling although there are several local factories for each region. Processing starts from sun drying of nuts for 2-3 days. Before shelling nuts are boiled for 2-3 hours. Shelling is done manually by hand and leg operated shelling machines. The kernel is scooped out by means of a sharp needle. On average one operator can shell 1-1.5 kg per hour depending on individual skill. After shelling, kernels are oven-dried at 50°C in a home-made gas oven to reduce the moisture and to loosen the adhering testa. Peeling of the testa is later done by hand. Then kernels are graded into three grades, namely, Jumbo, A and B grades. Labor costs for shelling, peeling of testa and grading amounts to about Baht 20-25 per kg of finished kernels. Although seed coats and seed testa can be utilized, they offer only marginal returns. Cashew kernels are usually sold to a central market in Bangkok and are then subsequently traded for domestic consumption and export. In addition, particularly in small scale processing in the South, after separating nuts from the fruit, the nuts are roasted to drive off the caustic cashew nut shell liquid (CNSL) and then opened individually using hand shelling machines.

9. POTENTIAL FOR CASHEW NUT PRODUCTION DEVELOPMENT

Although cashew was considered to be a low-potential crop as indicated by an obvious decrease in planting extents, especially in the North and Northeast, it is increasingly becoming an important commercial crop in the Eastern region. The market price of cashew in this area remains high in comparison to other crops. It has also been found that the productivity of trees in this area is much higher than those grown in the North and Northeast. It is also noteworthy that farmers in the Eastern region have turned to cashew growing instead of sugarcane which requires very high labor inputs, especially at harvest time.

10. MAJOR CONSTRAINTS IN CASHEW NUT PRODUCTION DEVELOPMENT

During extension of cashew production in 1984, the major constraints included insect infestation from thrips, mosquito bugs, stem borers, and disease infection from anthracnose, all of which could be satisfactorily controlled by chemical application. In 1991, die-back of panicles and insect problems became widespread and adversely affected productivity of nuts. In addition, it was evident that trees with satisfactory flowering did not set fruit even if chemical sprays were appropriately applied. It is probable that trees had undergone environmental stress such as an extended drought period resulting in a marked drop in relative humidity and/or higher day temperatures. This affected flowering, fertilization and even fruit growth and development. Since the DOA varieties were mostly early types, they had a better chance of evading drought conditions, in comparison to Maboonkrong varieties. Nonetheless, under certain conditions, the DOA varieties which were selected for the wetter regions were less adaptable to long droughts. Starting in 1985, BAAC in conjunction with a commercial company, offered a medium term loan plan to farmers which resulted in a successful extension effort to increase the management skills of farmers. Using improved varieties, fertilizer and clean cultivation methods, farmers were given the technical knowhow by extensionist who made regular visits. Production inputs were provided in kind by the agency servicing the loan. Despite the fact that there was strong government backstopping for the program, many farmers were unable to exploit the situation to their advantage due to the poor production skills of workers.

11. CONCLUDING REMARKS

Cashew development in Thailand has declined since 1991 due to poor productivity of cashew orchards. Planting extents, particularly in the Northeast have rapidly decreased whereas in the South the change has only been marginal. In the East however, cashew production is expanding and several shelling factories have been installed which augurs well for the future of this region. It is possible that cashew production will play a significant role in the regional economy of the East.

Despite the relatively low cost of orchard establishment when seedlings are used, it is recommended that grafted plants be used for new plantations. The recommended varieties available now include Si Sa Ket 60-1 and Si Sa Ket 60-2 released by the DOA. In addition, the agro-techniques recommended should be strictly followed if higher productivity is to be achieved.

Further research on cashew improvement would have to focus on development of better adapted varieties with tolerance/resistance to biotic and abiotic stresses through conventional and non-conventional breeding programs. Other problems that research need to concentrate would be the physiological causes that affect fruit set. The germplasm thus developed would not only benefit Thailand but the neighboring countries as well.