Combined effect of carbon monoxide mixed with carbon dioxide in air on the mortality of stored-grain insects

Abstract

A study to determine the effect of carbon monoxide (CO) mixed with carbon dioxide (CO 2) in air on controlling stored-grain insects was conducted in the laboratory. Within modified airtight gas exposure units containing wheat at 15% moisture content wet basis (w.b.), mixed-age adults of rusty grain beetle, Cryptolestes ferrugineus (Stephens), red flour beetle, Tribolium castaneum (Herbst), and granary weevil, Sitophilus granarius (L.) were exposed for 48, 96, 144 or 192 h to three types of gas mixtures in air, 5% CO, or 30% CO 2, or 5% CO + 30% CO 2 at 20 °C and 30 °C, the balance of the gas being air in each case. Carbon monoxide alone had no effect on the mortality of adults of the three insect species. For C. ferrugineus, there was no difference in mortality between by CO 2 alone and the CO 2 + CO mixture at either temperature for all exposures. However, both T. castaneum and S. granarius had higher mortality in the CO 2 + CO mixture than the CO 2 alone at both temperatures. Moreover, S. granarius was more susceptible to CO 2 + CO mixture than T. castaneum. These results suggest that for certain species, CO could be used to increase the efficiency of CO 2, especially at high temperatures.