It is the common opinion of authorities that fruit-growers lose millions of dollars annually on account of diseases of their crops. It has been estimated that 75 per cent of this loss may be prevented by spraying - the chief method of fruit disease control.
In order to understand and to perform properly the measures of fruit disease control, it is essential that some knowledge of the cause of the disease in hand be acquired. In recent years scientists and laymen alike have recognized the importance of certain technical details regarding the cause in order to undertake the prevention of these losses. Similarly, the value of other facts must be apprehended, such as the history of a disease, where it originated, with what rapidity the pathogene has spread, the losses it is capable of incurring, and under what conditions these destructive outbreaks (epiphytotics) occur.
As evidence that the practicing agriculturists are rapidly becoming acquainted with the value of scientific knowledge regarding diseases of plants, it is only necessary to point to their interest and cooperation in the matter of obtaining accurate information under field conditions. The prejudiced and critical attitude of the grower is now for the most part of no consequence. Little self - protection is now needed by the experimental plant pathologist; the grower's attitude is no longer antagonistic, but he is friendly and, what is more encouraging, he seeks with confidence the advice of the phytopathologist.
At present, circumstances do not permit the plant doctor to call in person or by letter to advise with every fruitgrower regarding his many problems. No experiment station can furnish bulletins that will answer the purpose in every detail. And up to the present there have been no American texts or reference books dealing wholly, and in some detail, with the diseases of fruits. It is hoped that this Manual will give to the fruit - grower such information on fruit diseases as is available to date. The authors realize, however, that the best possible book on fruit diseases cannot entirely meet the situation. Possibly the day will come when each neighborhood will be provided with its own plant doctor; until this time the advice must remain qualified.
It may appeal to the critic that many technical details are included which will only confuse the grower. But the time has come when the grower and the plant pathologist must meet on an equal footing. No longer should the grower refuse to understand the philosophy of his operations. Any careful consideration of a disease involves the use of certain terms not common in the farmer's vocabulary. The terminology of the plant pathologist should be no more bewildering than that of the family physician or the veterinarian. To assist in an understanding of the usage of certain terms in the text, a glossary is appended. These terms may be found in dictionaries, but differences in the shades of meaning often lead to confusion.
The grower is in the habit of grouping his troubles as well as his labor and projects. In his own mind he classifies diseases on the crop basis. Accordingly, only fruits are included in this Manual. It is hoped that other crops may be the subjects of similar manuals in the future. In seeking guidance on any disease-control problem, the fruit - grower groups fruit diseases according to the fruit. It has therefore seemed best to discuss the diseases of a given fruit in one place. The arrangement of the fruits in the text, that is, alphabetically, is simple and therefore useful. The authors have attempted to discuss the diseases of each fruit somewhat in the order of their general importance and occurrence in the United States. Obviously, however, this arrangement is difficult to follow.
Some difficulty has been encountered in compiling certain parts of this book. The authors have had no opportunity to become acquainted with several of the diseases under field conditions. But in some instances inaccuracies have been eliminated by a careful criticism of the manuscript by competent men from other sections of the country. Many other parts of the manuscript have been read by colleagues in the Department of Plant Pathology at Cornell University. To the following contemporaries the authors would express their appreciation for valuable assistance along this line: Dr. H. M. Fitzpatrick, Mr. E. F. Hopkins, Professor H. S. Jackson, Dr. W. H. Rankin, Dr. Donald Reddick, Dr. J. R. Schramm, Dr. V. B. Stewart and Dr. J. L. Weimer. For specimens from which some of the photographs were made, and for other accommodations, the authors would make acknowledgment to the following: Dr. J. T. Barrett, Professor H. P. Barss, Dr. Charles Brooks, Mr. H. F. Dietz, Mrs. L. R. Hesler, Dr. F. D. Kern, Professor W. H. Lawrence, Dr. T. F. Manns, Mr. G. W. Martin, Mr. J. W. Roberts, Professor W. H. Sackett, Mr. F. N. Wallace, Dr. F.A. Wolf and Mr. L. A. Zimm. For photographs loaned to the writers due credit is given in each case.
Lex R. Hesler, H. H. Whetzel. Cornell University, Ithaca, New York.
October 1, 1916.