Geographical distribution and seasonal trend of parasitoids and hyperparasitoids of citrus aphids in the Iberian Peninsula

Abstract: Two species of aphids, the predominant species Aphis spiraecola and the secondary Aphis gossypii, are found at relevant levels on citrus crops of the Iberian Peninsula. The presence of primary parasitoids should minimize economic damage through the reduction of aphid populations, but their effectiveness is compromised by the action of hyperparasitoids. By weekly monitoring infested shoots and yellow sticky traps installed in 15 orchards distributed throughout the eastern citrus belt of continental Spain and two orchards in the Algarve (South Portugal), we carried out a program of identification and monitoring of the seasonal evolution of the aphids, parasitoids and hyperparasitoids between April and September in the years 2015 and 2016. A total of two species of aphid parasitoids (Binodoxys angelicae and Lysiphlebus testaceipes) and six of hyperparasitoids (Syrphophagus aphidivorus, Alloxysta sp., Dendrocerus, Asaphes suspensus, Asaphes vulgaris and Pachyneuron aphidis) were identified in the eastern citrus belt of continental Spain and south Portugal. Both parasitoids, Lysiphlebus testaceipes and Binodoxys angelicae, had similar abundance. The most abundant species of hyperparasitoids in eastern Spain were Alloxysta sp. and S. aphidivorus, and in south Portugal Alloxysta sp., Asaphes vulgaris and A. suspensus. All or most species are present in general at the local level, on each orchard sampled. Binodoxys angelicae shows the most irregular distribution among orchards, whereas Alloxysta sp. is the most regular. Comparing the two years sampled, the abundance of parasitoids was similar in 2015 and 2016, but hyperparasitoids were much more abundant in 2015 compared with 2016. This overall difference in hyperparasitoid abundance between the two years occurred for the six species of hyperparasitoids and in most orchards sampled. Observing the seasonal trend, all the three groups, aphid, parasitoids and hyperparasitoids, appeared almost simultaneously. At the species level, all of them reach their maximum population in similar periods except S. aphidivorus that appears later in time.