The effect of diapause and cold acclimation on the cold-hardiness of the warehouse beetle, Trogoderma variabile (Coleoptera: Dermestidae)

The warehouse beetle, Trogoderma variabile Ballion (Coleoptera: Dermestidae), is a stored-product pest with scant information on its cold tolerance. Ninety-two per cent of larvae reared in isolation at 30 °C went into diapause in the seventh instar, the remaining 8% emerged as adults in 50 days. Diapausing larvae died after 142 days in the 10th instar. The cold tolerance at 0 °C from highest to lowest was; old larvae > pupae > adult=young larvae > eggs. The LT50 (lethal time for 50% of the population) for grouped (non-diapause) non-acclimated old larvae at 0 °C, -5 °C, -10 °C, -16 °C, and -19 °C were; 20, 11, 5, 1, and 1 day, the LT95 were; 38, 15, 10, 5, and 1 days, respectively. The LT50 for isolated (diapausing), cold-acclimated old larvae at the same temperatures were; 275, 125, 74, 26, and 18 days, and the LT95 were; 500, 160, 100, 45, 20 days, respectively. The supercooling point (SCP) of different stages of non-acclimated insects ranged from -25.3 °C (eggs) to -16.1 °C (young larvae). The most cold hardy stage, isolated and acclimated old larvae, had a SCP of -24.9 °C. The potential of using low temperatures to control T. variabile is discussed.