Chapter XIII: Section X: Amendments to By-Laws (6)

MR. MACHOVINA: Mr. Chairman, members of the Association, I hope you will bear with me if I run 30 seconds over. Perhaps I had better point out that my training is that of an engineer and not a botanist, hence this report on the Merrick tree is that of a layman. I have not bothered to go into detail on the various features of the tree, such as leaves, buds, and so forth, because I have slides which you will see afterwards.

The Merrick Hybrid Walnut

P. E. MACHOVINA, _Columbus, Ohio_

The Merrick hybrid walnut is a natural cross between Persian and black walnut and is distinguished from most other such hybrids by the good crops it usually bears. The tree is located in Rome Township, Athens County, Ohio, on property owned by Mr. M. M. Merrick a farmer and fruit grower.

In August, 1950, Mr. Merrick first described his "English" walnut to the writer and arrangements were made to view the tree. Most striking at first sight was the large crop of nuts. The general outward appearance of the tree suggested it to be pure Persian; however, upon closer examination, mixed parentage became evident. As a hybrid, the tree's history was a matter of interest and the owner was happy to supply what information he could.

Mr. Merrick purchased the property on which the hybrid is located, in 1921. A few years prior to this, the previous owner had planted six Persian walnut trees obtained from a nursery in northern Ohio. These young trees bore their first crop of nuts during Mr. Merrick's first year of ownership. It is known that the nursery owners were also proprietors of a commercial Persian walnut orchard located in the vicinity of Niagara Falls. With this combination of date and orchard location, it seems not illogical to presume that the six nursery trees were of the Pomeroy strain. From Mr. Merrick's description of the nuts produced by these trees, they appear to have been two each of three different grafted varieties. In the early nineteen-thirties, Mr. Merrick planted several nuts from the Persian trees and raised a number of seedlings. One of these seedlings, transplanted to its present location, is the subject of this discussion and is presumed to be a cross between one of the six Persians and a native black walnut. During the late nineteen-thirties, all of the trees, Persians and seedlings, with the single exception of the existing hybrid, were killed by an unusually hard winter.

The Merrick hybrid walnut, now about 20 years of age, is an extremely vigorous and healthy tree. Its height is between 55 and 60 feet and its spread nearly as great. Trunk diameter is at present about 12 inches at breast height. The location of the tree is very favorable, being near the crest of a high ridge and with protection from the northwest by the house. A chicken yard is near and the kitchen drain empties close by to supply moisture.

In nearly all aspects excepting the nut itself, the tree favors its pistillate parent. This is evidenced by the general shape of the tree, by the texture and color of the bark of limbs and twigs, and by the shape and color of the leaves, the buds, the flowers, and the nut hull. Hybridity is indicated by the (usually) eleven leaflets to the leaf stem, by the nut, and in the disintegration of the hull which, after falling, quickly changes into a most disagreeable, dark-brownish, semi-liquidlike mess. The nut itself is much more like a Persian walnut in appearance than a black walnut. The shell surface is slightly rougher and somewhat darker than most Persian nuts. The suture of the Persian parent is prominent. Black walnut parentage is exhibited by the thick shell, the interior configuration and in the flavor of the small kernel. Nut size varies somewhat with diameters ranging from 1 to 1-1/4 inches and lengths ranging from 1-1/4 to 1-1/2 inches.

The bloom, which is strikingly like that of pure Persian trees, is always profuse and precedes that of the surrounding native black walnuts by a week or two. In the two years during which the writer has observed the tree, the greater part of the staminate bloom has preceded the pistillate by several days. This was noticeably the case during the current year, and either this, or the rainy weather, has resulted in a small set of nuts which the owner states to be unusual. During the years observed, the tree appeared to be self-pollinating.

It is recognized, of course, that the Merrick hybrid is worthless as a producer of edible nuts. The possible value of the tree lies in opportunities it offers in being the forbearer of more worthwhile progeny. We know of the vast possibilities in hybridization. We know of the difficulties involved in obtaining nuts from controlled crosses between Persian and black walnut trees; and we know that seedling trees raised from the nuts of such crosses are almost always sterile. The Merrick hybrid, yielding good crops, offers possibilities both in crossbreeding and in the raising of seedling trees from the nuts of the tree itself. In the latter connection, Drs. Crane and McKay, of the U.S.D.A., requested several pounds of Merrick nuts for planting purposes this spring. The writer himself planted five such nuts, of which four germinated. Of the four trees, one died early in the season, while the remaining three have thrived. The heights attained by the three remaining trees thus far this season are 1, 2, and 3 feet, respectively. These trees have the general appearance of young Persian seedlings.

The only crossbreeding attempted thus far ended in failure when a storm destroyed most of the bags prior to application of pollen. Persian pollen was used on the few bloom remaining covered but, unfortunately, no nuts were set. The experiment will be continued. Also, the Merrick will be topworked onto producing walnuts, both Persian and black, in the hope of obtaining nuts from which interesting and perhaps better second generation hybrids can be raised.

An interesting point of conjecture on which to terminate this report, and one to which nut experts will likely give little credence, may be found in a statement made by Mr. Merrick and vouched to by Mrs. Merrick. The statement is to the effect that the nuts borne by the Merrick during its early years, that is, prior to the time the adjacent Persians were killed, were of much better quality, being more like Persian walnuts both in appearance and in flavor. We've heard of "pollen influence" with chestnuts. Did it occur here?

