Abstract
Time-temperature-mortality relationships for egg, larval, pupal, and adult stages of the cigarette beetle, Lasioderma serricorne were investigated to determine disinfesting conditions for stored tobacco. Susceptibility to low temperatures changed according to the developmental stage. Eggs were most susceptible to low temperatures that were higher than −5°C. Larvae acquired cold tolerance during exposure to 15°C for 1 mo. These acclimated larvae were the most tolerant of all. LT99 values of acclimated larvae were calculated as 7.2 h at −15°C, 23.7 h at −10°C, 376 h at −5°C, 1,140 h at 0°C, and 1,880 h at 5°C. As the most susceptible stage, egg susceptibility to moderately low temperatures (16–20°C) was specifically examined. At 20°C, most eggs (>80%) normally hatched within 4 wk, but all eggs died within 6 wk at temperatures less than 18°C. This fact indicates that the reproductive cycle can be blocked at temperatures less than 18°C, and that tobacco stored in such conditions will never become infested, even if eggs are deposited by invading adults. Consequently, if the tobacco temperature is reduced to 5°C for 3 mo in winter and is subsequently maintained below 18°C throughout the rest of the year, tobacco can become and remain pest-free without any chemical control.
