NOTES ON THE ROTTING- OF POTATOES DUE TO 

 THE LATE BLIGHT FUNGUS. 



(Phytophthora infestans.) 



Chas. D. Woods. 



During the past few years, in connection with experiments at 

 this Station, considerable data have accumulated on the rotting 

 of potatoes due to the fungus that produces the late blight. 

 Such as are believed to be of general interest are here reported. 



ROTTING IN the; CIlLLAR DUE TO PREVIOUS INFECTION. 



In 1902 a three-acre field of Green Mountain potatoes, which 

 had been sprayed several times during the growing season and 

 which had been kept practically free from the late blight, was 

 harvested before the tops were dead, and stored in one bin in a 

 cool cellar. The day of digging was warm and rather muggy. 

 The tubers were fairly well dried off, however, before being put 

 in the cellar. The following days were unusually warm for the 

 season. At harvest there was very little evidence of rot. Per- 

 haps there was one bushel of discolored potatoes in 100, but no 

 really rotten potatoes were found. Early in November it was 

 noticed the potatoes were rotting badly. They were carefully 

 assorted and it was found that fully one-third of the crop was 

 more or less affected with rot due to late blight. 



As there were so few affected potatoes at harvest, and so 

 much rot had developed in a few weeks, it was thought possible 

 that the sound potatoes were infested after digging. To test 

 this, two barrels of sound potatoes were selected at the time of 

 assorting in November, and to each peck of sound tubers two 

 potatoes showing unquestionable signs of incipient rot were 

 added. To learn if the treatment of the tubers with different 

 substances would tend to decrease the amount of infection, five 

 lots of two barrels each of selected tubers were treated with ( i ) 

 flowers of sulphur, (2) copper sulphate, (3) air slacked lime, 



