Effect of diet on Epiphyas postvittana (Lepidoptera: Tortricidae) cold tolerance

Forecasting future distributions of invasive insects is a vital component of many management and regulatory decisions. However, several challenges exist in constructing biologically relevant models that are meaningful over time and space.  For much of North America, cold temperature is especially important in defining geographic boundaries of insect survival and is often used as a key parameter in risk models.  An insect’s response to cold, though, can be influenced by the host it consumes.  For highly polyphagous species, host effects could significantly alter distribution projections based on cold.  Here, we used the invasive light brown apple moth, Epiphyas postvittana (Walker), to explore potential effects of host on insect cold tolerance.  Epiphyas postvittana is a recent invader to the contiguous United States and has been documented to feed on more than 200 plant species, many of which are important to agriculture and forestry. The late instar is the purported overwintering stage and demonstrates partial freeze tolerance.  We reared larvae on five host-plant species, plus an artificial diet, and then compared their supercooling and freeze tolerance capacities. We show that E. postvittana cold tolerance differs based on larval host plant, and illustrate the implications of these data for models of future geographic spread and establishment.