THE RELATION OF TEMPERATURE TO THE 
FUSARIUM WILT OF THE TOMATO 1 
Edward E. Clayton 
(Received for publication April 19, 1922) 
There are three different tomato diseases in the United States, supposed 
to be caused by three different species of Fusarium. They are the “summer 
blight” of California, the “yellow blight” of the Pacific Northwest, and 
“Fusarium wilt,” which is one of the most serious tomato diseases in the 
southern states. Each of these geographical sections is subject to exceed¬ 
ingly high temperatures, and it has been observed that in periods of very 
high air and soil temperatures the Fusarium diseases cause the most serious 
damage. Edgerton (3) has recently published his observations on the 
relation of high temperatures to the Fusarium wilt disease. It is for this 
disease that the writer has attempted to determine definite temperature 
limits. The work herein described was carried on entirely under greenhouse 
conditions in the “Wisconsin soil-temperature tanks,” the primary object 
being to study the effects of (1) different soil temperatures and (2) different 
air temperatures upon the development of the disease. The influence of 
other environmental conditions on the development of the disease, and 
detailed observations, hitherto unrecorded, as to the nature of the disease 
have been described also. 
The Fungus 
The causal organism of the wilt disease under discussion is a vascular 
parasite of the tomato (Lycopersicum esculentum Mill.) which may live and 
retain its pathogenicity in the soil for considerable periods. Pure cultures 
of this fungus, designated as Fusarium lycopersici Sacc., were obtained from 
S. H. Essary of Tennessee, and in addition, isolations were made by the 
author from infected soil and infected plants sent from Maryland, Tennessee, 
Ohio, and Indiana. 
When inoculations were made with these various isolations, it was found 
that, under greenhouse conditions at least, some produced much more 
serious wilting than others. After a series of preliminary inoculation 
experiments, therefore, one Indiana isolation was chosen for the temperature 
experiments. This strain was not so virulent a parasite as a Maryland 
isolation, but it produced the disease under a wide range of temperatures 
and was about equal in virulence to several other strains from Indiana, 
1 Investigations carried on at the University of Wisconsin. The work was done under 
advisory relations with Professors L. R. Jones and E. J. Kraus, to both of whom the author 
expresses his indebtedness for suggestions and criticisms. 
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