Part 3

Here again I wished for my official photographer. These are the adults, darkish up here and light in the other end. They are about three-eighths of an inch long and they are a hopper. They have wings with which they can fly, but mostly you see them jumping about. They look like your tree hoppers.

I just wanted you to take a look down this magnificent orchard of Mr. Casper's. He has 75 of those trees. They are 31 years old, planted 55 feet apart. They are 75 feet high. I am going to have to use some of my boy scout ability and measure by proportion. He claims to have sprayed at least the lower three-fourths of the tree.

MEMBER: He uses a speed sprayer, doesn't he?

MR. CHANDLER: No, it's another kind. With all the pressure on one gun, he can get a long way up. One of the materials we used was too strong and we got a crinkling on the leaves. After that he cut it down to what I told him.

My data slide. I want to tell you about this. He sprayed first on July 16 in the orchard which I showed you. He sprayed the whole thing with parathion. He had been using it with his apples and he thought of that as being such a deadly poison that that must be the thing to do. We thought so the first day afterward. He sprayed in the evening. At nine the next morning we could find practically none of those terminals that seemed to have live spittle bugs, but in about two days we could see some were surviving that treatment so we came in again. That spray was applied July 23. At any rate, we sprayed one row with lindane, 1-1/4 lb. per 100 gallons. When I went through the original parathion sprayed plot there was well over half that had some live nymphs.

We started our tests over again. On July 30 we sprayed with lindane (25% wettable powder) with one pound to one hundred gallons of water. Only three terminals with any live nymphs out of a hundred were left in the lindane. The parathion has 38 per cent alive. TEPP which is teta ethyl pyrophosphate is a very quick acting material but doesn't last. Whatever it does, it has to do in an hour or two's time. It has lost its efficiency after that. But we know it might kill everything in a big hurry. There was still ten per cent. We could rule out parathion. We went back to this one row and sprayed on July 23 and on August 2 and 3. That would be nine days. There still were only four infested terminals. That lindane is a refined BHC, which is that material that stinks. It has been known to produce an off flavor in peaches, and it could very easily make an off flavor in pecans. In tests before this on Meadow spittle bugs on crops which might be used for food they did not use BHC, which would be cheaper. There are four or five different forms of the molecule that are important in making that and this gamma is the most important. We used a pound of this 25% gamma lindane and that apparently was the most successful. I didn't get this idea out of a clear sky. I talked to Dr. G. C. Decker and read one or two articles showing where they had been using dieldrin and lindane with the most success.

I guess that is all the slides now.

MEMBER: Do you get away from the bad effects of BHC by using lindane?

MR. CHANDLER: Yes. Now we feel that at any rate in the very short time in which we have known anything about the thing we have at least learned something about the pest and the distribution and the species and apparently we have got a lead on control. Mr. Casper thinks there is no reason why he shouldn't start in the first brood, although he has had about four years build up of the thing and no wonder it is bad. If we should try that another year, I would say we should start about the middle of June, because when he looked on the 27th of June the show was about over.

MEMBER: Your lattitude is about the same as Evansville?

MR. CHANDLER: Yes, Carbondale is almost on the due west line with Henderson, Kentucky, and Anna is 20 miles south of Carbondale.

MEMBER: One hundred miles north would be about two weeks later.

MR. CHANDLER: Yes, I wouldn't be surprised if it wouldn't be later. We thought maybe you might have to spray when the adults were out. We didn't know whether any material would go through that spittle. We thought you might have to spray and envelop the tree when the adults were around.

MEMBER: I saw some spittle bugs in Northern Michigan on wild hazel, and I am wondering if they are a pest on filberts.

MEMBER: We have no damage on filberts and I think we have spittle bugs in St. Louis. Our first brood comes between the first of June and the tenth, and in the last eight years they have been very serious.

MEMBER: Did you say Northern Peninsula of Michigan?

MEMBER: We have reports from Illinois and Missouri and Mr. Armstrong found it over at Princeton, Kentucky, and I know it is in Indiana.

MR. McDANIEL: I have seen some on pecans in Tennessee, but not as abundant as in Union County.

MEMBER: English walnuts in Ohio.

H. F. STOKE: I am in southwestern Virginia. I can say that we have spittle bug in the South. I am not sure it is the same species. When I get it determined, I will let you know.

DR. CHASE: That occurs in all the southern states. It is quite bad in Georgia and Florida and Alabama and in fact all the southern states.

MR. McKAY: It is very bad on weeds and grass in our orchards.

MR. CHANDLER: That's another species.

MR. McKAY: I have never seen any on our nut trees.

MEMBER: Just before this attack on the nut trees it was real bad on clover and grasses in our area.

