Part 9

Evidence that walnut trees may be infected for a considerable time prior to appearance of recognizable symptoms was obtained when 37 per cent of a total of 300 severely pruned trees exhibited brooming disease symptoms. These trees had looked healthy until they were pruned. Unpruned control trees showed a 4 per cent increase in disease during the same period.

[Footnote 12: Hutchins, Lee M., and Horace V. Wester. Graft-transmissible brooming disease of walnut. Phytopathology. 37 (1): 11. (Abstract) 1947.]

+Summary+

There is strong evidence that a virus disease is active among certain species of walnut in central and eastern United States. The disease exhibits distinctive symptoms and appears to damage infected trees, sometimes severely, over several growing seasons. Present data indicate that recognizable symptoms of the disease may not appear for some time after infection, unless the host is subjected to severe shock. Thus, nursery stock may be one means of spreading the disease into new areas. It is recommended, without experimental work to back up the recommendation, that walnut nurserymen remove infected trees in the vicinity of their nursery sites.

Investigation of this disease to the present time has been limited. General observations indicate that severely broomed trees produce poor nut crops. Mortality caused by the disease appears to be quite low among black walnut trees. Butternut and Japanese walnut trees are, in general, more severely affected by the disease than the black walnut and many seem to be killed by it, although the killing process is slow. As a result of experience with other virus diseases, orchardists who have only a few infected trees among their black walnuts are advised to remove them. Whether the disease can be kept under control by repeated roguing is uncertain. If an owner has just a few trees of value as ornamentals as well as nut producers, one hesitates to advise him to remove a lightly infected tree until more information is obtained concerning the disease.

This Division will welcome information from persons having experience with the brooming disease of walnut, as it is in a position to do only a limited amount of work on the disease.

+Persimmon Wilt+

Persimmon wilt is very destructive to the native persimmon (Fig. 4). It is caused by the fungus _Cephalosporium diospyri_, which was described in 1945 by Bowen S. Crandall[13]. The fungus grows in the wood of the trees, producing discolored streaks. Most trees are rapidly killed, with yellow, wilted leaves making quite a contrast to the normal green trees.

This disease was found in spots from central Tennessee south to the Gulf, east into Florida, and up the coast into North Carolina. The American persimmon seemed to be in danger, as this quickly killing disease appeared to be spreading. The limited work on this disease was discontinued because of the war and the transfer of Mr. Crandall to Peru. However, this summer Mr. Crandall and the senior writer spent two weeks surveying some of the old infections and nearby territory, and were pleased to note that the disease had made very little progress into new territory. On several small areas where the disease was present some six years ago practically all of the larger trees had been killed, but some new small trees were coming up. At Chattanooga National Park, where the wilt was rampant about six years ago, it is continuing to kill trees, but many new ones are coming up. No northward extension of the disease in Tennessee or North Carolina was noted in the limited time spent in inspection.

[Illustration: Figure 4.--Small persimmon trees killed by the wilt.]

What does the disease mean to the grower of grafted persimmons, both native and Oriental? The Japanese or Chinese persimmons do not grow as well on their own roots, although they are quite safe that way as these two species are very resistant to the wilt. In the East, most of the Oriental persimmons are grafted on American root stocks, and trees in one case were killed by the wilt fungus getting in on the susceptible root stock. No attempts to control the wilt have been made, and these recommendations are based on procedure with other diseases and on knowledge of the spore production of this fungus. An owner of a valuable planting of grafted trees in a region where the disease is present should watch his trees for the first indication of trouble. The planting will be safer, if there are no nearby native trees; and if native trees are growing nearby and cannot be removed, they should be given a general inspection. Prompt removal and burning of any infected trees found is advisable. The fact that usually fungus spore production does not take place until after the tree has been dead for a while makes the prospect for control better than with most diseases. Care should be taken not to bring in scions or trees from infected areas.

Most members of the Northern Nut Growers Association have only a few grafted persimmon trees, usually located outside of the infected zone and therefore in little danger. Persimmon scions and trees should not be shipped from infected to healthy regions. The disease has not been reported in nurseries, but it could occur there because it attacks small trees.

[Footnote 13: Crandall, Bowen S. A new species of +Cephalosporium+ causing persimmon wilt. Mycologia 37 (4): 495-498. 1945.]

+Thyronectria Disease of Honeylocust+

Honeylocust is widely distributed both in native stands and in plantations. Some farmers plant this species or leave native trees in their pastures for the pods, which have a high sugar content, up to 38 per cent. J. C. Moore, of the Alabama Agricultural Experiment Station, reported preliminary tests indicating a per-acre yield of livestock feed equal to that of oats.

