Every country conducts Import Risk Analysis (PRA) of a commodity before allowing its import from a specific country. Under this Pest Risk Analysis (PRA), it identifies the pests of quarantine importance that is likely to enter into their country. Further analysis is made to identify measures or treatments which could mitigate these pests, if possible. Such treatments, one or more, are specified to be carried out offshore to keep the pests at bay. There are many types of phytosanitary treatments which could be prescribed depending upon the commodity and the pest. These could be grouped under Fumigation treatment, Heat treatment, cold treatment, Radiation and Chemical treatments. Some of them are briefly described below:
The Insect pests or other pests found living on/in the produce, also hide in protected areas in storage premises, food processing units, equipments, etc. None of the insecticidal formulation which may be sprayed in such places, will be effective in containing the pests. It is only the fumigant which could penetrate such inaccessible spots and eradicate pests. Fumigant is a chemical which can exist in gaseous state in/at a required temperature and pressure and is lethal to organisms (insects, animals, plants and other pests) if they are exposed to a sufficient concentration and for a sufficient length of time. There are many chemical compounds which are volatile at ordinary temperatures and sufficiently toxic to fall within the definition of fumigants. In actual practice, however, most gases have been eliminated owing to unfavorable properties, the most important being chemical instability and destructive effects on commodities. Fumigation cannot be carried out unless: (i) the enclosure can be sealed to an adequate standard (ii) workers and other persons can be excluded from the enclosure and (iii) fumigant can be safely aired from the enclosure after the exposure period is complete. Adequate care is required to be taken while handling and use by the Operators. Moreover, Operators are required to have knowledge of fumigants registered in our country and situation under which they could be judiciously used. This would also help in overcoming the problem of pesticide residue in treated commodities. Most used fumigants are Methyl bromide, Phosphine, Sulphuryl fluoride, Ethylene oxide, Carbon dioxide, etc. Presently, in India, only three fumigants, namely, Methyl bromide, Aluminium phosphide and Magnesium phosphide are registered for use under the Insecticides Act, 1968. Their use has been restricted due to their hazardous nature or otherwise.
Methyl bromide is a broad spectrum fumigant effective against most of the storage pests. It has the ability to penetrate quickly and deeply into sorptive materials at normal atmospheric pressure and at the end of a treatment, the vapours dissipate rapidly and make possible the bulk commodities safe. Methyl bromide is nonflammable and non explosive under ordinary circumstances and may be used without special precautions against fire. Another important property is the fact that many living plants are tolerant to this gas in insecticidal treatments.
National Standard for Phytosanitary Measures No. 11 (NSPM 11) – Quarantine Treatments and Application Procedures: I. Methyl Bromide Fumigation has been developed by Government of India to provide guidance on quarantine treatments and application procedures for the approved fumigation agencies (Pest Control Operators). National Standard (NSPM 12) has also been developed for accreditation of these Phytosanitary Treatment Providers who have been authorized to undertake fumigation with Methyl bromide both for agricultural commodities and Wood Packaging Material in line with the requirement of ISPM 15.
Methyl bromide, in gaseous state, is released in an airtight enclosure with the required dose and specified length of time. Thereafter, the enclosure is degassed. Safety norms are kept in view while all this process is completed. The dose and exposure period is applied as per the requirement of the Importing Country. In case of Wood Packaging Material, dose at the rate of 48gm. per cubic metre at or above 21 degree Celsius is applied with the exposure period of 24 hours as per ISPM 15.
Although the methyl bromide fumigation acknowledged as having potential negative impact on environment, yet so far it is considered as the most appropriate treatment method in eradication of pest infestation in agriculture products. In consideration of above, the use of methyl bromide is strictly allowed for pre-shipment treatments and quarantine purposes including ISPM-15 compliance under Montreal protocol and any other critical use exemptions (CUE) subject to the approval by the United Nations Environment Protection Agency.
The demerit of Methyl bromide is that it is readily photolyzed in the atmosphere to release elemental bromine, which is far more destructive to stratospheric ozone than chlorine. As such, it is subject to phase-out requirements of the 1987 Montreal Protocol on Ozone Depleting Substances.
Phosphine or hydrogen phosphide (PH3) is a low molecular weight, low boiling point compound that diffuses rapidly and penetrates deeply into materials, such as large bulks of grain or tightly packed materials.The gas is produced from formulations of metallic phosphides (usually aluminium or magnesium phosphide) that contain additional materials like Ammonium salts for regulating release of the gas. It is formulated in tablets, pellets or small sachets of powder with additional materials such as ammonium carbamate, ammonium bicarbonate, wax, fillers, etc. to regulate release of fumigant and suppress flammability. 3 gm of tablet releases 1 gm Phosphine (PH3) alongwith NH3 and CO2.
Phosphine ranks as one of the most toxic fumigants of stored product insects. It is a slow acting poison that is effective at very low concentrations if the exposure time is long enough. Usually, exposure times of four or more days are required to control insects, depending on temperature. The toxicity of phosphine to insects declines as the temperature falls to 5°C, so that longer exposure times are required for it to exert its effect.
Phosphine is very toxic to all forms of animal life, hence exposure of human beings even to small amounts should be avoided. Guidelines for the use of Aluminium phosphide as NSPM-22 has been brought out by Department of Agriculture.
Sulphuryl fluoride has been developed as an effective fumigant for controlling dry wood termites. This gas has outstanding dispersion and penetrating qualities which permit it to infiltrate termite tunnels and crevices and destroy the insects.
Sulphuryl fluoride is generally very toxic to all postembryonic stages of insects , but the eggs of many species are extremely resistant. It has been suggested that this resistance is largely due to the impenetrable nature of the eggshell layers to this chemical.
