SEEDLING DISEASES OF SUGAR BEETS AND THEIR 

 RELATION TO ROOT-ROT AND CROWN-ROT^ 



By H. A. Edson, 



'{[Physiologist, Cotton- and Truck-Disease and Sugar-Plant Investigations, 



Bureau of Plant Industry 



INTRODUCTION • • 



The diseases of the sugar beet {Beta vulgaris L.) to be discussed in this 

 paper are damping-ofF and a more common but less familiar seedling 

 trouble which will be designated as "root sickness," together with the 

 associated rots of the growing or of the mature root. 



Damping-off is a disease which typically manifests itself by a charac- 

 teristic browning or blackening of that portion of the root or hypocotyl 

 near the surface of the ground. Plants may either be killed by the 

 progress of the disease or checked in growth for a longer or shorter time, 

 according to the severity of the attack and the environmental conditions. 

 The trouble is found in incipient form wherever the host is cultivated and 

 not infrequently becomes epidemic, completely destroying the stand. 



Root sickness is similar in some respects to damping-off, but the 

 attack in this case is confined to the root system, seldom appearing above- 

 ground. For this reason it has heretofore escaped general recognition as 

 a distinct disease and has received no treatment in American literature. 

 Diseased plants assume a slightly flabby appearance and are perhaps a 

 trifle lighter green than normal ones. In severe cases the entire field 

 may be wiped out, but more frequently enough plants survive to produce 

 at least a partial stand. The beets make practically no growth during 

 the continuance of the attack, which is usually for two or three weeks. 

 By carefully removing the sick plants from the soil so as to avoid breaking 

 the roots it may be seen that the side branches and taproots are blackened, 

 shriveled, and more or less completely killed. Healthy new shoots are 

 sent out here and there from the upper portion in an attempt at recovery. 

 If the plant survives, one of these eventually replaces the taproot. 

 However, such beets are not only delayed two or three weeks in growth 

 but they are likely to be short and branching. The stand is always more 

 or less imperfect in fields that have recovered from the disease. This 

 type of trouble is almost universal, and in some of the heavier soils of the 

 more northern areas it frequently becomes a limiting factor in sugar-beet 

 production. Even in the more favored sections it is annually the cause of 



1 The major portion of the work reported in this paper was carried out at Madison. Wis., in cooperation 

 with the Wisconsin Agricultural Experiment Station, which kindly supplied space and care for the field 

 plots and provided all necessary laboratory and greenhouse facilities. 



Journal of Agricultural Research, Vol. IV. No. 2 



Dept. of Agriculture, Washington, D. C. May is. i9is 



G— 46 



(135) 



