INSECTS INJURIOUS TO NUT TREES

A. L. Quaintance, Washington, D. C.

I have not very much to say because we have not yet accumulated much information on the subject of nut insects. I am glad to appear before you, however, and to assure you that attention is being given to the insect enemies of nuts by the Department. We are not nearly so far advanced in the subject, however, as Professor Waite, since our specific study of nut insects began only, this last spring. At that time we established a laboratory in the South, especially to study pecan insects, as the demand for information concerning these pests has been very strong. The Bureau of Entomology, however, for a number of years, has published more or less on nut insects, as opportunity offered, and I think I should call your attention to a few of the papers treating of nut insects, and which I recommend that you obtain, if possible:

The Nut Feeding Habits of the Codling Moth, Bulletin 80, Part 5, Bureau of Entomology.

The Fall Webworm, Farmers' Bulletin 99, U. S. Department of Agriculture.

The White-Marked Tussock Moth, Farmers' Bulletin 99, U. S. Department of Agriculture.

The Bag Worm, Circular 97, Bureau of Entomology.

The Apple-Tree Tent Caterpillar, Circular 98, Bureau of Entomology.

Nut Weevils, Circular 99, Bureau of Entomology.

The Red Spider, Circular 104, Bureau of Entomology.

The Leopard Moth, Circular 109, Bureau of Entomology.

The Walnut Borer, Fifth Report, U. S. Entomological Commission, page 329.

The Oak Pruner, Circular 130, Bureau of Entomology.

Insects Injurious to Pecans, Bulletin 86, Mississippi Agricultural Experiment Station.

Insects of the Pecan, Bulletin 79, Florida Agricultural Experiment Station.

The Walnut Weevil or Curculio, Twelfth Report, State Entomologist of Connecticut, page 240.

The Walnut Bud-Moth, Twelfth Report, State Entomologist of Connecticut, page 253.

The above list will furnish information on most of the important nut insects thus far known. Inasmuch, however, as the walnut, pecan, etc., are native trees, it is probable that when these nuts are cultivated they will be attacked by many of the insects which prey upon them in nature. This we have found to be true to a considerable extent in the case of the pecan. Many of the pests of hickory, for instance, are becoming important enemies of the pecan.

We have few requests for information as to the insect enemies of the hazelnut or filbert, practically none as to the almond. I surmise that there is comparatively little injury to the two former crops in the United States, and that in the case of the almond it is largely free from insect pests. The secretary has suggested that I make reference particularly to the insect enemies of the walnut. We have had complaints of severe injury to walnuts in California from the codling moth and walnut aphids. In this state and in the arid sections where walnuts are commercially grown, the codling moth, the well-known apple pest, has turned its attention to the walnut, and under some conditions does serious injury. If walnuts are growing adjacent to pears, the marketing of the crop, which occurs about the time the second brood of larvæ is at its height, deprives these insects of further food and they turn their attention to the walnut. The walnut plant lice in California have just been investigated by an agent of the Bureau of Entomology and we now have a paper in press on these insects. We think it probable that spraying will be a satisfactory remedy where the trees are not too large.

In the East injury is confined largely to certain caterpillars infesting the foliage, as the white-marked tussock moth, the fall webworm, a species of Datana, and occasionally reports of severe injury from red spider are received. Rather recently a good deal of interest has been aroused in the so-called walnut curculio by reason of its attacking the shoots and leaf petioles of the Japanese walnut. It attacks also other species of walnut, including the English walnut and the butternut. This pest has been well treated by Doctor Britton in his report as State Entomologist of Connecticut for 1912.

While pecans are perhaps not of particular interest to growers of nuts in the Northern States, yet brief reference will be made to some of the insect enemies of the pecan. There are two excellent publications on this subject, as indicated in the list of titles above. I should urge all interested in nut culture to obtain these papers, since some of the insects treated are quite general feeders and may be expected to occur on most all varieties of nuts.

The secretary also has asked that reference be made to the hickory bark beetle. This is essentially a forest insect and has been treated by Doctor Hopkins in Circular 144 of the Bureau of Entomology.

