LEADING VEGETABLE CROPS 229 



colters running on either side of the row to cut away 

 the vines. The tubers are usually allowed to lie 

 in the sun for a while before gathering, after which 

 they are hauled to the storage house on springs. 

 It is especially important that every operation in 

 connection with harvesting be carefully done in 

 order that injury to the roots may be reduced as 

 much as possible. 



The sweet potato is subject to a number of dis- 

 eases under storage conditions, and the losses at 

 this point are enormous every year. The usual 

 method of storage is to place them in large bins in 

 frostproof buildings especially designed for the 

 purpose. As the potatoes are being brought 

 in from the field a temperature of 85 to 90 degrees 

 should be maintained for ten days or two weeks in 

 order to drive out quickly the surplus water from the 

 tubers. After this period the temperature is gradu- 

 ally lowered to from 50 to 55 degrees, where it is 

 held during the remainder of the storing period. 

 Any sudden changes in temperature resulting in con- 

 densation of moisture on the roots usually prove 

 disastrous. 



Sweet potatoes are graded in various grades, due 

 to the demands of the market, and to meet local needs 

 for seed purposes. They are commonly marketed 

 in hampers and barrels. 



No serious insect pests are found attacking the 

 sweet potato, but the black and soft rots are often 

 very destructive. The black rot does most injury 

 to the crop while still in the field, while the soft rot 

 affects tubers only while in storage. Black rot can 

 be controlled by a wide crop rotation and by grow- 

 ing seed from slips unaffected. Disease-free tubers 

 may be most easily secured by the use of vine- 

 cutting plants, grown on clean soils. 