TUESDAY AFTERNOON SESSION

Producing Quality Nuts and Quality Logs

L. E. SAWYER, _Director, Division of Forestry and Reclamation, Indiana Coal Producers Association_

I was trained as a forester and having worked at the profession for nearly thirty years, my first thought of trees is for their utility in building or in cabinet work. In school we were taught that the fruit of forest trees was a by-product. Its economic importance was not emphasized nor was the possibility of establishing stands of some species specifically for the production of their fruit.

Through the years the value of the nut crop from some species has increased so that the fruit is now the primary crop and any wood materials that may be derived are the by-product. This production of valuable food and necessary materials of high quality for the building of quality furniture and interior finish is a combination that will work well together.

Black walnut, the most highly utilized of any of our native timber for furniture, veneer, and cabinet work is becoming increasingly more difficult for the mills to obtain in larger sized logs. Native chestnut, almost completely destroyed in our timbered areas by the chestnut blight, is in demand for interior finish. Pecan, which has had only a limited use in the past, is now enjoying a market for the manufacture of flooring.

The production of nuts from plantations or orchards of these three species will no doubt produce greater economic returns for many years after the initial planting than could be derived from the sale of the trees for the wood they contain. There will come a time in the life of any tree when it is no longer a profitable producer and should be replaced by a younger, more thrifty tree. When that time comes, the tree to be removed will have no economic value unless it contains products that industry can use. With the thought in mind that the wood from the tree is to have some future economic value the trunk of the tree should be kept free of all limbs to a height of about nine feet above the ground. The development of a large spreading top above that point will be desirable for nut production. The space below that top will give ample head room for maintenance work in the orchard and that clear length of trunk will produce a high quality log eight feet long. That is the minimum standard length normally used by the lumber industry. Some shorter lengths are utilized by the veneer industry but those lengths usually command a lower unit price.

The production of figured walnut could be combined with the production of one log per tree but it would take several more years to bring the trees to nut producing age. Mr. Wilkinson has successfully demonstrated that the figure of the Lamb Walnut does carry over through a graft or bud.

A double budding operation should not be difficult to perform. It would simply consist of budding the figured stock on the root at as low a point as possible, then when the figured growth has reached sufficient height, of budding again to the desired variety for nut production. This procedure would no doubt require a few additional years before the first crop of fruit would be harvested but it would produce an extremely valuable log when the tree is finally cut.

I would be remiss in my present job if I did not bring the revegetation program of the Indiana coal stripping industry into the discussion. That industry produces over fifty percent of the coal mined in Indiana today and is recovering coal that could not be mined by any other means.

In driving to Rockport many of you no doubt passed by areas of newly mined land, rough, barren desolate looking areas with no vegetation. They have the appearance of complete desolation and give the impression that those lands are forever lost. In that same vicinity you no doubt passed plantations of pine, or mixture of pine or Locust with our native deciduous species. Those too were mined areas that a few short years ago were just as desolate in appearance as the bare areas you saw. These plantations are the direct result of a reclamation program started by the members of the Indiana Coal Producers Association, a program that has attracted national attention.

The first record of an attempt at the reclamation of coal mine spoil is here in Indiana. In 1918, the Rowland Power Company, now owned by the Maumee Collieries Company, planted peach, apple and pear trees on mined land in Owen county. The records show that for a period of years the trees thrived and were good producers. Then, because the topography was rough and no spraying was done, disease and insects took their toll of the peaches and apples. Seedlings of the original apple and peach tree still grow on the area. The original Kieffer pear trees still stand and produce large crops of fruit.

In 1926, the larger, more far sighted companies began a definite program of reforestation of their mined lands under the direction of Ralph Wilcox, at that time assistant State Forester and fortunately our State Forester today. That voluntary program was carried on until 1941 when the Indiana Coal Producers Association, the Association of the mining companies, sat down with representatives of the Indiana Department of Conservation, representing the state, and the Indiana Farm Bureau, representing the people, and drafted a bill which was enacted into law. This law required each company to obtain a permit from the state to operate and required that each company revegetate an area each year equal to 101% of the area they had mined. To insure compliance, a bond was required. This law remained in effect for ten years. In 1951, representatives of those same groups again sat down together and drafted several amendments to the original act. Some grading is now required where areas lie adjacent to public roads. Access roads must be provided and areas to be devoted to pasture must be graded so that they can be traversed with agricultural machinery.

Under this program, sponsored by Industry, the Farm Bureau, and the Department of Conservation, 79% of the area that has been mined to date has been successfully revegetated. The remaining 21% is a natural lag and represents lands newly mined or areas that have not weathered to the point where they will support revegetation. The demand for recreation lands and home sites where water is available is constantly increasing. At least 13% of the revegetated area is now being used for public recreation or for home sites. Near the more heavily populated sections the price commanded by mined territory containing good lakes often exceeds the value of the land before it was mined.

These lakes, formed in the final cuts and in low lying areas of the strip mines, furnish the only clean, clear water available for public recreation and fishing in the south western part of the state.

The reforestation being carried on under the reclamation program consists of planting several species of pines, as well as a large variety of our native deciduous trees. The older plantations are being used as a guide as the research started in the last eight years has not progressed far enough to give conclusive results on many points. Until the last few years the Agricultural Experiment Station has devoted little or no time to the problem of reclaiming strip mine spoil. The area of the state that is involved, less than 1/4 of 1%, has been too small to justify the use of their limited funds. However, since funds have been made available to that Station, through the Industry, to establish research fellowships, the Station has given whole hearted cooperation. The information being obtained through these fellowships and through work being carried on cooperatively with the Central States Forest Experiment Station is going to answer many of the questions on reclamation we have been confronted with.

