116 The Sweet Potato 



tion with the sweet potato is the controlling of insect 

 pests and fungous diseases which in sections seriously 

 hamper the development of the industry. In speaking 

 of control measures for the sweet potato weevil, which 

 in Texas alone is exacting an annual toll of nearly 20 

 per cent of the crop, Chittenden ^ writes " Rotation of 

 crops is a necessary measure in the eradication of this 

 pest; indeed, injury may be prevented to a large ex- 

 tent by the selection of the field for planting." (See 

 Chapter VII.) Miller^ says, "A rotation in which 

 sweet potatoes are grown on the land once in three or 

 four years combined with seed selection and hot-bed 

 sanitation, is effective in preventing loss from stem-rot, 

 black-rot and other injurious diseases." The New Jer- 

 sey Station recommends a rotation calling for sweet 

 potatoes not oftener than once in four or five years for 

 old sections and every three years for new ground if 

 disease is to be controlled. 



Some crops are favorable to the growth of accom- 

 panying weeds which are likely to become firmly estab- 

 lished if the crop is continually grown on this same land. 

 In the South, crops of the short-vined varieties of sweet 

 potatoes may be almost completely choked out by Ber- 

 muda-grass which can easily be held in check by the 

 use of a heavy cover-crop such as cowpeas. Johnson- 

 grass, " nut-grass " an.d " Kerless " weeds are obnoxious 

 enemies of the sweet potato. All can be controlled and 

 sometimes completely eradicated by proper rotation. 



Rotation to he used. 



The crop rotation with sweet potatoes will necessarily 

 have to be determined by the individual grower. It will 



1 F. H. Chittenden, Pannera' Bull. 1020, p. 18. 



2 Fred E. Miller, Farmers' Bull. 999, p. 5. 



