Vegetable and Field Crops 251 



Leaf-spot (Septoria bataticola Taub.) is similar to leaf- 

 blight, lint with smaller spots. Charcoal-rot (Sderotium 

 bataticola Taub.) is similar in general character to Java dry- 

 rot. Rust {Coleosporium ipomcem (Schw.) Burr.). — The 

 alternate host is the pine. Rust is injurious in the tropics. 

 Trichoderma-rot (Trichodcrma koningi Oud.) and Root-knot 

 (nematodes) do some damage. 



TEA '''^ 



The diseases of the tea plant are mmierous and destructive, 

 but since the crop is little grown in the continental United 

 States, they may be enumerated, merely, as follows: Gray- 

 blight (Pestalozzia) and Brown-blight (Colletotrichum) spot- 

 ting the leaves ; Blister-blight (Exobasidium) ; Thread-blight 

 (Stilbum) which kills l)ranches or even the entire plant; 

 Copper-blight (Lcestadia) causing copper-colored leaf-spots; 

 Red-rust due to the alga, Cephaleurous, Canker due to 

 Nectria; Blight due to Marasmius. 



TOBACCO. 



Root-rot '''■ '^' {Thielavia basicola (B. & Br.) Zopf.). — 

 Known in Europe since 1897, this disease was first reported in 

 the United States, in 1904, as occurring upon tobacco, 

 though it has probably been long prevalent in tobacco sec- 

 tions. It has l)een noted upon other hosts; namely, violets 

 in Connecticut, Maryland, and District of Columbia; 

 ginseng in Ohio and New York; also upon begonia, catalpa, 

 and clover. Upon tobacco it is now known in Ohio, Con- 

 necticut, Kentucky, and North Carolina, and its territory is 

 increasing yearly. See also p. 23. 



Root-rot in the seed bed often causes the entire crop of 

 seedlings to be discarded, delaying planting or compelling 

 a change of crop. In the field the loss sometimes amounts 

 to 25 per cent. 



The disease is recognized l)y the black decay upon the 

 roots, sometimes by a cracking and deformation on the stem 