Included in our reforestation has been a liberal scattering of black walnut. A breakdown of species is not available on much of the earlier work but since 1940, when accurate records have been maintained, we have planted 239,000 black walnut seedlings or seed. Initial survival is not high, averaging only about 50 percent but we still have a general distribution of seed trees that are providing a source of seed for natural reproduction. Trees from plantings made in 1927 to 1934 have grown well and we now have walnut trees over 10 inches in diameter and 60 feet in height. The average for all areas would probably not exceed 5 inches but individual trees have made remarkable growth. These trees are only seedlings, but they are bearing heavily and their fruit is sought by the local people.

In 1946 and 1947, budded stock of walnuts and pecans and seedlings of Chinese chestnut were obtained from Mr. Wilkinson and were set out on six selected areas. A wide variety of sites were picked and a wide variation in both survival and growth has been obtained. No special treatment was given the areas where the trees were to be planted nor were the trees mulched or watered after planting. Even under these rugged conditions we have a survival of over 60 percent of all trees. The walnut trees now range from 5 to 12 feet in height and the pecans up to 6 feet. The chestnuts vary in form from low spreading plants 4-1/2 to 5 feet in height and as much as 8 feet across to well formed trees 8 to 10 feet tall. Pruning on all three species to produce a clear butt log has been started.

Pasture seeding on areas high enough in available lime to support legumes is following a pattern laid down by three years of graduate study, financed by the Indiana Coal Producers Association, at Purdue and by work done by the Illinois Agricultural Experiment Station under a similar arrangement with the Illinois Coal Strippers Association.

Unfortunately, we have only a small portion of the spoil area in Indiana that is suitable for the development of improved pasture. Not over 10 percent of the area mined to date is good enough and that percentage will decrease. Modern operations are deeper than the early ones and are exposing more hard rock and shale. Fortunately, most of these areas can be reforested after three or four years. In exceptional cases less than 5 percent of the area mined the exposed materials contain large amounts of sulfides. These break down into acid that in some cases require ten to twelve years to leach out before revegetation can be undertaken.

The fact that these stands of trees established on raw spoil will produce merchantable timber has been proven. In 1951, an area was clear cut at the Enos mine in Pike county. The pines on this tract were planted in 1933-34. The products from that cutting, peeled posts and poles, were sold to the Indiana Wood Preserving Company at the rate of $335.59 per acre. An increase in value of $16.48 per acre per year.

Pasture, forests and fishing are not the only products. Game of all varieties is abundant in the worked out areas. One of the largest herds of white tailed deer in the state, now referred to as the strip mine herd, is located in northern Warrick and southern Pike counties. In the Indiana deer season of 1951, the first open season since 1893, the second largest recorded kill came from the strip mine herd. The Pitman-Robertson report of the Division of Fish and Game carries the following comment on deer from that area. "The superiority of the diversified range of the strip mine herd was reflected in above average weights and measurements in most age classes."

From the evidence at hand, there is every reason to believe that most of the mined area will again be highly productive forest land. It has completed the entire cycle of land use. Originally it supported magnificent stands of hardwood timber. This timber was cut and the lands devoted to farming. Poor management and erosion soon depleted the supply of top soil and many areas were abandoned to broom sedge, blackberries and gullies. Because it was close enough to the surface the coal has been removed and the areas replanted to many of the same species of trees.

With this reestablishment of the forest cover and the creation of the lakes in the final cuts, we can again have our forest resource combined with fishing, hunting and other forms of outdoor recreation, some areas of pasture and, I believe, others that can be profitably devoted to the production of nut crops and the by-product of quality logs for the veneer and lumber industry.

PRESIDENT MacDANIELS: If you ever think you are going to sell your logs for veneer or lumber, don't nail hammocks or other things on the trees. The metal is very soon buried and causes no end of difficulty. We will go to the next paper, which is, "Colchicine as a Tool in Nut Breeding," Mr. O. J. Eigsti, Funk Brothers Seed Co., Bloomington, Illinois.

MR. EIGSTI: Three years ago this project was conceived in a discussion between Mr. Best and myself. Then during the two-year period, all I did was turn over some Colchicine to Mr. Best. Mr. Best took the material, treated the trees and performed as well as any graduate student I had ever graduated in the 13 years that I was in university work. It is through his fine cooperation that we are able to start this project, and I look forward to this developing into a rather important nut breeding venture. But as you all know, it will take a long time. I have this paper written. It's only four pages double-spaced.

Colchicine for Nut Improvement Programs

O. J. EIGSTI and R. B. BEST, _Normal, Illinois, and Eldred, Illinois_

Colchicine (1, 2) as a plant breeders' tool is universally well known. Only limited use has been made of this technique for nut improvement. Early work was started by Dr. J. W. McKay, a member of the N.N.G.A., but numerous other problems demanded his attention and the Colchicine project was not carried to final completion. Other reports are at hand from Sweden and Japan but these results do not shed direct light on the problems under discussion today at Rockport, Indiana.

