Vegetable and Field Crops 247 



Normally it cannot enter a sound potato; a wound must 

 furnish a passageway. Therefore all wounded roots should 

 be laid aside for immediate consumption, and pnly sound 

 roots put in storage. 



Potatoes for storage should be fully matured, carefully 

 handled to avoid bruising, thoroughly cured, and kept at 

 uniform temperature, 26° to 29° C. (80° to 85° F.), while 

 curing, and at 12° C. (55° F.) after curing. Properly ven- 

 tilated storage houses should l)e built when possible. Kiln 

 drying at 29° to 35° C. (85° to 95° F.) for 10 to 15 days is a 

 good practice. 



It is well to destroy all infective material, rotten roots, 

 etc., in or near the stoi-age place, and if the house has been 

 infested, to spraA^ its walls and floors thoroughly with a good 

 disinfectant, such as Bordeaux mixture or formalin. 



Black-rot {Sphwronema fimhriatum (E. & H.) Sacc). — 

 This is among the most destructive of all sweet potato 

 decays, causing much loss in storage as well as in the field. 

 It is said to equal in damage that of all other sweet potato 

 diseases combined. Infected potatoes are bitter and worth- 

 less. Black-rot has been reported from nearly all states that 

 raise sweet potatoes, also from the West Indies and New 

 Zealand. 



The rot may be known by its dark brown to l^lack, irregu- 

 lar patches upon the potato surface. These begin as points 

 and gradually extend in all directions, involving the whole 

 root. Older spots, 2-5 cm. across, often break or crack 

 irregularly near the center. This decay differs from the 

 soft-rot in that the spots are dry and hard and that it is 

 present upon the roots before digging. With a hand lens, 

 very small, hairlike, black structures, 1 mm. high, are seen 

 studding the centers of the diseased areas. These are the 

 beaks of the pycnidia of the causal fungus. 



Upon young sprouts before they are set out the disease 

 causes black, dead patches, especially at the base of the 

 shoot or even upon the young leaves. The wood of the stem 

 may be browned. Such sprouts result in enfeebled plants 



