Sooty Mould, the unsightly black stuff which often covers the foliage, is a parasitic fungus not upon the leaf itself but upon the "honey dew" deposited by Green Fly. If therefore the honey dew is kept off by destroying the Aphides which secrete it, Sooty Mould will not appear.
Insect Pests.
Green Fly, or Rose Aphis, is alas! too well known in every garden to need much description. But the reason why it is so difficult sometimes to get rid of this pest is not so commonly known. The Aphides breathe through pores at the sides of their bodies. And in order to kill them, some substance must be used which will close these pores. Therefore syringing with water or any clear liquid is absolutely useless; for if a few Green Fly are knocked off one shoot they will only settle on some other. We often hear people say after a thunderstorm, "This will clean the roses and wash off the Green Fly nicely." Far from it. They only increase the faster; while the caterpillars rejoice, and flaunt themselves openly on every bush. Then in despair some one uses paraffin or some violently caustic wash for spraying the Green Fly, and destroys his roses thereby.
Nature has mercifully provided some enemies to prey on the Green Fly—and these help in some small degree to keep the pest down. The chief of these is the Ladybird, which both in its adult and in its larval state devours them ceaselessly. The pretty green Lace-wing Fly or Aphis Lion is also useful, as its larvæ are provided with "large sickle-shaped jaws for picking the Green Fly off the plants."
The Hover Fly—which looks like a small, slim two-winged bee or wasp—lays its eggs in the thick of a mass of Green Fly, and its green and grey leech-like maggots feed upon them. And the Ichneumon and Chalcid Flies lay their eggs in the bodies of the Aphides and their maggots feed on them from within.
But all these are of comparatively little help to the unhappy rosarian, who must therefore devise unnatural means to clear his plants.
As far as I know, with the exception of an Aphis brush—a useful invention, but one which needs very gentle handling—there are only two safe remedies for this universal plague. The usual one is a wash of soft-soap and quassia, in these proportions—
| Best soft-soap | 1 lb. |
| Quassia chips | 2½ lb. |
| Water | 25 gallons. |
Even this wash, excellent as it is, will sometimes fail to get rid of the scourge in a bad year. But I have found "Abol, White's Superior," a never-failing remedy. It is also much easier to use, as one only has to mix it with cold water according to the directions on each can, and it is ready in a minute.
If either of these remedies are used the moment the Green Fly appears, and the dose repeated a couple of days later in order to kill any that may have escaped the first spraying, we have very little more trouble until the second crop of Green Fly appears in September. It is well to syringe the plants thoroughly with pure water a few days after the second dose of either of these washes, as this knocks off the dead Aphides, and leaves the foliage clean and sweet.