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.

    30/98 (page 22)
    this being particularly marked when the mill is of loose construction or contains much old woodwork and resistant species of insects. In this connection, chemical measurements of the gas concentrations present in mills undergoing fumigation have shown that doses often used in practice leave no reserve for penetration of lethal concentrations into cracks, between boards, or into anv residues of stock left in machinery or caked on to shutes, even although the apparent results, (as judged by superficial examination, e.g. by the numbers of adult moths killed by the treatment) may have been satisfactory. ‘his position justifies the expenditure of very special efforts to ensure that maximum results are obtained at the time of fumigation. A number of factors, in addition to the above-mentioned degree of preparation, should decide the dosage specifications to be employed. Within the normal limits, insects are more susceptible at higher temperature and, if possible, treatments should therefore be carried out during the warmer months of the year. ‘This should not be considered as absolute however because lower temperatures can be compensated for by using higher doses of gas. Insects also vary considerably from species to species in their resistance to fumigation. For example, the grain weevil Calandra granaria is much more resistant to hydrogen cyanide than the mill moth, /phestia kithniella. ‘The variation in the habits of different species can also influence the results obtained by fumigation. For example, meal worms (Tenebrio molitor) often survive because they burrow deeply into floor cracks, whereas other species may remain on the surface and be exposed by the prefumigation cleaning.