Since herbivorous insects normally choose plants suitable for the nutrition of their offspring as sites for oviposition, insect eggs are the first stage of an actual attack of a plant by larvae. As such they are the first stage to induce defense responses of the plant. Defense induced by eggs has therefore been termed "early herbivore alert".
This PhD thesis focuses on the chemoecological analyses of interactions between pine, pine sawflies and parasitoids specialized on sawfly eggs laid on pine. The thesis is based on knowledge about the induction of defensive responses in Pinus sylvestris by egg deposition of the pine sawfly Diprion pini. Egg-induced pine releases odor attracting the egg parasitoid Closterocerus ruforum. The egg-induced pine odor is known to be characterized by enhanced quantities of the sesquiterpene (E)-β-farnesene.