Mortality of adult Cryptolestes ferrugineus (Stephens) exposed to changingCO2 concentrations

The concentration of carbon dioxide (CO2) in a grain bin declines during a fumigation due to leakage, but mortalities of adult Cryptolestes ferrugineu s (Shephens) have been obtained and reported at constant CO2 concentrations . A procedure for predicting the mortality of adult C. ferrugineus exposed to conditions of changing CO2 concentration was developed. Based on publish ed data, a regression equation was obtained for mortality of adult C. ferru gineus exposed to elevated CO2 concentrations at a temperature of 25 degree s C. The regression equation was used go calculate a cumulative lethality i ndex. Complete mortality should occur when the cumulative lethality index e quals one. Agreement between the observed insect mortality and the correspo nding cumulative lethality index was good in five experimental fumigations conducted in sealed, welded-steel hopper bins, but the cumulative lethality index over-predicted the insect mortality in the sixth experimental fumiga tion. (C) 1999 Elsevier Science Ltd. All rights reserved.