Temperature conditions affecting winter survival of the cigarette beetle, Lasioderma serricorne (F.) (Coleoptera: Anobiidae)
The cigarette beetle is a cosmopolitan pest of tropical origin and is not fully adapted to temperate climates. Several studies have described winter extinction of this pest under constant laboratory conditions, but studies under natural winter conditions have been limited. In this study, we examined winter survival of the last instar larvae in three tobacco warehouses and three sheds at five locations in Japan to determine critical temperature conditions for eradication under natural situations in locations where temperatures fluctuate seasonally and diurnally. In the tobacco warehouses, where mean diurnal temperature variations were less than 1 °C, the combined exposure to temperatures lower than 7 °C for 9-10 weeks and lower than 6 °C for 1-2 weeks inside tobacco cases was found to be required for eradication. Temperatures inside tobacco cases approximated the 7-day moving averages of outside temperatures but were about 1 °C higher. To disinfest the larvae living inside, tobacco cases should be exposed to outside temperatures lower than 6 °C for 7-8 weeks and 5 °C for 3-4 weeks. Near the critical conditions, larger diurnal temperature ranges resulted in higher winter survival rates. This result suggests that the larvae may survive even in areas cold enough to normally cause eradication provided that daytime temperatures rise sufficiently. The information obtained has been practically considered when locating new tobacco warehouses so as to reduce the infestation of this pest without chemical control.