MEMBER: That comes a little earlier. We ought to be sure that we get that determined. Dr. Milton W. Sanderson has had to send some specimens to a specialist in this group in Lawrence, Kansas.[1]

MEMBER: Are there just two broods?

MR. CHANDLER: There might possibly be three. I have another cage in my check block in which I collected the live ones, and I am going to find out whether they produce or don't.

MEMBER: There are two broods in Iowa.

MEMBER: Do I understand the common spittle bug is an enemy to nut trees?

MEMBER: That is for young nursery seedlings.

MR. CHANDLER: Did you see these big trees where I told you about having the crop? I explained for several minutes that there must be two varieties.

MR. FERGUSON: There is a spittle bug that bothers the June berries.

DR. ROHRBACHER: We have a spittle bug we had a year or two in Iowa on the elm trees.

At this time Dr. Colby would like to make a few announcements.

DR. COLBY: I just had a call from Tubby Magill. He is over in Danville and he has burned out a bearing and he is going to get over here for this afternoon. We will have to pinch-hit the rest of the morning.

DR. ROHRBACHER: We will now have a presentation by Dr McKay on the Preliminary Results of the Training of Chinese Chestnut Trees.

FOOTNOTES:

[Footnote 1: Dr. Kathleen G. Doering, at the University of Kansas identified the spittle bug from the Illinois pecans as _Clastoptera achatina_, a species not hitherto recognized as an important pecan pest. Spittle bugs from southeastern pecans have been referred to a different species.--Ed.]

Preliminary Results from Training Chinese Chestnut Trees to Different Heights of Head

J. W. MCKAY AND H. L. CRANE[2]

Introduction

Many growers of Chinese chestnut (_Castanea mollissima_) want to know how soon their young trees may be expected to bear their first crops of nuts. This is determined by several factors, but perhaps one of the most important is the amount and kind of pruning the trees receive during the first four or five years they are in the orchard. One reason for the importance of type of pruning is the characteristic habit of the species to form branches low on the trunk, so that low-headed and spreading tops result if trees are left unpruned.

It has long been accepted by most horticulturists that any kind of pruning of fruit trees tends to be a dwarfing process. Hence, pruned trees would be smaller than similar unpruned trees. Pruning of young fruit trees, though reducing the size of the top and the number of growing points, tends to stimulate the growth of the remaining shoots. This has a marked tendency to delay the formation of fruit buds. Hence, unpruned trees come into bearing earlier than even lightly pruned trees. Tufts (2)[3] reported that lightly pruned deciduous fruit trees, such as apple, pear, apricot, and peach, came into bearing one to three years earlier than similar trees that had been heavily pruned. Crane (1) found that height of head in apple trees had little effect on yield for the first nine years in the orchard, but at the time the experiment was terminated the trees were still too young for him to expect much fruit production. He found, however, that the low-headed trees made more shoot growth and a larger gain in trunk diameter than the high-headed ones, and thus the bearing area was larger. Because the tree form of the horticultural varieties of Chinese chestnut is somewhat comparable to that of apple varieties, it would be expected that the two might give similar growth and yield responses to pruning or training procedures. The experiment described in this paper was initiated for the purpose of determining the response made by trees of Chinese chestnut varieties pruned and trained to three heights of head.

Experimental Procedure

The three varieties used in the experiment are Meiling, Nanking, and an unnamed variety carried under the accession number 7916. The last variety is characterized by dwarf, heavy-bearing trees that mature their crops very early in the fall, whereas Meiling and Nanking are vigorous, fast-growing varieties that mature their nuts in midseason. In the early spring of 1948 thirty-six two-year-old grafted trees were planted 25 feet apart in the orchard in four short rows of nine trees each. The three treatments consisted of (1) no pruning; (2) pruning to a 2-foot head; and (3) pruning to a 4-foot head. Three trees, one of each variety, were included in a plot or treatment. Thus, the experiment was arranged in a randomized block design with the three treatments randomized in each row and the four rows serving as replications. Each spring the trees received a liberal application of a 10-6-5 fertilizer. Strips six to eight feet wide on each side of the contoured rows received frequent cultivation each growing season, while strips of orchard grass sod were left between the rows to prevent erosion. The soil is Riverdale (tentative series) sandy loam that had been in orchard grass sod for ten years before the experiment was begun. It has been necessary to spray the trees each year with DDT, parathion, or both to control Japanese beetles and mites.

