It is assumed that this pest has cost agriculturists many millions of dollars during the past decade; not only in the loss of trees, but the time—as it seldom appears until after the first crop—consequently the land, manure, labor, enclosure, and taxes are not insignificant items. Climate, soil, and cultivation have utterly failed, so also the nostrums, such as "carbonate of lime" suggested by the best authority, and the experts now admit that parasites (such as cause the rust or smut in our cereals) are the cause of this mischief. The only question is whether they act directly or indirectly: this question determines whether it is remediable. If these parasites accomplish all this mischief by direct contact, as in the case of rust, their ubiquitous character is so demonstrated that we are utterly discouraged; whereas, if we prove that their indirect action is the only one that is to be dreaded, and that indirect action is remediable we are encouraged to cultivate the pear, though we have lost more than five hundred of one variety and almost all of the other varieties before we discovered the real cause of the failure. "Where you lose you may find;" success does not indicate merit, and "fools never learn by experience." As a celebrated surgeon said in his lecture. "A good oculist is made at the expense of a hatful of eyes."
The celebrated Johnson who wrote the Encyclopedia of Agriculture a few years since, is now regarded as an old fogy, because he assumed that the spores of smut travel from the manure and seed of the previous crop in the circulation of the plant to the capsule, and thus convert the grain into a puff-ball, so also the ears of corn, the oats, and rye. This monstrosity on the rye grains is called ergot, or spurred rye, and when it is eaten by chickens or other fowls their feet and legs shrivel or perish with dry gangrene, not because the spores of the fungus which produced the spurred rye circulate in the blood of the chicken, nor that the spawn or mycelium thus traverses the fowl, but the peculiar and specific influence acts upon the whole animal precisely like the poison of the poison oak, producing its specific effect on the most remote parts of the system, and not as mustard confined to the part it touches. The mustard acts directly, but the "poison Ivy" acts indirectly; so also the virus of cow-pox poisons the whole system, but usually appears in but one spot unless the lymphatics of the whole arm are weak, and in that case crops of umbilicated pustules precisely like the original, may recur on all parts of the arm for several months. The specific effect of ergot or the fungus when indirect is manifested by contracting and even strangulating the tubes or capillaries causing them to pucker up (as a persimmon acts directly on the mouth), but in this case permanently though indirectly, so that rye bread sometimes causes dry gangrene in the human subject; the shins and feet shrivel precisely as those parts of the limbs of the pear do, moreover a dark fluid exudes (as the circulation is arrested where a patch occurs) in both cases alike, consequently if the remedy in both cases is based on the same principles, and is demonstrated to be equally effectual, the cause and the disease are similar.
I have seen dry gangrene in the human subject originate apparently from an old "frost bite;" which means merely chronic debility of the capillaries of the foot or shin. Thus the extremities of the pear, or the weakest part, always succumb first, and the most vigorous trees never manifest it until they are weakened by their first crop of fruit. All are familiar with the fact that an old frost bite will swell or succumb to a temperature which will be innocuous to any other part of the body. The microscope may invariably reveal fungi in the patch of pear blight precisely as the housewife discovers the mold plant in her preserves and canned fruit, and even in the eggs of fowls, the mycelium (or spawn) penetrating the fruit or preserve though it be covered while boiling hot. If so, the reason why all parts of the tree are not attacked at the same time, is not because the fungus is not ubiquitous. We first notice the action of strychnia in the legs, or in paralyzed limbs exclusively, because they are weaker and become subject to its influence more easily; so also the same tree may escape for a long time after the limb which has succumbed is removed. Moreover the grafts, however numerous, may all be blighted, but the standard seedling on which so many varieties were grafted has survived more than fifty winters, and it fruited last year.
David Stewart, M. D.
Port Penn, Del.
Treatment of Tree Wounds.
Valuable trees that have been wounded or mutilated are often sacrificed for lack of the discreet surgery which would repair the injury they have suffered; and Professor C. A. Sargent, of the Bussey Institution, has done good service to farmers, fruit-raisers, and landscape-gardeners, by translating from the French the following practical hints, which we give with slight abridgment:
Bark once injured or loosened can never attach itself again to the trunk; and whenever wounds, abrasures, or sections of loose bark exist on the trunk of a tree, the damaged part should be cut away cleanly, as far as the injury extends. Careful persons have been known to nail to a tree a piece of loosened bark, in hope of inducing it to grow again, or at least of retaining on the young wood its natural covering. Unfortunately the result produced by this operation is exactly opposite to that intended. The decaying wood and bark attract thousands of insects, which find here safe shelter and abundant food, and, increasing rapidly, hasten the death of the tree. In such cases, instead of refastening the loosened bark to the tree, it should be entirely cut away, care being taken to give the cut a regular outline, especially on the lower side; for if a portion of the bark, even if adhering to the wood, is left without direct communication with the leaves, it must die and decay. A coating of coal-tar should be applied to such wounds.
Loosened Bark.—It is necessary to frequently examine the lower portions of the trunk, especially of trees beginning to grow old; for here is often found the cause of death in many trees, in large sheets of bark entirely separated from the trunk. This condition of things, which often can not be detected, except by the hollow sound produced by striking the trunk with the back of the iron pruning-knife, arrests the circulation of sap, while the cavity between the bark and the wood furnishes a safe retreat for a multitude of insects, which hasten the destruction of the tree. The dead bark should be entirely removed, even should it be necessary, in so doing, to make large wounds. Cases of this nature require the treatment recommended for the last class.
Cavities in the Trunk.—Very often, when a tree has been long neglected, the trunk is seriously injured by cavities caused by the decay of dead or broken branches. It is not claimed that pruning can remove defects of this nature; it can with proper application, however, arrest the progress of the evil. The edge of the cavity should be cut smooth and even; and all decomposed matter, or growth of new bark formed in the interior, should be carefully removed. A coating of coal-tar should be applied to the surface of the cavity, and the mouth plugged with a piece of well-seasoned oak securely driven into the place. The end of the plug should then be carefully pared smooth and covered with coal-tar, precisely as if the stump of a branch were under treatment. If the cavity is too large to be closed in this manner, a piece of thoroughly seasoned oak board, carefully fitted to it, may be securely nailed into the opening, and then covered with coal-tar. It is often advisable to guard against the attacks of insects by nailing a piece of zinc or other metal over the board in such a way that the growth of the new wood will in time completely cover it.