Sublethal effects of low temperature on the light brown apple moth, Epiphyas postvittana (Walker)

The light brown apple moth, Epiphyas postvittana (Walker) (Lepidoptera: Tortricidae), a leafroller native to southern Australia, continues to invade new areas of California and Oregon. This insect is highly polyphagous and threatens many agricultural and horticultural crops, with the potential to cause millions of dollars in damage annually. Damage estimates, however, are sensitive to the final national geographic distribution of this pest. Current predictions assume the insect will not establish in areas with temperatures below -16°C but do not account for sublethal effects of cold exposure. The potential for such effects could restrict the areas of establishment and impact, but no prior studies have documented these effects in Epiphyas postvittana. This study measured the direct and indirect effects of cold temperature on larvae, pupae, and adults of Epiphyas postvittana. Cold exposure included -10°C, a low, but not immediately lethal, temperature, and the supercooling point, the temperature at which internal fluids freeze. Cold treatments were applied to late larval instars and pupae. Surviving insects were mated with untreated adults. We measured larval and pupal development time, pupal weight, adult longevity, and fertility of treated females and mates of treated males. Initial results suggest that survivors of supercooled larvae may have a slight increase in total larval development time and decrease in adult longevity.