174 Report of the Botanist of the 



II. POWDERY MILDEW ON FIELD-GROWN 



CUCUMBERS. 



In July, 1891, Humphrey'' announced tlie occuiTcnce of a pow- 

 dery mildew on cucumbers in America. In his annual report*^ for 

 that year he gave an extended account of the disease and stated 

 that it had been found on hot house cucumbers at Fitchburg, 

 Mass., and Ithaca, N. Y. His next annual report^ contained 

 drawings of the fungus and a brief recapitulation of the matter 

 contained in the previous report. In Cornell Experiment Station 

 Bulletin 31, page 31, Bailey has given a brief account of some 

 experiments on the treatment of cucumber powdery mildew in the 

 greenhouse. 



So far as known to the writer, the above mentioned articles 

 constitute the whole of the literature of powdery mildew on 

 cucumbers in America. In the Ninth Massachusetts Report^ 

 Humphrey states that in America it is not known to him to 

 attack cucumbers grown in the open air. It is therefore worthy 

 of mention that in September, 1899, we received from F. L. Esta- 

 brook, of Athens, Pa., several leaves of field grown cucumbers 

 which were thickly covered with a powdery mildew. Mr. Esta- 

 brook states that the mildew made its appearance some time in 

 August and by September 22 was to be found upon every vine in 

 the field and upon all parts of each vine excepting the younger 

 leaves. In almost every case the older leaves near the root were 

 the most severely attacked while the newer leaves toward the tip 

 of the vine were generally free from it. The fungous was con- 

 spicuous and occurred chiefly upon the upper surface of the leaves 

 but occasional spots of it were to be found upon the under surface. 

 The fruits were exceedingly bitter and many were misshapen, but 



5 Humphrey, J. E. The Powdery Mildew of the Cucumber. Mass. State 

 Agr. Exp. Sta. Bui. 40: 3. 



6 Ninth Ann. Kept. Mass. State Agr. Exp. Sta., 1891: 222-226. 



7 Tenth Ann. Kept. Mass. Agr. Exp. Sta., 1892: 225-226. 

 81. c, p. 222. 



