RECENT WORK ON THE CHESTNUT BLIGHT

Keller E. Rockey

Forester in charge of Demonstration Work, Pennsylvania Chestnut Tree Blight Commission

The history of the blight, briefly outlined, is as follows:

In 1904 the diseased condition of the chestnut trees around New York City was noted and an examination of them showed that they were being attacked by a disease at that time unknown. Investigations since then have shown that the blight had been at work there and elsewhere for a number of years before that time, but it has been impossible to determine just when it first appeared or where. The disease was studied and described at that time.

On display here are specimens and photographs showing the appearance of the blight so that I will not go into that part of the subject in detail. I hope that you will notice, however, the symptoms by which the disease is recognized: 1st. The small red pustules which produce the spores and, on rough barked trees, appear only in the crevices. 2nd. The peculiar mottled appearance of the inner bark of the canker. 3rd. The discoloration of the outer bark. 4th. The danger signals, such as withered leaves in summer or persistent leaves or burrs in winter, suckers which develop at the base of cankers, and the yellowish cracks which soon appear in the bark over the cankers.

Workers in the Bureau of Plant Industry, Washington, D. C., have been studying the blight since 1908. In the Spring of 1911, a bill creating the commission for the investigation and control of the blight in Pennsylvania was passed, and the active work began in August 1911. The method upon which the Commission is working is outlined in Farmers' Bulletin No. 467, of the Department of Agriculture, and consists briefly of determining the area of blight infection and in removing diseased trees west of a certain line, with the purpose of preventing the western spread of the blight.

This Commission has ascertained as accurately as possible the amount of infection in the various parts of the state and the results are given in a map on display here. The state is divided into two districts by a line drawn along the western edge of Susquehanna, Wyoming, Columbia, Union, Snyder, Juniata and Franklin Counties, which is approximately the western line of serious blight infection. West of this line a large portion of the state has been scouted, and the remainder will be finished early in 1913. We have learned by experience that in the winter, after the fall of the leaves, the best scouting work can be done. Persistent leaves and cankers along the trunk are readily seen, and more and better work can be accomplished than in the summer, except when the snow is very deep.

Blight infections have been found in counties adjacent to this line: also in Fayette County, near Connellsville, in Warren County, near Warren, and in Elk County, near St. Mary's. These three infections were directly traceable to infected nursery stock, and in one case the blight had spread to adjacent trees. A large area of diseased chestnut in Somerset County illustrates the harm done by shipping infected nursery stock. The centre of this infection is a chestnut orchard where about 100 scions from an infected eastern orchard were grafted to native sprouts in 1908. The percentage of infected trees in the orchard from which the scions were obtained, according to a count made this Fall, averages 80 per cent. Evidently these scions brought the disease into this region, for the grafts have all been killed by the blight and every tree in the orchard is killed or infected by disease. On adjoining tracts over 5,400 infected trees have been cut, and there are a number of others in process of removal, radiating in all directions from the orchard as a center to a distance of three miles. Another infection of 143 trees was found in Elk County. It is thought that three trees at the centre of infection were diseased in 1909, although it is possible that one of these trees was already infected in 1908. In 1910, 27 additional trees were infected; in 1911, 50 additional trees, and in 1912, 228 additional trees. The disease spread in all directions from the center of infection to a distance of 700 feet.

These infections are interesting in showing the rate at which the blight may travel in healthy timber.

These infections have all been removed and it is the expectation that by the end of January 1913 all scattered spot infections will be removed from the territory west of the line previously mentioned, and that, to the best of our knowledge, these western counties will be free from blight. In 1913 the field force will be concentrated on the advance line and the work will be carried eastward. The Commission has the power to compel the removal of infected trees. In the western part of the state this power has been exercised in the few cases where it was necessary. As a rule, however, the owners are not only willing but anxious to get rid of the infected trees, and our field men are given hearty support by individuals, granges and other organizations. The timber owners of Elk County had printed and posted an announcement that the chestnut blight had been found in the locality and warned the people to be on the look-out for it. In addition the Commission has had a man, for a short time at least, in each of the eastern counties of the state, and their time has been taken up principally by those who requested inspections of timber with the view of determining the percentage of blight infection and the best method to be pursued in combating it and realizing on their timber. Our men are all deputy wardens, with the authority which is attached to this office, and are instructed to do their utmost to prevent fire damage.

