CHAPTER V. 

 WILTS. 



WILT OF 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 to- 

 gether gently and separated slowly, this sticky liquid will string out in 

 fine threads two to three centimeters in length. 



METHOD OF INFECTION. Under field conditions, the disease is 

 spread principally by insects, especially the striped cucumber beetle 

 and the common squash bug. 



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



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