SWEET POTATOES 427 



a small trowel, similar to that used by brick masons, will be a help. 

 With this a man can become so proficient that he can plant from 

 5000 to 8000 sets in a day of ten hours. The usual method, how- 

 ever, is to use the planter shown in figure 1 1 , page 46, which 

 opens the furrow, waters the plant, and packs the soil around it. 

 Boys or men riding on the machine place the slips in position. 

 Transplanters are expensive, but for large areas they are in reality 

 an economy. 



Thorough cultivation to prevent the growth of weeds must be 

 given these young plants as soon as they have taken root, for after 

 they begin to run it is impossible to use horse-power cultivators. 

 The ridges should be kept in as good form as possible to provide 

 for the protection of the roots and to keep the land well drained. 



Insects and diseases. The sweet potato is not troubled by many 

 enemies. Very few insects work upon the vines, and these do com- 

 paratively little damage. The diseases which are most destructive 

 are the rots of the roots, of which there are two forms the soft 

 rot, which affects the roots while in storage, and the black rot, 

 which does most injury to the crop while still in the field. In the 

 Southern states the black rot is quite prevalent and does much 

 damage, destroying the roots and interfering with the growth of 

 the plants. Wherever this disease is prevalent it is necessary to 

 select soil which has not been used for sweet-potato culture for 

 several years, and to grow seed from slips which are not affected. 

 Vine cuttings planted on clean soil is the surest way of securing 

 disease-free seed. 



The treatment of the soft rot consists chiefly in carefully sorting 

 and handling the tubers at harvest time and placing them in a 

 storeroom, heated to 80 or 90 F. while the work of storing is 

 in progress and for ten days thereafter, gradually lowering the tem- 

 perature to between 50 and 60 F. for the general storage 

 period. Treating the seed roots before bedding with the standard 

 formalin solution used for potato scab (see page 348) has proved 

 very effective. 1 



1 For further information on this subject see Bulletin No. jo, 2d Series, Louisi- 

 ana Experiment Station ; Bulletin No. 76, New Jersey Experiment Station ; Bul- 

 letin No. 36, Texas Experiment Station ; and Farmers* Bulletin, No. 324, United 

 States Department of Agriculture. 