Attention should be called to an insect rather recently introduced into the New England States, which will probably attack nut crops, namely, the so-called leopard moth, already indicated in the list of titles on nut insects. This pest will prove a difficult one to control, as it infests the trunk and larger limbs.

The whole question of the control of nut insects is complicated by the often enormous size of the trees, so that operations, effective in the control of insects, say affecting the apple, are not entirely practical. It is a point to be determined whether it will be profitable to spray large nut trees, such as the pecan. In some instances we believe that it will be, and the Bureau of Entomology now has in Florida one of the large power spraying outfits, formerly in use in the gipsy moth spraying, to determine the cost and benefits of such work.

In concluding these brief remarks I wish again to reiterate my pleasure in having the opportunity of appearing before you, and to assure you of the interest of the Department in the insect problems confronting nut growers. Nut culture is bound to increase enormously and insect injuries will probably correspondingly increase. I believe, however, that these injuries will be found controllable, as has been determined to be true in the case of practically all important native or introduced crops.

The Chairman: We are glad that Professor Quaintance has told us about the different bulletins. The secretary will have a list of these. I am now going to call for Mr. Rhodes, who is an expert propagator of Persian walnuts, and he is going to give a demonstration on methods of propagating the walnut.

Mr. Rhodes: I am employed over at Arlington and I have been helping Professor Lake in his work there at the farm. Last year about the 15th of July we put in about seventy-five grafts using the cleft graft, and the side graft, and at the same time we put in some chip buds. Professor Lake has a little instrument which is known as a chip budder. We used an ordinary bandage, such as surgeons have, which we dipped in a mixture of about two parts wax, one part tallow and one part rosin. We put the bandage in when the solution was at a boil—that made it sticky enough to hold to the bud, and then we cut a hole large enough for the bud to come out. We found budding at that season, in August, more successful than grafting. The stocks were about two inches in diameter; we put in grafts anywhere from two to three feet above the ground, sometimes as many as three grafts. In a great many cases we lost all, and in some cases we lost two. I tried also bench or root grafting, and put in about fifty along about December, and when I took them out in the spring, the scion had covered up nicely, but we had a very dry spell, and through lack of attention, as much as anything else, we didn't get a graft to pull through. I am going to try the same thing this year. Along in July I took several cuttings and put in, and out of ten I got one to live. One proved successful in the soft wood and this coming year I hope to get some of the hard wood kinds to pull through.

In grafting I always try to get the cuts as smooth as possible and to make them in one cut, because if you make a second cut you are bound to make some unevenness in it. These cambium layers have to fit right up flush with the edge of the bark. Then we usually wrap them in raffia. We used also what Professor Lake called a bark graft.

We got about 10 per cent of those to live. We had better success with the cleft graft and the side graft. In cutting the scion for this side graft I usually cut one side a little longer than I do the other which makes the scion lie closer to the stock. We leave the top on. You can put several on each of those stocks.

We were pretty successful with that sort of a graft. For my own personal use, I like this graft for walnuts, and I think we will eventually have better success with that than with any other type.

We put the majority of the grafts in I think about the latter part of June or July.

I have been afraid to cut the top off before the scion has started to grow. There is too great a flow of sap for the small scion to take up and as a consequence it drowns out the scion.

Professor Smith: How far toward the center did you make the cut?

Mr. Rhodes: About two-thirds of the way through.

The Chairman: You go past the middle?

Mr. Rhodes: Yes. The only thing you have to be careful of is not to cut too far, as then there is danger of breaking off.

Mr. Jones: Do you have any particular length for the cut on the scion?

Mr. Rhodes: No. A great deal depends on the cut you make into the stock. I don't like to cut the scion any further up than the depth we go into the stock wood.

Mr. Jones: Any other rule?

Mr. Rhodes: No, it all depends on the size of the stock. If you get a large stock you can cut it larger.

The Chairman: We thank you for these explanations. Mr. Rush is an experienced propagator of walnuts and pecans and I want to give him some time to show his methods. I will ask Mr. Rush to give his demonstration.

Mr. Rush: I am very glad to show you some of my methods. The only difference between mine and Mr. Hutt's is that he is right-handed and I am left-handed.

