BULLETIN No. 169. 



TWO RECENT EPIDEMICS OF LATE BLIGHT AND 



ROT OF POTATOES IN AROOSTOOK COUNTY. 



W. J. Morse. 



The summer and fall of 1907 and that of 1909 presented ideal 

 weather conditions for the development of late blight and rot 

 of potatoes in Aroostook county and some other parts of ]\Iaine. 

 As a direct result of these weather conditions and the conse- 

 quent development of the blight, by very conservative estimate, 

 the loss in diminished or damaged crops in each of these years 

 amounted to several hundred thousand dollars. Much of this 

 loss occurred on fields wdiere the owners were attempting to 

 spray with bordeaux mixture, and in many cases felt that they 

 were spraying carefully and thoroughly. 



During the season of 1907 the writer was engaged in carry- 

 ing on spraying experiments in Houlton and in Foxcroft, both 

 to test the relative efficiency of thorough spraying as compared 

 with that usually practiced by most growers, and to test the 

 relative efficiency of certain substitutes for standard bordeaux 

 mixture. No such experiment was conducted in 1909 but dur- 

 ing both seasons the conditions in various parts of the State 

 were closely observed and carefully followed uj) as soon as 

 weather conditions indicated that an outbreak was imminent. 

 Repeated visits w-ere made to the various potato growing sec- 

 tions, particularly where blight was appearing and careful notes 

 were made of spraying operations and the resulting successes 

 or failures therefrom. 



The results secured from the experiments of 1907 and the 

 field observations during the two seasons of severe epidemic 

 blight and rot, taken in connection with results previously 

 obtained bv Director Woods of this Station under similar con- 