An exhibit which consists of specimens showing the blight in various stages together with photographs, literature, etc., was placed in about 30 of the county fairs throughout the state. The appreciation of the public has been so clearly shown that next year it is the intention of the Commission to continue and perhaps increase this phase of the work, and to place large permanent displays at the Commercial Museum, Philadelphia, the State Capitol, Harrisburg, and other places.

Many of the Annual Teachers' Institutes have been reached with a display and lecture. We have arranged also to have a speaker at fully one hundred of the Farmers' Institutes this winter. We are also arranging to have a permanent display at many of the public schools, normal schools and colleges, where instruction on the blight is given. An effort was made last winter to enlist the service of the boy scouts and we are indebted to them for considerable work, chiefly in an educational way. The successful outcome of all our work will depend in a large measure upon the owners themselves, and it is our purpose to give them all the information possible upon the whole subject.

The Commission established a Department of Utilization which is collecting information on the various industries which use or might use chestnut wood, listing the buyers and owners of chestnut wood, thus assisting owners of blighted chestnut trees in marketing their timber to the best advantage. The Department is trying to increase the use of chestnut wood by calling attention to its many good qualities, and thus utilize the large quantity which must necessarily be thrown upon the market. There has been more or less discrimination against blighted chestnut timber. This has been in many cases unjust, since the blight does not injure the value of the wood for most purposes for which it is used. However, the owners sometimes fail to realize that the blight cankers are the most favorable places for the entrance of the borers, and that where a large number of trees are being considered, a percentage of them will be materially injured by insects which follow blight infection. Where telegraph poles are barked, it is often seen that borers have attacked the wood under blight cankers, and have not touched any other part of the tree. All blighted timber should be cut before death to realize its best value, since insects and wood-destroying fungi cause the very rapid deterioration of dead, standing timber. There has been a good market in almost every locality for poles, ties and the better grades of lumber. Cordwood presents the difficult problem of disposal. The best market for this is in the central part of the state, at the extract plants. The Commission has secured from the Pennsylvania R. R. a special tariff on blighted chestnut cordwood so that this product may be profitably shipped from greater distances than before.

The Commission has inspected all chestnut nursery stock shipped from nurseries within the state and has also provided for inspection of all chestnut stock entering the state. This should prevent a repetition of infections in the western part of the state which might destroy millions of dollars worth of timber.

From time to time publications have been and will be issued by the Commission, which are obtained free of charge upon request, or they may be consulted in the leading libraries throughout the state.

An appropriation for $80,000 was given by the last Congress for scientific research work upon the blight disease and work is being carried out in cooperation with the various states. Several of the Government investigators are now at work upon our force. Some of the most important unsolved scientific problems of the blight, as given by Secretary Wilson, in his message, to Congress, are as follows:—

First, the relation of the disease to climate.

Second, the relation of the parasite to the varying tannin content of the tree.

Third, the origin of the disease.

Fourth, relation of birds and insects to the dissemination of the disease.

Fifth, the nature and degree of resistance of the Asiatic species. Another problem in relation to tree treatment may be added, that is, the relation of spores and mycelium to toxic agents.

The Pennsylvania Commission maintained laboratories during the summer at Charter Oak, Centre County, and at Mt. Gretna, Lebanon County. The latter has been moved to Franklin and Marshall College, Lancaster, for the winter. We have also had a laboratory at the University of Pennsylvania, which has been greatly enlarged this fall.

The number of people who informed us that they had discovered a sure "cure" for the blight made it necessary to obtain an orchard near Philadelphia where all such discoverers were given an opportunity to demonstrate the efficacy of their remedies. It might be noted that in every case the blight is thriving as usual. These cures consisted largely of an injection of a toxic principle by some means into the circulation of the tree. In some cases this was accompanied by a fertilizer of some kind, and this fertilizer may account for the apparently improved condition of the tree in some cases, after such remedies were used, since the growth was increased and the leaves and branches had a healthier appearance. This increased growth has not had any appreciable effect upon the rapidity of spread of the blight mycelium. As the experiments are not officially finished and recorded it is too early to give any further data. Our pathologists have also conducted experiments in this same line but no medicinal remedy or fertilizer has yet been found.

The varying chemical constituents of chestnut trees, principally tannic acid, have often been suggested in regard to the origin and spread of the blight. Investigators are now working along this line and we hope, for valuable results before long.

The origin of the disease, as already stated, is something of a mystery, and there is as yet no generally accepted theory, although many people have very pronounced views on the subject. Many puzzling facts have been noted since investigating the disease in Pennsylvania, among them being the large percentage of infection in eastern York and southern Lancaster counties, the relative small percentage in certain localities around which the blight is generally prevalent, and recent infections found in Warren and other western counties, a great distance from what is known as the western advance line of the disease.

