204 The Sugar-Beet in America 



appearance. The shortened petiole resulting from it 

 makes the plant resemble one having curly-top, although 

 the two diseases are easy to distinguish. The roots of 

 plants having the mosaic disease are likely to be dwarfed 

 and are often hairy. 



Damping-off. 



The damping-off of seedlings near the surface of the 

 ground when they first come up results in considerable 

 loss in some districts. This may be caused by a number 

 of organisms, among which are Rhizoctonia, Phoma, and 

 Pythium. The conditions which favor damping-off are 

 heat, abundant moisture, and a weakened condition of 

 the seedlings. The elimination of any of these condi- 

 tions greatly reduces the difficulty from this cause. Plants 

 on heavy clay soils are more subject to the disease than 

 those raised on lighter soils. Improving the tilth of these 

 soils also reduces the likelihood of injury from damping- 

 off. 



