PROTECTION OF WOUNDS IN NUT TREES
I have been asked to discuss briefly the handling of wood decay in top-worked nut trees. I am not sure that I know very much about the latest methods employed in this type of work. Personally I have had no practical experience with it. I understand, however, that nut trees are top-worked by cutting off limbs and inserting one or more scions. I am informed that limbs as large as six inches or more in diameter have been cut for this purpose, particularly on pecan trees in the South, and that decay has started at the top of these stubs after the scions have become established, resulting in a pocket of decay. I assume that it is about such places as these that you want me to say something. Such conditions, whatever their origin, call for straight tree surgery methods. My work on tree surgery has been almost entirely with shade trees and chestnuts, and only to a very limited extent on other nut trees.
The general methods of handling decay are essentially the same on all trees, as also are the fundamental principles underlying the same, whether on nut or shade trees. I must admit I do not know just what methods are being employed by nut growers at the present time to counteract such decay in top-worked trees, so my suggestions may include nothing with which you are unfamiliar. Again, they may include some methods that you have already tried and found wanting so far as nut trees are concerned.
As a prevention of decay my suggestions, based on my own shade tree experience, would be:
(1) Avoid cutting large limbs when smaller ones are available and will serve the purpose just as well or better.
(2) Keep the scars thoroughly and continuously covered with some good waterproof and antiseptic material so as to prevent infection of any part of the cut surfaces.
(3) Always make the cut somewhat slanting so that rain water will readily run off, and insert the scions preferably at the upper extremity of the cut. Such an oblique cut normally heals quicker and better on shade trees than a transverse cut, particularly if a vigorous young sprout is left at the peak of the cut. I am quite certain the same statement will hold true with scions of nut trees placed at the peak of the oblique cut.
After decay has started, I would suggest—
(1) Cut out all the decayed woody matter, preferably from one side, so that a free and easy drainage of the wound may result. If necessary, when several scions have been placed around the stub, sacrifice one of the grafts and make a rather long oblique cut or groove from which all decayed matter has been removed. Use shellac, liquid grafting wax or melted paraffine over the cut bark, cambium and adjoining sapwood immediately after the final cut is made.
(2) Cover the entire wound with some good preparation to keep out disease germs and water. Preferably use for a covering such materials as will be more or less permanent and which have been found by practical experience to be least injurious and most effective on the particular nut tree that you are treating.
(3) Keep the wound thoroughly painted or covered at all times until it is completely sealed over by a new growth of callus.
(4) If the top-working was originally done in such a manner that the removal of all the decay results in a cavity that cannot be properly drained, it is advisable to fill the cavity with some waterproofing and antiseptic material in order to prevent it holding water and also to assist the cambium in covering the wound. The cavity must first be treated in accordance with approved tree surgery practices. In shade tree work, quite a variety of substances have been used to fill cavities with more or less success; e. g., wood blocks and strips, asphalt and sawdust, asphalt and sand, clear coal tar, clear asphalt, elastic cement, magnesian cement, Roman (or Portland) cement, etc. Of these only two—wooden blocks and Portland cement, have been in general use more than a few years. Blocks of wood were used in France to fill cavities more than 60 years ago, and in this country to some extent about 50 years ago. Later, Portland cement was used in preference to wood for fillings, probably mainly because it was more easily handled. To us of the present generation, Portland cement in combination with sand is the one material that seems to have been in general use sufficiently long to allow us to draw any seemingly reliable conclusion as to its real merits.
For the personal use of the average orchardist, Portland cement is one of the last in the list mentioned above that I would recommend. According to a few reports that have reached me, wooden blocks and tar proved to be fairly satisfactory half a century ago, and strips of wood embedded in some flexible and antiseptic material, are proving very satisfactory today. An excellent preparation to use between the strips of wood, containing asphalt and asbestos, can be readily bought on the market, and it has the advantage of being mixed ready for use. For cavities with horizontal openings that will hold semi-fluid substances, clear asphalt or gas-house (coal) tar may answer all purposes. For cavities with oblique or vertical openings, or for those on the underside of a limb, probably some of the magnesian cements, which readily adhere to wood, will be found more satisfactory when properly mixed and applied.
Although I have said more about filling cavities than of other phases of the work, I do not wish the impression to go forth that I recommend such work except as a last resort, so to speak. The one thing that I do most emphatically recommend above all others is the prevention of decay so far as possible by practices that are less likely to allow decay-producing organisms to gain entrance in the first place, or at any other time.
THE PRESIDENT: Does anyone care to discuss this paper?
MR. KAINS: Mr. President: During the last five years, I have planted several hundred nut trees, including the English walnut, black walnut, the heartnut, pecan (northern ones) and some hybrid hickories. I have noticed that in this nursery stock there has been a good deal of dying-out of the original stock where the trees had been grafted, and where the scion had not covered over. In some of those cases decay has set in, and the trees have died before they could be attended to or have been broken down by the wind. The point is, I think it a mistake for nurserymen to use as large stocks as they have been using in many of these cases, because the stump of the stock is too large for the slowly growing scions to cover over quickly enough. My experience in the planting of fruit trees has been uniformly successful with smaller stocks (that is, trees smaller than I have been able to buy for nut trees) with peaches one year from the bud and with apples not more than two years; with berries and stone fruits, not more than two years. In every case, with the fruit trees, one year stocks have given me better results. First, because they healed over more quickly, and second, because I could cut to better advantage in the trees. In no case have I been able to get nut trees as small as I can apples and peaches. I believe that with the smaller trees amateurs will have better success. I bring this matter to the attention of those men who are devoting their lives to the propagation of nut trees.
THE SECRETARY: The subject of transplanting nut trees was treated fully by Mr. Bixby in his paper this morning and will be treated by Mr. Hicks this afternoon in his address on the subject. Mr. Hicks will give a lecture, illustrated with slides, showing how the larger nut trees may be successfully transplanted.
DR. MORRIS: Mr. Kains' thought was that there was a good deal of difficulty from using stocks that were too large. Paraffine will keep them safe from microbes.
MR. KAINS: We had difficulty from the drying of the scions.
DR. MORRIS: I find that if raw pine gum is put in it prevents the paraffine from cracking.
MR. O'CONNOR: In regard to wounds on the trees I find that creosote makes a very good antiseptic. I use coal tar and creosote, mixed to a consistency of cream. I have used Portland cement but I treated with creosote first. In some cases I used bichloride of mercury.
MR. REED: It seems to be the experience in the South that, so far as the amateur is concerned, he gets better results with the pecans by planting trees of from three to five feet. Trees smaller than that are regarded as dwarfed; but the man who is in a position to exercise greater care could get quicker results from buying the large-sized trees. Yet it requires more care in transplanting, more fertilizer, and more attention.
MR. REED: I wish to make the motion that the chair name a nominating committee at this time.
THE PRESIDENT: Is that agreed? All right; then I name Mr. O'Connor for chairman, Mr. Reed, Mr. Olcott, Mr. Bartlett and Mr. Hershey on the committee. Are those names acceptable? (Vote shows unanimous acceptance).
THE PRESIDENT: The convention will adjourn until two o'clock.