A FUSARIUM BULB ROT OF ONION AND THE RELATION 
OF ENVIRONMENT TO ITS DEVELOPMENT 1 
By J. C. Walker, Pathologist, and E. C. Tims, Collaborator, Office of Cotton, 
Truck, and Forage Crop Disease Investigations , Bureau of Plant Industry, 
United States Department of Agriculture 2 
INTRODUCTION 
The Fusarium bulb rot of onion was first brought to the attention of the 
senior writer in 1918 by its occurrence in the large onion-set-growing region in 
the vicinity of Chicago. It was then one of the three most serious diseases of 
the onion-set crop, and since that time its importance has increased rather than 
diminished. A similar disease had been reported from Ohio in 1910 by Selby 
(8, p. from Connecticut in 1915 by Clinton (I), and from Japan in 1914 
by Hanzawa ( 4)• Since 1918 the reports of Fusarium rot of onion in the field as 
well as in storage and transit have become more numerous and widespread, 
while the toll of losses due to this disease is rapidly increasing (2, 3, 6). 
Laboratory investigations of the disease were begun by the writers in 1921 
with material collected in Illinois. Shortly after that time it was learned that 
Dr. G. K. K. Link was initiating studies upon the disease as it occurred in various 
other onion-growing regions. Since he was in the better position to assemble 
and study strains of Fusarium on onion from widely different sources, the writers 
have not attempted to determine whether or not one or more species of Fusarium 
may cause the bulb rot. On the contrary, they have confined themselves to the 
study of a single strain of Fusarium which appears to be the primary cause of 
the bulb rot in the onion-set sections of Illinois. It is not maintained however 
that this is the sole cause of the disease in this or other sections, for further 
survey and study may show other strains or species to be pathogenic on onion 
bulbs. 
This strain belongs to the section Elegans and resembles Fusarium hyper - 
oxysporum Woll. in some respects and in others it is similar to F. redolens and F. 
oxysporum. The description of Fusarium cepae by Hanzawa, though not as 
complete as might be desired, coincides very closely with the organism under 
discussion, and the symptoms of disease are identical. Therefore the present 
strain is referred‘to this binomial and a fuller description of its characters is 
given. 
DESCRIPTION OF THE DISEASE 
Under midwestern conditions this disease appears usually some time after 
the 1st of July. A progressive yellowing and dying back from the tips of 
the leaves is the first sign. (See PL 1.) The rapidity of this development will 
vary, sometimes the aerial part dying completely within one or two weeks 
and in other cases the decay extending over a much longer period. Appearance 
of newly affected plants may continue until harvest. When the early signs of 
the disease appear above ground, decay has already started at the stem plate. 
1 Received for publication Feb. 20,1924. 
* The writers are indebted to the department of plant pathology, University of Wisconsin, for laboratory 
and greenhouse facilities placed at their disposal during the course of this investigation. 
* Reference is made by number (italic) to ‘‘Literature cited," pp. 693-694. 
Journal of Agricultural Research, 
Washington, D. C. 
( 683 ) 
Vol. XXVIII, No. 7 
May 17, 1924 
Key No. G-381 
