Bidirectional movement of aphid parasitoids (Braconidae: Aphidiinae) between crops and non-crop plants in agroecosystems of central Argentina

Abstract

The movement of predators and parasitoidsbetween natural and cultivated habitats is a common processin agroecosystems, which may be afected by diferentbiotic and abiotic factors, mostly related to the availabilityof resources. Here, through a broad approach, we aimedto obtain an overview of factors afecting the bidirectional movement of aphid parasitoids (Braconidae: Aphidiinae)across cultivated habitats and their natural vegetated borders.Using bidirectional fight traps, we measured the numberof parasitoids moving from borders to crops and viceversa, in felds of three common crop species (alfalfa, oatand wheat) in the Pampean region, Santa Fe, Argentina. Theefects of the abundance of aphid prey, abundance and richnessof fowers in both habitats, as well as temperature andwind speed on parasitoid movement, were assessed throughgeneralized mixed models, considering sampling date andfeld as random factors. The relationship between parasitismpercentages and parasitoid movement from the bordersto the crops was explored separately for three pest aphidspecies: Aphis craccivora Koch, Rhopalosiphum padi (L.)and Schizaphis graminum (Rondani). Overall, we found aprevalence of parasitoids moving in the border-crop direction,mainly in wheat and alfalfa crops. Aphid abundancein the arrival habitat afected parasitoid movement in bothdirections. A link between parasitoid movement and parasitismpercentages was observed for the aphid species S.graminum in wheat, suggesting a benefcial role of naturalvegetation in pest control.