Unshu mandarin (Citrus unshiu Marcow.) is widely known as satsuma mandarin or unshu mikan in Japan. This mandarin probably originates in Japan (USDA 2008). For this reason, reference to unshu mandarin or satsuma mandarin and information pertaining to both are considered equivalent and are used interchangeably in this report.
Japan stated that citrus production in the export areas is limited to unshu mandarins, consisting of the Aoshima and Miyagawa Wase varieties grafted on the trifoliate orange (Poncirus trifoliata) rootstock (Figure 3.5). Both of these seedless varieties are grown in about equal proportion in the export areas. Trees are relatively small (about 2 metres in height) and thornless. Leaf flush of these mature trees occurs once per year during spring/early summer in June/July, prior to flowering. Fruit of both varieties ripens during December. This report assesses the fruit of the species unshu mandarin (C. unshiu Marcow.).
Orchards within the designated export areas are well established and consist of mature trees at a density of about 1000 trees per hectare. The commercial life of an orchard is estimated to be 30–40 years. In the Shizuoka Prefecture, yields of unshu mandarin average 15 tonnes per hectare. Mature (i.e. more than 10 year old) plantings can achieve yields of about 30 tonnes per hectare (Harty and Anderson 1997).
On their field visit to orchards in the proposed unshu mandarin export areas in July 2007, Biosecurity Australia officers observed that the health of unshu mandarin trees, developing fruit and general orchard hygiene was very good. This included orchards that were not registered for the existing export programs to the USA and New Zealand and instead supply the domestic market.
Unshu mandarin trees in the designated export areas were of equal size and evenly spaced. Foliage, stems and fruit were healthy. Citrus leafminer damage was only found in single incidences in orchards that were visited. Leaves appeared to be free from wind damage.
The hygiene and maintenance standard of orchards not registered for any of the existing export programs appeared to be the same as that of export orchards. Very few replanted unshu mandarin trees were observed. No obvious overgrown and neglected orchards were encountered in the whole of the visited production area. The number of unshu mandarin orchards in the visited area is declining as these orchards, for economic reasons, are replaced with either tea or Cryptomeria plantations.
Unshu mandarin trees within the designated export areas are well established (Figure 3.5). Mature trees are pruned during February to March prior to a single annual leaf flush during spring/early summer in June/July. This is in contrast to immature unshu trees, which would flush three times per year during spring, summer and autumn. Biosecurity Australia officers visiting the designated export areas in 2007 were informed that fruit set does not undergo thinning.
Orchards are slashed (by hand) for weed control. There is no evidence of intercropping between tree rows (Figure 3.6). Pesticide control in the designated export areas is carried out manually without the use of mechanised spray equipment. The existing commercial practice for the control of insect pests and diseases of unshu mandarin production in Japan are listed in Table 3.5.
Japan informed Biosecurity Australia that all orchards exporting fruit to Australia would operate under existing commercial practices. Growers are responsible for maintaining adequate records relating to pest control, spray diaries and orchard monitoring to confirm that the nominated existing commercial practices are used, and exporters will need to comply with other relevant standards such as Australian Food Standards3.
Table 3.5: The indicative unshu mandarin spray calendar (2007) for Japan4
Post-harvest disease (e.g. Blue mould, Green mould, White mould)
Iminoctadine acetate; Benomyl; Thiophanate-methyl
§The term ‘machine oil’ refers to what is commonly known as ‘agricultural/ horticultural mineral oil’ in Australia.
Fruit is harvested by hand and immediately and directly transported to the current packing house. The current packing house is situated about 5 km from the designated export areas in nearby Fujieda City (Figure 3.2). The packing house receives citrus fruit for processing, for the domestic market and a number of existing export markets. Fruit grown on about 25 hectares is packed for export.
The current packing house viewed by Biosecurity Australia officers in 2007 was built in 1998 and received its first fruit for processing in 1999. Two methyl bromide fumigation chambers (remodelled containers) are present at the facility. An image of the packing house is shown in Figure 3.7 and the schematic processing steps at this facility are presented in Figure 3.9. Fruit processing is fully segregated depending on its destination to either the domestic market or to any of the export markets.
On receipt at the facility, the fruit is identified according to the registered grower and processed on an orchard basis. It is then loaded onto a conveyor belt and sorted visually for blemishes, bruises, peel puff and colour. Fruit for export to the USA is then fully submersed for two minutes in a post-harvest dip, which consists of a chlorine solution with a minimum of 200 ppm of available chlorine. New Zealand does not require a post-harvest dip. After cool air drying, fruit undergoes further sorting and testing for fruit sugar content. It then is packaged into 8 kg cardboard boxes (Figure 3.8), each containing 50–60 fruit. Fruit is not waxed.
Fruit is processed on the day of picking. There is no processing of fruit at night. On the following day after inspection, cartons destined for export are palletised and moved in secure, fully enclosed transport trucks to the port of export at Shimizu in the Shizuoka Prefecture. On arrival at the port, cartons are re-loaded at a bonded warehouse from the fully enclosed truck into a sea container. The container is sealed and customs procedures are completed.
Japan advised that fruit destined for markets in the USA and New Zealand are shipped in refrigerated containers maintained at 6ºC and 4ºC, respectively. Voyages to these countries take about four and two weeks, respectively. Biosecurity Australia has not been advised of the reason for the variation between shipping temperatures.
Post-harvest treatment is not included in assessing the unrestricted risk for the identified quarantine pests (Chapter 4).
Japan stated that the designated export areas to Australia already have established export programs in place. Japan has been exporting to countries with phytosanitary requirements such as the USA, New Zealand and Thailand since 1968, 2000 and 2007, respectively.
Export quantities from the designated export areas have been small. Exports to the USA averaged a total of 230 tonnes per year from 1995 to 2005 (APHIS 2006). Since February 2000, small quantities of fresh unshu mandarins have also been exported from the same export areas to New Zealand. An above average production of 600 tonnes was expected for the combined designated export areas for the 2007/08 harvest season.
Fruit ripens during December (refer to Section 3.4.1), the expected export season.
Figure 3.9: Schematic layout of the processing steps at the current packing house at Fujieda City
Pest risk assessments for quarantine pests
Quarantine pests for pest risk assessment
Pest categorisation (Appendix A), using the pest list for Japan, identified 34 pests associated with fresh unshu mandarin fruit from the production area. These quarantine pests are listed in Table 4.1.
Table 4.1: Quarantine pests for fresh unshu mandarin fruit from the production area
The relevant state or territory for pests of regional concern are shown in parentheses.