SOME WAYS IN WHICH A PARAFFIN OIL IMPEDES APHID TRANSMISSION OF POTATO VIRUS Y

In laboratory tests with a light white paraffin oil, transmission of potato virus Y by viruliferous adults of Myzus persicae (Sulz.) was impeded by (a) allowing aphids to probe on a leaf coated with oil, (b) manually touching the end of the labium to an oil-coated leaf, or (c) inserting the bare stylets directly into the oil. The first two of these but not the third also impeded for some minutes the uptake and transmission of virus Y by nonviruliferous aphids. Oil sprayed on plants kept in the laboratory continued to cause these effects for some weeks. If infected plants, used as virus sources for aphids, were coated with oil, transmission from them was impeded. It is still not clear why oil impedes transmission. But the results give good reasons to believe that oil can be used in the field to prevent spread of certain aphid-borne viruses.