THE GRAY BULB-ROT OF TULIPS 



CAUSED BY RHIZOCTONIA TULIPARUM 



(KLEBH.) N. COMB. 



H. H. Whetzel and John M. Arthur 1 



The gray bulb-rot of tulips, long known in Holland and Germany, 

 apparently has not until recently (Whetzel and Arthur, 1924) been 

 reported from North America. In April, 1922, Dr. William Crocker, 

 Director of the Boyce Thompson Institute for Plant Research at Yonkers, 

 New York, sent some diseased bulbs from a bed in a near-by garden to the 

 Department of Plant Pathology at Cornell University for diagnosis. 

 Dr. L. M. Massey obtained from these bulbs pure cultures of a sclerotial 

 fungus. These cultures were turned over to the senior author the follow- 

 ing June. Their marked similarity to cultures of Sclerotium tuliparum 

 Klebahn which he had obtained from Holland some years ago and was still 

 carrying along, seemed to warrant a further investigation of the disease. 

 A cooperative undertaking for this purpose was at once arranged between 

 the two institutions, the results of which are here set forth. 



THE DISEASE 

 HISTORY 2 



This disease was known in Holland at least as early as 1884, when it 

 came to the attention of Wakker (1885:22), who was then engaged in 

 an investigation of bulb diseases for the Dutch Bulb-Growers' Association. 



Wakker appears to have been the first to describe the disease, which he 

 designated merely as the " tulpenziekte " (tulip disease). His observa- 

 tions on the symptoms of the disease and the character of the pathogene 

 are extraordinarily clear and accurate. 



Ten years later Ritzema Bos (1894:229) began an investigation of the 

 disease, which he found very destructive in certain sections of Holland at 

 that time. Although lie refers to the earlier work of Wakker, he appears to 

 regard it as of little importance. In his later report (1903 a: 178 [p. 23 

 Centbl.]) he describes symptoms which are undoubtedly those of the gray 

 bulb-rot, but confuses t his disease with I he Botrytis blight, which he also had 

 before him (Hopkins, 1921:316-317). Ritzema Bos apparently assumes 



1 Biochemist of the Boyce Thompson Institute for Plant Research. 



2 In view of the fact that no previous paper on this disease lias appeared in English, and since several 

 of the riK.st important articles cited in this discussion are not readily accessible to American pathologists, 

 a rather full review of the previous' literatim- on the bulb-rot is here presented. 



3 



