Field experiments on potato aphids and virus spread in South Wales 1966/9

In 1966-9 the spread of leaf roll and severe mosaic (Virus Y) was investigated in seed and ware areas in South Wales. The use of disulfoton granules at planting time greatly reduced the spread of leaf-roll virus in both areas but had less effect on the spread of severe mosaic. Foliar sprays with formothion did not reduce the spread of either virus. Practical considerations are briefly discussed.