This section is from the book "Commercial Gardening Vol3", by John Weathers (the Editor). Also available from Amazon: Commercial Gardening, A Practical & Scientific Treatise For Market Gardeners.
This Aphis forms a mealy mass under the Plum leaves but does not curl thern up. This Mealy Aphis appears on the Plums in June and July. It comes from rushes and reeds, being the same as Hyalopterus arundinis, which feeds on those plants. They form much honey dew, which falls on the fruit and which becomes covered with the black soot fungus, and so ruins the fruit for market. In early autumn this Aphis flies back to the rushes and reeds.
It cannot be killed with soft soap and .quassia nor paraffin emulsion, but if 1 lb. of liver of sulphur is added to every 100 gal. of the paraffin emulsion they are easily destroyed.