Colchicine, acting on cell-division, ultimately causes a doubling of the number of chromosomes within those cells in contact with the substance at the time of division. Such changes are transferred to succeeding generations by the hereditary chain familiar to plant breeders. Several species of nuts are among this class of plants with doubled chromosomal numbers, however, such duplications occurred in nature. A report on this phase was given at a recent meeting of the N.N.G.A. Therefore such excellent nut producing species as the pecan are naturally doubled types, called polyploids. We find numbers such as 32 representative of a polyploid situation.

Since colchicine is effective in doubling the chromosome number and that variations in chromosome number exist among species, the authors planned a series of experiments to determine the best methods of applying colchicine toward a nut improvement program. Seedlings of pecan were available and out of this experience a schedule is submitted that may be of use for other members of this association confronted with particular problems applicable to colchicine techniques.

The most satisfactory schedule for doubling the number of chromosomes is given in a number of steps as listed below.

1) Select expanding vegetative buds in the earliest stages of development.

2) Use seedlings or branches from mature trees.

3) Prune leaves and probe to the growing cone without damage to tissue.

4) Pack a small wad of cotton into the terminal point.

5) Soak this cotton by dropping .2% aqueous solution of colchicine on same.

6) Add glycerine to cotton to improve penetration of colchicine.

7) Place drop of colchicine on cotton morning and evening for four days.

8) Remove cotton wading from bud on 5th day.

9) If sufficient tests at hand, allow cotton to remain on some buds.

10) Try for at least one hundred buds treated.

11) Observe growth during first season and also next season.

12) If treated bud dies, watch for growth among lower laterals.

13) Evidence of changes appears in the new leaves, darker, thicker, greener.

14) Conclusive evidence of doubling rests with microscopic and anatomical analysis which is a task for trained technicians only.

The above procedures are suggestions for a start and everyone will wish to make changes suited to his particular needs. The concentration of colchicine need not be exact as in an analytical experiment in chemistry. One gram dissolved in 500 ml. water is an adequate and a sufficiently careful measurement. The local pharmacist or physician is well acquainted with colchicine in the practise of medicine since this drug is a standard for gout.

Effective use may be made from two specific areas of plant breeding. First, doubling of chromosomes changes sterile hybrids into fertile individuals. This is a promising field and whenever such hybrids are discovered, efforts should be made to apply the colchicine technique. Second, doubling of the chromosome number makes possible hybridization of individuals heretofore unsuccessful in such effort. In both instances germ plasm of wide genetic difference is incorporated into a new propagating breeding stock. In the case of the sterile hybrid transformed into fertile individuals, no counting of chromosomes is necessary because restoration of fertility is evidence of changes in the chromosomal makeup. However, the second type of experiment requires microscopic analysis.

There are a number of fundamental research problems in the plant sciences associated with the treatment of plants with colchicine. From horticultural subjects such as the apple,(3) pear, cranberries,(4) and grapes, it is obvious that periclinal chimeras will be of prime importance in analysis of results in treatment of nut trees. Following the treatment of a growing point with colchicine the outer layer of cells may be doubled by colchicine but the lower layers may remain unchanged. Or a reverse of this situation may obtain, and even other types. Since the formation of pollen takes place from a certain layer it is very important that such specific layers are changed. The course of plant breeding can be altered by these kinds of changes. To our knowledge, no investigations of periclinal chimeras have been made with nuts, following treatment with colchicine.

Specific experiments were conducted at Eldred, Illinois in the spring of 1951 with seedlings of pecan. The cooperation of the R.B. Best Farms and Nut Plantation made this project possible. Several types of treatment were tried. Out of this experience the above schedule listed in 14 steps was developed. Other details may be obtained by contacting the authors direct. Observations of the new growth in 1951 and 1952 were made and the shape of leaves, color, texture and general appearance suggest that doubling of chromosomes has been induced. Up until the present time, no microscopic analysis has been made but this is a contemplated step and facilities are at hand to complete this work.

While this paper is not a completed research, the authors hope that the presentation of technique will aid and stimulate interest in this new approach to nut improvement. In such instances where certain members may have a particular problem such as a true hybrid-sterile as a result of hybridity, it is hoped that the suggestions given in the above pages may lead into a new field of improvement. There are rewards in store for the plant breeder willing to master this new technique, but the mastery requires careful study and diligent work.

Literature Cited

1. Eigsti, O. J. and Dustin, P.--Colchicine Bibliography. Lloydia 10:
65-114. 1947.

2. ----, ----.--Colchicine Bibliography. Lloydia 12:185-207. 1949.

3. Dermen, H.--Ontogeny of tissues in stem and leaf of cytochimeral
apples. Am. Jour. Bot. 38:753-60. 1951.

4. Dermen, H. and Bain, H. F.--Periclinal and total polyploidy in
cranberries induced by colchicine. Proc. Am. Soc. Hort. Sci. 38:
400. 1941.

PRESIDENT MacDANIELS: The Resolutions Committee for this meeting is: John Davidson, chairman, and Dr. Rohrbacher working with him. If you have anything in mind that should be brought up in the resolutions, see one of these two men.

The next paper is:

An Early Pecan and Some Other West Tennessee Nuts

AUBREY RICHARDS, M.D., _Whiteville, Tenn._

MR. RICHARDS: There came under my observation in the latter part of last summer a seedling pecan tree growing in the city limits of my home town. It seemed that this tree had been growing unnoticed for possibly 50 years, judging by the size of the tree. The outstanding thing about this tree and what called it to my attention was a patient who came into my office complaining with a backache from picking up pecans on the 20th day of August.

