266 
ELEMENTARY AGRICULTURE 
times during the period of growth to mulch them close up 
to the plants and free the land of grass and other harm¬ 
ful weeds. The cultivation should be shallow with some 
horse drawn implement such as harrows and cultivators. 
In turning the vines for plowing, exercise care not to 
bruise them. 
Insect Pests and Diseases of Sweet Potatoes.—■ 
Cutworms are probably the most troublesome insect pest 
Fig. 190.—Storing sweet potatoes. Corn stalks are placed over and under 
the pile. They are then covered with earth. 
of the potato plant. They cut down the young sets as 
soon as they are transplanted into the open ground, 
which results in a poor stand. If the sweet potato crop 
follows a clean cultured crop they are not so harmful. 
Avoid planting sweet potatoes on sod land. 
The sweet potato is also subject to several kinds of 
rots known as black-rot, stem-rot, soft-rot, and dry-rot. 
The best method of controlling these rots is to rotate the 
crop, select seed and plants that are free from the disease, 
