Comparative study of freezing time and temperature for effective Plodia interpunctella control using typical storage containers

Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae) is a moth species that is able to feed on various vegetable commodities. Its control is economically critical for commercial food storing facilities such as warehouses. P. interpunctella causes quantitative and qualitative damage by eating important stored food crops such as dried Welsh onions (Allium fistulosum L.), and freezing treatment is a common method of control. To examine the effectiveness of freezing treatment, we changed the length of time of the conventional freezing method. The conventional method involves treatment below −15 °C for 48 h, but we predicted that it would be effective with only 24 h freezing at −25 °C. To test our theory, we conducted an experiment using three different frozen storage containers and assessed if the modified method was effective on the eggs and fourth instar larvae of P. interpunctella. Despite the temporary malfunctioning of one of the containers used in the experiment after incubation at 28 °C and 70% relative humidity for 10 days, the larval mortality rate was 100% and egg hatching rate was 0% in all samples, regardless of the treatment time. Further research is needed as this method is expected to decrease production costs and energy consumption and has the potential to be applied to other crops and pests.