Abstract
Winter survival of cigarette beetle larvae in three tobacco warehouses and three sheds at five locations in Japan was examined 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 to 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 to 8 weeks and 5 °C for 3 to 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.