I wrote my friend, Mr. J. C. McDaniel, about this pecan, and when he visited me during the Christmas holidays I gave him a sample. The only thing that he could say bad about the pecan was that it was slightly on the small side. I know personally that at least three or possibly four bushels of good quality nuts were harvested from that tree, most of them on the ground by the 20th of August.

In my section the Stuart pecan, which we use more or less as a yard-stick, was ripe the latter part of October, and we thought that possibly this tree, since it had undergone an unusually low temperature the winter before of 20 below zero, might have possibilities.

But let's dispense with this pecan and say that we believe in the old adage that one raindrop doesn't make a shower. It has a fair crop this year, and they are just as green as my Stuarts now.

There is another tree that originated in West Tennessee which Mr. McDaniel chose to call this nut "Rhodes heartnut." This tree is 7 years old from a dormant bud on a 2-year-old black walnut seedling growing on my back yard. It bore two clusters its second growing season, and since that time it has borne annually, the crops increasing in proportion to the size of the tree. This year's crop consisted of 88 clusters of nuts, with an average nut count of 10.2 nuts per cluster, giving a total of almost 900 nuts on this 7-year-old tree.

There is one more figure I'd like to give you. The count of clusters compared to the number of terminals we had this spring is better than 90 per cent clusters. I have a few bud sticks here cut from green water sprouts. That's the only kind I can find a sprout on. I brought them up to Mr. McDaniel. If anybody can talk Mr. McDaniel out of a bud he wanted to try, but I don't really know what plans he had for these bud sticks. The 7 or 8 other varieties of heartnuts I have growing don't have any that have clusters like the Rhodes.

Scab Disease in Eastern Kentucky on the Busseron Pecan

W. D. ARMSTRONG, _University of Kentucky, Princeton, Kentucky_

MR. ARMSTRONG: Mr. Chairman, ladies and gentlemen: It is nice to be here at the Northern Nut Growers meeting. This is my second session. I attend all the pecan and nut sessions in the country. I have attended Georgia-Florida Pecan Growers Association and Oklahoma and Texas Pecan Growers Association.

These plates that I have contain some of the Busseron pecans affected with pecan scab. The disease has shown up in Southeastern Kentucky, about a hundred miles southeast of Lexington, a hundred miles west of the Virginia line, and about a hundred miles north of the Tennessee line, on a straight line west of Roanoke, Virginia.

These trees were planted in bottom soil, rather well drained, and they made a rapid growth. In the original planting there were two Green River pecans, one Major, one Busseron and two walnuts, a Stabler and a Thomas.

About 1946 we noticed that all of the pecans on the Busseron were like these that we have here--did not mature, completely covered with scab fungus and dropped off the tree. The shells were so thin that you could just crush the whole pecan, hull, shell and all with no meats in them. The Major tree right beside it and the two Green River trees had none of this trouble, and they have none of it as yet. And each year now that this Busseron tree has borne there, practically all of the nuts have been like this.

At the time we located this disease first in 1946, I sent samples to the U.S.D.A. at Washington and also to the Southeastern Pecan Laboratory at Albany, Georgia, and Dr. Cole, there identified it as pecan scab.

I reported the presence of the disease to Mr. Wilkinson and to Dr. Colby and they were surprised to see the disease on Busseron in any location, and particularly that far north.

In the south this disease frequently affects Schley, Delmas, Alley and Van Deman and some others. Formerly the trees were sprayed with Bordeaux Mixture. I think they are using Zerlate now. It's a problem to be reckoned with. It occurs on the nuts and on the leaves, and it is carried over winter on the stems and the one-year shoots.

Further News About Oak Wilt

E. A. CURL, _Illinois Natural History Survey, Urbana, Ill._

In 1951 a review of the oak wilt situation was given in a paper, "Present Status of the Oak Wilt Disease", at the Forty-Second Annual Meeting of the N.N.G.A. at the University of Illinois. The following report is aimed at bringing up to date the present known distribution of the oak wilt disease, recent developments in scientific research on the disease, and possible control measures.

The oak wilt disease is caused by the fungus _Chalara quercina_ Henry and is characterized by a very noticeable bronzing and wilting of leaves that drop prematurely. Brown streaks are usually present in the outer sapwood. These symptoms may be seen from June to September or until normal autumn colors of the foliage develop.

More than 30 species of oak are known to be susceptible to the disease. Other susceptible genera of the family Fagaceae are Chinese chestnut, _Castanea mollissima_, golden chinquapin, _Castanopsis chrysophylla_, tanbark oak, _Lithocarpus densifiora_, and _Nothofagus_ from South America. The red and black oaks seem to be most susceptible and are often killed within 6 weeks after infection.

Distribution

During the past few years the oak wilt disease has spread with such rapidity and destructiveness among valuable forest and shade oaks in parts of the eastern half of the United States that its seriousness is now well recognized. At present oak wilt is known to be in the following states: Wisconsin, Iowa, Minnesota, Illinois, Missouri, Indiana, northern Arkansas, eastern Kansas, southeastern Nebraska, Ohio, Pennsylvania, West Virginia, northwestern Virginia, western part of North Carolina, eastern Tennessee, northeastern Kentucky, western Maryland and southern Michigan. Aerial surveys for 1952 are not yet complete, but there are indications of extensive new infections in Pennsylvania, Ohio, and West Virginia while the other states show a moderate increase in the number of infections.

