CULTURAL DIRECTIONS 449 



known as the "sweating" stage, after which the temper- 

 ature is gradually lowered and maintained between 55 

 and 60 degrees. For a full discussion of storage, see 

 Farmers' Bui. 324, pp. 29-34. 



638. Returns. In the large commercial districts it is 

 estimated (Farmers' Bulletin 324, p. 38) that the acre- 

 cost of production is about as follows: Rental of land, 

 $8; plowing and fitting, $5 ; fertilizers, $20; 10,000 plants, 

 $10; planting, $5; cultivating, $5; digging and market- 

 ing, $25; total, $78. Average yield, one barrel to 100 

 hills or 100 barrels an acre. Prices range from $1.25 to 



I 





FIG. IO5. HARVESTING THYME 



$3 a barrel (sometimes more) and $75 is about the aver- 

 age profit to the acre, although $100 to $150 is some- 

 times realized. 



639. Insects. The sweet potato has fewer insect ene- 

 mies than many other vegetables. Cutworms are trouble- 

 some sometimes, especially in sod lands. The sweet 

 potato borer, destructive to the roots of the plants, causes 

 the greatest damage to the crop in the Gulf Coast States. 



640. Diseases. Although there are several diseases 

 that cause more, or less trouble in the field or when the 



