This short report is a summary of a full report Kabocha and Japanese Pumpkin in Australia (RIRDC Publication Number 02/167) by Professor David Midmore et al. who can be contacted on Phone 07 4930 9770, Fax: 07 4930 9255, Email: d.midmore@cqu.edu.au, Web: http://science.cqu.edu.au/psg/  The full report will be available in hardcopy for $26 from RIRDC (Phone: 02/ 6272 4819) or can be downloaded for free from RIRDC’s website: www.rirdc.gov.au/reports/Index.htm The report can also be purchased online from RIRDC’s web shop: www.rirdc.gov.au/eshop

Trials in various states have shown Australia has the potential to grow and export all year round the varieties of pumpkin favoured by the Japanese.

But Australia will have to fi nd ways of eradicating fruit fl y infestation to be able to take advantage of these fresh product mainland export opportunities to Japan (Tasmania is fruit fl y-free).

The trials – partly funded by the Rural Industries Research and Development Corporation (RIRDC) – focused on Japanese Pumpkin (Cucurbita moschata) and Kabocha (Cucurbita maxima).

The research involved compiling earlier data and conducting fi eld trials from 1998 to 2001.

Results confi rmed that the most successful variety, outyielding the traditional Delica and Pacifi ca varieties, was the nutty-fl avoured Tetsukabuto, and that it provides a particularly promising export opportunity.

Professor David Midmore from the Plant Sciences Group at the Central Queensland University led the work with participation from a range of other industry and research groups. The report was coordinated by Dr Wendy Morgan.

Japan imports 130,000 tonnes of Kabocha annually meaning there is an opportunity for Australia to increase its current exports, fresh and frozen, which actually total just 1000 tonnes a year.

New Zealand is one of the main suppliers of Kabocha to Japan, however there is a three month window between our neighbour’s harvesting season and Japan’s and this provides an added export opportunity for Australia.

 The Research

The project reports on Australian research undertaken at regional, state and national levels to identify overall production capability and supply and productivity solutions for development of domestic and export markets.

It looks at fruit quality and work undertaken to reduce storage rots and identifi es or lists the highest yielding cultivars at each location.

Data collected shows that marketing opportunity studies were conducted for the Queensland Department of Primary Industries and Victorian Department of Natural Resources and Environment, Tasmanian Department of Primary Industries (1998) and private industry between 1995 and 1998.

These studies clearly identifi ed the potential for Kabocha exports to Japan at that time.

But Japanese quarantine regulations on fruit fl y mean only Tasmania with its fruit fl y clean status has been able to take advantage of this to export small quantities of fresh Kabocha to Japan.

Despite industry-funded projects to investigate low temperature disinfestation, mainland Australia so far has been limited to exporting processed frozen pumpkin pieces.

Varieties grown in Tasmania from seed obtained directly from Japan, for fresh export over the past 10 years between March and May have included Delica, Hokkori (T110), Nishiki, Ajehei and Kurijiman.

In the recent past, value added pumpkin products have been successfully exported from Queensland. Choice of cultivars grown for export needs discussion with the Japanese importer.

New replicated fi eld trials were carried out at Gosford NSW, Gatton in Queensland, Katherine in the Northern Territory, Tatura and Nathalia in Victoria and at Mareeba in North Queensland.

Observation trials were also carried out in NSW at Yanco and Gosford, in central Queensland, and at Tatura in Victoria.

Various randomised block designs with inter-row spacing of 1.5-3.6 metres and intra-row spacing of 0.65-1.5 metres were used.

The location, soil type, maximum and minimum air temperature during the growing period, relative humidity and irrigation method at each site were recorded and cultivars evaluated.

 The Results

With yields ranging from 16-53 t/ha, the research showed Kabocha can be grown in all states of Australia. The interspecifi c hybrids (C. moschata x C. maxima) tended to be the highest yielding varieties, due to their greater fruit set.

Where fruit set was high, such as at Katherine in the Northern Territory, two successive harvests could help maximise annual yield. Higher temperature ranges may have promoted more fruit set at Katherine than at other sites.

Maturity of fruit from when it set to harvest was also longer at Katherine and Gatton (Qld) where daytime temperature ranges were greater than at Tatura (Vic) and Mareeba (Qld).

A protocol established in the trials comprised only one harvest, which may have led to yields less than the potential if smaller later-set fruit were to have also been harvested.

Across all trials, the new variety Tetsukabuto out-yielded the traditional Delica and Pacifi ca, encouraging adoption of this variety for the domestic market. This variety needs either C.

maxima or C. moschata planted nearby for pollination.

When evaluating the effect of site on growth and yields, the Northern Rivers region of NSW was considered unsuitable, due to disease (downy and powdery mildew), most likely induced by high humidity.

Similarly, plantings that resulted in harvest beyond January in SE and Central Queensland invited sunburn. Winter plantings in the NT and summer plantings in NSW (Gosford) and Victoria (Tatura) resulted in highly acceptable yields, as did sowings in Queensland (Mareeba).

As with yield, signifi cant difference between varieties within sites, and between sites, for quality measurements were recorded. The varieties often fell into three separate groups: • the older varieties of Delica and Pacifi ca; • the interspecifi c hybrids, Tetsukabuto (late Potkin); and • the Australian developed Ken’s Special.

 Diameter, height, and therefore shape, was constant for most varieties across sites, but not for Tetsukabuto, reinforcing an impression that fruit of this variety was not always mature at harvest.

Tetsukabuto also had darker rind colour, fewer skin warts/blemishes, and more total carotene levels than Delica.

Fruit visual characteristics were relatively insensitive to growing location, but the ratio of sucrose, glucose and fructose in the fl esh varied between varieties, trials and sites. There is some evidence that the sucrose:glucose ratio increases with fruit maturity, and that fruit age may be a useful tool upon which to base harvest decisions.

As fresh fruit is exported from Tasmania to Japan, efforts were undertaken to reduce the extent of post-harvest rot (Fusarium colmorum) during storage. Older fruits appear to be more susceptible to rots, and this could infl uence the optimum time for harvest.

While heat shock treatment (two, eight or 16 hours at 36 or 38°C) was ineffective in reducing extent of rot, cold treatment (7°C for 28 days) was more useful.

The use of acetic acid was effective at 50 µl/l airspace in reducing spore germination and fungal rot, but it was poisonous to the fruit, leading to skin blackening.

 The Summary

The trials confi rm that Australia can produce Kabocha of acceptable quality all year round, if the variation in locations and planting dates is optimised. The newer interspecifi c variety, Tetsukabuto, offers greater returns to growers.

But its acceptance as a processed product for Japan requires verifi cation.

Australia’s opportunity to export Kabocha is at the end of the New Zealand season and before the Japanese season, in May and June. Competing with existing suppliers from October to January also is recommended. Australian fresh exports to Japan are small but the price received is high relative to other exporters.

 Seasonal margins for Kabocha and Japanese pumpkin production in Australia*


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