Comparative efficacy of controlled atmospheres against two stored product insects

Effect of controlled atmospheres (CAs) at various concentrations of CO2, N2 and O2 on the lethal times of Tribolium castaneum and Trogoderma granarium was investigated at 20 and 30 ºC. Experiments were performed using a recirculatory multi-flask apparatus. The results revealed that, the shortest times (0.1, 0.3 and 0.9 day for adults, larvae and pupae, respectively) required to obtain 50% mortality of T. castaneum stages were at 100% CO2 followed by 75% CO2, 50% CO2, 99% N2 + 1% O2 and 25% CO2, at higher tested temperature (30 °C). Adults were more sensitive to the different treated CAs than larvae, pupae the most tolerant stages. Diapausing larvae of T. granarium were the most tolerant to all treated CAs at tested temperature degrees. The effectiveness of CAs to decrease its LT50 values were 100% CO2 followed by 99% N2 + 1% O2 and 98% N2 + 2% O2 at 30°C. It may be concluded that diapausing larvae are more difficult to control with CAs than normal larvae. A treatment with N2 relying on the absence of O2 will take a longer treatment time to control the diapausing larvae and in late winter, exposure times needed for control may be even longer. If CAs were to be applied under such circumstances, a high content of CO2 would be the best option to achieve control in a comparatively short time.