This is, undoubtedly, the greatest enemy known to the apple-tree. They seem to destroy the tree by attacking the roots under ground, and not the tree above ground, as is supposed by many. As far as my observation goes, they are perfectly harmless as long as they confine themselves above ground to the body and branches of the tree; or, at least, out of hundreds of trees that I have examined that showed signs of injury from these insects, not a single one but had the aphis in abundance among the roots.

After experimenting with various substances, in search of a remedy, without success, I tried pulverized charcoal (the kind used was the cinders from the pipes of the common locomotive), with complete success. This remedy, though slow in its action, is certain. It was applied by removing the earth from the roots around the body of the tree, then freely applying the charcoal. No danger need be apprehended of applying too much, as it is entirely harmless to the tree, yet so offensive to all kinds of insects, or even animalcules, that they cannot live long in, or even very near it. Charcoal, being an indestructible material, continues to act for an indefinite time, thereby becoming a preventive as well as a remedy.

Again: It not only acts as an absorbent, retaining the volatile gases (valuable food for plants that would otherwise be lost), but makes one of the very best substances ever used for mulching, as it is, for reasons given above, entirely free from the objections that obtain to ordinary substances used for that purpose, which afford a kind of harbor or protection for different kinds of insects that finally attack the tree. This remedy has been only tried on the apple-tree. It is very probable that it would protect the roots of this kind of fruit from the various insects with which they are infested.