In many areas the growth of honeylocust is seriously affected by a canker and twig fungus, _Thyronectria austro-americana_. The disease often kills many twigs and branches and sometimes results in death of the tree. In most areas it causes only slight injury. Bowen S. Crandall and Jesse D. Diller have made a few observations on the prevalence and damage by this disease, which is present from New England south into the Gulf States and west into the Great Plains States.

The fungus causing this disease is morphologically somewhat similar to the chestnut blight fungus, having two spore stages produced in reddish-brown pinhead-size fruiting bodies on the bark. Cankers are produced on the smaller branches, but they usually are not noted until some of the affected ones wilt and die. In the exposed outer wood of a branch cut above or below the canker there are reddish-brown streaks several inches long, indicating that the fungus has grown in the vascular system.

As no control experiments are known, recommendations are based on general knowledge of sanitation. If an owner has only a few valuable planted trees, he should cut off the diseased parts a foot or more back from the lower edge of the affected bark and burn or bury them in the soil. If he has many trees scattered over extensive pasture areas, it is questionable whether any action other than elimination of the more susceptible trees is justified. We will be interested in the results obtained from control work.

* * * * *

President Davidson: Now I will turn over the chairmanship of the meeting to Mr. Chase, who will have charge of the Round Table Discussion.

Round Table Discussion on Chestnut Problems

SPENCER B. CHASE, Presiding

_Panel of Experts_: Max E. Hardy, Carroll D. Bush, H. F. Stoke, G. F. Gravatt, J. C. McDaniel.

Mr. Chase: Gentlemen, in the last hour and a half we have heard perhaps more about chestnuts from qualified specialists than we will ever hear in any meeting of ours, and we requested each one to withhold questions until this point. So now we will have some questions from the floor, please.

Mr. Slate: What is the present status of breeding chestnut species for timber purposes?

Mr. Gravatt: The prospects are coming along. We have one cross between a none-too-promising Chinese chestnut and an American chestnut, with a good bunch of hybrids and they are different from other hybrids. It looks like they will stand up against blight. They will have blight canker growth from 10 feet down to the ground but it doesn't go into the cambium region. It is too early to evaluate the hybrids, but they do have the upright form and rapid growth of the American chestnut.

Now when we take these first-generation hybrids, cross them back with the Chinese and get more resistance, as we have done so many times in the past, we lose that rapid and more upright growth habit of the American chestnut. But we have a lot more work to do before we are ready to say anything final on this question.

Dr. Arthur H. Graves, formerly at the Brooklyn Botanic Garden is now consulting pathologist at the New Haven, (Conn.) Experiment Station. We have been working with him and partially supporting his chestnut breeding for a good many years. He has a lot of hybrids up there. We expect to have something later, but have nothing to release yet.

A Member: Do you have any sprays to control diseases and insect pests in the tree that when they go into the soil won't destroy our ground friends?

Mr. Chase: Mr. Gravatt?

Mr. Gravatt: I don't know what insects you are after, in the first place. We have a lot of trouble with Japanese beetles. Around Washington, Dr. Crane's and my plantings there would be defoliated if they weren't sprayed for Japanese beetle control, and it is the same way with filberts.

A Member: The same sprays have a tendency to work against most of the pests, do they not? Of course, DDT will take one, the arsenate of lead takes another, Black Leaf 40 another, but if we had a spray that we can use around on--well, not limited to the chestnut--that would be neutralized in the earth. Now, we have a good deal of friendly bacteria and insects in the soil that we want to keep.

Mr. Gravatt: I would say that I am a pathologist, and insect work is out of my line.

Mr. Chase: Does anyone else have a comment on that? Dr. Cross, did you hear the question?

Dr. Cross: I didn't get his question.

Mr. Chase: Would you stand and repeat your question?

A Member: Is there a spray that we can use for combating the insect pests of our trees that when it is washed off and goes into the soil doesn't kill our soil friends. We have the friendly bacteria in the soil, as well as insect and worm life. Do we have a spray that will be neutralized as it hits the soil so we can spray the tree and not kill our lower friends?

Dr. Cross: Sorry, Mr. Chase, that's beyond me.

Mr. Gravatt: You are thinking of arsenate of lead poisoning the soil where you keep on spraying with it?

A Member: Yes.

Mr. Gravatt: I think DDT may build up a little in the soil, but it is broken down, isn't it, Dr. Crane?

Dr. Crane: Yes, DDT is broken down and it is not a fungicide and it is not a bactericide. It is an insecticide that kills insects through affecting the nervous system, according to my understanding of it. I am not an entomologist, but that's what the entomologists say. So far we haven't any evidence to my knowledge of any build-up of DDT in soils that has been detrimental. I don't know what the situation would be if DDT was used to the same extent as arsenate of lead. It was not uncommon for some growers to put on anywhere from 6 to 15 lead sprays in a season in order to control codling moth, as they used to do in certain apple orchards, particularly in the West.

