Labelling of Aphid Saliva with Rubidium-86

THE amount of saliva injected into the host plant by an aphid is of considerable interest to plant pathologists. While it has long been known that aphids produce a discrete salivary sheath when penetrating the leaf, it is not known whether the production of saliva is continuous during feeding or whether it ceases once the phloem tissue has been reached. The autoradiographs of Kloft 1 show that some movement of radioactive saliva of Myzus ascalonicus Donc. into the leaf tissue occurs around feeding sites. The experiments reported here indicate that saliva production in Aphis fabae (Scop.) continues for at least 6 h at a constant rate after feeding commences, contrary to the findings of Kloft 1 with phosphorus-32 and M. ascalonicus .