New cold treatment opens doors for citrus exports to Japan

Andrew Jessup and his technical officer David Daniels
Research by Andrew Jessup (left) and his technical officer David Daniels has resulted in new storage techniques for citrus.

Citrus growers in eastern Australia now have greater access to the Japanese market as a result of research by the NSW Department of Primary Industries (DPI).

Trials undertaken at NSW DPI’s Gosford Horticultural Institute have proven that cold storage at temperatures of 2° or 3°C can effectively kill Queensland Fruit Fly in citrus stored for 14 to 16 days.

Cold treatment at these temperatures provides greater market flexibility and reduces problems associated with cold chilling such as internal fruit and skin damage.

This new cold treatment is the Australian citrus industry’s preferred method and Japan formally accepted it after the Federal Government advised them of the results of extensive replicated trials conducted at Gosford and in Western Australia.

At Gosford, post-harvest researchers lead by NSW DPI’s Andrew Jessup examined the effect of the cold treatment on QFF on citrus sourced from the Murrumbidgee Irrigation Area (MIA), Victoria’s Sunraysia and South Australia’s Riverland regions.

In WA, researchers from the WA Department of Agriculture examined the impact of the same treatment on the Mediterranean Fruit Fly (MFF) in local citrus.

(QFF is endemic to the east coast of Australia, extending inland for 600 kilometres or more, while MFF is found in pockets around major townships in WA.)

Mr Jessup says the QFF, Bactrocera tryoni, is more suited to tropical and subtropical conditions and is more susceptible to cold treatment than the MFF.

The trials show that QFF were killed after 14-16 days storage, compared with 16 to 20 days for MFF.

The previous cold treatment at 1° C, if not managed correctly can cause chilling injury to fruit.

Mr Jessup said that "the new higher temperatures for dis-infestation help to conserve fruit quality and are easier to maintain in-transit.

"They also provide an alternative to methyl bromide fumigation, which is toxic to citrus and shortens its shelf life. Methyl bromide is also being phased out in Australia because it is ozone depleting", he said.

The research is expected to assist in gaining market access for Australian citrus to other countries in the northern hemisphere.

Further information on the research trials is available from the New Zealand Journal of Crop and Horticultural Science, 2007, Vol.35:39-50.