Parasitism of <i>Acrosternum arabicum</i> (Hemiptera: Pentatomidae) by the egg parasitoid, <i>Psix saccharicola</i> (Hymenoptera: Scelionidae) as a function of female age, host age, and host density

Acrosternum arabicum (Hemiptera: Pentatomidae) is a major pest of pistachio in Iran and successful nut production relies heavily on biological control via augmentation of its egg parasitoid, Psix saccharicola Mani (Hymenoptera: Scelionidae). We investigated the effects of parasitoid age, host egg age, and host egg density, on P. saccharicola parasitism success and progeny survival and life history. Parasitism rate was affected by parasitoid age (range: 1 to 16 d) and host egg density (range: 30 to 110); older females parasitized fewer eggs at higher egg densities and their progeny had lower survival, slower development, and reduced sex ratios (fewer daughters) compared with progeny of younger females. The negative effects of increasing host egg age (range: 1 to 4 d) were more pronounced for older parasitoids than younger ones, and included lower parasitism success, reduced progeny survival, and lower sex ratio. The results are discussed in the context of parasitoid biology and provide guidelines for optimization of parasitoid age and host egg age for P. saccharicola quality control in mass cultures.