BP Singh

Plant Quarnatine Treatments for Salvaging Gem/plasm Infested with Insects and Mites 197f) Equipments required to conduct a fumigation include anairtight enclosed space/chamber with or without a pump, fan orblower, a heating mantle, dose dispenser, concentration mOnitoringunit, leak detector, pressure gauge and temperature recorder.On the basis of pressure at which a fumigation is tonductedit is termed as atmospheric or vacuum fumigation. .a) Atmospheric fumigation: This is a fumigation conducted atno!mal air pressure (NAP) in any airtight enclosure i.e. apolyethylene bag, under a tarpaulin or tent, a laboratory autoclaveor a steel drum, which can retain a fUmigant during the exposureperiod without appreciable loss through leakage. Airtightness canbe tested by an open arm manometer filled with kerosene.Ahnospheric fumigation takes care of most of the insects/mites/stages thereof that are external! surface feeders. For examplefumigation with ethylene dichloride- carbon tetrachloride ceOCT)@ 320 mg/1 for 48 h at NAP and 30°C is effective for most of thecommon stored product insects. .b) Vacuum fumigation : In this process most of the air in thechamber is removed. For this purpose, a specially designed /constructed chamber is required which is usually made up of steeland is capable of withstanding external pressure upto oneatmosphere. The installation includes a pump to evacuate the· .chamber, and valves and ducts for introduction and exhaustion offumigant. The primary opject is to hasten the penetratiqn of thefumigant through tightly packed material or internal .infestation.The operation generally gets completed in 1-4&1/2 h as comparedto atmospheric fumigation which takes a minimum of 24 h.Fumigants which can be ~afely used in vacuum include ethyleneoxide imd carbondioxide mixture, hydrogen cyanide gas andmethyl broJl!ide. Specific quarantine fumigation schedules havebeen summed up in Plant Quarantine Treatment Manual, USDA(Anonymous,1985). Fumigation with MB @ 64 mg/l or HCN@ 47.1 mg/l for 2 h at reduced pressure equivalent to 200 mm ofHg at 27°C gives quarantine' control of internal infestation ofphytophagous chacidoids in the seeds of Sesbania, Coriander andfennel (Verma, 1991).Aeration ,is ventilation of fumigant after treatment so as toremove the fumigant from the space and the material.Complete diffusion back to the atmosphere/desorption