158 Diseases of Truck Crops 



Rhizopus; however, the spores of the fungus preserve 

 their vitality for a considerable time. When we 

 consider how abundant these spores are in nature, 

 it is not difficult to conceive how easy it is for soft 

 rot to get a start every year. The storage house is 

 undoubtedly the place where the greatest amount of 

 Rhizopus spores are carried over from year to year. 

 The main problem, therefore, is to prevent the Rhizo- 

 pus spores from germinating or to use some fumigant 

 which will kill them all together. 



Ring Rot 



Caused by Rhizopus nigricans Ehr. 



Ring rot is a form of soft rot. The disease is 

 prevalent as soft rot and is found in poorly venti- 

 lated houses. The amount of loss varies from i 

 to 20 per cent. 



Symptoms. There are two forms of ring rot. 

 The first stage is the soft ring which is characterized 

 by a rotted area which girdles the root at any point 

 (fig. 25 h-i). As the roots are usually put in bins in 

 bulk and as soft ring, like soft rot, is confined to the 

 roots more or less buried in the bulk of the bin, the 

 onset of the disease is usually overlooked. It is at 

 first odorless, but in a week or ten days it is followed 

 by a characteristic fermentation. The soft ring 

 gradually begins to dry, resulting in a shrinkage and 

 contraction of this area, and thus a slight groove is 

 formed (fig. 25 h). In two to six weeks, it becomes 



