Semiochemicals associated to spacing behaviour of the bird cherry-oat aphid Rhopalosiphum padi L. (Hem., Aphididae) do not affect the olfactometric behaviour of the cereal aphid parasitoid Aphidius rhopalosiphi De Stephani-Perez (Hym., Braconidae)

Volatiles produced by the interaction of Rhopalosiphum padi and wheat, and semiochemicals which elicit the spacing behaviour of R. padi on wheat and o at, were evaluated in an olfactometer against the cereal aphid parasitoid A phidius rhopalosiphi. The parasitoid was attracted by volatiles produced by the R. padi-wheat interaction at high density of aphids, but not by the R. padi-wheat interaction at low density. Compounds produced by the interacti on of wheat or oat that was infested with a high density of aphids (approxi mately 9 aphids/cm(2)), 6-methyl-5-hepten-2-one (MHO), 6-methyl-5-hepten-2- ol (MHOH), 2-tridecanone (2-T), and methyl salicylate (MS), neither attract ed nor repelled A. rhopalosiphi as pure compounds or in the naturally occur ring mixture. The results are discussed in terms of the use of semiochemica ls and parasitoids in the integrated management of aphid pests.