Validation of hydrogen cyanide fumigation in flourmills to control the confused flour beetle

Abstract

In the milling industry, the Tribolium confusum is hard to exterminate pest. We measured the concentration time product (Ct-P) achieved during the hydrogen cyanide (HCN) fumigation and examined whether the Ct-P levels in the explored Czech pilot mill were sufficient to control the field strain of T. confusum. Using an originally constructed, gastight fumigation chamber, it was estimated that the Ct-P required for the complete killing of the field strain of T. confusum was 4× higher (4.35 g/h/m3) than the levels required to kill the laboratory strain (1.25 g/h/m3). The Ct-P levels (ranging from 79 g/h/m3 to 100 g/h/m3) reached during the mill fumigations with HCN were less than half of the labelled HCN rate (240 g/h/m3). Nevertheless, the current HCN dosage is still sufficient since the Ct-P reached during the mill fumigations was at least 99× higher than that required for the exterminating to the lab strain and 18× higher than that required for the field strain extermination. These results were confirmed in mill validation testing, where 100% mortality of T. confusum adults was achieved.