Insect pests of food ; the control of insects in flour mills / [by J. A. Freeman and E. E. Turtle] ; with a foreword by the Director of Infestation Control.

  • Great Britain. Ministry of Food
Date:
1947
Catalogue details

Licence: Public Domain Mark

Credit: Insect pests of food ; the control of insects in flour mills / [by J. A. Freeman and E. E. Turtle] ; with a foreword by the Director of Infestation Control. Source: Wellcome Collection.

    18/98 page 10
    grains. ‘lhe machine should be fitted into the flow at an early stage in the passage of grain through the screenroom. It is necessary, however, to remove large impurities, sticks, stones, string etc., the last-mentioned, in particular, is liable to reduce the efficiency of the machine. EREATMENT OF (BAGS There is considerable evidence to show that returned flour bags are the chief carriers of insects into the mill, particularly the mill moth (phestia kiihniella), whose caterpillars and pupae are often in cocoons firmly attached to the bag fabric ; other insects commonly found on bags include the flour beetle, Trzbolium confusum, the cadelle, Tenebroides mauritanicus and the brown spider beetle, Péonus tectus. Ideally no bags should be employed a second time, or they should be sterilised by fumigation or by heat prior to return to the mill premises. ‘The practice, becoming common before the war, of using non-returnable bags, is a good example of the former procedure. A further possibility of solving this problem is offered by recent experimental work on the impregnation of the bags themselves with insecticidal preparations : the chief difficulties in this connection are that the impregnation must remain effective under practical conditions for a considerable period whilst it must not be accompanied by a risk of contaminating the foodstuffs stored in the treated bags. HEAT TREATMENT “OF BAGS. Theémoteseiven m the precedme section regarding the times and temperatures necessary to effect sterilisation of grain apply equally to sacks, it being essential to ensure that the required minimum temperatures are reached even in the coolest spots. A modified sack drying plant circulating a hot air current over the bags and using steam as a source of heat, preferably by live injection, can be employed for this purpose and, being quite simple, can be operated by the sack cleaning staff. FUMTGATION. OF ‘BAGS (PlatesSiand 6): his as as eiiicient-ac heat treatment although a higher degree of technical supervision is necessary because, to some degree, the available fumigants are all toxic to human beings. For this reason, before undertaking fumigations, expert advice should be obtained regarding the construction of the chamber, dosages and safety precautions, and other matters connected with the operations. Of the fumigants available, hydrogen cyanide is perhaps the most effective, but, also, the most dangerous in use. Although some risks from fire are involved in the use of ethylene oxide with carbon dioxide, the mixture is very much less toxic to man and, | in the hands of any but the most skilled operators, is therefore to be preferred. Of the chlorinated hydrocarbons which are at present available, ethylene dichloride is the most practicable. This fumigant may readily be applied as a spray ; the liquid is only very slightly inflammable and the gas has a readily detectable odour. For these reasons, ethylene dichloride is suitable for use by the normal mill personnel after only an initial technical supervision. Bags readily “‘sorb”’ all of these fumigants which must, therefore, be used in fairly high dosages ; dense bundles and stacks also must be thoroughly opened up. Methyl bromide has not yet been employed on any scale in this country. It possesses physical and chemical properties very suitable for the treatment of bags, which sorb the gas relatively slightly, rapid penetration and subsequent airing being obtainable. Very special care must be employed in using the gas, however, because it is very toxic and only possesses a slight warning odour.
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