I was talking to Dr. Van Leeuwen just a day or two before I had to leave for the meeting, and he is not ready yet to say anything about it, but he has already tested some very promising insecticides as far as the control of weevil is concerned. This DDT and some of the other new insecticides are very easily decomposed, and, of course, that's one of the disadvantages of them. Under certain climatic conditions they would need to be less readily decomposed to give control over a longer period. I know that we have not had enough experience to know all about those new spray materials.

Mr. McDaniel: There has been one instance reported where DDT _in the soil_ was injurious to fruit plant growth. That was Goldsworthy's and Dunegan's work on strawberries. Where they used large amounts of technical DDT in the soil, they found that it inhibited the growth of the strawberry plant. I believe that's the only instance I've heard of, where soil application of DDT hurt growth of fruit plants. Benzene hexachloride, and some other chlorinated hydrocarbons, and parathion actually appeared to have a stimulating effect on the berry plants.[14]

Mr. Frye: Why would there be any more danger of affecting the soil in a chestnut orchard than there would in the apple and peach orchard by spraying seven, eight and ten times? That's the only question that arises with me.

Mr. Chase: Let's get back to chestnuts specifically, now, gentlemen.

Mr. Kays (Oklahoma A. & M. College): Since I don't come from a chestnut area, my impression of the nut samples supplied by Mr. Moore of Auburn, was: "I'd like them if they had salted them." I am wondering if it wouldn't have affected their rancidity if they had been treated--salting material added, prior to or in the process somewhere along the line.

Mr. J. C. Moore: I'd just like to say I have tried putting salt in the water, to boil the nuts with salt, and then I have tried shelling them and sprinkling salt, and I find that salt does not add anything to the flavor. Tasting the nuts raw, I, too, get the impression salt is what I want, but I haven't been able to add it satisfactorily. I don't say that it cannot be done.

Dr. MacDaniels: Mr. Chairman, in view of the whole situation of chestnut incompatibility of stock with scion, what would be the position that we in the Northern Nut Growers Association can take in advising people what kind of chestnuts they should plant? Should they be encouraged to try to get grafted trees? What should be our position?

Mr. Chase: Mr. Stoke, would you care to comment on that?

Mr. Stoke: You are asking me to stick out my neck, and it seems as if I have always done that. The Chinese chestnut is in the Johnny Appleseed stage, in my opinion, and we are investigating to find out the best varieties, that is, the best specimen, best performance, best quality, best in blight resistance, growth, and other qualities and when we winnow out all we have and arrive at the best, we are going to find--now, this is just my personal opinion--I will say that for myself I'd rather have one acre of the best selections we have budded or grafted--asexually propagated, than five acres of seedling trees as a financial good bet, because I say that one acre of our very best produce virtually as many nuts as five acres of seedlings. I have trees from seed I imported through the Yokahama Nursery Company, and I think it came from Korea. The nuts run very small, and compared with those I am sure the others will pay much better, and I think it would be profitable to pay three or four or five times as much for your trees if you get good trees of good, known varieties and grafted or budded.

Don't misunderstand me. We shouldn't ask the American public to wait until those can be furnished, because they won't wait, and they shouldn't. But I say as a commercial proposition, to plant trees commercially, I would exercise caution and I would encourage my customers to exercise caution unless they are willing to follow up and do their own top working later on, and a Chinese chestnut doesn't top work as readily as a black walnut.

Mr. Chase: I don't believe that's quite the answer he wanted. The comment that I think Dr. MacDaniels is after is what position should the Northern Nut Growers Association take in regard to planting seedlings or planting grafted stock. Is that the point?

Dr. MacDaniels: Yes, it seems to be seedlings against grafted stock.

Mr. Stoke: May I answer? I don't think the Northern Nut Growers Association should take _any_ position. They should present the facts and let the buyer decide. I don't think we need to go on record, and I don't think we should. There is too much diversity of opinion.

Dr. MacDaniels: Between ourselves--and this is not an academic question--we get continual inquiries regarding the Chinese chestnuts and what should they plant and where can they get the trees, and so forth. It isn't good enough in most of these cases to write several pages explaining what the whole situation is, the _if's_, _and's_, and _but's_. But I just wonder what the opinion is of the people who know best in this regard. Who has a good orchard of 20-year-old grafted Chinese chestnuts? Where are they? I don't know: I am asking for information.

Mr. Chase: Dr. Drain, are those trees you have grafted trees or seedling trees?

