Kabocha

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Kabocha Links

• GPPIS (FAO) 
• Purdue University, Indiana

Species: Cucurbita maxima x Cucurbita moschata

Family: Cucurbitaceae

Crop status: Established

Varieties

The word 'Kabocha' in Australia refers to varieties of pumpkin that are preferred by Japanese consumers, genetically similar and bred from the same lines as Delica (Ebisu). These pumpkins are typically quite small (1-2.5 kg) and have a distinct sweet nutty flavour. Agronomic requirements are similar, but not identical, to pumpkins traditionally grown in Australia, but Japanese expectations of taste and quality are substantially different to Australian expectations. Kabocha is a commercial hybrid bred from a Cucurbita maxima x C. moschata cross. The name 'Japanese pumpkin' is also used, though originally it was a collective term used only for varieties of C. moschata grown in Japan. C. moschata is the species of stronger influence in commercial Japanese hybrids, so the confusion is not surprising. Japanese varieties have become smaller over time, reflecting family needs, such that newer varieties are now 1.5-2.2 kg/fruit (Vong Nguyen 1998, pers. comm.).

Seeds are available from numerous Australian seed suppliers. No publicly funded breeding is conducted in Australia, despite the potential for creating disease resistant varieties (see Pests and Diseases), because seed of the parent lines of the 'kabocha' type pumpkin has not been obtained. There is also concern that an Australian bred variety may not be accepted by Japanese importers (Mark Herrington 1999, pers. comm.). Some breeding may have been conducted privately. Varieties grown in Tasmania for fresh export include Delica, Hokkori, Nishiki, Aijehei and Kurijiman (Frank Hay 1999, pers. comm.). Forth Farm obtain seed directly from Japan.

Delica, also called Ebisu, was developed by Takii and is distributed through Yates and Henderson Seeds. It is an older variety with an average weight of 2.5 kg/fruit, and is suitable for sea freight (Pan 1995). New Zealand exports this and Kurijiman to Japan, and imports all their seed from Japan (Brown et al. 1996) via Yates (Bryce de Rossi 1999, pers. comm.). Mac Fresh preferred Pacifica for processing, but has swung back toward Delica in 1999 as it appears better quality. This may be just location effect (Bryce de Rossi 1999, pers. comm.). Delica is associated with better texture, taste, sweetness and pulp density per crate, but also lower yields and poorer climatic resistance.

Kurijiman F1 was developed by Kyowa Seed Co. (Japan) and is distributed through Fairbanks. In Victorian experiments it shared highest average marketable fruit weight and high fruit/m2 with Delica (Murat Top in Anonymous 1997). New Zealand exports this and Delica to Japan, and imports all their seed from Japan (Brown et al. 1996) via Yates (Bryce de Rossi 1999, pers. comm.). Yield in New Zealand is typically 95% of Delica but becomes higher in later plantings. Kurijiman shared highest average marketable fruit weight and high fruit/m2 with Delica in Victorian experiments (Murat Top in Anonymous 1997).

Pacifica was developed and is distributed by Yates, to combine Japanese fruit quality characteristics with traits suitable for Australian production. It has large fruit and a reasonable yield, and is therefore suitable for processing. Seed is larger, affecting planting rate and seed cost.

Victorian farmers mainly produce Kens Special as seed is cheap ($200/kg compared to $800) and quality OK, but profits would probably be higher with Kurijiman (Paul Heseltine 1999, pers. comm.).

Tetsukabuto is the most common variety now in Japan. It is characterised by a high yield and nutty, small fruit (Vong Nguyen 2000, pers. comm.). It appeared to outperform the older varieties Delica and Pacifica in trials conducted in 1999 at Gosford, Yanco and Katherine. Yields were higher, external appearance was better, and fruit size was in the smaller range preferred by the Japanese for fresh fruit.

Industry group

Two associations have existed in Queensland, the Southern Heartland Group (about 9 producers) and the Northern Heartland Group (Emerald). Groups have not been ongoing due to difficulties in selling produce.

Agronomic trials

Fertiliser x season trials are being conducted in 1999 in northern NSW and various locations in South East Queensland. A variety x season trial is underway at Gosford, and fertiliser trials are being conducted in Victoria. QDPI have previously conducted trials at Gatton, Bowen and Atherton.

Production

Kabocha is grown in NSW, Vic, Tas (Lee 1995) and Qld. Victorian yields and quality are generally better north of the Dividing Range. It has been grown in Tasmania since the 1988/89 season (Botwright et al. 1998), with approximately 600 ha/year planted on the North West coast for fresh export to markets in Asia and Japan.

