REPORT OF THE MYCOLOGIST. 



F. C. STEWART. 



I. THE DOWNY MILDEW* OF THE CUCUMBER; 

 WHAT IT IS AND HOW TO PREVENT IT.f 



SUMMARY. 



The 1896 crop of late cucumbers in southeastern New York 

 was unusually small — from 17 to 25 per cent of a full crop. The 

 chief cause of the short crop was a disease which caused the 

 leaves to turn yellow and die prematurely. This disease, which 

 is known as downy mildew, was first observed in this country in 

 1889, since which time it has been rapidly spreading and has 

 become very destructive to cucumbers, muskmelons and water- 

 melons. 



In an experiment made at Woodbury, Long Island, the disease 

 was successfully prevented by spraying once every ten days with 

 Bordeaux mixture. Sprayed plants remained green and con- 

 tinued to produce cucumbers for four weeks after unsprayed 

 plants in the same field had lost their foliage and ceased to pro- 

 duce fruit. The net profit from spraying on the experimental 

 plat of one and three-fourths acres was more than one hundred 

 and sixty dollars per acre. 



It is probable that the same treatment will protect musk- 

 melons and watermelons against the disease. 



There is no good reason for believing that the disease will 

 disappear; on the contrary, it is likely to become more wide- 

 spread and more destructive. Therefore, it is earnestly recom- 

 mended that farmers prepare to fight the disease as follows: 

 Beginning when the plants are very small, spray thoroughly 

 with Bordeaux mixture (l-to-8 formula) once every eight or ten 



* Plasmopara ciii nsU (B. & C.) Humph, 

 t Reprint of Bulletin No. 119. 



