Influence of Methoprene, Low Temperature, and Starvation on the Incidence of Diapause in the Codling Moth (Lepidoptera: Tortricidae: Olethreutinae)

Abstract

Short-day (SD) photoperiods are the primary stimuli for diapause induction in the codling moth. Larvae held through the penultimate stadium under long-day (LD), 25°C conditions are committed to pupate; however, starvation, methoprene treatment, or exposure to cooler temperatures, concurrent with transfer to SD photoperiods during the final instar, cause the population to reprogram and enter diapause. Reprogramming depends upon an extension of the last stadium, a delayed gain of the maximal larval weight, and exposure to approximately 25 SD photoperiods. Exposure to high temperature (30°C) nullifies the diapause-inducing effect of SD photoperiods. Rapid larval development does not allow exposure to enough SD photoperiods to program for diapause. Low temperatures alone do not override LD photoperiods, but some last instars treated with methoprene and transferred to 15°C entered a 6-month diapause regardless of photoperiod.