Sulphuryl fluoride does not escape through plastic sheets used in structural fumigation as rapidly as methyl bromide or other organic fumigants
Under Forced hot air Treatment (FHAT) wood must be heated so that the core reaches a minimum temperature of 56 degrees Celsius for at least 30 minutes.Kiln-drying (KD), chemical pressure impregnation (CPI), or other treatments may be considered HT treatments to the extent that these meet the HT specifications.
Hot Water treatment
In this treatment the fruits are exposed to a temperature of at least 46.1-47.8 0C (1150 and 1180F) by immersing in heated water for a specified period of time depending upon the specific pest, type of fruit (species/variety) and size of fruits. It is further essential to maintain constant and uniform temperature during the period of treatment to ensure effective treatment.
The facility shall under take all the treatment operations as per NSPM – 15 “Guidelines for Certification of Hot Water Immersion Treatment Facilities for Mango Fruits”. This standard describes the guidelines and procedures required for certification of hot water immersion treatment facilities for fresh fruits of mango, as a quarantine treatment against fruit flies, to facilitate their export in compliance with phytosanitary requirements. The time-temperature relationship varies with the commodity and pest.Usually, the pulp temperature of the fruit raised using heated water between 46.1-47.8 0C (115 F and 118 F) for prescribed period of time.
Vapour Hot air Treatment (VHT)
The International Standard Phytosanitary Measures (ISPM) prescribes the guidelines/procedures for certification of Vapour Heat Treatment facilities (VHT) for fresh tropical fruits & vegetables against target pests, primarily fruit flies.( ISPM-26) Treatment units and facilities are required to be approved or certified by the NPPO before any treatment commences in accordance with RSPM No. 1. Guidelines for the development of heat dis-infestations treatments for fruit fly commodities.
For proper implementation National Standard Phytosanitary Measures (NSPM-20) has been prepared as a Guidelines for Certification of Vapour Heat Treatment Facilities for Fresh Fruits & Vegetables, to accredited the VHT facility. The official performance test will be carried out in three stages: (1) calibration of the portable sensors; (2) calibration of the permanent sensors installed in the VHT chamber; and (3) performance of an actual test treatment, the chamber temperature around 50-52 0C and the pulp temperature of 46-48 0C. The exposure period starts when all the pulp sensors indicate the required treatment temperature and then holds it for the minimum amount of time required by the particular treatment schedule.
VHT treatment uses heated air which is saturated with water vapor to raise the temperature of the commodity to a required point and holds the temperature for a specified period. The latent heat released by the condensation of the vapor on the commodity raises the pulp temperature quickly and evenly and thus prevents damage.
This VHT system helps to protect consumer health while also preserving the global environment.
The temperature-time relationship varies with the commodity and the pest involved. In case of treatment against fruit flies, the pulp temperature of the commodity will be raised by the saturated water vapor to 46-48 0C during a ramp up time of 4 hours and then the fruits will be held at the required temperature for a period of 30 min. The exposure periods and the treatment temperatures will vary with kind of fruit fly species and commodity involved
Forced Hot Air Treatment-(FHAT)
International Plant Protection Convention (IPPC) framed International Standards for Phytosanitary Measures 15 (ISPM) “Regulation of wood packaging material in international trade for Regulating Wood Packaging Material. ISPM 15 is a standard on which many countries packaging material Wood (WPM ) regulations are based upon.
To operate the international standard ,a National Standard of Phytosanitary Measures i.e. “Guidelines for Certification of Forced Hot-Air Treatment Facilities for Wood Packaging Material” has been prepared.The requirement for setting up a forced hot air treatment facility would include a heat treatment chamber , which should be adequatel insulated at least 15 cm thickness with rock/glass wool on all sides to ensure proper retention of temperature during the period of treatment.
A heat delivery system consisting electric heaters with required heat capacity and the blowers to blow heated air into the chamber through a close ended duct with provision to recycle the heated air and a motorized damper for exhausting 10% return air to remove moisture from the chamber after 10-15 min of the process time. A process control and interlocking system to provide adequate safety of operations and a PID single loop Temperature Controller holding a minimum of 6-8 temperature sensors connected to a paper- less temperature recorder and any sensor that deviates by plus or minus 0.30 C from the standard should not be used for calibration of permanent sensors.
During operation sensors should be inserted into holes drilled in different solid wood blocks up to a depth of 6 cm and positioned at different heights in the chamber loaded with pallets. The warm-up time should be determined and run the dwell-time portion of treatment and hold for the minimum time specified by the approved treatment schedule i.e. 560 C for 30 minutes.
These wood packaging material made of unprocessed raw wood can spread pests, which can lead to serious problems around the world. Globally approved measures have now been established to reduce this threat and protect local environments.
Methyl bromide (MB), a chemical fumigant that is highly effective against this pest, has been identified as an important atmospheric ozone-depleting substance and the industry is 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.
Disinfestations treatments of agri- product may need to gain the specific approval of quarantine authorities in each importing country. Therefore the supporting data required may differ from country to country. Such differences are usually minor and this generalised protocol will provide most of the information required by most importing countries
Signatories to International Plant Protection Convention 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 and irradiation treatment for Conotrachelus nenuphar ISPM 28 Annexure -9, Irradiation treatment for Grapholita molesta ,ISPM 28 Annexrure 10.
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
Indian Government has set up a Standard Operating Procedures- Irradiation Treatment of Indian Mangoes for export to USA approved by MOA (NPPO-India), wherein the mangoes for export should 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.
A Guidelines for Certification of Irradiation treatment facilities for meeting the phytosanitary requirements, (NPPO) has been develop by BRIT India