Climate: Potential production dates across Australia are given in Table 2. The crop requires a 3-4 month growing season (Larkcom 1991).. Brazil sees higher yields in the dry season than the wet season (Resende et al. 1996).

Temperature: Mild to warm conditions are preferred, with 20-30°C days and 15-20°C nights. Soil temperature should be over 15°C, and frosts cause severe damage.

pH: Optimum is 6.0 - 6.4. A pH below 5.5 produces growth problems, and up to 7.2 is tolerated (Top and Ashcroft 1997).

Salt sensitivity: The crop has medium to low salt tolerance.

Plant density: 1.5-1.8 m spacing between rows and 0.3-0.8 cm within rows (Top and Ashcroft 1997). A study at Cambridge, Tasmania, found highest marketable yield of 18 t/ha at 1.1 plants/m2 (Botwright et al. 1998), equivalent to 1.5 x 0.6 m spacing. Fruit size is smaller at higher plant densities. Need about 1.25 kg/ha seed.

Sowing depth: 3-4 cm, but may be different in warmer areas (Top and Ashcroft 1997).

Germination: Temperature range 15-35°C, but 18-25°C is optimum. Emergence occurs in 5-7 days.

Transplant: Transplant 6-14 days after emergence, at the first true leaf stage. Direct seeding is preferred in optimal conditions.

Water: Use overhead sprinklers in the morning only so that wet leaves dry quickly, reducing spread of disease (Top and Ashcroft 1997).

Nutrition: Requires high nitrogen early in the crop for growth, and high calcium later to improve firmness and colour. Approximately 180 kg/ha N is required. Drill in half at sowing and apply the rest two weeks after emergence (Top and Ashcroft 1997). Excessive application can reduce yields by increasing vegetative growth. Members of the Southern Heartland Group were applying 3-5 L/ha CaNO3 three times postfoliar.

Harvest: Use a sharp knife to cut the stem and take care to minimise damage, as stem damage is one source of rot entry (Rubatzky and Yamaguchi 1997). There are typically two harvests for a crop, as it is rare that one harvest date is suitable for the whole field (Jeff Hastings 1998, pers. comm.). The most effective way of estimating the optimum harvest date for shipping fresh fruit is by measuring skin hardness and heat accumulation. Earliest possible harvest for Delica in New Zealand conditions was at a penetrometer score of 7 kgf, but fruit harvested this early required a postharvest ripening period to optimise sweetness, texture and sensory quality (Harvey et al. 1997).

Yield: Yields average 18-22 t/ha, but 35-50 t/ha is possible. Trials in Cambridge, Tasmania yielded 18 t/ha (Botwright et al. 1998). Variety 'Evis' produced 28.9 t/ha in Korea (Cho et al. 1997). Japanese average yields have fallen from 17.71 t/ha in 1975 to 14.63 t/ha in 1996 (Figure 3). Tasmanian yields are around 10-15 t/ha (Frank Hay 1999, pers. comm.).

Margins: A Tasmanian estimate of gross margins, modelled from New Zealand production and a yield of 15 t/ha, came to $1 351/ha at $250/t, and $2 101/ha at $300/t (DPIF Tasmania 1998).

Postharvest

Handling: Fruit should be handled carefully and not left in sunlight for more than an hour after picking to avoid rots during storage and transport. Kabocha is best stored in single layers without touching, with good air circulation around each pumpkin (Top and Ashcroft 1997). Containers are often transported with the doors removed to improve air circulation (JETRO 1992).

Curing: Some cuts and bruises can be treated to minimise rots, by storing at 27-30°C and 80% RH for about 10 days before transferring to long term storage (Rubatzky and Yamaguchi 1997).

Temperature: Store at 10-15°C (Yamaguchi 1983), preferably closer to 15°C (Jeff Hastings 1999, pers. comm.). At higher temperatures the pumpkins dry out (Larkcom 1991) and at lower temperatures they suffer chilling injury, even if the low temperature is only for a few days (Rubatzky and Yamaguchi 1997).

Relative humidity: 55-60% (Rubatzky and Yamaguchi 1997), 60-70% (Welby and McGregor 1997).

