The effect of Agonoscena targionii (Licht.) (Homoptera: Psylloidea) on seed production by Pistacia terebinthus L.

This study investigated the potential negative effect that psyllids may have on the production of viable seeds in Pistacia terebinthus, a wild plant species with a circummediterranean distribution. Manipulative experiments, involving the application of insecticide, showed that the reduction in fruit maturation is rather low, not exceeding 10%. This is mainly due to other factors that determine seed inviability. Such factors include those intrinsic to the plant, such as parthenocarpy and seed abortion, and extrinsic to it, such as seed predation by chalcidoid wasps. There is much variation in the frequency of psyllids per plant; such variation appears uncorrelated with variables decribing plant size, fecundity, and distance to fruiting conspecifics. No consistency in the incidence of psyllids on a given individual plant was found between years.