Presence of less-preferred hosts of the aphid parasitoids Aphidius ervi and Praon volucre reduces parasitism efficiency Muhammad Mubashir Saeed & Abu Bakar Muhammad Raza & Muhammad Afzal & Anjum Aqueel & Muhammad Farooq & Thierry Hance Received: 16 January 2017 /Accepted: 2 January 2018 # Springer Science+Business Media B.V., part of Springer Nature 2018 Abstract Parasitoids are characterized by a defined range of hosts, either more specialist or generalist. Un- der natural conditions, females may encounter different host species on the same plant or in the same location. In this case, their preference for one host could influence their choice. However, the presence of less suitable hosts may also affect their choice and, in some cases, may reduce their interest in a patch where both preferred and less preferred hosts are available. The aim of the present study was to test the consequences of the simul- taneous presence of three cereal aphids (Sitobion avenae Fabricius, Metopolophium dirhodum Walker, and Rhopalosiphum padi Linnaeus) on the parasitism by two of their parasitoids, Aphidius ervi Haliday and Praon volucre Haliday. Firstly, in the no-choice exper- iment, A. ervi parasitized on S. avenae at a significantly higher rate as compared to M. dirhodum, whereas no parasitism on R. padi was observed. P. volucre parasit- ized the three species of cereal aphids with a significant preference for S. avenae. Interestingly, when two or three host species were offered simultaneously in the same quantity to pairs of parasitoids, the level of para- sitism was less than that observed for one host species alone. This observation exhibits a distractive effect on non-host species, from the defense mechanism of a non- suitable host or from the perception of bad quality patches. These results raise the question of the practical application of inundative release of parasitoids for bio- control when several hosts are available simultaneously. Keywords Host preference . Parasitic potential . Host specialist . Host generalist . Apparent mutualism and distraction effect Introduction Parasitoids are the insects that develop on or in a single host and kill or paralyze it at the time of oviposition (idiobiont) or during its development (koinobiont) (Eggleton and Gaston 1990; Godfray 1994). They seem to have restricted host ranges (Memmott et al. 2000) and their specialization range may vary from a single host to all potential hosts of a particular habitat (Stilmant et al. 2008). The number of potential species and their taxo- nomic diversity define parasitoid host specificity (Futuyma and Moreno 1988). Host ranges of parasitoid in insects raise the question of competition, including apparent competition or coexistence between parasit- oids (Hawkins and Sheehan 1994; Langer and Hance 2004; Stireman 2005), how parasitoid communities are functioning and have evolved (Shaw 1994; Stireman and Singer 2003a, b; Van Driesche 2004), and the ways Phytoparasitica https://doi.org/10.1007/s12600-018-0637-y M. M. Saeed (*) : A. B. M. Raza : M. Afzal : A. Aqueel Department of Entomology, University College of Agriculture, University of Sargodha, Sargodha, Pakistan e-mail: mubashir1443@gmail.com M. M. Saeed : T. Hance Earth and Life Institute, Biodiversity Research Centre, Université Catholique de Louvain, Louvain-la-Neuve, Belgium M. Farooq Cotton Research Station, Ayub Agricultural Research Institute, Faisalabad, Pakistan