Pruning of the trees was begun during the first winter following the planting in the orchard, but only a few of the lower limbs were removed in order not to dwarf the pruned trees severely. The second winter a few more lower limbs were removed and at this time the two-foot-head treatments were complete. A third pruning was necessary before the heads of the trees in treatment three could be raised to four feet. Detailed records and measurements were made of the diameter of each tree trunk one foot above the ground, and of the weight and number of nuts produced (yield).

Experimental Results

=Table 1. Effects of training to different heights of head on the average diameter of tree trunk and yield of nuts of three varieties of Chinese chestnuts at the end of the third season (1950) after transplanting=

===========+=============================+==============================+ | | | | Average diameter of tree | | | trunk (millimeters) | Yield of nuts (pounds) | Treatment +-----------------------------+------------------------------+ | | | | Meiling No. Nanking Tree | Meiling No. Nanking Tree | | 7916 average| 7916 average | ------------+-----------------------------+------------------------------+ | | | No pruning | 43 43[1] 47 45 | .19 .43[1] .05 .16 | 2-foot heads| 25 19 21 22 | 0 .12 0 .04 | 4-foot heads| 27 22 25 25 | 0 .03 0 .01 | ------------+-----------------------------+------------------------------+

=============+==============================+ | | | | | Number of Nuts | Treatment +------------------------------+ | | | Meiling No. Nanking Tree | | 7916 average | -------------+------------------------------+ | | No pruning | 11 22[1] 2 10 | 2-foot heads | 0 7 0 2 | 4-foot heads | 1 4 0 2 | -------------+------------------------------+

[1] 2 trees missing.

Data on the diameters of the tree trunks and yields of nuts at the end of the third year in the orchard are given in table 1. It should be pointed out first that these grafted trees produced some nuts the third growing season they were in the orchard. This is very much earlier than seedling trees ordinarily could be expected to bear nuts. It will be noted that trees of Number 7916 developed a somewhat smaller trunk on the average than the other varieties did, but Number 7916 outyielded them about two to one, both in weight and in number of nuts produced. The tendency of Number 7916 to bear nuts earlier and on smaller trees than other varieties may prove to be a valuable characteristic that will justify naming and releasing this clone as a new variety. The fact that it matures its nuts early may also make it suitable for growing in more northerly areas than other varieties, because the length of season required for maturing the crop presumably is shorter than for other varieties. However, this cannot be determined without extensive tests in the North, which are now being made by a number of growers.

It will be noted also in table 1 that the trunk diameters of the unpruned trees were about twice as great as were those of trees trained to two-and four-foot heads; and furthermore, the yield of nuts was more than four times as great. This means that cutting off the limbs that formed below the 2-foot level checked growth so that the bearing surface of the tops was greatly reduced as compared with that of unpruned trees. Also, growth of the tops of these trees was etiolated and spindly, and the shoots produced few or no catkins as compared with the abundant catkins produced by the unpruned trees. Several of the trees with four-foot heads became so top-heavy that staking was necessary, and nearly all the pruned trees leaned to some extent. At the end of the third year in the orchard, the unpruned trees were much taller than trees headed at two and four feet, and the spread of branches was also much greater. Preliminary results from this experiment indicate that early pruning of young Chinese chestnut trees causes severe dwarfing and consequent delay in the formation of catkins and the bearing of nuts. All pruning operations should, therefore, be delayed until the trees reach bearing age, and from that time on low limbs may be removed gradually from year to year until the trees are trained to the proper height.

Literature Cited

(1) Crane, H. L. The effect of height of head on young apple tree growth and yield West Virginia Agr. Exp. Sta. Bul. 214. 1928

(2) Tufts, Warren P. Pruning young deciduous fruit trees California Agr. Exp. Sta. Bull. 313: 111-153. 1919

Discussion

MR. McDANIEL: What age and height were these trees when planted?

DR. McKAY: These trees were grafted on two year old stock and allowed to grow a year. They were three years old. They have grown in the orchard three years, so they are now six years old and about five feet high.

They were grafted about a foot from the ground and they grew three feet or so. They were a good size grafted tree.

MEMBER: May I ask the time of the year when you pruned?

DR. McKAY: In the dormant season.

MR. SHERMAN: I have been pruning some Persian walnuts. Just as the side branch starts I rub that bud off and I can't see that I am dwarfing it any.

MEMBER: Maybe you aren't pruning enough to do any dwarfing. We have removed whole limbs.

MEMBER: I have taken it off and allowed the center to go up.

DR. McKAY: It may have different effects. We actually removed wood from the tree.

MEMBER: Is that 7916 a pretty good sized nut?

DR. McKAY: It is a smaller nut. The 7916 is a potentially high bearer. It bears quickly after it is planted and that is one of the things a lot of us are interested in.

MEMBER: How about eating quality?

