Host discrimination by the endoparasitoidPsyllaephagus pistaciae(Hymenoptera: Encyrtidae): A case of time-dependent ability

Host-discrimination behavior by the koinobiont parasitoid, Psyllaephagus pistaciae Ferrière (Hymenoptera: Encyrtidae), the major biocontrol agent of the common pistachio psylla, Agonoscena pistaciae Burckhardt & Lauterer (Hemiptera: Psyllidae), in Iran, was investigated in the laboratory. The results demonstrated that P. pistaciae quickly detected and avoided freshly parasitized hosts, either after antennating or by probing with their ovipositor. However, this discriminatory ability declined with time, probably influenced by both external and internal markers left by the previous ovipositing female. The results also confirmed that female P. pistaciae responded to changes in host quality associated with the parasitoid's larval development 4 days after the initial parasitization, clearly indicating that the second female could detect the presence of the larvae and adjust her host-selection decision. In addition, psyllid nymphs treated topically with a solution of Dufour's gland were rejected by the parasitoid, showing that Dufour's gland secretion had a significant effect as a host marking chemical. The current study also showed that superparasitism increased the host-mortality and that the rate of encapsulation decreased, suggesting that, when two eggs are laid in the same psyllid nymph, only one parasitoid develops to an adult.