Dr. Drain (University of Tennessee): They are seedling trees. They have produced a rather nice quality nut, and we have enjoyed propagating seedlings from them. That's really all we know. We haven't grafted any.

Mr. Chase: Mac, would you care to comment on this?

Mr. McDaniel: I am ashamed to say that at present we have no grafted chestnut trees on my own north Alabama farms. We have about 50 trees that are 8-year-old seedlings from imported (Chinese) nuts, growing next to a commercial peach block, and find the production quite variable on the different trees. I am aiming at top-working most of these with the named varieties, beginning this year. At present I can't answer the question of seedlings vs grafted trees. I have been advising people who are interested in trying them in Tennessee that _for their first planting_ (to test the adaptability of their locations) they can get the seedlings generally quite a bit cheaper than the grafted trees. With the experience we have had over the State and the high mortality of trees, both grafted and seedling--killing of the tops and in some cases the whole tree--the seedling might be best economically _to begin their_ experimenting with. I am _not recommending_ that anyone plant seedlings commercially, but just in a small way for trial. They are well worth a trial anywhere peaches are doing well. When we find a _suitable site_, then is the time to think about using the more expensive grafted trees.

Pres. Davidson: I just want to give a little bit of my experience along that line. Way back in 1934 I planted a few seeds that I got from Amelia Riehl. They were nuts of the Riehl hybrids. [Ed. note: Mostly American--European crosses.] She named one Dan Patch and another Gibbons. They are now about 13 years old. Each of them is bearing burs this year. They have borne burs, a few of them, in the past, but no nuts. So far in 1948, the burs that have fallen to the ground, of course, have no nuts, but whether the burs that are still on the trees have nuts I don't know. I want to know whether those trees are normal---whether a hybrid of that kind is likely to be sterile or not. That's another matter that might be discussed. Anyhow, you are taking a chance, no question about that, when you plant seedlings.

Mr. Stoke: Mr. Chairman, if you will pardon me for saying one more word, here is a suggestion I will make. Now you can check for yourself. The whole thing hinges on whether we can get _permanent_ grafts on the tree and get the characteristics in the grafted tree that the parent has--in the good selected tree. Now you take the reports sent us by Mr. Hemming; you take the reports of the station at Albany--of individual trees in those plots. You take the worst trees and you will find they are nothing but boarders. You take the best and you will find they are very profitable. You take the average and it will fall somewhere in between.

Now, why keep a lot of boarders that don't pay--free boarders--or why use run-of-mine seedlings, _if_ we can graft successfully--and some people like to dispute that--and produce nothing but the best? And you can check it on any of those tables. [Mr. Hardy's paper.] We have a few tables in our former Reports. You can check it and figure it out for yourself.

Dr. Crane: To clear up this situation I wanted to ask Mr. Hardy a question, and then I wanted to make a statement. In this report from the 1938 and 1940 planting at Albany, Georgia, in the Brown tract in 1947 there were 188 trees that bore crops, but that planting consisted of 274 trees planted in 1938 and 60 trees planted in 1940. Why weren't those 274 trees plus those 60 trees represented in the 100 with the yield records of 1947?

Mr. Hardy: Dr. Crane knows the answer, so I will let him ask the question and answer it, too.

Dr. Crane: In 1936 we planted 1,000 trees of the same Peter Liu selections on the Station farm at Beltsville, Maryland. They were of the same number and letter designations as others that were distributed to cooperators. Out of the thousand trees that we planted on the Station farm some of them came into bearing at four and five years after planting. But the nuts were small in size and were not much good. With one or two exceptions, out of that planting there were none bearing satisfactorily to suit us after ten years. In 1945 we applied the ax, because a Chinese chestnut tree, from an orchard standpoint, if it's not in bearing in ten years after planting is not worth keeping. We haven't got time to wait. So out they came. And in addition to that we have had other trees that have done the same thing.

Now, out of this 274 plus the 60 at Albany, Georgia, we have three trees that we now figure are good enough to be raised to a variety status, plus possibly two or three more. Now, you can figure your percentage of good trees when you plant seeds.

Dr. Overholser: Mr. Chairman, may I ask a question, whether these three seedlings to which they propose to give variety status have been propagated in sufficient number that they are able to give distribution in other areas.

Mr. Hardy: Dr. Overholser, they are not available yet in quantity. That same answer is part of the answer I wanted to make to Dr. MacDaniels. The present situation in the chestnut industry is that there are very few nurserymen who know how to propagate nursery grafted trees successfully. There is going to have to be quite a bit of work done on that. If some of you here know how to do it, I would like to know, myself. There are a lot of nurserymen who would like to know, according to the reports I have, how to graft or bud a nursery chestnut tree.