Effect of sublethal tebufenozide applications on the mortality responses of Epiphyas postvittana (Lepidoptera : Tortricidae) larvae exposed to a high-temperature controlled atmosphere

First-, 3rd-, and 5th-instar Epiphyas postvittana (Walker) were exposed to a range of tebufenozide concentrations (0-200 ppm) incorporated into synthe tic diet and their subsequent development and mortality responses were dete rmined. Tolerance of tebufenozide increased with an increase in larval stag e (1st instar < 3rd instar < 5th instar). Percentage of larval mortality in creased with increasing tebufenozide concentration and exposure time. The h ighest mortality increase for Ist and 3rd instars occurred over tebufenozid e concentrations of less than or equal to 3 ppm. No larvae first exposed to tebufenozide as 1st or 3rd instars survived to pupation if ingesting conce ntrations of greater than or equal to 1.5 and 2.5 ppm, respectively. Althou gh 5th instars ingesting tebufenozide displayed mortality earlier than more immature life stages, mortality was less than or equal to 85% regardless o f tebufenozide concentration or exposure time because of early pupation. Te bufenozide consumption by any instar tested neither significantly delayed p upation nor resulted in an increase in the incidence of pupal deformities. Third and 5th instars were exposed to sublethal tebufenozide concentrations (0-3 ppm) for 7 and 2 d, respectively, and 5th-instar survivors of both in stars subjected to high-temperature controlled atmosphere treatment (2% O-2 , 5% CO2, 40 degrees C). Third instars ingesting 2 and 3 ppm tebufenozide w ere significantly more susceptible to the high-temperature controlled atmos phere treatment as 5th instars than larvae not exposed to tebufenozide. How ever, 5th instars that had ingested sublethal tebufenozide concentrations d isplayed the same mortality responses to high-temperature controlled atmosp here treatments as 5th instars not exposed to the insect growth regulator.