Our pathologists have reported some very interesting facts in regard to the dissemination of the blight. In the preliminary report of the summer's work at our field laboratories the results tend to show:

First, the prolific ascospore stage is very important in causing the spread of the blight, the spores at this stage being forcibly ejected from the pustules and borne through the air for some distance. This ejection of spores takes place under natural field conditions only when the bark has been soaked by rain, but the expulsion of spores is also dependent upon temperature conditions and ceases entirely at temperatures from 42 to 46 degrees F. and below.

Second, the wind plays a large part in local ascospore dissemination.

Third, birds and insects (except ants) are apparently of very little importance in the dissemination of the blight except in providing wounds. Further investigations of the importance of ants is being made during the present winter.

Several kinds of beetles have been observed eating the pustules and are in this way beneficial, since tests show that they digest and destroy the spores. It has also been suggested by workers in the Bureau of Entomology that such beetles, which are of several kinds, may be of value in the attempt to control the disease. These are perhaps the only natural enemies discovered to date.

The proper classification of the chestnut blight fungus has also been the subject of much discussion. Last winter specimens of what in external characteristics appeared to be Diaporthe parasitica were found in western Pennsylvania, Virginia and elsewhere, growing upon chestnut, oak and other species. This condition was puzzling and the subject of some controversy. It has been found, however, that this fungus, called the "Connellsville fungus," is a distinct species closely related to the true blight fungus, being, however, entirely saprophytic. Cultural distinctions are apparent and the ascospores differ in size and shape so that no further confusion need occur.

Upon the question of immunity of certain kinds of Asiatic stock, there is very little to report beyond what was known one year ago. In the investigations made the work has been hampered by the fact that much of the so-called Japanese stock is in reality a hybrid of European or American species. In 1909, 45 Japanese seedling trees were set out at Gap, Lancaster Co., for experimentation along this line. A recent examination showed that 90 per cent are infected. Concerning the variety or purity of this stock, I have not been informed. Our force as well as others are at work upon the problem which will require many years' study.

Previous investigations seem to show that certain pure strains of Japanese and Korean chestnut are resistant to the blight. Blight cankers may be found upon them but they are less easily infected and suffer less than the more susceptible varieties. With this as a working basis, considering the results that have been attained in other fruit by selection and hybridization, the situation is hopeful. Prof. Collins said at the Harrisburg Conference in February that "There is no reason to doubt that we may eventually see an immune hybrid chestnut that will rival the American chestnut in flavor and the Paragon in size".

In southern Europe chestnut orcharding is a well established and profitable industry. In the United States chestnuts have been considered a marketable commodity ever since the Indians carried them to the settlements and traded them for knives and trinkets. The demand has always exceeded the supply and at the present time about $2,000,000 worth of nuts are imported from Europe annually. With the development of the better varieties of the American nut has come an increased activity in the United States and the chestnut orchard industry promises to become one of very large importance. It has an added advantage that the trees can be grown upon the poorer types of soil which are not adaptable for farming or the raising of other fruit.

At the present time there are in what is known as the blight area of Pennsylvania, or eastern half of the State, about 100 orchards ranging from 12 trees up to 400 acres in extent. These orchards are in varying stages of blight infection, some of them being almost entirely free, due to the attention which has been given them. In order to protect such orchards the Commission is compelling the removal of infected trees within a certain radius of them.

As you know the blight has been a very serious factor in this industry. Some of the orchards have been completely annihilated and the income reduced from several thousand or more dollars per year to nothing. Whether or not the blight will completely wipe out the orcharding industry is a subject of large importance. Personally I believe that chestnuts will be raised commercially in Pennsylvania in increased abundance, and as the various phases of the blight subject are brought to light, keeping the disease under control can be more easily accomplished. At the present time this is being done in certain orchards by the present methods of examining the trees often, treating each infection, or removing the tree. If this policy is successfully pursued for several more years it will demonstrate conclusively that chestnuts can be grown in spite of the blight and this will mean an opportunity to use vast areas of waste land in Pennsylvania and in the other states, in a highly profitable manner.

The Chairman: The subject of the next paper is Some Problems in the Treatment of the Chestnut. It will be presented by Mr. Pierce, after which we will have a general discussion of the entire subject.

Mr. Pierce: Mr. President, ladies and gentlemen: I see that, as we wrote our papers separately, some of the things I had in mind will be similar to those Mr. Rockey had.