574 STATE BOARD OF AGRICULTURE. 



A PHOMA EOOT ROT OF CELERY*. 



Technical Bulletin No. 53. 



BY C. W. BENNETT. 



Introduction. 



There are several million acres of muck lands in Michigan which consti •■ 

 tute an appreciable percentage of the possible farming area of the State. 

 Some of this is highly improved and forms some of the most valuable land 

 to be found in any of the great agricultural sections of the country. This 

 type of soil, on account of its high organic content and physical properties, 

 is peculiarly adapted to the growing of truck crops. Celery, cabbage, let- 

 tuce, and onions, in particular, are crops which thrive well and which yield 

 good returns. The growing of these crops for the markets of Chicago, De- 

 troit, and other large cities of the north central and middle west, constitutes 

 an important part of Michigan agriculture. 



On account of the liberal returns per acre and the brisk market demand, 

 celery has become a leading crop on muck land favorably situated in rela- 

 tion to markets. The high organic content of muck soil is conducive to 

 rapid vegetative growth which produces the very best quality in celery and 

 also enables the grower to put his product on the market early in the season. 

 In some areas two or three crops are gro^\^l on the same soil each year. In 

 such cases the second and third crops are put in between rows just before 

 the preceding crop is placed in boards for bleaching. Thus, the land is in 

 celery the entire growing season. Along with this intensive culture, the 

 value of the crop has led to an almost complete absence of rotation in many 

 of the chief celery growing districts. Not infrequently do we find fields 

 which have grown celery continuously for a period of more than thirty years, 

 the fertility of the soil not only being maintained but greatly improved by 

 liberal application of manure. 



The absence of rotation, the interchange of plants, and the procuring of 

 seed from a great many sources has resulted in the introduction of practi- 

 cally every disease known to the celery plant. One of the most recent of 

 these invaders is a Phoma disease, which, in Michigan, was first discovered 

 at Kalamazoo in the spring of 1914 by Dr. G. H. Coons of the Michigan 

 Agricultural College (2) . The disease, since its introduction has not spread 

 rapidly in epidemic form, but in several cases it has been very destructive 

 on small acreages. These destructive outbreaks have seemed serious enough 

 to warrant a systematic study of the disease with a view to adding some- 

 thing to the knowledge of its relation to weather and soil conditions and to 

 our methods of coping with the problem which this disease presents to cel- 

 ery growers. 



•Presented to the Faculty of the Graduate Schocl of the Michigan Agricultural College as a thesis 

 in partial fulfillment of the requirements for the degree of Master of Science. 



The writer wishes to acknowledge his indebtedness to Dr. E. A. Bessey and to Dr. G. H. Coons of 

 the Department of Botany for valuable aid and suggestions during the course of this work as well as 

 for aid in the preparation of the manuscript. 



