“…If oils, such as paraffin (Bradley, 1963) or the mineral oil, albolineum (Asjes, 1974(Asjes, , 1975, are sprayed on to the leaf surfaces of plants, aphid transmission of viruses may be prevented. Oil sprays have been effective in controlling the spread of a number of non-persistently transmitted viruses (Loebenstein et at., 1970;Mowat and Woodford, 1976;Vanderveken, 1977), but their effect against persistent viruses has been variable.…”