Shelf life: Pumpkins can be stored for 3 or 4 (Top and Ashcroft 1997), up to 6 months, depending on variety and conditions (Larkcom 1991). Fruit harvested early is less susceptible to storage rots (Harvey et al. 1997). Time and heat accumulation during transport and storage can significantly improve the quality of early harvested fruit (Harvey et al. 1995). Tasmanian produce is sold to consumers within one month of harvest.

Processing

Only one Australian company has attempted to process kabocha in commercial quantities, to the authors knowledge. Mac Fresh Foods processing included removing rind and centre, cutting to a 'roast dinner' size and freezing using 'Independent Quick Freeze': liquid CO2, to -18°C in 8 minutes. The company has since disbanded.

Dr Vong Nguyen has investigated dried kabocha slices (Nguyen 1996), and has worked with Parle Foods, Griffith to investigate semi-processing methods (Vong Nguyen 1998, pers. comm.).

Pests and diseases

Viruses: Mosaic type viral diseases are common in southern Queensland, particularly on the coast, appearing in December to January in warmer years and February to May in cooler years. Control is difficult to impossible if conditions favour the disease. Genetic resistance for Zucchini Yellow Mosaic virus, Papaya Ringspot virus and Watermelon mosaic virus is available, but has not been bred into kabocha varieties (see Section 1, Mark Herrington 1999, pers. comm.). Other resistant germplasm has also been reported (eg; Kristkova and Lebeda 1997). Potential viruses are listed at Plant viruses online (Brunt et al. 1996).

Bacteria and fungi: Powdery mildew is common throughout the east coast of Australia, destroying the canopy and leaving fruit vulnerable to sun scorch. It attacks older leaves and main stems, producing a circular white, powdery spot which spreads over the entire leaf, causing it to wilt and die (Top and Ashcroft 1997). Control is difficult to impossible if conditions favour the disease. Queensland producers currently use Benloate against Fusarium, but it isn't very effective and a wider range of chemical control methods should be used. In Victoria the disease tends to establish in January (Top and Ashcroft 1997). Downy mildew has been observed in northern NSW and Victoria during periods of wet weather. It is characterised by yellow leaf spots which turn brown (Top and Ashcroft 1997). Pythium affects Pacifica but not Delica. Penicilium spp. have been observed as a postharvest rot in Victoria (Chew and Morgan (1997). Japan has occasionally ordered large volumes of kabocha to be sorted and/or destroyed due to rot caused by Penicillium and Fusarium. The loss of a large amount of pumpkins may be related to heavy rain during harvesting, careless sorting because of the rapid increase in exports and improper control of temperature and humidity due to inadequate air circulation during transportation (JETRO 1995).

Pests: Heat disinfestation for Mediterranean fruit fly (Ceratitis capitata), has been studied and appeared promising, but is not ongoing. Cold disinfestation does not work on Queensland fruit due to chilling injuries, though it did not harm Tasmanian fruit. Spider mites, leafroller moths, owlet moths, thrips and armored scales have often been found on pumpkins exported to Japan. To prevent infestation by such pests, measures such as brushing the surface of pumpkins and squashes, in addition to thorough field control, may be effective (JETRO 1995). Moderate tolerance to root knot nematode was found in accessions from Malawi (Chigwe and Saka 1994).

Quality assessment

Japanese consumers prefer firm pumpkins with dark green skin and dark orange flesh. Eastern Japanese prefer drier, crunchier pumpkins than those in Western Japan (Brown et al. 1996). A dulled (not shiny), evenly distributed green is most marketable (Jeff Hastings 1998, pers. comm.). Evenness of colour is most affected by the earth mark (where the fruit sits on the ground) and sunburn. 'Warts' and other blemishes can also be a problem (Jeff Hastings 1998, pers. comm.). Warts are superficial raised corky lesions thought to be associated with maturity and excessively moist soil conditions. Susceptibility to both warts and sunburn varies among varieties, with sunburn being at least partially dependent on leaf coverage and time of harvest. The variety Unebi was very prone to warts, while Ajehei and Potkin Early appeared resistant (Loader 1998).

Size of seed cavity can be an issue for consumers, as well as increasing transport costs. Delica and Pacifica appear to have large cavities. Japanese grade kabocha according to size (Table 4), and issues influencing purchases were surveyed by Brown and Breinl 1995 (Table 3).

BRIX and b -carotene are both increased by greater exposure to sunlight and diurnal temperature variation. Hence, quality tends to be better when grown inland. Market specifications vary with the market, particularly between fresh and semi-processed. b-carotene is considered to have health benefits, so a market could be developed around high nutrition fruit based on carotene levels (Jeff Hastings 1998, pers. comm.).

