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March 2005. Information was requested on the use of controlled atmosphere in refrigerated contaners (reefers) with fresh produce (fruits and vegetables). Palau quarantine says that no live insects were found on produce when this treatment was used (amount of oxygen reduced and amount of CO2 was increased). Could it be an acceptable quarantine treatment for export of fresh produce?
Presently, this treatment is recommended because it prolongs the storage life of fresh produce. However, there are statements (from companies) that controlled atmosphere can be used for the management of insects. Is there more information available on using controlled atmospheres for insect control on fresh produce in refrigerated containers?
From the experience of 1994 or 1995 in Samoa, the fruit fly team tested the effects of low temperatures with low percentage oxygen and high percentage carbon dioxide on the survival of Bactrocera kirki fruit fly larvae in the first and third instars (may have done B xanthodes as well) in artificial diet and in fruit (pawpaw) for a company called Transfresh (http://www.transfresh.com/index.html).
Because the fruit fly larvae live in the fruit anyway, we found the gases did not have any effects on the larval development, but the low temperature did. Studies in the Cook islands (possibly) found the modified atmospheres were more effective killing surface pests (mealybugs, thrip, aphids, etc.). A useful link is rics.ucdavis.edu/postharvest2/index.html, click on modified atmospheres; and another useful one for a list of fruit and possible treatment regimes is ucce.ucdavis.edu/files/datastore/234-58.pdf.
It was reported from Port Moresby, Papua New Guinea, that a surprisingly high number of different insects are present on a variety of fruit and vegetables imported – especially the leafy greens. These importations posed a very significant risk for the accidental introduction of pests, such as fire ants, and that better treatments were needed.
Some general comments about quarantine in Pacific Island countries.
1. In relation to the limited capacity of most Pacific Islands to undertake treatment of quarantine pests, it is a general rule that all treatments of commodities should be conducted at the point of export.
2. In the case of the detection of live insects at the point of entry the issue is, firstly, has a treatment been required overseas and is this the indication of a treatment failiure. In this case, the consignment should be re-treated, or reconsigned or destroyed.
3. If PNG is capable of undertaking treatment, then the issue is the identification of the live insects. If the pests are already listed as quarantine pests, then treatment can be undertaken with a suitable set of conditions. If the pests are not quarantine pests then the consignment may be released without treatment.
4. The main problem is that with fresh fruit and vegetables, the time taken to identify the pests as quarantine/non-quarantine is longer than the shelf life of the commodity and the option of destruction/reconsingment/re-treatment is not taken, and the commodity is often released in contravention of all logical reasoning.
Given the problem is not only with identification of the pests, but also the risk that the consignment contains undiscovered pests, that is, those that might be present other than the ones identified in looking through a selection of boxes. Therefore, the commodities should be either retreated, reconsigned or destroyed. Where possible, retreatment is the best option. In this case (the PNG vegetables), the consignment was required to be further treated (methyl bromide) before the consignment was released. It must be remembered that any cold treatment must be able to kill resilient insects, such as ants.
5. There are numerous factors that contribute to one finding live insects in conveyances (rather it be reefer, ordinary containers, or palleted LCLs or whatever). These includes hitchhiking, contamination, poor/failed quarantine treatments and can happen anywhere along the pathway. Quarantine services world over work on the premise of mutual acceptance of each others risk management/mitigation and certification system provided that the national systems meet the minimum standards as agreed internationally (e.g.. ISPMs) and also have in-built checks and balances to identify non-compliances and how to deal with them. The issue of quarantine integrity of consignments along the pathway from point of inspection and certification at the export facility to the points for entry where on-arrival inspections are conducted for various reasons including compliance to import conditions is important.
6. Some Pacific island countries make an assumption that commodities coming from some countries are safe, because standards of quarantine are high. But the standards for commodities leaving countries may not be the same as for those arriving. The treatment provided to the commodities leaving the countries relies to a great extent on the requirements placed on them by the importing country. This may not always be appreciated.
