This section is from "The Horticulturist, And Journal Of Rural Art And Rural Taste", by P. Barry, A. J. Downing, J. Jay Smith, Peter B. Mead, F. W. Woodward, Henry T. Williams. Also available from Amazon: Horticulturist and Journal of Rural Art and Rural Taste.
It is commonly believed that insects eat through the bark of healthy trees, and then enter the wood itself. I have already stated that this is not my belief. The workings of boring insects would not shorten the life of a tree, by consuming a portion of the wood, provided there were enough of wood left to ensure the tree against the formidable assaults of the wintry blast. And, as for the bark; if the tree were healthy, every hole which the insect had made through it would be repaired in due time by the fostering hand of nature.
During the proper season for increase of new wood, it is invariably formed at the periphery; and it steadily rolls on over the old wood already made. Insects do not possess the power of raising up the bark from the wood. The borers merely perforate it. When we discover different insects lurking between the bark and the wood, we must not accuse them of mischief; but we must attribute the separation of the two component parts of a tree either to some injury from without, or to disease from within. The insects assemble there merely for safety and comfort.
Bark once separated from the wood, which it has covered, will never more adhere to it. The disaster which the separation has made evident can only be repaired by new bark; and this new bark will appear exactly at the place where the effect from the accident has ceased, or where the internal disease has worn itself out. No actual renovation of wood ever takes place after the wood itself has once been formed. Holes made in it will always be holes; and they will retain their original shape and size, so long as the tree itself exists.
Now, if you take a butcher's knife, and cut your way deeply into the bowels of an animal, (an ox, to wit,) the animal in a minute or two will be as dead as Julius Caesar. Not so with a tree. You may use your axe, and hew out two-thirds of the bole of a tree, without destroying its vital powers. In the course of time Dame Nature from without, by her admirable process at the periphery, will assist the tree in its need, and eventually will heal the gaping wound.
So that I am never much alarmed, or down in the mouth, at huge limbs being torn from the trees by the raging winds. Their loss of limbs is undoubtedly very great in some cases, and gives an unsightly appearance to the trees. Still these trees will live on, be the extent of the accident what it may. I am speaking of healthy trees only.
But when I examine a magnificent tree, with round holes made by the insect through its bark, oh, dear me! I shake my head in sorrow - my very heart misgives me, and I exclaim, "Grand ornament of our groves and lawns, it is nearly over with thee. Thy ' days are dwindled to the shortest span.1 Some dire disease must have tainted thy once healthy juices, long before the Scolytus applied for a residence within thee. Should the wants of the oven-man not demand thee for the present, thou mayest yet remain erect for some time to come. But, of this be certain - that, although thou hadst no attractions for the boring-insect in thy day of health, believe me, now that thou art sick and feeble, he is sure to pounce upon thee; and he will ultimately bring thee to the dust in useless ruins; and that, too, at the very time when all the neighboring trees are vigorous around thee - setting thy keen devourer at defiance".
I invite the anxious reader to pay attention to any tree at which the Scolytus is pursuing his ordinary calling. Then, let him examine the same tree during the following summer, and he will find the little round holes in the bark, just as the insect had made them, without any alteration whatever. After this, let him take a gimlet, and bore as many dozens of holes as he may think fit in the sound bark of some undeniably healthy trees. Let him visit these in the course of the next summer, and he will perceive every gimlet hole made up, by new bark underneath the old bark.
This being the case, I trust it would tend to convince him that, while the Scolytus singles out some sickly tree wherein to form a lodgment for his wife and children, he knowingly neglects a healthy one. - Charles Waterton, Walton Hall.