Comparative efficacy of controlled atmospheres against two stored product insects

Effect of controlled atmospheres (CAs) at various concentrations of CO۲, N۲ and O۲ on the lethal times of Tribolium castaneum and Trogoderma granarium was investigated at ۲۰ and ۳۰ ºC. Experiments were performed using a recirculatory multi-flask apparatus. The results revealed that, the shortest times (۰.۱, ۰.۳ and ۰.۹ day for adults, larvae and pupae, respectively) required to obtain ۵۰% mortality of T. castaneum stages were at ۱۰۰% CO۲ followed by ۷۵% CO۲, ۵۰% CO۲, ۹۹% N۲ + ۱% O۲ and ۲۵% CO۲, at higher tested temperature (۳۰ °C). Adults were more sensitive to the different treated CAs than larvae, while pupae were the most tolerant stages. Diapausing larvae of T. granarium were the most tolerant to all treated CAs at tested temperatures. The effectiveness of CAs to decrease its LT۵۰ values were ۱۰۰% CO۲ followed by ۹۹% N۲ + ۱% O۲ and ۹۸% N۲ + ۲% O۲ at ۳۰°C. It may be concluded that diapausing larvae are more difficult to control with CAs than normal larvae. A treatment with N۲ relying on the absence of O۲ 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 CO۲ would be the best option to achieve control in a comparatively short time.

Keywords:

Tribolium castaneum , Controlled atmosphere , Trogoderma granarium , Recirculatory multi-flask apparatus