The propagation of the Persian walnut may be divided into three divisions, the preparative, the operative and the nursery, and one is as important as the other. Good wood, good weather conditions, good technique and after this you must nurse them.

(Mr. Rush gives demonstration of budding.)

The Chairman: This is the method I outlined yesterday, but I think Mr. Rush has it better in his hands than I have in my head.

Mr. Rush: It is practically the same. I have a good knife with two parallel blades that can be taken off, and put on the grindstone, and got as sharp as a razor. For some things I use a surgeon's knife.

The Chairman: We have with us another very expert propagator from a little farther south. I am going to ask Mr. Wiggins to give us the benefit of his observations along this line.

Mr. Wiggins: I have not had experience in propagating walnuts, except in an experimental way. I have had some experience in the propagation of pecans. Much depends on the condition of the stocks. If they are in a good healthy, vigorous, growing condition, you will do better.

(Gives demonstration on grafting.)

The best time in South Carolina is in August and early September. I use but one method of budding and grafting. It is the only one I am successful with. What you call chip budding, I call bud grafting. I get 95 per cent of chip buds to take in the spring. I get the wood when it is dormant. I can find dormant wood even in May and June. I usually get it earlier than this, but this year it was in May. Part of these trees were in the shade in the orchard and I got the wood from them. Ninety-nine out of one hundred were dormant, and about that many lived. The wood was thoroughly dormant and plump. I cut it right out of the orchard in May or June and got them to live. Of course if you cut scions from the ends of branches, you haven't a chance at all.

One thing to remember in the chip graft is not to cut your chip too thin. If you do you will lose a good many. I go right into it. If you do it right it will hurt your finger so you can only work for two or three hours at a time. It won't dry out so quickly if you cut it thick and will stand a better chance to live. I try to get the scion to fit the first time.

The Secretary: What do you tie it with after you put on the waxed cloth?

Mr. Wiggins: I use a strip of common cloth out of the store. Your fingers will be waxed enough in working so that the strip does not need to be waxed. You tie it after wrapping it.

A Member: Would you protect that with a paper bag?

Mr. Wiggins: No.

A Member: Do you place it on the north or south?

Mr. Wiggins: The point that decides the exact place on the stock is the smoothness and greenness and health of it. I pick out the cleanest and best places. The whole top of the tree is above the graft.

A Member: When do you cut off the tree?

Mr. Wiggins: According to the weather. It takes two or three or four weeks for proper healing. I open up a few and if they are all right, I open all of them. Just as soon as it heals, I cut the top off.

Professor Smith: What is your ordinary practice in cutting scions?

Mr. Wiggins: Last year I was sick and got behind with my work so I cut them each day as I needed them. I usually cut them earlier and bury them in a shady place to keep the wood dormant. I can get 100 per cent by chip grafting and in no other way. I don't use the cleft graft at all. The better fit you get in this method of propagating the higher the percentage will run. If you make a fit that is not quite a fit, you will be astonished to lose about 95 per cent. If you are just a little more careful, you might get 100 per cent to grow. I can tell by the way it feels when it is right. I use a crude method but succeed with it. I do four hundred in a half day. What is the use of going to another method when I get good results with this?

Professor Smith: You say a half-inch scion on a four-inch stock?

Mr. Wiggins: Yes, on a four-inch stock you get a cut an inch or one and a half inch wide. You have a large space that is not covered at all.

Professor Smith: They live?

Mr. Wiggins: Yes, of course.

Professor Smith: Only touch in spots?

Mr. Wiggins: On top and bottom and on one side. I get cambium together at top—I am careful about that—and then I get on the left side an exact fit but not on the other sides.

The Chairman: Have you had much experience with walnuts?

Mr. Wiggins: No. I should think the best results with walnut as well as with pecans would be by cutting the scion wood the year before.

The Chairman: This is certainly a very interesting discussion, but I have another grafter here yet. A demonstration by Mr. Jones will close this morning's session.

(Mr. Jones gave a demonstration of cleft grafting stating that he used that method practically altogether.)