Cold Treatment
Cold treatment has not only found to increase the shelf-life of some of the fruits & vegetables but also mitigate the pests associated with them. Some fruits like Apples are stored for months together at temperatures which are lethal to most quarantine pests, so that disinfestations can be accomplished during post-harvest storage. Furthermore, cold treatment can be applied to fruits after packing and ‘in transit’ during lengthy transport by sea during their exports. Cold treatment is free of chemical residues and is being internationally accepted and preferred. The main disadvantage is its long treatment time. Generally Tropical fruits require less of lower temperatures that the temperate fruits so as the tropical pests. Temperatures at 10°C can be lethal to tropical fruit flies given long exposure time, say, several weeks; but 3.3°C is about the highest temperature suggested as a phytosanitary cold treatment in order to accomplish the treatment in a reasonable period of time, such as 3 weeks maximum for the most cold-tolerant tropical fruit flies. For pests, such as, codling moth, Cydia pomonella, cold treatment alone at above injury level thresholds to fruits is inadequate and must be combined with fumigation, again at above injurious dosage thresholds to the commodity.
- Quick freeze Treatment: It is adopted for most of the thick-skinned fruits and vegetables. Lower the temperature of the commodity to 0°F or below initially and thereafter hold the temperature of the commodity to 20°F or below for atleast 48 hours. The commodity could be transported during these 48 hours treatment period but the temperature of 20°F should be maintained.
- Cold treatment for Mediterranean fruit fly: Disinfestation treatment of tropical fruits flies, quarantine pests especially Ceratitis capitata, could be achieved at 1.1°C for 12 days and could be tolerated by the Citrus fruits. However, at a later stage, interceptions have been made in some citrus varieties which has resulted in prescribing combination treatment with Methyl bromide fumigation (32 gm/m3) followed by cold treatment, by some of the countries.