EFFECTS OF AGE ON RESPONSE OF EGGS OF INDIANMEAL MOTH AND NAVEL-ORANGE WORM (LEPIDOPTERA, PYRALIDAE) TO SUBFREEZING TEMPERATURES

The response of eggs of two pyralid moths to exposure to subfreezing temperatures was studied. Egg age at the time of exposure greatly affected the tolerance of Indianmeal moth, Plodia interpunctella (Hubner), and the navel orangeworm, Amyelois transitella (Walker), to low temperatures. Indianmeal moth eggs incubated at 28-degrees-C for 33 +/- 8 h were more tolerant of exposure to temperatures of between -12 and -18-degrees-C than eggs 57 +/- 8 h old. Additional studies showed that Indianmeal moth eggs between 27 and 51 +/- 8 h old and exposed to -15 and -19-degrees-C were the most tolerant and that eggs older than 57 +/- 8 h were the least tolerant. Navel orangeworm eggs showed a similar response, with eggs between 34 and 74 +/- 6 h old being the most tolerant and eggs older than 82 +/- 6 h being the least tolerant. Because of their comparative tolerance to low temperatures, middle-aged eggs of both species are most suitable for development for low temperature treatments of between -15 and -19-degrees-C.