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Effect of an ecdysteroid agonist, tebufenozide, on the completion of diapause in susceptible and resistant strains of the codling moth, Cydia pomonella
- Sauphanor, B., Bouvier, J.C., Brosse, V.
- Entomologia experimentalis et applicata 1999 v.90 no.2 pp. 157-165
- Cydia pomonella, tebufenozide, ecdysteroids, agonists, larvae, diapause, molting, metamorphosis, dose response, toxicity, diflubenzuron, deltamethrin, insecticide resistance, insect control, pupation
- Codling moth Cydia pomonella (L.) (Lepidoptera, Tortricidae) larvae kept under a short photoperiod enter a diapause which can be broken by exposure to 25 degrees C following an extended chilling period. We investigated the effects of the ecdysteroid agonist tebufenozide on the diapause of this species, both on a laboratory strain susceptible to insecticides and two strains selected for resistance to diflubenzuron or deltamethrin. The treatment induced moulting by breaking diapause of the susceptible strain when applied at the end of the growth period, or by reducing the pre-emergence period when applied after chilling. The strains exhibiting resistance in the neonate instar were also resistant to the ecdysteroid agonist applied to diapausing larvae, indicating that mechanisms of resistance remained active during this arrest of development. High doses of tebufenozide were lethal for the most resistant insects, but neither reduced the pupation delay nor produced the larval-pupal moults which occur in the susceptible strain. As diapausing larvae of C. pomonella can be easily collected, the expression of resistance to tebufenozide both in the target instar, i.e. neonates, and during diapause may contribute to early detection of resistance to this insecticide in field populations.