A minimum total carotene level of 400 mg/g DW was considered acceptable for export (Hurst et al. 1995).

Figure 1: Monthly prices of fresh kabocha imported to Japan by country, during 1997. This material provided courtesy of the Asia Regional Agribusiness Project/Fintrac Inc. through the Market Asia web site at http://www.marketasia.org.

(A)

(B)

Figure 2: Japanese imports of fresh kabocha from 1988 to 1997 (A) and by country during 1997 (B). This material provided courtesy of the Asia Regional Agribusiness Project/Fintrac Inc. through the Market Asia web site at http://www.marketasia.org.

Figure 3: Japanese production of pumpkins and squashes (MAFF 1999).

Export market

(click here for exchange rates).

Japan is the only importer of kabocha (Pan 1995). Mainland Australia is currently restricted from exporting fresh kabocha to Japan due to fruit fly. Therefore until disinfestation procedures have been worked out, only Tasmania can export. Tasmanian first grade has been exported to Asia and Japan for the last 6-10 years, with current volumes at approximately 1000 t/year. About 30% is rejected for skin blemishes and sunburn. Australia must produce for a top quality niche market to be competitive against New Zealand. A volume of 10 000 t/year may be achievable (DPIF Tasmania 1998).

Japan imports approximately 120 000 t of fresh kabocha annually to supply its off season, which lasts from October to May (Kay 1998). The 1997 import price averaged ¥89.8/kg, but Australian produce averaged ¥114.3/kg (Figure 1). The 1997 import volume was 135 665 t worth ¥12.18 billion, of which 1 305 t worth ¥149 million was from Australia (Figure 2). A 4.7% tax is imposed on the CIF price (Brown et al. 1996). Japanese consume approximately 2.5 kg pumpkin/person/year (Otsubo 1996) and consumption is increasing (JETRO 1995), but domestic production is fairly static (Figure 3). The opportunity for Australia lies at the end of the New Zealand season and before the Japanese season, in May and June (Pan 1995), though QDPI reports have recommended competing with the existing suppliers from October to January (Brown and Breinl 1995, Brown et al. 1996). Australian fresh exports to Japan are small but the price received is high relative to other exporters. Japanese pay highest prices for domestically produced kabocha, though Mexican produce is considered to be superior in taste (Brown and Breinl 1995). Tonga receives the highest price for imported kabocha. They have a uniform colour from being grown on straw, and are well regarded (Brown et al. 1996). Prices received tend to decline at the end of season for most countries (Figure 1). The pumpkin market is very price sensitive because consumers have many alternative sources. About 85% of people eat the skin (Brown et al. 1996).

About 28 000 t of kabocha was processed in Japan in 1991, yet there were few processed imports. Most was processed by freezing and cutting for both food service and retail markets (Pan 1995). Frozen produce is used for soup and to produce sweet cream for cakes, and is also sold in supermarkets for home use (JETRO 1996). Australia could well establish a market in this product as long as the price is internationally competitive (¥140/kg). Another possibility is dehydrated strips of pumpkin sold in dehydrated mixed vegetable packets (Lee 1996), but the potential market is much smaller (Pan 1995). Pre-cut vegetables are attractive to the food service industry as it reduces the cost of Japanese labour (Brown et al. 1996). Tasmania does not have suitable facilities for kabocha processing.

Chinese consume the seeds as a snack (Yang and Walters 1992).

References

Anonymous (1997). Exploring varieties for niche markets. Good Fruit and Vegetables (April): 20-21.

Botwright, T., Mendham, N. and Chung, B. (1998). Effect of density on growth, development, yield and quality of kabocha (Cucurbita maxima). Australian Journal of Experimental Agriculture 38(2): 195-200.

Brown, F. and Breinl, J. (1995). Preliminary research on the market for pumpkin exports to Japan. Brisbane, Queensland Department of Primary Industries 19 pp.

Brown, F., Devlin, M. and Egan-O'Reilly, D. (1996). The Pumpkin Market in Japan. Brisbane, Queensland Department of Primary Industries 13 pp

Brunt, A.A., Crabtree, K., Dallwitz, M.J., Gibbs, A.J., Watson, L. and Zurcher, E.J. (eds.) (1996 onwards). `Plant Viruses Online: Descriptions and Lists from the VIDE Database. Version: 16th January 1997.'

Chew, M. and Morgan, W. (1997). List of identified pests and diseases affecting Asian vegetables. Access to Asian Vegetables. (2): 1.

