10 



BULLETIN 1256, U. S. DEPARTMENT OF AGRICULTURE. 



wholly recover under conditions which are unfavorable for the 

 disease. 



Cause. — The similarity of this disease to bed-rot, or damping-off. 

 previously described, is evident, excepting that the former rot is 

 characteristically located in the plant beds, whereas the disease now 

 under consideration occurs under field conditions. It seems to be 



fairly well estab- 

 lished that the dis- 

 eases are identical 

 and that often the 

 field disease arises 

 from the trans- 

 planting of infected 

 seedlings, although 

 the causal organisms 

 concerned are com- 

 mon soil organisms 

 and infection from 

 field soil is not im- 

 probable. The dis- 

 ease has been re- 

 ported from differ- 

 ent sections as due to 

 Rhizoctonia solani 

 BudPytMum debary- 

 anum, both common 

 damping-off fungi, 

 and to undescribed 

 bacteria. Stem-rot, 

 caused by Sclero- 

 tium rolfsii (Sclero- 

 tinia sp.), falls into 

 this group of dis- 

 eases as far as gen- 

 eral symptoms, ori- 

 gin, and control are 

 concerned (PI. II, 

 fig. 1). This dis- 

 ease is frequently 

 characterized by the 

 production of small 

 sclefotial bodies on 

 the surface of the 

 diseased area. A 

 number of other 

 cultivated plants are 

 affected in a similar 

 way by Rhizoctonia 

 in particular. 



Conditions faro ring the disease. — It is believed that most cases 

 of sore-shin are a result of transplanting plants more or less affected 

 with the damping-off disease in the plant beds. This primary lesion 

 may make little or no development for weeks after transplanting, 

 but finally, under favorable weather conditions and especially when 



Fig. 5. — Sore-shin, or black-leg. The rotting of the stalk at 

 the surface of the ground is characteristic. Sometimes 

 the decay extends a considerable distance up the stalk and 

 into the lea vs. 



