Irradiation has been demonstrated to be effective in killing or devitalizing organisms that may contaminate and do harm to commodities or the ecosystems to which the commodities move. This energy source can thus be authorized for use in the treatment of regulated pests. Treatment may be mandatory, as a condition for the entry or movement of consignments, or it may be prescribed, based on the detection of regulated pests in commodities intended for transport. Alternatively, importers or exporters may voluntarily subject commodities to irradiation treatments in order to prolong their acceptability and desirability. Irradiation may thus be a treatment option, or it may be the only treatment, which is approved for the pest and commodity in question. As with all pest mitigation treatments, the objective is to minimize the risk of pest introduction through the use of exclusionary measures. The minimization of pest risk may be achieved through the use of treatments that have an acceptable level of efficacy. Irradiation treatments are approved to minimize the impact on the commodity and its ultimate use as a pest mitigation treatment. The purpose of these treatments is to minimize the pest risk and to maximize the safety associated with the movement and use of the commodity. Treatments and associated procedures are based upon science, and are no more restrictive than necessary to protect plant health. Government of India has developed Guidelines for Certification of Irradiation Treatment Facilities for Fresh Fruits to meet the Phytosanitary Requirements.
Although Methyl bromide (MB), a chemical fumigant is highly effective against these pest but has been identified as an important atmospheric ozone-depleting substance and the authorities are looking seriously for an alternative. Ionizing radiation has been recognized as an alternative to MB for treating fresh agricultural products in order to overcome quarantine barriers in trade.
The purpose of a quarantine disinfestation treatment is to prevent the establishment of a pest associated with a commodity to be imported into a country or region where it does not already occur or where its presence is restricted. Irradiation is particularly suited to this purpose with applications over a wide range of commodities and pests. It meets the current consumer requirement of freedom from chemical residues that are associated with fumigation and insecticide treatments.
Ionizing radiation may be provided by radioactive isotopes (gamma rays from cobalt-60 or cesium-137), electrons generated from machine sources (up to 10 MeV), or by x-rays (up to 5 MeV) (limits set by Codex Alimentarius). The unit of measurement for absorbed dose should be gray (Gy). The absorbed dose varies from commodity to commodity depending upon the regulated pest in question.
The quarantine security level required of a treatment will need to be ascertained from the importing country. Although USA uses 99.9968% extensively (probit-9) other countries have lower levels (e.g. 99.99% or 99.5% for fruit flies and 99.5% to 95% for other pests). These security levels may be assured by treatments with appropriate minimum efficacy levels which can be confirmed at a required confidence level by testing against appropriate numbers of pest individuals.
Irradiation Treatment of Mango Fruits
A Standard Operating Procedures- Irradiation Treatment of Indian Mangoes for export to USA approved by MOA (NPPO) India has been developed wherein the mangoes for export are be irradiated with a minimum absorbed dosage of 400 Grays at the approved and certified irradiation treatment facility using Cobalt- 60. The source and equipment used for pest mitigation treatments must be capable of safely and effectively irradiating the commodities to the specifications that are required for target pests.
Signatories to International Plant Protection Convention (IPPC) have agreed to abide by the principle of equivalence so there should be some flexibility , in an equivalent manner and framed a Guidelines for the use of Irradiation as a Phytosanitary Measure, 2003, ISPM No. 18 https://www.ippc.int/file_uploaded/1146658925161_ISPM18.pdf
IPPC has further developed an International Standard No. 28: Phytosanitary treatments for regulated pests. This standard presents in its Annexes phytosanitary treatments evaluated and adopted by the Commission on Phytosanitary Measures (CPM). It also describes the requirements for submission and evaluation of the efficacy data and other relevant information on a phytosanitary treatment that can be used as a phytosanitary measure and that will be included in Annex 1-8 after its adoption. So far the following Irradiation treatments have been adopted :-
Annex 1 Irradiation treatment for Anastrepha ludens
Annex 2 Irradiation treatment for Anastrepha obliqua
Annex 3 Irradiation treatment for Anastrepha serpentina
Annex 4 Irradiation treatment for Bactrocera jarvisi
Annex 5 Irradiation treatment for Bactrocera tryoni
Annex 6 Irradiation treatment for Cydia pomonella
Annex 7 Irradiation treatment for fruit flies of the family Tephritidae (generic)
Annex 8 Irradiation treatment for Rhagoletis pomonella
In addition to above, the following treatments have been subsequently adopted:
1) Irradiation treatment for Conotrachelus nenuphar ISPM 28 Annexure-9,
2) Irradiation treatment for Grapholita molesta ,ISPM 28 Annexrure 10
3)Irradiation treatment for Grapholita molesta under hypoxia, ISPM 28 Annexure 11: https://www.ippc.int/file_uploaded/1273483393_ISPM_28_Annex11_2010_E.pdf