| Summary: | The probing behavior of Myzus persicae (Sulz.) was examined on the ornamental plant Aurinia saxatilis (L.) Desv. that has not been known as a host of M. persicaein nature, and compared to the behavior on cultivated plants of the genus brassica, B. rapa L. ssp. pekinensis L. and B . oleracea var. gongyloides, that are known hosts to this aphid. The purpose was to determine whether A. saxatilis can be exploited by M. persicaethus providing a potential refuge for the aphid population. The EPG (Elelctrical Penetration Graph) study demonstrated that on A. saxatilis, M. persicae showed mainly non-probing activities that occupied 70% of experimental time. The remaining time, which was probing, consisted mainly of pathway activities divided into numerous short probes not reaching beyond 1–2 cell layers and very few aphids reached phloem vessels. None aphid was able to ingest sap in a sustained way. In contrast, on bBassica plants, the probing of M. persicaewas rarely interrupted, all aphids reached sieve elements elements and ingested sap for long and uninterrupted periods. It is postulated that high content of glucosinolates in the outer tissues of A. saxatilis leaves may be responsible for the termination of M. persicae probing at the very early stage, thus preventing the contact with vascular elements and the ingestion of phloem sap. In consequence, A. saxatilisis rejected as a host plant by M. persicae.
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