SELECTING AND HANDLING SCIONS

J. F. Jones, Nut Specialist, Lancaster, Pennsylvania

In the selection of scions of nut trees for grafting the propagator should keep in mind the fact that the wood selected must be full of vitality and must be of solid, well matured growth, that will stand the maximum amount of exposure and hardship after being grafted, as the grafts and stocks of nut trees callous or heal very slowly in comparison to fruit trees, and the scions must be of solid, well matured growth if good results are to be obtained. These requirements usually go together however and if we select scions of solid, well matured growth, we usually get scions in which the tree has stored the maximum amount of "starch" or vitality.

How to Judge Scions

The experienced propagator of nut trees can quickly distinguish between good and poor scions for grafting, but the beginner, not knowing the ear marks of good scions, often fails to select the best scions for grafting. The common mistake made by the beginner in the selection of scions of nut trees, is in selecting the smaller growth. The smaller growth is usually more pithy and lacking in vitality and gives poor results in grafting. Poor scions are usually characterized by pithy wood and a light colored, thin bark. The buds are usually farther apart than they are on good scion wood, though this is not always true, as good scions sometimes have the buds set well apart, except near the terminals. The distinguishing marks of good scions are solid, well matured growth, and a thick, dark colored bark. The buds are also larger and usually set closer together.

When to Cut Scions

Scions must be cut while the tree is still dormant and, in the case of trees that the wounds bleed when the tree is cut, as do the English and Japan walnuts, under certain conditions, we must guard against cutting scions soon after severe freezing weather and before the tree has fully recuperated. This semi-sappy condition of the trees following low temperatures that freeze the wood, seems to be a provision of nature to restore the moisture or sap lost from evaporation, and although more noticeable in some species of trees, notably the English walnut, this condition undoubtedly exists in other species of trees to a greater or less extent and we always try to avoid cutting scions of any kind soon after hard, freezing weather. I have found scions of the English and Japan walnuts, cut from trees in this condition, to be practically worthless for propagation, although the scions may have been cut in late winter, long before the sap gets up in the tree, naturally.

Handling and Keeping Scions

Scions of nut trees for grafting should be handled carefully to avoid rubbing off the buds, although this is not so important with nut trees as with fruit trees, for the reason that the more important nut trees such as the various walnuts, pecan and hickories have compound buds and if the larger buds should be destroyed the secondary buds may be counted upon to grow. The scions should be tied in bunches of a convenient size to handle and, after being well tied and carefully labeled, should be packed in paper lined boxes that will prevent evaporation of moisture in the parking material. Any material that will absorb and hold moisture and that will not heat when bulked, will answer the purpose for packing scions, but we have found sphagnum moss to be the best material for this purpose. This material can be obtained from the local florists or dealers in cut flowers usually. Sphagnum will absorb a good deal of moisture without actually becoming wet and will also hold this moisture and give it off more slowly than any other packing material with which I am familiar. This is especially important in keeping scions of nut trees in good condition for grafting, because, if packed too damp, the scions are soon spoiled for grafting, even if kept at a low temperature.

As a precaution against fungi, we usually use bordeaux mixture, two thirds standard strength, to dampen moss for packing scions, especially if they are to remain in storage several months.

Our rule is to use moss only slightly damp to the touch and if used in sufficient quantity, say two or three times as much bulk as we have of scions, we find no trouble in keeping scions in perfect condition for months. In fact, as an experiment, we have carried pecan scions in cold storage and without re-packing for fifteen months and then get a fair stand of grafts to grow.

We usually advise putting scions in cold storage where convenient, especially if they are for use in late May or June, but this is not at all necessary if the scions are packed in moss only slightly damp. In fact scions kept in an ordinary cellar at a temperature around 50 degrees have given us better results on the average the past two years than have those from cold storage.

The association adjourned until 2 p. m.

Afternoon Session, Friday, October 8, 1920, 2 p. m.

The President: We very fortunately have with us a gentleman from the Bureau of Entomology, Mr. F. E. Brooks, who will talk to us about nut insects for a time and we will be very glad to listen to him.

Mr. Brooks: I believe your program is full for this afternoon and I shall keep you but a few minutes.

A little more than a year ago the problem of insects affecting the nut crop of Northern United States was assigned to me by the Bureau of Entomology. I wish to say the work has been very delightful to me from several standpoints. In the first place, it has brought me into association with a delightful group of workers. I want to express to you the pleasure I have had in meeting the various nut growers of the northern part of this country and noting the hearty way in which they are ready to co-operate in solving the nut insect problems. The field of work is interesting because there appear to be in sight no insect pests that promise to embarrass or overwhelm the nut grower. We have a few quite serious insect problems, perhaps none more serious than that occasioned by our old acquaintance, the "chestnut worm." That problem, however, is being solved rapidly in many localities by the chestnut blight.

