WILT OF CUCURBITS. 



297 



So far as known to the writer, no one has studied carefully the relative resistance of 

 different varieties of melons, cucumbers, squashes, etc., to this disease. Possibly careful 

 field work covering a number of seasons and many varieties would develop some interest- 

 ing differences which might be turned to practical account in the production of resistant 

 varieties by cross-breeding and selection. 



To recapitulate. Prompt removal of diseased plants and wholesale destruction of cucur- 

 bitaceous insects are the best available means for holding this disease in check. 



PECUNIARY LOSSES. 



This disease has proved an extremely vexatious one to a great many growers, but the 

 writer has no means of knowing the full extent of the losses. Numerous complaints have 

 reached the Department of Agriculture. The disease is particularly bad in some regions 

 where cucumbers are cultivated extensively for pickles. The writer has seen entire fields 



\ 



V 



" <: -.. 



Fig. 97/ 



of cucumbers, of cantaloupes, and of winter-squashes destroyed by it in the vincinity of 

 Washington, and knows from personal observations in other places (Delaware, New York, 

 Michigan, etc.) that it is capable of doing serious damage over a large region of country. 



According to Sturgis (1899) a destructive muskmelon disease in Connecticut is caused 

 by B. tracheiphilus. "That this is actually the disease which, for the past five years at 

 least, has destroyed a large percentage of the melon vines in Southern Connecticut there 

 can be no doubt. Continuous observation in the field, in three separate localities, during 

 the past season, convinced me that the chief source of trouble was the bacterial organism 

 above mentioned." 



*Fig. 97. Petri-dish poured-plate of nutrient gelatin densely sown with Bacillus tracheiphilus, covered with 

 impervious paper except central star-shaped part which was cut away, and then exposed to sunlight for 3 hours at 15 

 C. There was prompt growth of the bacteria in the form of a white clouded mass in covered part, and almost no growth 

 in part exposed to light, i. e., only about 1 colony in 1,000 survived as shown by a count on the seventh day. The 

 figure also illustrates a bit of badtechnic. A mold spore germinated at x, and threatened to swamp the plate. When 

 the cover was removed to cut it out the dish was exposed to a draft of air, the result being the entrance and growth 

 of 30 or 40 other organisms so that when the plate was old enough to photograph (4th day) these also were visible. 



