368 The Spraying of Plants. 



edy. Kerosene emulsion is also effective, but there is danger of 

 tainting the fruit. 



SWEET POTATO. 



FUNGOUS DISEASES. 



Black Rot (Ceratocystis Jimbj'iata, E. & H.). Description. 

 The fungus causes large, greenish-black patches to appear upon 

 the tubers ; the dark color eventually extends deeply into the 

 potato, entirely ruining it. The disease may attack the young 

 plants in the seed beds, the infection coming either from the 

 soil or from unhealthy tubers. When the young sprouts are 

 affected, the stems near the ground become discolored by dark 

 lines or blotches, and the lower leaves frequently suffer in the 

 same manner. The shoots frequently die beyond the point of 

 attack. 



Treatment. The use of unaffected potatoes for producing the 

 sets is essential. No diseased sprouts should be planted, and, if 

 possible, land that is free from the fungus should be used for 

 the crop. Spraying with copper compounds may materially 

 assist in checking the trouble in the field, and soaking the 

 tubers a short time in the ammoniacal carbonate of copper 

 before storing them may prevent its spread in the bins. 



Leaf Spot (Phyllosticta bataticola, E. and M.). Description. 

 Sweet-potato foliage attacked by this disease dies at the points 

 of infection, the dead portions turning nearly white. The 

 plants may suffer severely from the disease, the yield being 

 correspondingly reduced. 



Treatment. Spray with the Bordeaux mixture at the first 

 appearance of the fungus. 



White Mold; Leaf Mold (Cystopus 2pomo3ce-pandurancc, Farl.). 

 Description. This fungus causes the leaves to turn brown, 

 the older ones being particularly affected. Small white patches 

 also appear on the under side of the discolored areas. 



Treatment. Spraying the vines with a good fungicide will 

 probably prove valuable in checking the disease. 



INSECT ENEMIES. 



Sawfly (Schizocerus ebenus, Norton; S. privatus, Norton). 

 Description. These two sawflies are not, as a rule, very seri- 

 ous, but occasionally they develop in sufficient numbers to do 