7. The fact that countries trust developed countries cargo is because cleaning of containers is normally a requirement prior to loading, and they have facilities to do this. However, in other countries, containers are used without any consideration for their sanitary and phytosanitary condition, and are loaded in areas where contamination readily occurs (near to the production field, not at a container depot or a packing shed), hence the risk of the movement of pests/AIS continues.
8. In terms of mixing commodities with different treatments in a consignment, this does not present any increase in pest risk. If a pest moves from one commodity to another this is not a problem, because each commodity, subjected to a PRA, has the regulated pests identified and treated. A country does not accept a quarantine pest on one commodity and not on another. If a pest is identified as a quarantine pest on a commodity pathway it requires treatment. The reason that commodities are treated in different ways is that the pests are different, or that the treatments are selected because of the tolerance of the commodity to the various treatment options. In all cases commodities treated before shipment should not have live quarantine pests on them. Treatment for fruit flies in Citrus involve cold treatment, that for mangos and papaya would be HTFA treatment, but they could be shipped in the same container after treatment. In all cases treatments for all identified quarantine pests should be applied at rates considered to be effective (Probit 9, etc).
9. Risks of hitchhikers are also considered in the PRA in terms of the production/harvest/packing system and are addressed through treatment/inspection at point of exit and entry, etc. Ants are not necessarily difficult to detect. They are relatively large insects that would be detected by visual examination compared with mites and thrips. There is no need for sophisticated equipment to detect them, inspection with a hand lens would be sufficient to address the overall pest risk. If ants are found in a consignment, then the export inspection system is at fault.
10. If the consignment in the above scenario came from Australia, AQIS would be pleased to know why the system failed. In accordance with the IPPC and ISPM 13, did PNG report non-compliance to AQIS? Only when such incidents are reported can regulatory remedial action take place and the reason for the problem be addressed? Experience is that countries do not report non-compliance and as a consequence the problem persists. This is a major failiure of NPPOs in all developing countries.
General comments on cold temperatures and atmospheres
1. The use of cold temperature/modified/controlled atmospheres as a treatment has been devised and adopted based upon commodity specific requirements and is in place because specific pests have been identified in/on the commodity. As such, those treatments are only effective against commodity pests and are specific for commodity/pest/country combinations. Some commodities are packed in the field, and may be liable to contamination, but this would have to be dealt with at point of entry through inspection prior to export. A contaminated consignment should be denied issuance of a phytosanitary certificate and not permitted export.
2. The risks of importation of other insects, etc., as contaminants or hitchhikers is pathway specific, and occurs no matter what the commodity might be. Cold treatment is not, as far as I am aware, considered as effective against pathway pests, such as those that would be found in/on containers, because of poor procedures at the time the container was loaded. Reduction of the risk of such contaminants depends upon the inspection and treatment of the conveyance (container) before, during and after loading. As a general rule, produce should only be loaded clean containers. Contaminated containers should be washed or steam cleaned or, if necessary, fumigated. These treatments are accepted as effective against a wide range of organisms, including risks associated with soil, eg., GAS.
3. Cold treatment is working well for importation into the FSM of citrus, apples and some stone fruits at 1oC for 16 days. For other commodities, e.g., leafy crucifer ,this temperature would cause cold damage. Therefore, there are different treatments for different produce, e.g., insecticide dip, methyl bromide fumigation, cold treatment and high temperature forced air.
The difficulty with thrips and aphids from USA
In the Fedretated States of Mincronesia. the main problem is with shipments of produce from USA. According to the paper (reference below) the controled atmosphere treatment gives good control. I can imagine that it also would give a good control for ants, too, but ants were not included in the study. It is necessary to convince importers in FSM, Palau and Marshall Islands to use this treatment, in addition to other import requirements, e.g., area freedom from fruit flies. Unfortunately, the cost to treat one container is US$1,000 and most importers are not prepared to pay this amount.
Reference: Potential of controlled atmospheres for postharvest insect disinfestation on fruits and vegetables Dangyang Ke & Adel A Kader. This is available from the SPC library.
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