CHAPTER V 



WILTS 



WILT or CUCURBITS 

 Bacillus tracheiphilus Erw. Smith 



HISTORY AND DISTRIBUTION. The bacterial wilt of the muskmelon, 

 cucumber, squash and pumpkin was first reported by Erwin Smith* in 

 1893. It is widely distributed over the United States east of the Rocky 

 Mountains and seems to have different host preferences in different 

 localities. 



SYMPTOMS. The disease is characterized by a wilting of the vine, 

 pure and simple, without any visible external cause such as mildew, 

 rust or leaf spot. The leaves and runners wilt suddenly as if from lack 

 of water or too hot sun, the runner becoming prostrate on the ground. 

 From two to three days usually elapse before the wilting of the whole 

 vine is complete, and it may remain in this wilted condition for several 

 days, after which the leaves begin to dry up, but retain their green 

 color for considerable time. One runner may die at a time, beginning 

 at the tip and working back toward the root, after which a general 

 infection is to be expected. If inoculation takes place upon the main 

 stem, several or all of the runners may show the wilt at the same 

 time. 



The disease is caused by a bacillus whose growth fills the water ducts 

 or tracheae with a white, viscid material which prevents the rise of 

 water, and wilting follows. If the severed ends of a diseased vine are 

 rubbed together gently and separated slowly, this sticky liquid will 

 string out in fine threads 2 to 3 cm. in length. 



METHOD OP INFECTION. Under field conditions, the disease is 

 spread principally by insects, especially the striped cucumber beetle 

 and the common squash bug. 



* Smith, Erwin: Cent. f. Bakt., Bd. I, II.. Abt., pp. 364-373, 1895. 



988 



