428 Report of the Mycologist of the 



LoiLg Island until after August 1, and downy mildew did not 

 appear until three weeks later. The time of appearance of both 

 these diseases is more dependent upon the weather conditions 

 than upon the stage of growth of the plant. Both early and late 

 cucumbers are attacked at about the same time. 



The very thorough spraying which the plants received gave 

 complete protection against downy mildew but only partial pro- 

 tection against the anthracnose. In the latter part of the season 

 there was sufficient anthracnose among the sprayed plants to 

 seriously affect the yield. By consulting the table on page 427, 

 it may be seen that the last picking was made September 18, 

 whereas there was no frost until September 28. After Septem- 

 ber 18, the anthracnose became so severe on the sprayed plat 

 that the plants dried up and produced thereafter only deformed 

 fruits or " nubbins." From this it appears that anthracnose is 

 more difficult to manage than downy mildew, and that to prevent 

 it the spraying must be done very thoroughly and repeated at 

 short intervals. Of course this test was a severe one because of 

 the close proximity of the diseased plants on the unsprayed plat. 



An unexpected result of the experiment was the influence 

 which the spraying seemed to have in checking the wilt disease. 

 The wilt disease killed about fifty plants on the unsprayed plat 

 and only five or six on the sprayed plat. Considering the small 

 size of the plats this difference is worthy of note. 



Until near the close of the season the percentage of deformed 

 fruits produced by the sprayed plants was very small — much 

 smaller than in the case of the unsprayed plants. 



Why Plasmopara cuhensis Was More Abundant in 1896 Than in 



1897. 



Halsted* has published obsei-vations which indicate that th^ 

 Peronosporese, in general, thrive best in wet seasons. For Plas- 

 mopara cubensis no such observations have been recorded, but 

 from the following it appears that this fungus is influenced more 

 by temperature than by rainfall. 



♦Halsted, Byron D. Downy Mildews in a Dry Season. Bulletin from the Botanical 

 Department of the Iowa Agricultural College, 1888; and, Peronosporeae and Rainfall. 

 Journ. Myc, Vol. V, pp. 6-11, 1889. 



