American Pomology. Apples

by J. A. Warder

"2d. That Black-knot is a gall.—As already stated, there is no true gall-making insect that inhabits the Black-knot, so far as I can discover on the fullest and most extensive investigation that I have been able to give to the subject. The minute holes commonly found in the old dry Black-knot, which are too large either for the 'Curculio' or for the small moths bred by myself from Black-knot, are of a suitable size for either of the two dipterous' insects which I have enumerated in a note as bred by myself from Black-knot. Consequently the argument which I based upon the existence of these minute holes (Proc. Ent. Soc. Phil. III, p. 614) falls to the ground; and although I found on one occasion the larva of a Gall-gnat embedded in a cell in a Black-knot, yet this was most probably that of the Guest Gall-gnat which I actually bred from Black-knot, as stated in the note, and not of a true gall-making Gall-gnat.

"3d. That Black knot is a fungus.—Just as Dr. Fitch, having proved to his own satisfaction that Black-knot is neither a gall nor a fungus, infers by the method of exhaustion that it must be a disease; so, having proved that it is neither a disease nor a gall, we may infer by the method of exhaustion that it must be a fungus, or rather an assemblage of funguses. In confirmation of this theory may be adduced the very remarkable analogies between the structure of the Black-knot and that of the fungus, described above as occurring on Red Cedar. That this last is really and truly a fungus and not a gall, is shown by the fact, that it is scarcely ever inhabited by insects; for out of hundreds of specimens that I have cut into, both green and dry, not more than two or three contained the larvæ of the moths, but one contained what was probably the larva of an Ichneumon-fly, and all the rest were perfectly solid and unbored. On the other hand, Black-knot is so infested by insects, that it is almost impossible to find a mature specimen that is not all bored up by them. The cause of this remarkable difference may be attributed to the well-known repugnance of almost all kinds of insects for Red Cedar.

"If, then, Black-knot is a fungus, and if, as I think I have shown, it is an annual plant propagating itself by seed or the so-called 'spores,' and the 'spores' make their appearance about the end of July in latitude 41° 30', then it must be obvious that if all the Black-knot on a particular tree is cut off and destroyed in the fore-part of July, or a little earlier or later as you go further south or further north, an effectual stop will be put to its further propagation. It is true that the 'spores' are in the form of an impalpable powder, so that they may be carried some considerable distance from other infected trees by the wind; and it may possibly be further true, that certain 'spores' may lie dormant in the bark for over a year, as the seeds of weeds will often lie dormant in the ground. Still, with all these possible drawbacks, I have little doubt that the above remedy will, as a general rule, if applied according to directions, be found effectual."

The foregoing is interesting as giving the conclusions of an entomologist who had investigated the subject, and arrived at the same result that had been reached by a botanist many years before. Schweinitz, in 1832, published the correct history of the Black-knot in the Transactions of the American Philosophical Society. In the American Agriculturist, April, 1863, p. 113, Mr. C.F. Austin confirmed Schweinitz's observations, and gave a popular account of the botany of this fungus, with figures. It may be considered as fully established that the knot is of vegetable origin; and whenever insects or larvæ are found in it, it is only because they find a diseased portion of the tree suited to their necessities.

Rot and Mildew upon the grape both destroy our crops, and render the vines unhealthy. Would that I were able to give the reader some encouragement as to its cause and prevention, or cure; but some of our oldest and most experienced vine-planters have come to the conclusion, as to treatment, that "the more they find out, the more they don't know." It is now generally conceded that it is caused by a fungus growth. That on the leaves is probably the Oidium Tuckeri, and it is generally supposed that the mildew and rot of the berries is owing to the same cause. The microscope clearly indicates its fungoid character. As to the causes, it must be admitted that the weather favors or prevents its access, and that so far it is a proximate cause, but that the spores are the true origin of the trouble. The Cincinnati Horticultural Society, whose members have long had opportunities of studying this malady, have come to the following conclusions, which, it will be seen, are not very satisfactory.

To the Cincinnati Horticultural Society:—We have been appointed by you to discharge a certain function. Having examined the premises and considered the subject, we do now report: That, notwithstanding the discouragements attendant upon the experience of most vine-dressers during the past season, we are determined to persevere in viticulture, for the following among other reasons:

We have our capital invested in a way which has been profitable, and we believe will be so again.

Our lands are occupied with a growth that has required time and labor to produce, and which we are unwilling to sacrifice.

We do not believe that the diseases to which the vines and fruit have been subjected, are dependent upon long pruning or short pruning, upon deep culture or shallow, nor any of the causes to which it has been attributed, that are under the immediate control of man, but that the cause is CLIMATIC.

We do not believe that the rot and mildew can be warded off by leaving the wood upon the vines, nor that the usual vineyard method called short pruning, will render our vineyards more subject to this disease.