Variability in the Development of Cereal Aphid Parasitoids and Hyperparasitoids in Oceanic Regions as a Response to Climate and Abundance of Hosts

Abstract

Experiments were conducted to understand how parasitoids and hyperparasitoids of cereal aphids in oceanic regions survive the periodic disappearance of their hosts. We recorded the number of parasitoids and hyperparasitoids emerging from mummies collected in summer on winter wheat and corn and in winter on cereal volunteers. In addition, we studied the duration of both summer and winter development of Aphidius rhopalosiphi De Stefani-Perez, the main parasitoid species of cereal aphids. In summer, interruption in development occurred in primary parasitoids which resulted in a longer development time (up to 4 m). These interruptions were fairly infrequent but they did ensure the survival of part of the population when there was a large decrease or disappearance of the aphid population. A longer duration of summer development also was recorded in a few hyperparasitoids. In winter, an important variability in the length of the development of primary parasitoids was noted which reflected their adaptive closeness to the aphid cycle. All hyperparasitoids studied here had long interruptions in their development and emerged only at the end of winter.