New York Agricultuii.\l Experi.mext Station. 



42!) 



In 1896, Plasmopara cubcnsis made its first appearance on Long 

 Island about August 7. In 1897 it did not appear until August 

 24, and was not nearly so destructive as in 189G. Witliout 

 doubt this difference was due to some diiference in the weather 

 conditions prevailing during the two seasons, and inasmuch as 

 August is the month in whi(,'h the fungus commences its ravages, 

 it is likely that the variable factor should be sought in the wea- 

 ther records of that month. The New York State Weather 

 Bureau has stations on Long Island at Brooklyn, Willets Point, 

 Brentwood and Setauket. A comparison of the records of these 

 stations for August, 189(5, with the records of the same 

 stations for August, 1897, shows that the only important differ- 

 ence is in the temperature for the first fifteen days of the month. 

 This difference is brought out in a striking manner in the follow- 

 ing taible of daily mean temperature* which shows that the 

 average temperature for the first half of August, 1896, was 7° 

 higher than for the same period in 1897. 



Temperature Record, August 1-15, 1896 and 1897. ^ 



August, 1896. 

 August, 1897. 



72° 



80'^ 78° 

 660,700 



810|83o 

 700 69° 



15 



75° 



The rainfall for August was somewhat greater in 1897 than in 

 1896, and this alone should be sufficient evidence that the rainfall 

 is not the controlling factor in the development of downy mil- 

 dew. However, if it is desired to go back to the month of July 

 we find that 1897 was much the wetter. The records are as fol- 

 lows: 



Rainfall Record, July and August, 1896 and 1897. 



♦Computed from records published in Report of the New York State Weather Bureau, 

 Vol. VIII, No. 8, p. 8, and Vol. IX, No. 8, p. 8. 