The first case of oak wilt in Illinois was seen in Rockford in 1942. Today 54 of the 102 counties in the state have oak wilt areas. The disease is present in both the extreme northern part and the southern-most tip of the state. Practically all wilt areas in the southern half of Illinois consist of 5 trees or less that appear to have died within the last 4 years, indicating a recent spread of the disease southward. A similar condition exists in southern Missouri and northern Arkansas.

Developments in Research

In 1942 a report from the Wisconsin Agricultural Experiment Station revealed that the oak wilt disease was caused by a fungus, and research programs were started early in Wisconsin and Iowa. Neighboring states were quick to follow as surveys showed a wider distribution of the disease. Now almost every state in which oak wilt occurs is taking part in efforts to learn more about the disease and its causal agent so that practical control measures may be applied before the spread of the disease gets out of hand. The National Oak Wilt Research Committee at Memphis, Tennessee, supports in part an intensive oak wilt research program in coordination with several midwestern universities and with the U.S.D.A., Bureau of Forest Pathology.

Until recently the causal fungus of oak wilt was known only in its asexual or imperfect form living in the sap stream of infected trees. The most important question to be answered now is how the fungus spreads over long distances from diseased to healthy trees. Before this could be accomplished, however, we had to know how the fungus escapes from the inside to the outside of diseased trees where it can be exposed to agents of dissemination.

In the late summer of 1951 clearly visible mycelial mats of the oak wilt fungus were found in Illinois under the loose bark of wilt-killed trees. These mats were usually located beneath cracks in the bark; thus, they were exposed to the outside air and to visiting insects. Most wilt-killed trees contain beneath the bark numerous insect larvae of wood and bark boring beetles. Larvae were frequently found in direct contact with mycelial mats of the fungus. Larvae of the two-lined chestnut borer, _Agrilus bilineatus_, were most abundant, but larvae of species of the families Scolytidae and Cerambycidae were also present in large numbers.

In addition to the mycelial mat under the bark there was often present a thick dark pad usually in the center of the mat. It is not known yet what part this pad plays in the life history of the fungus but we do know that it is produced by the same fungus which causes oak wilt.

We also found in Illinois that the oak wilt fungus often develops into visible mats from chips of bark and wood that have been chopped from wilt-killed trees and allowed to lie on the moist forest floor. This should be remembered when considering sanitation as a partial means of controlling the disease.

In 1951 the sexual or perfect form of the oak wilt fungus was produced on laboratory media in Missouri by crossing different strains of the fungus. The sexual form is recognized by the appearance of microscopic, black, short-beaked fruiting structures or perithecia that are filled with sticky ascospores. This sexual form is a species of _Endoconidiophora_.

The sexual form of the fungus was first found in nature in Illinois in the autumn of 1951. The perithecia are produced on the mycelial mats beneath the loose and sometimes cracked bark of diseased oaks. Both the ascospores of the sexual form and the endospores or conidia of the asexual form will cause wilt if the spores are injected into oak trees.

From the foregoing information it is apparent that several methods by which the disease might be spread over long distances are possible. First, and what seems to be most probable, is transmission by insects. Adult beetles, such as the two-lined chestnut borer, which emerge from dead trees in the spring and feed on the leaves of healthy trees might transmit the spores of the fungus. Other insects might feed on the fungus mats that are exposed through cracks in the bark and carry both the sticky ascospores and conidia to other trees. Additional agents that must be considered are woodpeckers, squirrels and air currents.

Besides searching for the vector or vectors that spread the disease other important studies are in progress. Among these is the consideration of chemotherapy as a possible means of controlling oak wilt. For our purpose, plant chemotherapy may be defined as the control of disease by chemicals which are introduced into the plant. According to Dr. Paul Hoffman of the Illinois Natural History Survey, a number of chemicals have shown promise in curing small diseased oak trees when treated in a very early stage of the disease. In one instance, trees that were inoculated with the oak wilt fungus then treated with chemicals 2 years ago are still alive. The most promising results were obtained by injecting the chemicals into the soil where they are taken up by the roots and by applying chemicals directly to the foliage in a spray. Trunk injection showed least promise because of the limited distribution of the chemicals through the tree.

The use of chemicals for curing wilt-infected trees is still in the early experimental stage and is not yet recommended as a practical control measure.

In 1949 Wisconsin workers demonstrated the local spread of oak wilt through natural root grafts. They found that the poisoning of a single healthy tree with sodium arsenite often killed as many as 15 other trees nearby, indicating that their roots were connected.

Recently the results of experiments in Wisconsin explained in part what causes the leaves of diseased trees to wilt. When a tree becomes infected it is stimulated to produce tyloses or swellings in the vessels of the wood. Therefore, the flow of water from the roots to the tree top is restricted and the leaves wilt and die. It is also known that the fungus itself produces a toxin which might be responsible for the actual killing effect on the tree.

In Illinois experiments are being conducted with insects in relation to the spread of oak wilt. Insects of various species are collected from wilt-killed trees and allowed to run over or feed on laboratory cultures of the oak wilt fungus. The insects are then caged on parts of healthy trees to feed on the leaves. A single red oak treated in this way contracted the disease and died. This shows that the disease can be transmitted by an insect.