Thus far in the work, I have devoted most of my time to a study of the species attacking the fruit of nut trees, and I may mention three groups that have been given special consideration. First, the group to which the chestnut worm, or chestnut weevil, belongs. There are two very similar species of these weevils which attack chestnuts, one which attacks hickory nuts and pecans, one which attacks hazel nuts and numerous species which attack acorns. The adults of these weevils are medium-sized beetles, yellow, brown or gray in color, and all have enormously long snouts. The mouth is located at the point of the snout and the beetles use these snouts to bore through the covering of the nuts after the kernel is partially or fully formed. When the puncture into the nut is completed one or more eggs are inserted by means of an extensile, thread-like tube, or ovipositor, of the same length as the snout. The eggs hatch into the familiar worms found in ripe chestnuts, hickory-nuts and hazel nuts. The large hole in the shell of the nut is made by the full grown worm as it escapes to enter the ground, where it completes its transformation into a beetle. An interesting thing in connection with these weevils is that each species confine its attacks to one particular kind of nut. Even those species that attack acorns show a decided tendency to distinguish between oak species and confine themselves as groups very largely to particular species or botanical groups of oaks. There is, therefore, no danger that any of these weevils will multiply, for example in an oak forest, and then migrate into nearby plantations of chestnut, hickory or hazel. Hazels might be used for interplanting among chestnut or hickory trees with no danger that the hazel nuts would become infested by the weevils that develop in the chestnuts or hickory nuts. This habit of the weevils is greatly to the advantage of the person who would plant a particular kind of nut outside its natural range, or at a considerable distance from any other trees of its kind. He could do so with reasonable assurance that the weevil attacking his species of nut would not occur upon his trees until brought into the locality by artificial means.

There is another group of weevils, nearly related to the common plum curculio, the species of which attack immature nuts. In this group the snout is much shorter than in the group just described, and the insects are considerably smaller. There is one species, Conotrachelus juglandis, that confines its attacks to the young fruits and shoots of walnuts of the butternut group, another, Conotrachelus retentus, that seems to attack exclusively the black walnut fruits from the time they set until they are half grown, still another, Conotrachelus affinis, that appears to attack only half-grown hickory nuts. Another species, Conotrachelus aratus, feeds abundantly in some localities within the leaf petioles of hickory. At least two other species of the group commonly attack acorns. Those injuring walnuts lay their eggs on the concave side of crescent-shaped punctures which they eat in the husks of the young nuts. The larvae developing from the eggs cause the nuts to drop within a few weeks and the larvae enter the ground to complete their transformation. There is a divided tendency with some of these species to attack the young wood and leaf stems of the introduced species of walnut. Dr. Morris states that he has had young Japanese walnut trees killed by C. juglandis feeding in the grub stage within the branches. He has, however, found that the pest succumbs to an arsenate of lead spray.

Species of this group are apt to have alternating periods of increase and decrease and a year of great abundance may be followed by a year of comparative scarcity. This variation is due, at least in part, to the fact that the larvae, as they feed within the tissues of their host plants, often become rather heavily parasitized by certain two-winged and four-winged flies, the parasitized larvae dying before they reach the adult stage. Nature in this way does considerable toward holding the pests in check, but artificial means of control will often need to be considered.

The third group referred to is represented by a two-winged fly, about the size of the common house fly, known technically as Rhagoletis suavis, and commonly as the walnut husk-maggot. The fly is light brown in color, with broad, irregular, dark brown bands on the wings. It appears when walnuts are nearly grown and deposits clusters of small, white eggs within punctures in the husks. Maggots hatch from the eggs and at the time the walnuts drop these maggots are often found converting the inner parts of the husk into a blackened, pulpy mass. Infested nuts are disagreeable to handle and the husk does not part readily from the shell. I have found the fly attacking black walnuts, butternuts, Persian walnuts and Japanese walnuts, within the states of West Virginia, Maryland, Pennsylvania, Ohio, New York, Connecticut and Massachusetts. It probably occurs over the natural range of the black walnut and butternut. It is proving to be a rather serious pest, especially of the Persian walnut. Some of the infested walnuts appear to drop prematurely and others adhere to the branches beyond the regular harvest time. The shell of infested Persian walnuts parts poorly from the husk and the nut is discolored, soiled and unmarketable.

The fly has rather interesting habits. I found that by pricking a nearly mature black walnut with a pin, the wounds would almost invariably be used in a little while by the female flies for depositing their eggs. In one such wound, 180 eggs were laid within 24 hours. When the husk was pricked a slight flow of juice would take place and the male flies would soon find the spot, and, recognizing, I suppose, a suitable place for the females to come to oviposit, they would stand guard at the puncture awaiting the coming of the female. On one occasion I made minute punctures in the husk of eight black walnuts and in a little while a male fly was located at each puncture. Pairing took place usually as soon as the female came and began to lay eggs. Sometimes a male would be found at a puncture in the early morning and would hold its position against all coming males throughout the entire day. When another male would come to the nut the two flies would rear up facing each other and engage in a brief sparring bout with their front legs. Usually, the original occupant of the nut would be the victor. In some experimental spraying of Persian walnut trees in Maryland and Pennsylvania the past season with a sweetened arsenate of lead spray apparently good results were obtained. In one case it seemed that the spraying was about 75 per cent efficient in controlling the pest. In in another case, whereas last year 75 nuts in 100 were infested, this year, after spraying only four nuts in 100 contained the maggots at harvest time.

I desire to state to the nut growers that I am interested in any nut insect problems that you may encounter and shall always be glad to receive reports and specimens. Your co-operation in this work is greatly appreciated and I hope we may continue to work together and that before long we may have more definite knowledge of the means of preventing, to some extent at least, the various forms of injury by insects to the nut crop.

Mr. Rush: I cannot help but express a word of gratitude and appreciation to my friend Mr. Brooks in helping me out of a serious difficulty that I had in connection with walnut culture at Lancaster. A year ago I was ready to throw up the sponge. In fact I might say that my whole crop last year was destroyed by this husk-maggot. This year I have a very fine crop. Last year it was practically worthless. This year I have very few walnuts that were affected by the maggots, largely owing to the successful spraying that he gave the trees at the proper time. I think the future has a bright prospect for making walnut culture more profitable.

The President: We are certainly under obligations for the very interesting talk and glad that Mr. Brooks could be with us.

The first thing on the program for the afternoon session, according to the published program, I know will be of a most interesting character, Top-Working Hickories, by Robert T. Morris.