Cucumber Diseases 137 



Mosaic or "White" or "Little Pickle" 



Cause unknown. 



Symptoms. The first sign appears as a yellow 

 mottling near the stem end of the fruit. Later the 

 light areas are found all over the cucumber, and 

 the darker portions frequently form protuberances. 

 Some fruits retain their green color and show the 

 disease only by being distorted. The leaves become 

 mottled light to dark green (fig. 21, a), and some- 

 times wrinkled, while the stems and petioles are 

 dwarfed and distorted. Affected leaves die prema- 

 turely and are replaced by others, which in turn con- 

 tract the disease. The trouble is spread principally 

 by the melon louse. Aphis gossypii Glov., and to a 

 lesser degree by striped cucumber beetle, Diabrotica 

 vittata Fabr. Satisfactory methods of control are 

 still wanting. Affected plants should be destroyed 

 to prevent further spread of the disease. 



Bacterial Wilt 



Caused by Bacillus tracheiphillus Ew. Sm. 



The symptoms and the damage caused by this 

 wilt will be found discussed under the muskmelon, 

 p. 155. Recent investigations by Rand and En- 

 lows * have shown that seeds from diseased plants 

 fail to reproduce wilt. This is true not only for 

 the cucumber, but also for all the other cucurbit 



•Rand, F. V., and Enlows, E. M. A., U. S. Dept. of Agr. Jour. 

 Agr. Research, 6 : 417-434, 1916. 



