Mortality of Cryptolestes ferrugineus (Stephens) adults and eggs in elevated carbon dioxide and depleted oxygen atmospheres

Abstract

A modified-atmosphere unit capable of generating accurate gaseous composition in the laboratory using three gases, carbon dioxide (CO 2), nitrogen (N 2) and oxygen (O 2) in the range of 0–100% for each gas, was designed and fabricated. The unit was used to determine the effect of gas composition, exposure time, temperature and relative humidity on the mortality of adults and eggs of Cryptolestes ferrugineus (Stephens). Carbon dioxide levels of 70, 80 and 90%, O 2 levels of 0, 4 and 8% (balance of mixture N 2) and relative humidity of 65, 75 and 85% at a flow rate of 55 ± 2 ml/min with exposure times of 24, 48, 60, 72, 84 and 96 hr were related to the mortality of adults of C. ferrugineus at 10, 15 and 20°C. The mortality of eggs of C. ferrugineus was determined at two levels of O 2 (0 and 4%) and two temperatures (10 and 20°C) with the same CO 2 concentrations, relative humidities and flow rate. For gas compositions containing 68–91.7% CO 2, 0–5.0% O 2 and the balance N 2, the mortality of adults was higher than eggs in a given exposure period. The mortality of eggs was more influenced by a decrease in O 2 from 4 to 0% than was the mortality of adults, whereas an increase in CO 2 from 68.0 to 91.7% increased adult mortality more than that of eggs. Gas composition and relative humidity (60–84%) affected the mortality of eggs and adults more than the other variables. Maximum mortality for both adults (99%) and eggs (85%) was obtained at high CO 2 (88–91.7%), low O 2 (0–0.5%), high temperatures (19.5–20.5°C) and low relative humidities (60.0–63.9%) at an exposure of 96 hr.