DR. McKAY: It is just as good.

Our preliminary conclusion is that early pruning in this species causes severe dwarfing and delay in the fruiting of Chinese chestnuts. Just let them alone. Plant them and forget about pruning them until they come into bearing. Let them alone and you will get nuts two or three years sooner than if you start taking those lower limbs off. Once you get it into bearing then start in and take off a few limbs on the bottom. You could still over-do the thing. The point is to wait at least three or four years. We will have some recommendations in another year when we shall know more ourselves.

MEMBER: What do you disinfect those cuts with?

DR. McKAY: We don't figure it is necessary to be too particular about painting the wounds. Those wounds heal over very quickly. Use an asphalt tree wound compound.

MR. SILVIS: Personally it appears to me that Walter Sherman's method of rubbing off the buds or very young shoots just as they start growth is to be preferred. Your method of cutting off limbs is destructive pruning. Though you say pruning dwarfs the tree, actually the root is still there and given enough time will not the tree recover?

DR. CRANE: I carried on pruning experiments for many, many years, with apples, peaches, pears and cherries. Since then I have been working on nut trees. As for this debudding, the reason he doesn't know he was injuring, was that he didn't have checks and experiments. When you have, you will see that debudding or even pinching the terminals will actually dwarf the tree, although not as badly if it is not done in the summer time. If you do it in the springtime, and if you keep on debudding along in June and July, you are dwarfing your trees.

MR. McDANIEL: In the University orchard you will see some Chinese chestnuts which have been pruned heavily, and the results aren't good.

MR. CORSAN: I visited a sweet chestnut orchard in Michigan, and the grower told me that there were two types of Chinese chestnut trees, one that grew tall and the other squatty. The one that grew shorter was much later than the tall one. Then I would like to tell you about an experience I had years ago. I imported from this state of Illinois from Miss Amelia Riehl, and I also planted about a bushel of seed of Chinese chestnut trees grown in the Niagara district. These Niagara seedlings are quite large and the amazing thing is they didn't grow any nuts. So I came across another orchard in the Niagara district where they were growing that large pointed type of nut and I got some grafts from that and I put them on these non-bearing trees and they all took at once. A bunch of them would all grow up without any failure. That was easy and now they are growing fine. I just thought I would tell you that peculiar experience, and that knocked me cold. The trees from Illinois and the trees from the seeds of the large good sized nuts were equally good.

MEMBER: Did they bear after you grafted them?

MR. CORSAN: They sent out sprouts that far. [Indicating.] The trees were all right.

MR. STOKE: I think you are both wrong. I think you will take the tree and plant it without pruning and then it starts and then in the summer after it is in full leaf pinch off the leader in the lower branches. That will retain the value of those lower leaves. By doing that and suppressing the lower you will get better results than either of the other ways. Nature will remove and make unfruitful the lower ones. You can help nature in forcing the upper growth and removing the lower.

DR. McKAY: That is one way of doing it. A lot of people want to get ahead of nature. If you wait for those lower limbs to die, the tree will have to be pretty large. Lots of people want to get under their trees before that. You sometimes want to get there after three or four years. I think it would take ten years for the shade to do it.

MR. STOKE: I didn't mean to let the shade do it. We after three or four years can remove the limbs ourselves with less shock and much better results. That will work on any tree.

DR. McKAY: I don't see how you can remove.

MEMBER: You force stronger leaders at the top and hasten the growth of the top.

MEMBER. You will get a delay of fruiting.

MEMBER: I think you make up for it.

DR. CRANE: That may be true. We have seen very conclusively that when you prune even a little you are going to destroy fruiting.

MR. STOKE: You will have a larger tree in five years by my method than by yours.

MR. A. M. WHITFORD: I have trees of that very spreading type of Chinese chestnut, that are lying on the ground and I should have removed those limbs five or eight years ago. You should remove them in not more than five years after planting.

DR. McKAY: I want to make a comment. Some grafted trees are not bearing. This to us shows the importance of varieties. This difference between 7916 and the two others is so striking it means in the future we have to pay more attention to the varieties. There is no question that some varieties will bear sooner than others. We have to talk about grafted trees because that is the only thing that can be developed. Every grafted tree is potentially like every other of the same variety.

MEMBER: What factors suppress them? In pinching back, do you mean that the actual growth rate is changed, or that debudding will suppress the entire tree?

DR. McKAY: We mean the amount of the top itself. Usually it is the spread and the height together. When you prune, you tend to hold back the total amount of the fruiting area of the tree. If you allow it to develop untouched you have a greater fruiting area.

MEMBER: The chestnut tree often will sprout from the trunk. What are the processes to check that?