Neil E. Stevens

Recent developments in plant diseases in the United States

The present summary of information regarding certain diseases in the United States through the season of 1940 is in large part a continuation of one published earlier in this journal (23) which contained information up to and including 1935. As in the earlier paper, the choice of diseases to be included has been determined by the present interest of the disease due to its recent appearance in this country or to marked fluctuations in extent or severity, and by the completeness or reliability of available information regarding its incidence. Miss Jessie I. Wood, who collaborated in the preparation of the earlier paper, has aided in this one with numerous valuable suggestions. Much of the material here summarized is, of course, taken from the Plant Disease Reporter. For economy and convenience, references to this publication are made merely by volume and page, italicized, in parentheses inserted in the text.

Plant disease control by unusual methods

This article, like the preceding (13), is admittedly incomplete. All that is attempted is a description of some of the less usual methods of plant disease control that have been suggested or have come into more general use during recent years. Naturally no claim is made that these methods are better merely because they are different. A new spray material or a new method of applying spray materials might actually have greater economic significance. If, however, the profession of plant pathology is to avoid stagnation, continuous search for new means of disease control must be maintained.

Plant diseases during the years 1941–1945 in the United States and Canada

The achievements of American agriculture during the war years have been widely acclaimed. The part played by the abundantoften record breaking-crops produced on this continent in supplying food to our fighting forces and to allied civilian populations needs no further comment. The fact is too little known, however, that during this period there were few disease outbreaks which caused critical losses in major food crops in the United States or Canada. No reader of this journal will be tempted to misconstrue the foregoing statement. Plant diseases certainly reduced the yield of many, probably of most, crops. The losses were, however, usually not dramatic. There was nothing approximating the epidemic of stem rust of wheat which in 1916 cut American wheat yields more than a third and tragically upset national and world food plans. The major losses sustained from plant diseases were of a quite different sort. They were of the type which students of plant diseases often seriously discuss but too rarely mention in print. For example, in the opinion of some of the keenest and most experienced plant pathologists the yields of important clonal crops are regularly cut from 50% to 60%o by root rots. However, not even the editor of The Botanical Review is likely to call for a summary of unpublished estimates of losses from plant diseases. This article, like its two predecessors (12, 13), must be based largely on information already available through publication. Thus the choice of the diseases to be included must be determined largely by the availability of records. Numerous colleagues in the profession have been consulted and have made helpful suggestions as to which diseases should be mentioned.