The effect of sub-zero temperature on the mortality of Ephestia elutella (Hübner)

The effects of sub-zero temperature (-10, -15 and -20 oC) on the most cold tolerant stages (eggs and diapausing larvae) of Ephestia elutella were assessed in the laboratory as alternatives to the use of chemical control methods for the disinfestation of stored tobacco. Test insects were exposed for five exposure periods at each test temperature following a gradual acclimation to simulate practical freezing of a tobacco bale. Mortality was evaluated after a gradual return to and incubation at 25 oC. Eggs were less cold tolerant than diapausing larvae with hours of exposure being required to produce complete mortality as opposed to days. Complete mortality of eggs was achieved after 1 and 7 hours at -15 oC and -10oC respectively, whereas complete mortality of diapausing larvae was achieved after 1, 3 and 22 days at -20 oC, -15 oC and -10 oC respectively.