Chigwe, C. F. B. and Saka, V. W. (1994). Collection and characterization of Malawi pumpkin germplasm. Zimbabwe Journal of Agricultural Research 32(2): 139-147.

Cho, Y. D., Kang, S. G. and Chung, J. H. (1997). Cultivars and sowing date for summer season production of sweet pumpkin in Cheju Province. [Korean]. RDA Journal of Horticulture Science 39(2): 33-38.

DPIF Tasmania (1998). Website. Department of Primary Industries and Fisheries, Tasmania (URL: http://www.dpif.tas.gov.au/domino/dpif/IndustryProfiles.nsf).

Harvey, W. J., Grant, D. G. and Lammerink, J. P. (1997). Physical and sensory changes during the development and storage of buttercup squash. New Zealand Journal of Crop & Horticultural Science 25(4): 341-351.

Harvey, W. J., Lush, A. and Grant, D. G. (1995). Manipulating the quality of buttercup squash (Cucurbita maxima cv. Delica) by pre- and post-harvest management. Agri food quality: an interdisciplinary approach. Proceedings of the international conference 'Agri food quality', Norwich, UK.

Hurst, P. L., Corrigan, V. K., Hannan, P. J. and Lill, R. E. (1995). Storage rots, compositional analysis, and sensory quality of three cultivars of buttercup squash. New Zealand Journal of Crop and Horticultural Science 23(1): 89-95.

JETRO (1992). Frozen Vegetable. Japan External Trade Organisation, Market Report

JETRO (1995) Fresh Vegetables: Access to Japan's Import Market - Mini Report 1995 August. Japan External Trade Organisation, Market Report.

JETRO (1996) Process Vegetables: Your Market in Japan-1996. Japan External Trade Organisation, Market Report.

Kay, A. (1998). New Zealand squash feeds Japanese appetite. Asia Fruit (May): 66.

Kristkova, E. and Lebeda, A. (1997). Possibilities of using wild Cucurbita species in breeding via interspecific hybridization. [Czech]. Zahradnictvi 24(3): 113-120.

Larkcom, J. (1991). Oriental vegetables: the complete guide for garden and kitchen. London, John Murray 232 pp.

Lee, B. (1995). Audit of the Australian Asian vegetables industry. RIRDC Research Paper No. 95/13. Canberra, Rural Industries Research and Development Corporation 97 pp.

Lee , B. (1996). Assessment of economic benefits for Asian vegetables. RIRDC project CON-4A review meeting 14 November 1996.

Loader, L. (1998). Kabocha pumpkin variety trial. Mareeba, Queensland Department of Primary Industries: 17.

MAFF (1999). Abstract of statistics on agriculture, forestry and fisheries. Statistics and Information Department, The Ministry of Agriculture, Forestry and Fisheries of Japan.

Nguyen, V. Q. (1996). Research and development of Asian vegetables for Asian markets, particularly Japan. First Australian New Crops Conference, The University of Queensland Gatton College, Rural Industries Research and Development Corporation.

Otsubo, M. (1996). Asian vegetables into Japan: export potential, opportunities and myths. In: Proceedings of an Asian Food Industry Conference (Ed; Lee, B. and Prinsley, R.). RIRDC Research Paper No. 96/9: 22-28.

Pan, C. (1995). Market opportunities for fresh and processed Asian vegetables. RIRDC Research Paper No. 95/14. Canberra, Rural Industries Research and Development Corporation 117 pp.

Resende, G. M., R. A. de Silva and A. C. P. Goulart (1996). Yield of squash cultivars and 'Tetsukabuto-type' hybrids at different sowing dates. [Portuguese]. Horticultura Brasileira 14(2): 228-231.

Rubatzky, V. E. and M. Yamaguchi (1997). World vegetables; principles, production, and nutritive values. New York, Chapman and Hall 843 pp.

Top, M. and Ashcroft, B. (1997). Growing Japanese pumpkin - kabocha: a production manual for Victoria. Melbourne, Agriculture Victoria 15 pp.

Welby, E. M. and McGregor, B. (1997). Agricultural Export Transportation Handbook. USDA Agricultural Handbook 700, United States Department of Agriculture.

Yamaguchi, M. (1983). World vegetables. AVI (Van Nostrand Reinhold Co.), New York

Yang, S. L. and Walters, T. W. (1992). Ethnobotany and the economic role of the Cucurbitaceae of China. Economic Botany 46: 349-367.