158 The Sweet Potato 



sublimate should not be used more than two or three 

 times, since it loses its effectiveness after repeated use. 

 If for any reason corrosive sublimate can not be used, 

 the potatoes may be immersed for five minutes in a solu- 

 tion of formaldehyde made by adding 1 pint of com- 

 mercial formalin to 30 gallons of water. They should 

 be rinsed in water and dried before bedding. 



The continued use of the same soil for the seed-bed 

 year after year is the chief source of many of the dis- 

 eases of sweet potatoes. A change of bedding soil or 

 ground should be practiced each year. In fact, clean 

 sand hauled in from the woods is one of the best ma- 

 terials to use in the bed. Stable manure is not essen- 

 tial to the production of healthy draws and is much 

 more likely to become infected with disease germs than 

 this fresh new sand. Many farmers throw aside the 

 diseased potatoes as they bed down the good ones ; fowls 

 or dogs running loose around the place will easily take 

 the disease to the bed on their feet. All such careless- 

 ness should be strictly avoided. 



FOOT-EOT (Plates VI and VII) 

 {Plenodomus destruens) 



Of the various diseases to which the sweet potato is 

 subject, foot-rot (die-off) is one of the most serious. 

 In the field, foot-rot first manifests itself as dark spots 

 or areas at the base of the stem. The diseased areas 

 may extend from 1 to 5 or 6 inches up the stem, the 

 remainder appearing more or less normal. The tissues 

 within the diseased area of the stem are killed and the 

 fruiting bodies of fungus develop below the surface. 

 The woody part of the stem becomes blackened and 



