342 Bulletin 163. 



observed in one or two other sections of the country. It may be 

 the same trouble that has several times been very destructive to 

 the sugar beet industry in Germany. Again, as subsequently 

 noted, this beet root-rot is caused by the same fungus which 

 causes a stem rot of carnations; and probably by the same fungus 

 which produces some damping off diseases, so that we may pre- 

 dict that it has a wide distribution even at the present time. 



b. Appearance of Affected Plants. 



Under favorable conditions for its spread, this beet root-rot 

 generally secures its first foothold at the bases of the leaves. 

 These parts are moist with the slightest rain or dew, and inocu- 

 lation experiments show that in those regions the disease 

 "takes" very readily. The first evidence of the attack is mani- 

 fest in the blackening of these leaf bases, the outer leaves first, 

 so that the stalks soon become unable longer to support the 

 blades, and the leaves may lie prostrate on the ground. The 

 leaves do not, however, lose their green color very readily. 

 Figure 49 shows this blackening of the leaf bases, before any in- 

 jur}^ is manifest in the other parts. 



The disease soon works into the crown and root proper, caus- 

 ing the infested parts to turn brown. With further spread of the 

 fungus in the root region, cracks appear, as shown in figure 50. 

 If the conditions continue to favor the disease, in time the whole 

 top rots away, and the beet gradualh' disappears. Cold weather 

 or dry conditions may so retard the disease that plants only 

 slightly affected may recover entirely. Ordinarily the trouble 

 was scattered throughout the entire field affected, but numerous 

 small areas indicate that the fungus passes rapidly from plant to 

 plant in the row^ spreading radiall3^ 



Even when the bases of the leaves alone are affected, upon 

 careful examination one will find that there are to be seen the 

 brown m^'-celial threads of the fungus growing over the surface. 

 After the root has become affected, a considerable weft of the 

 fungus wall be evident in the cracks. A diseased beet sliced 

 lengthwise and placed in a moist chamber 3'ields in a da}^ or two 

 a luxuriant growth of the mould-like hyphse. From this out- 

 growth of mycelium it is very easy to secure a pure culture of 



