Rapid Cold Hardening Confers a Transient Increase in Low Temperature Survival in Diapausing Chilo suppressalis Larvae

The striped stem borer, Chilo suppressalis (Walker), overwinters as a diapausing larva. The diapausing larvae were tested for a rapid cold hardening (RCH) response and its role in the insect's survival of sub-zero temperatures. When laboratory-reared diapausing larvae were transferred directly from the rearing temperature of 25 degrees C to -14 degrees C and maintained there for 2 h, 21% survived. Acclimation of diapausing larvae for 4 h at 5 degrees C before their exposure for 2 h to -14 degrees C increased survival to approximately 41%, indicating an RCH response. Durability of RCH effects on low temperature survival was less than 1 h. Although transient in the test, the increased survival acquired through rapid cold hardening may play a role in preparing the diapausing larvae for abrupt temperature drops in the field that would otherwise be lethal.