BP Singh

196 Manju Lata KapurFumigationThis is one of the most effective methods used as quarantinetreatment. Due to technicalities involved specifically trainedpersonnel are required to undertake the operations.Fumigation is a process in which chemicals effective astoxicant gas (fumigants) are used in an enclosed space tokill the pest organisms.A fumigant may be a gas (methyl bromide), liquid'(ethylene dichIoride~carbon tetrachloride mixture), solid(aluminium phosphide) or a crystalline powder(naphthalene) at room temperature, but for effective plantquarantine usage it must be highly volatile with goodpenetrability ., Specially designed dose dispensers are required to applygaseous fumigants, whereas heating may be required forvolatilization of liquids and solids.A fumigation schedule generally comprises dosage/concentration of fumigant (C), exposure period (T),temperature and pressure. 'Following factors need to be considered while undertakinga fumigation.a) Concentration Time Product (CTP) is constant for a schedule.After a minimum concentration build up, exposure period can beadjusted or vice-versa to have required CTP.b) Sorption is uptake of gas by solids in a system. This resultsin the loss of some fumigant and necessitates monitoring ofconcentration during the fumigation.c) Penetrability is capacity of a gas to diffuse through air andthe commodity and this can be improved by using fans/blowersor vacuum i.e. reducing air (pressure).d) Temperature affects physical absorption of a fumigant as wellas the insect respiration, thus determines the dosage requirement.e) Permeability of the containers holding the commodity andairtightness of the enclosed space are also equally important indetermining the efficacy of a fumigation.