Can delayed flight activity serve as an indicator for insecticide resistance?

Abstract: Together with the codling moth, Cydia pomonella, the summer fruit tortrix moth, Adoxophyes orana, is a major pest insect in apple orchards of western Switzerland. Whereas codling moth developed simple, cross and multiple resistances to various classes of insecticides over the last decade, A. orana seemed to be still susceptible to these pesticides. However, since 2004, fruit growers indicate more and more failures of conventional control schemes against summer fruit tortrix moths. Using laboratory bioassays we established that A. orana shows resistance to insect growth regulators and to insect growth inhibitors. This resistance becomes manifest in the slower development of A. orana larvae. Field observations showed that the flight of resistant moth populations is delayed. Delayed flight activity might therefore serve as a reliable indicator of insecticide resistance in summer fruit tortrix moths. In conclusion, the key to successfully managing insecticide resistance is to reduce selection pressure. This can be achieved by incorporating cultural, biological and pheromonal control practices, by minimising the use of insecticides and by the alternate use of insecticides with different modes of action.