Plant- Diseases. 



59 



Sweet-Potato (Stem-Rot), continued. 



tubers, causing the tubers to rot away above, and to send up 

 sprouts below the injured portion. 



Preventive. — Rotation. Heat the soil used for seed-bed. 

 White-Mold or Leaf-Mold (Cystoims Ipomwa-pandurancey 

 Farl.)— The leaves become pale and brown patches appear, 

 and small whitish patches occur on the under surface. It 

 thrives upon the wild potato-vine or man-of-the-earth 

 (Ipomcea pandurata) . 



Preventive. — Destroy the wild potato-vine upon which the 

 fungus grows. 



Remedy. Some copper fungicide applied in a spray. 

 White-Rot. — This disease causes portions of the tuber to 

 become white and chalk-like, and sometimes the whole tuber 

 assumes a chalk-like consistency. 



Preventive. — Use only healthy stock, and probably a rota- 

 tion of crops will be useful. 

 Tomato. Blight {Cladosporium fulvum, Cooke). — Soft brown 

 irregular spots appear on the under surface of the leaves, 

 and the upper surface becomes spotted with yellow. The 

 leaves finally shrivel. Most serious in greenhouses. 



Preventive. — In houses, keep the temperature as even as 

 possible. In particular, avoid sudden changes. 



Remedy. — Bordeaux mixture or ammoniacal carbonate of 

 copper sprayed on the plants every week or ten days. 

 Rot {Macrosporium tomato). — The rotting of the nearly grown 

 or ripe fruit. 



Preventive. — The small cherry and plum tomatoes are not 

 attacked, and the old-fashioned angular sorts are compara- 

 tively free. Training the vines so as to give the fruit plenty 

 of light and air is usually useful. Heavy applications of 

 fresh stable-manure appear to augment the injury. Burn 

 all infested ^nines and fruits in the autumn. 



Remedy. — Spray with Bordeaux mixture. 



The bacterial potato-blight or rot also attacks tomatoes. 

 See under Potato. 

 Verbena. Rust {Oidium erysiphoides) . — A rust which appears on 

 the leaves, eventually destroying the plants. 



Preventives. — Start with perfectly healthy and vigorous 

 stock, and give good culture. In the house, endeavor to 

 avoid drafts, but give plenty of air on bright days. 