Controlling the Disease

The spread of oak wilt in local areas may be stopped by preventing the underground movement of the disease from tree to tree through natural root grafts. This can be done by (1) poisoning all healthy trees within 50 feet of diseased trees, (2) cutting a ditch 30 inches deep with a small trenching machine between diseased and healthy trees to sever root connections or (3) severing root connections with a tractor drawn plow on which a knife blade is attached. Unfortunately the use of such heavy equipment is not practical in rocky and hilly areas. Chemicals used for killing trees are sodium arsenite and ammate. Ammate is safe to use but does not kill trees as rapidly as the other poison. In some localities 2,4,5-T used as a trunk spray has given satisfactory results in killing small trees.

If infected trees are left standing mycelial mats with their numerous spores develop under the loosening bark. It is therefore advisable to cut and burn all parts of diseased trees as soon as possible after symptoms appear.

A combination trenching and eradication program was started in the summer of 1950 in the Forest Preserve District of Cook County in Illinois. According to Mr. Noel B. Wysong, Chief Forester, 2 newly wilted trees were found in the Forest Preserve in 1948, 72 trees in 1949, 141 trees in 1950, and 96 trees in 1951. The count for 1952 is not complete but a continued decrease in the number of new infections would indicate good control.

There is no information on resistant species of oak. In very rare cases, however, trees have been observed to recover after showing symptoms in the early spring.

Future Outlook

Among the many things that we need to know yet about the oak wilt disease and its causal fungus one is outstanding. How does the disease jump from one infection center to healthy trees 200 yards, 2 miles or even 100 miles away? Although spread through root grafts may be controlled by severing root connections, the value of such a control measure is limited as long as the agent or agents responsible for long distance spread remain unknown. The discovery of other methods of spread might result in the development of control measures that are cheaper and less drastic than those known at present.

A great deal remains to be done and research is increasing in the various states concerned. There is reason to believe that oak wilt can be checked before it reaches devastating proportions comparable to chestnut blight which wiped out our American chestnuts.

MR. SLATE: What is the origin of the fungus? Is it a native fungus, or imported?

MR. CURL: Yes, it is a native fungus, as far as we know.

MR. SLATE: Any evidence that the fungus is mutating to make more virulent strains?

MR. CURL: That's something that hasn't been found yet. There are several strains of the fungus, what we call strains, because they will form the sexual stage, and a strain alone will not. There is not too much known about that yet, the strain business.

MR. GRAVATT: Just a word. We had a conference in Beltsville all day Sunday about the recent developments on the oak wilt. There has been very extensive spread in Pennsylvania, Ohio, West Virginia and Maryland this year. We are very much alarmed about the situation. The Chinese chestnut is very severely affected. We have learned that in Missouri. One year there were three Chinese chestnuts killed by the fungus, the next year 60. The oak wilt is a serious threat to the chestnut orchards.

Life History and Control of the Pecan Spittle Bug

STEWART CHANDLER, _Associate Entomologist, Ill. Nat. History Survey, Urbana, Ill., Consulting Entomologist, Southern Illinois University_

Since it was a year ago that this subject of spittle bug was first brought to the attention of the Northern Nut Growers Association, it might be well to review briefly the high lights of that report. I told you at the annual meeting at Urbana, something of the life history. There are two broods, one appearing in June and one in July. The adult is a small sucking bug about an eighth to a quarter inch long. The species at that time was uncertain but now has been determined by specialists in that group as _Cercoptera achatina_ Germ. This insect, I reported, is not the same as the one occurring on meadow and other field crops, not only the species but the genus being different. The distribution was found to be in every area where pecans are grown. As to its importance I pointed out that in Illinois it had become very serious in the past three or four years, apparently causing a marked reduction in crop. Control measures were directed against the nymphal stage, which is protected by the spittle which the insect emits continuously while feeding. Three insecticides were tested at Anna, Illinois, Lindane, parathion, and tetra ethyl pyro phosphate, known as TEPP. Lindane proved to be approximately 95% efficient, parathion roughly 60% and TEPP about 10%.

In 1952 the work was resumed in the orchard of Conrad Casper near Anna, Illinois and was begun at the Richard Best place at Eldred, 175 miles northwest.

In 1952 five phases of the work with pecan spittle bug were undertaken as follows:

1. A study of the importance of the pecan spittle bug.
2. The hibernation of the insect.
3. Life history and occurrence of the various stages and broods of
the insect in relation to nut development of the pecan.
4. Control measures.
5. Varietal susceptibility to the insect.

1. Importance of the insect

_Hibernation Studies_

To learn to what extent if any the insect reduces the crop of pecans, terminal shoots from trees sprayed the previous season with three different materials were compared with the unsprayed check. These are shown in Table 1.

Table 1. Pecan spittle bug effect of 1951 sprays on terminal shoots in spring of 1952

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Dead shoots
Treatment per hundred

Check 87
TEPP 62
Parathion 17
Lindane 4
===================================================

Since these terminals shoots later develop most of the nuts it would appear that the pecan spittle bug is responsible for much of the loss of crop under these heavy infestations.

It was planned to follow this up with later examination of nuts, and this was done with the assistance of Mr. J. C. McDaniel, but unfortunately it was found that this was the off year and the crop was very small, so we could not definitely settle that point. This will be a job for the future.

2. Hibernation studies.

In August of 1951, I introduced adult bugs into a cage placed over a branch of an unsprayed pecan tree for the purpose of determining whether there was possibly a third brood. Finding none the branch was removed and examined to study the hibernating eggs and the egg slits in which they were layed. The slits were not over a quarter inch long and frequently in pairs. Eggs were deep enough that they were rarely seen without opening the slits. Many slits were found containing egg shells, presumably from the previous brood, but possibly from a season earlier as the slits are corked over.

