Pre- and postharvest effects of lufenuron on Epiphyas postvittana (Lepidoptera : Tortricidae)

First-, third-, and fifth-instar Epiphyas postvittana (Walker) were exposed to a range of lufenuron concentrations (0-200 ppm) incorporated into synth etic diet and their subsequent development and mortality responses were det ermined. For all instars the greatest change in mortality response occurred over lufenuron concentrations less than or equal to 3 ppm. However, third and fifth instars displayed an increase in mortality earlier than first ins tars, and were more sensitive to the lower lufenuron concentrations in this range. Only first and third instars subjected to less than or equal to 2.5 ppm lufenuron survived the 26-d exposure trial. No larvae first exposed to lufenuron as first or third instars survived to pupation if ingesting conc entrations of greater than or equal to 1 and greater than or equal to 3 ppm , respectively. Consumption of lower lufenuron concentrations by these larv ae delayed pupation and resulted in pupal deformity. In contrast, fifth ins tars subjected to 100 ppm were capable of surviving the 26-d trial period a nd displayed a slower progressive reduction in survival to pupation with in crease in lufenuron concentration. Also in contrast to more immature stages , fifth instars exposed to lufenuron developed more rapidly to pupation tha n larvae not exposed to the insect growth regulator (IGR), and all resultin g pupae were normal. Third instars were exposed to sublethal lufenuron conc entrations (0-3 ppm) for id and the fourth-instar survivors subjected to a controlled atmosphere cold storage treatment (2% O-2, 2% CO2, 0.6 degrees C ). Larvae ingesting diet containing 0.5 ppm (and to a lesser extent 1 ppm) lufenuron required longer exposure to the postharvest treatment to achieve greater than or equal to 95% mortality than larvae not ingesting the IGR. H owever, the analogous mortality response of larvae exposed to 3 ppm lufenur on was comparable to the control.