TOM A TO — VIOLET 283 



roots. Where tobacco is grown under shade (as is now a common 

 practice) the soil should be steam-steriHzed. 

 Tomato. Bacterial blight. — See Tobacco Wilt. 

 Blight or Scab {Cladosporium fulvum). — Soft brown irregular 

 spots on the under surface of the leaves. The upper surface be- 

 comes spotted with yellow. The leaves finally wither and die. 

 Most serious in the greenhouse. 



Control. — In mild cases the disease can be prevented by pick- 

 ing off the affected leaves. In severe cases spray with bordeaux 

 mixture, 4-4-50, at intervals of ten days. 

 Downy mildew^ (Phytophthora infedans). — The same fungus that 



causes Potato-blight, which see (p. 279). 

 End-rot. — Not well understood, and no method of control is known. 

 Leaf-spot (Septoria lycopersica) . — A serious disease attacking leaves 

 and stems. At first small spots appear, which spread until the whole 

 leaf is consumed. In severe cases the fruit may also be attacked. 

 Control. — Spray with bordeaux mixture, 4-4-50, making the 

 first application two weeks after the plants are set out, and repeating 

 every two weeks throughout the growing season. 

 (Edema. — A diseased condition of forced tomatoes characterized 

 by rolled or curled leaves, distended veins, and by swollen 

 areas having a frosty appearance on leaf veins, petioles and stem. 

 This condition may be brought about by insufficient light, too 

 much water in soil, excessive fertilization, high soil temperature. 

 Prevention. — Avoid conditions favorable for the disease. Pro- 

 vide good ventilation in forcing-house; in field, cultivate deep 

 and avoid topping plants. (See p. 260.) 

 Violet. Leaf-spots and leaf-blights. — A number of different or- 

 ganisms are responsible. Usually not very destructive. 



Control. — Destroy affected plants; use fresh soil for new 

 plantings; spray the fohage in the summer and fall with bor- 

 deaux mixture, 4-4-50. 

 Root-rot {Thielavia hasicola). — The same as the root-rot of 

 tobacco. The plants make poor growth, owing to the fungus on 

 the roots. 



Con^roZ. — Start in steam-sterilized soil, and transfer to sterilized 

 beds. 

 Wheat-Smut. — See under Smut of cereals (p. 260). 