Following this study branches were cut from the sprayed and unsprayed blocks and gone over very carefully to find the numbers and location of the egg splits and the numbers containing live eggs and egg shells. Each split would contain as many as 5 or 6 eggs. Table 2 show their numbers and locations, and Table 3 the effect of sprays on numbers of live eggs.

Table 2. Pecan Spittle Bug Location of egg slits in branches

=================================================================
Diameter of branches, inches
1/8 to 1/4 3/4 3/8 1/2 1/2 to 1 inch
-----------------------------------------------------------------
Live eggs 2 9 3 1 0
Egg shells 5 42 94 23 0
-----------------------------------------------------------------

Table 3. Pecan Spittle Bug Effect of 1951 sprays on number of eggs Examinations made March 4, 1952

=======================================================
Inches wood Number of Slits with
Treatment examined live eggs egg shells
-------------------------------------------------------
Check 508 10 63
TEPP 795 5 25
Lindane 478 0 13
-------------------------------------------------------

3. Life history and correlation of stages of insect and nut development.

It was soon found that the pecan spittle bug was putting in its appearance earlier according to the calendar than in 1951 so an effort was made during the season to correlate insect life history and nut development during the season. Table 4 give some of the principal points in both.

Table 4. Pecan Spittle Bug and Nut Development Anna, Illinois, 1952

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Insect Date Tree
--------------------------------------------------------------
Egg stage Apr. 24 Catkins 1/2 to 3/4 inch
First nymphs May 5 Catkins 1 to 1-1/2 inch
Many nymphs and spittle May 12 Catkins 2 to 3 inches
Fruit buds
Peak hatch May 20 Female flowers
Spittle drying June 2 Nuts developing
1st. 2nd brood June 27
Hatch mostly over July 7
Spittle drying July 26
--------------------------------------------------------------

Another phase of life history which is of practical importance is the increase of second brood over first. Records were made both at Anna and at Eldred in unsprayed blocks at approximately the peaks of occurrence of nymphs and spittle, and are tabulated in Table 5.

Table 5. Pecan Spittle Bug Infestation, first and second broods, 1952 Number of spittle masses per 100 terminals

==========================================================
First brood, June Second brood, July
----------------------------------------------------------
Anna 41 62
Eldred 23 50
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This table shows an increase of approximately 50% at Anna and 100% at Eldred. It is thought that a 3 inch flash flood which occurred at Anna might have reduced the first brood infestation somewhat after the counts were made and been responsible for no greater increase and possibly that the heat and drought in both places might have resulted in a reduction. Be that as it may the total infestation was not as severe in 1952 as in 1951.

4. Control.

_First Brood Sprays_

It was originally planned to spray in both places but at Anna the owner sprayed all but the 1951 check block with parathion early and the infestation was reduced to the point where later hatch did not build up to a sufficient point that good results could be observed so no spraying was done at Anna till the second brood. At Eldred two materials only were available, Lindane and Dieldrin.

At Eldred we had two difficulties in spraying. One was the type of machine with which I was not familiar and the other the inaccessibility of some of the trees. The machine is probably more fitted for field crop work than for large trees. It is called a Mechanical Aresol Generator, manufactured by the Hessian Microsol Corporation of Darien, Conn. The engine is a Wisconsin Air cooled motor made in Milwaukee, Wisconsin. The machine was mounted on a platform and transported in the orchard on a truck. Two fifty gallon barrels constitute the tank. Due to the nature of the machine and to lack of agitation only liquid materials can be used in it. It uses a much smaller amount of material than I had been accustomed to, and my first job was to learn to what extent the materials must be concentrated to compensate for the small output and how to get a comparison with the amounts used in regular orchard sprayer. In concentrate tests on fruit trees we arrive at this by judging the number of gallons which a tree would normally receive with a standard sprayer. There was little background to go on with nut trees and the problem was further complicated by the arrangement of trees which were not planted but grafted in their original positions in the woods. A clump of trees which could not be approached individually might have to receive not much more material than one tree which could be hit from both sides. Sizes of trees also varied. It was decided to use only 25 gallon lots of material and even this small amount sprayed from 55 to 65 trees of varying sizes. It was soon seen that the tops of the moderate and large sized trees were not covered very well. For the first brood sprays at Eldred about six times as much material per 100 gallons was used as had been successful at Anna the previous season. The results are shown in Table 6.

Table 6. Spittle Bug Control, Eldred, 1952 First brood, sprayed May 23, examined June 9

=========================================================
Treatment Amount in Spittle masses
100 gallons 800 terminals
---------------------------------------------------------
Dieldrin 1 gal. of 18-1/2% 18
Lindane 1 gal. of 20% 27
Check ------ 189
---------------------------------------------------------

It will be seen that the reduction over the unsprayed blocks was about 90% with Dieldrin and 85% with Lindane.

For second brood sprays at Eldred materials were increased to about 8 times normal in hopes of getting better results. In this test 10 trees were selected in each block that could be reached moderately well and sprayed separately before the entire block was sprayed. Records were made the day before spraying, 3 days after spraying, and 10 days after spraying. Four materials were available, making five blocks with an unsprayed check. The results of these sprayings are given in Table 7.