228 



Diseases of Economic Plants 



blight is also serious on tomatoes in the South, on leaves and 

 on fruits, where it produces a rot. It is found also upon 

 eggplants. This is a disease characteristic of dry soils and 

 seasons, and is likely to be associated and confounded with 

 tip-burn. 



General spraying (p. 236) will hold this blight in check. 

 Tip-burn. -^^' ^-^ — Leaves die at the edges and tips, curl 

 somewhat, and eventually the whole top withers. This 

 condition occurs when the sun 

 is hot and the winds dry, and 

 is especially noticeable when 

 a cool, wet period is followed 

 by hot, dry weather. It has 

 been asserted that the primary 

 cause is attack by leaf-hop- 

 p(^rs. Though not due to a 

 parasite, spraying with Bor- 

 deaux mixture lessens the loss. 

 ^ilt 2^0- 477. 531 ^Fusarium 

 oa-yftponmi Schl. and Fusarium 

 .s/;,s'.). — This wilt is definitely 

 known in many states, and is 

 probably identical with a very 

 destructive potato disease of 

 England, Germany, France, 

 and Belgium. 

 When the plants are about a foot high, or in mild cases a 

 little later, the first trace of the wilt is noticeable. The 

 leaves, which are usually light-colored, assume a dull, un- 

 healthy appearance, with rolling or curling of the margins. 

 Progressive disease gradually causes the top to fall, and 

 gives a general effect of premature ripening. When the 

 diseased plants are pulled up, the partially dead roots are 

 found to be quite brittle, and frequently bear a white or pink 

 mold. If the imderground portion of the stem is cut across, a 

 pronounced l)rown discoloration is visible. This brown stain 

 is also found in the l>ranches leading to the tubers, and a thin 



Fig. 126. — Potato early-blight 

 spots enlarged. After Whetzel. 



